[RESOLVED] misfire help P0300 - ISC & coil results

[bboyalan]

Hey guys! I've been trying to fix this w/ my dad since Friday night, but I must resort to asking for help now as it is simply too time consuming w/ college and all...

Long story somewhat shorter [so I can explain the current situation]:
-A'PEXi dp + high flow cat installed friday noontime [nice, powerful drive home]
-installed boost/vac gauge on that friday afternoon [easy source taps]
-tried drilling through passenger footwell w/o looking
-ended up going through steering wheel boot [success!]
-key in ignition = no go for instrument cluster
-car would crank, but not start
-ends up I drilled through the wires behind and beneath the battery...
-reconnected and wrapped up wires
-car cranks, starts, but has terribly low, bogging idle [200RPM near death]
-smells like unburnt gas [not enough air in mixture for combustion?]
-checked plugs and wires
-replaced 1-month old NGK G-power platinums [toasted] w/ *new* NGK iridiums
-did the throttle SAS + BISS adjustment properly to help idle @ 400-500 RPM
-test drove and had POOR acceleration + threw p0300 code for random misfire
-erased code & grounded the brown plug for ignition timing adjustment
-boost and vac leak check
-test drove again w/ the same poor acceleration, P0300 code, but <400RPM now

SO NOW [and I apologize for the brief summary] I'm here w/ some diagnostics/results and hoping to get some good direction and recommendations. We pulled the plugs out after the code was thrown to see if any weren't firing and they all checked out okay. I also tested the ISC [Idle Speed Control] and came up with 41 Ohms on each [supposed to be 28-33]. In addition, I tested both the primary and secondaries of my coil pack. The secondary checks out within proper range, BUT the primaries were showing 11.2 for each [should be 0.70 - 0.86]. My NGK wires are 1-month old and have good resistance in them.

What should I be testing for or replacing next? I have such a terrible headache from thinking about this on the constant and I've devoted practically ALL of my study time towards searching the forum + trying out new things. If there is any other information that's needed, then I'll try my best to provide them. Any help is appreciated!

ps: this thread seems to have a similar problem minus the first half of b.s. I had went through.

 

[voodoogsx]

I had a similar issue due to a short that I had caused. Seeing as how you mentined that you drilled through the firewall and damaged some wires beneath and below the battery I thought I'd throw the thread that I had started a while back as I had damaged a wire in a similar location which caused the havok and several weeks of trying to figure out wtf happened.
It contains some testing procedures that I did based on Luvs2ralley's posts. His help was extremely valuable I can't express this enough. I can tell the things I had wished I'd done was start looking for a short sooner and also using the test light(simple yet extremely useful) to test various signals that would go to the ignition system, not just the components themselves . This is what helped me to pinpoint and trace the wiring to the point that it had shorted....that and the wiring diagrams at the back of the hanes manual. Anyway, look for similarities and see if the tests that I ran end up helping you out.

Good luck!

http://www.dsmtuners.com/forums/problem-diagnosis/270379-fried-coil-1-4-extremly-low-idle-issue.html

 

[super97gst]

Don't worry. You're not the only one who dreams about problems with his DSM.

Regarding the alternator. Is anyone willing to give it a shot? Any spare alternator's lying around?

Tom

i've got a brand new one sitting in the shop in my parts room. but it'll be sunday before i'll be able to get it on there. and you know, when i think about it, if the alternator went out i guess it is possible the diodes inside it could cause it to be an intermittent problem at first before it just outright failed?? i'll get mine changed and we'll see.

 

[bboyalan]

voodoogsx: Thanks for the helpful thread. Pretty similar indeed that it traced back to touching wires. I'm almost certain that I patched up all that was there, but I'll make certain to trace/test again if the ECU swap + NGK BPR6ES plugs don't do it for me. Also, my tachometer was acting just the same as yours. During my testdrives, I noticed that sometimes it would just die and barely be above "zero" if above it at all...

This alternator idea sounds good actually. It does suck to think that ours just died spontaneously though =/

//Edit// Not to get ahead of what we're all going to be testing next, but is it possible that something in our fuel delivery system is causing this too? Perhaps our fuel pump or FPR? ...just a thought

 

[Artago]

i've got a brand new one sitting in the shop in my parts room. but it'll be sunday before i'll be able to get it on there. and you know, when i think about it, if the alternator went out i guess it is possible the diodes inside it could cause it to be an intermittent problem at first before it just outright failed?? i'll get mine changed and we'll see.

That's great. I can't wait to see how it goes. I'm doing an ECU swap this weekend (if it doesn't rain all weekend long again). I hope we get lucky and stumble on the answer here.

This alternator idea sounds good actually. It does suck to think that ours just died spontaneously though =/

//Edit// Not to get ahead of what we're all going to be testing next, but is it possible that something in our fuel delivery system is causing this too? Perhaps our fuel pump or FPR? ...just a thought

Regarding the Alternator. On the thread I was reading, the guy mentioned that the power steering pump (I think it was power steering) leaked onto the alt (maybe because it got too hot) and killed the alternator. Now I'm not saying that's what happened to all of us but I am having problems with under hood temps and engine temps. So I guess it could be possible.

I finally got my JM Fab heat shield for my FP manifold (been running without one) and I just ordered a new rad and slim fan from MaPerformance (it'll be here within a week or two) so hopefully I'll get my temps under control.

Just out of curiosity, is anyone else here having high under hood temps or engine temps? Anyone running without a heat shield?

Regarding the fuel pump and FPR, I was thinking about this too but I don't know how those components would cause a misfire. I don't even know how to test them.

 

[voodoogsx]

voodoogsx: Thanks for the helpful thread. Pretty similar indeed that it traced back to touching wires. I'm almost certain that I patched up all that was there, but I'll make certain to trace/test again if the ECU swap + NGK BPR6ES plugs don't do it for me. Also, my tachometer was acting just the same as yours. During my testdrives, I noticed that sometimes it would just die and barely be above "zero" if above it at all...

This alternator idea sounds good actually. It does suck to think that ours just died spontaneously though =/

//Edit// Not to get ahead of what we're all going to be testing next, but is it possible that something in our fuel delivery system is causing this too? Perhaps our fuel pump or FPR? ...just a thought

I have to say, the biggest help in solving was to step back, think to where I knew how the car ran prior to things going batcrappy and start from there. I had to stop testing all of the components and just test the wiring to be sure....Also considering that I have a 95 with the cas located at the cam sprocket, I'd have to take the timing belt off....I really didn't want to deal with that just then... I also didn't want to keep spending money testing things that worked and finding I wasted all that money and time. I'd check the most obvious, wires, and make sure all of the signals are correct. It saved me the stress of thinking I had a bad alt or even worse, a newly dsmlinked ecu....

 

[voodoogsx]

I finally got my JM Fab heat shield for my FP manifold (been running without one) and I just ordered a new rad and slim fan from MaPerformance (it'll be here within a week or two) so hopefully I'll get my temps under control.

Just out of curiosity, is anyone else here having high under hood temps or engine temps? Anyone running without a heat shield?

Do you have the coated or uncoated fp mani? I have a coated one, but won't have time to put it on until the 19th.
What sort of underhood temps are you seeing? what sensor are you using for the temps? I have dsmlink, I've seen my coolant temps around 210 I think....this is pretty normal.

 

[super97gst]

its been so long since i've been able to drive my car with it correct that i barely remember what all it did when this happened. but i was thinking about it this morning and i do remember my volt guage was reading really low when all this first happened. like 9 volts or so. i just didnt think that had anything to do with it at the time.

 

[Artago]

its been so long since i've been able to drive my car with it correct that i barely remember what all it did when this happened. but i was thinking about it this morning and i do remember my volt guage was reading really low when all this first happened. like 9 volts or so. i just didnt think that had anything to do with it at the time.

9 volts? dying battery or alternator?

I had a dying battery. Replaced it with a new one. The car still throws the P0300 but less frequently. Maybe it is the alternator... it's at least worth checking.

 

[Artago]

Do you have the coated or uncoated fp mani? I have a coated one, but won't have time to put it on until the 19th.
What sort of underhood temps are you seeing? what sensor are you using for the temps? I have dsmlink, I've seen my coolant temps around 210 I think....this is pretty normal.

Normal driving temps for me are 200-210. Idle temps just climb till the car boils over. Like 240+. But this is because I have a high idle issue (like 2000 rpm idle due to a Vac leak which I hope to fix this weekend).

Under hood temp is high to, driving intake temp is 70-90. Idle intake temp is 110-130. This is because of the lack of heat shielding. I plan to get a FMIC and build a cold air box for my filter to hopefully get the intake temps down. I don't know my oil temps because I don't have my oil temp gauge hooked up (yet. Also want to do this on the weekend) but I'm assuming they are high because I'm running a oil cooled turbo with no oil cooler (need one of those too).

So as you can see I have heat all over the place. I just thought I'd bring it up in case it was related to the problem. Anyone else having heat problems with the P0300?

Tom

 

[bboyalan]

Hmm, could under the hood temperatures really be a factor? It's kind of interesting though because we've all experienced a random code popup, but could that be from the heat building up? The reasoning is kind of weird , but if THAT's the case... I have the Punishment Racing budget manifold and that b*tch is raising hell in there hahaha. I've never had any heating issues since the previous owner changed the coolant prior to my purchase.

PS: I'll go ahead and change my plugs + check on those wires again this afternoon. I might get lucky! I haven't touched my car in so long that I've decided to remove that piece of upper plastic for the front bumper's mouth & paint my lip

 

[voodoogsx]

Normal driving temps for me are 200-210. Idle temps just climb till the car boils over. Like 240+. But this is because I have a high idle issue (like 2000 rpm idle due to a Vac leak which I hope to fix this weekend).

Under hood temp is high to, driving intake temp is 70-90. Idle intake temp is 110-130.

I took a look at my temps from the logs I did this morning while going to work.
--Int temps--
driving were 70-92
idle climbed up to 118 after about five mins(trying to calibrate the fuel trims this week)
coolant temps stayed at around 200 when driving, while idle peaked at 211 before the fans kicked on.
This is of course with the idle ranging from 730-780(due to fans kicking on and off) it stayed pretty close 740-760 the rest of the time.

 

[Artago]

Yeah I doubt that high temps are causing this error code but I just figure I'd throw it out there and see what you guys think.

I think the prime suspects so far (ignoring the ones we have eliminated) are:

1. MAS
2. Alternator
3. ECU
4. Faulty (or damaged) wiring

The only item on that list that has me worried is number 4. I have no idea how to test for bad wiring and I'm assuming it would be a long intensive process.

Tom

 

[super97gst]

would anyone care to enlighten me as to an easier approach at getting the alternator off the car?? i've never had it off before, and there's not much room in there. the shop manual says i've gotta pull the front slash shield out, their calling the inner fender well the front splash shield. that makes it a real PITA. if anyone knows a shortcut let me know, if not i'll do it this way.

im gonna finish pulling the alternator off tomorrow, then i'll put the other one on there saturday night or sometime sunday. i'll post back and let everybody know how it went. hopefully there'll be lots of smiles and thumbs up!!!

btw, i dont know about high temps causing a problem on others cars, but on mine i know that has nothing to do with it. i did the grey forest hood mod after i first bought the car 5 years ago and have never had underhood temp. problems
Blake

 

[voodoogsx]

would anyone care to enlighten me as to an easier approach at getting the alternator off the car?? i've never had it off before, and there's not much room in there. the shop manual says i've gotta pull the front slash shield out, their calling the inner fender well the front splash shield. that makes it a real PITA. if anyone knows a shortcut let me know, if not i'll do it this way.

im gonna finish pulling the alternator off tomorrow, then i'll put the other one on there saturday night or sometime sunday. i'll post back and let everybody know how it went. hopefully there'll be lots of smiles and thumbs up!!!

btw, i dont know about high temps causing a problem on others cars, but on mine i know that has nothing to do with it. i did the grey forest hood mod after i first bought the car 5 years ago and have never had underhood temp. problems
Blake

just find the bolts that hold the alt on. I think you may have to unbolt the ps pump, but you can leave the hoses on.

 

[voodoogsx]

Yeah I doubt that high temps are causing this error code but I just figure I'd throw it out there and see what you guys think.

I think the prime suspects so far (ignoring the ones we have eliminated) are:

1. MAS
2. Alternator
3. ECU
4. Faulty (or damaged) wiring

The only item on that list that has me worried is number 4. I have no idea how to test for bad wiring and I'm assuming it would be a long intensive process.

Tom

I'd be looking at 4 as the major suspect, you know for a fact that this was damagaed, find each damaged wire and trace it to it's source and destination. Test them and make sure the signal, voltage or continuity is correct.

You should be able to find what wire goes where based on it's color pattern and by looking at the sensors.

 

[ken06]

My car has thrown the P0300 code three times now, all at 70 miles an hour in 5th gear after an hour of driving under load, twice uphill one time with passengers and cargo. The last time the car was definetely running on 3 cylinders, went away when I let the engine reach idle. Also the p1400, manifold differential pressure code was present. Plugs look good going to get a multimeter and compression tester tommorow. '95 GSX with MAFT blowthrough, so i don't think its the MAS or in my case the MAF. Oddly this all started within 500 miles of installing a Spec Stage 2+ clutch. After the clutch install I've had a terrible rattle on deceleration, probably exhaust. I'm thinking TPS or CAS, but my alternator is somewhat weak, but other than the freeway misfire my car runs great. I drove for an hour at 60 miles an hour no code, one minute at 70=misfire.

 

[super97gst]

My car has thrown the P0300 code three times now, all at 70 miles an hour in 5th gear after an hour of driving under load, twice uphill one time with passengers and cargo. The last time the car was definetely running on 3 cylinders, went away when I let the engine reach idle. Also the p1400, manifold differential pressure code was present. Plugs look good going to get a multimeter and compression tester tommorow. '95 GSX with MAFT blowthrough, so i don't think its the MAS or in my case the MAF. Oddly this all started within 500 miles of installing a Spec Stage 2+ clutch. After the clutch install I've had a terrible rattle on deceleration, probably exhaust. I'm thinking TPS or CAS, but my alternator is somewhat weak, but other than the freeway misfire my car runs great. I drove for an hour at 60 miles an hour no code, one minute at 70=misfire.

umm......... the p1400 code should be a pretty good guess to what your problem could be. since its throwing that secondary code its most likely the MDP sensor. just take it off the intake manifold and swap it out. it is highly unlikely the clutch install has anything at all to do with the po300 code. the MDP sensor sends no voltage to the ecu at idle, thats the reason its throwing a po300 at cruising speeds. also, if it was the TPS or the CAS for that matter it would pull a po300 at idle as well.

as you said your alternator is weak, that could be a possibility as well, but i would definitely start with the obvious since its throwing a code for the MDP sensor. hope that helps you out. if not you should just start testing sensors. TPS, CAS, CPS, coil pack, transistor. you get the idea. any shop manual will tell you what values each sensor should be within to be considered good.

 

[bboyalan]

I noticed something when I pulled out the Iridiums this afternoon for the Coppers. TWO of them [#4 & #3] were good looking, whereas the OTHER TWO [#1 & #2] had considerable buildup. This would explain why the car feels like it's running on 2 cylinders. I'm going to check + redo the damaged wiring right now and see if it makes a difference. The test ECU comes in tomorrow too, so there's more to try out on my side. Let's keep on attacking this!

 

[super97gst]

I noticed something when I pulled out the Iridiums this afternoon for the Coppers. TWO of them [#4 & #3] were good looking, whereas the OTHER TWO [#1 & #2] had considerable buildup. This would explain why the car feels like it's running on 2 cylinders. I'm going to check + redo the damaged wiring right now and see if it makes a difference. The test ECU comes in tomorrow too, so there's more to try out on my side. Let's keep on attacking this!

i believe the buildup on the plugs has to do with this po300 code. that was the first thing i did when all this happened a couple months ago. i dont remember which two it was, but there were two different cylinders that the plugs on those had a lot of buildup on them as well. it just seemed to be a consequence of whatever is causing the po300.

 

[Artago]

I'd be looking at 4 as the major suspect, you know for a fact that this was damagaed, find each damaged wire and trace it to it's source and destination. Test them and make sure the signal, voltage or continuity is correct.

You should be able to find what wire goes where based on it's color pattern and by looking at the sensors.

Actually it was someone else who said they damaged their wiring. Although I do have cut/damaged Rear O2 wiring near the ECU (throwing and P0136, bad rear O2 circuit code). In any case, I should start checking the wiring sensor by sensor.

My car has thrown the P0300 code three times now, all at 70 miles an hour in 5th gear after an hour of driving under load, twice uphill one time with passengers and cargo. The last time the car was definetely running on 3 cylinders, went away when I let the engine reach idle. Also the p1400, manifold differential pressure code was present. Plugs look good going to get a multimeter and compression tester tommorow. '95 GSX with MAFT blowthrough, so i don't think its the MAS or in my case the MAF. Oddly this all started within 500 miles of installing a Spec Stage 2+ clutch. After the clutch install I've had a terrible rattle on deceleration, probably exhaust. I'm thinking TPS or CAS, but my alternator is somewhat weak, but other than the freeway misfire my car runs great. I drove for an hour at 60 miles an hour no code, one minute at 70=misfire.

Hmm... now we are getting somewhere. I had a P1400 code as well. I replaced the MDP and the P1400 went away. The car "felt" strong and smoother and threw the P0300 less frequently. But it did not eliminate the P0300.

My code appeared when I had a new engine put in. Along with the engine came a new clutch. PieEyedPiper has pointed out (on another thread) that a lot of people experiencing this code have had a clutch job. My car also feels and sounds weird under deceleration. Also, there are some funny intermittent problems and noises coming from the clutch. Sometimes is goes completely soft for 1 or 2 minutes.

Someone has already tried the CAS with no success. I don't know if anyone has tried the TPS. Can anyone chime in on that?

 

[bboyalan]

super97gst: Yes, I totally agree with you. It's those 2 cylinders that aren't firing correctly and burning the fuel properly/on time.

from voodoogsx's thread:

I pulled the battery...then I noticed something....after I pulled the battery holder...I found this....(see image below)

The battery holder had rubbed up against the big pack of wires and eventually got through...this caused the wire to ground out....

needless to say, I covered the wire, put the battery in , made sure nothing was touching that wire plugged everything in, and started the car......

I actually went back tonight to reconnect the wires that were actually cut apart, but cut off more wire sheath to expose more fibers. The car is improving, but it wasn't just right [I could actually get to 6psi, but no more than 2k rpm]. SO, as I pulled back into the driveway I was thinking about the other wires that I simply "covered up" from the beginning so that they wouldn't touch [the ones that had their sheaths stripped open a bit]. I was thinking about your situation and relating it to mine. It just so happened that my blue wire, and what so little fibers it DOES have, was cut so that only some of the fibers were connecting [if that makes sense]. From reading your thread w/ posts between you and "luv2rallye", that MIGHT be my problem as well. I was too tired tonight so I'm going to check out ALL the wires that I covered and reconnect those that need it w/ more fibers. If that doesn't work, then I'll shoot for that ECU swap afterwards

 

[PieEyedPiper]

My car has thrown the P0300 code three times now, all at 70 miles an hour in 5th gear after an hour of driving under load, twice uphill one time with passengers and cargo. The last time the car was definetely running on 3 cylinders, went away when I let the engine reach idle. Also the p1400, manifold differential pressure code was present. Plugs look good going to get a multimeter and compression tester tommorow. '95 GSX with MAFT blowthrough, so i don't think its the MAS or in my case the MAF. Oddly this all started within 500 miles of installing a Spec Stage 2+ clutch. After the clutch install I've had a terrible rattle on deceleration, probably exhaust. I'm thinking TPS or CAS, but my alternator is somewhat weak, but other than the freeway misfire my car runs great. I drove for an hour at 60 miles an hour no code, one minute at 70=misfire.

This is unreal.

You have no idea how ironic this is. Mine, logged in old threads strewn across the forum, came about right after I had a Spec Stage 2+ clutch put in. After that clutch install, the car has become damn near unstreetable. I may not have the fanciest foot work around, but my clutch is ridiculous on the street, but on the other hand it is freaking amazing during WOT pulls.

One difference is that you are running a MAF-t setup, where as I'm stock in that department.

This is not the first case, either, with a Spec Stage 2+ clutch, or probably even more likely just any clutch job, being a potentially key event surrounding this ailment that occurs when cruising on the hwy at 70mph or ~3krpm, idle conditions or other.

I'm still holding out for news on the alternator though.

My code appeared when I had a new engine put in. Along with the engine came a new clutch. PieEyedPiper has pointed out (on another thread) that a lot of people experiencing this code have had a clutch job. My car also feels and sounds weird under deceleration. Also, there are some funny intermittent problems and noises coming from the clutch. Sometimes is goes completely soft for 1 or 2 minutes.

Someone has already tried the CAS with no success. I don't know if anyone has tried the TPS. Can anyone chime in on that?

Tom, I wrote the above reply prior to reading your post. Also ironic is how I was bitching about the clutch, and you mention an exact symptom I experience. The pedal will go soft every so often. And I have experimented extensively with regards to modification of my hydraulic system.

And the plot thickens..

EDIT: Here's one more for thought.
http://www.dsmtuners.com/forums/pro...ing-intermittently-during-highway-cruise.html

 

[voodoogsx]

Actually it was someone else who said they damaged their wiring. Although I do have cut/damaged Rear O2 wiring near the ECU (throwing and P0136, bad rear O2 circuit code). In any case, I should start checking the wiring sensor by sensor.



Hmm... now we are getting somewhere. I had a P1400 code as well. I replaced the MDP and the P1400 went away. The car "felt" strong and smoother and threw the P0300 less frequently. But it did not eliminate the P0300.

My code appeared when I had a new engine put in. Along with the engine came a new clutch. PieEyedPiper has pointed out (on another thread) that a lot of people experiencing this code have had a clutch job. My car also feels and sounds weird under deceleration. Also, there are some funny intermittent problems and noises coming from the clutch. Sometimes is goes completely soft for 1 or 2 minutes.

Someone has already tried the CAS with no success. I don't know if anyone has tried the TPS. Can anyone chime in on that?

Sorry man, I got mixed up with all of the postings!!! I'll read through again...and correctly respond!!!

 

[super97gst]

This is unreal.

You have no idea how ironic this is. Mine, logged in old threads strewn across the forum, came about right after I had a Spec Stage 2+ clutch put in. After that clutch install, the car has become damn near unstreetable. I may not have the fanciest foot work around, but my clutch is ridiculous on the street, but on the other hand it is freaking amazing during WOT pulls.

One difference is that you are running a MAF-t setup, where as I'm stock in that department.

This is not the first case, either, with a Spec Stage 2+ clutch, or probably even more likely just any clutch job, being a potentially key event surrounding this ailment that occurs when cruising on the hwy at 70mph or ~3krpm, idle conditions or other.

I'm still holding out for news on the alternator though.



Tom, I wrote the above reply prior to reading your post. Also ironic is how I was bitching about the clutch, and you mention an exact symptom I experience. The pedal will go soft every so often. And I have experimented extensively with regards to modification of my hydraulic system.

And the plot thickens..

EDIT: Here's one more for thought.
http://www.dsmtuners.com/forums/pro...ing-intermittently-during-highway-cruise.html

no kidding??? i dont see how an aftermarket clutch install could possibly have anything to do with a trouble code that has nothing to do with the transmission. the po300 code must have some really weird and crazy causes, obviously. do you think it might be something in the hydraulic part of the clutch system is somehow malfunctioning, even if its just intermittently, and causing these codes??

 

[Artago]

no kidding??? i dont see how an aftermarket clutch install could possibly have anything to do with a trouble code that has nothing to do with the transmission. the po300 code must have some really weird and crazy causes, obviously. do you think it might be something in the hydraulic part of the clutch system is somehow malfunctioning, even if its just intermittently, and causing these codes??

I was thinking about this yesterday but I don't see how the two are related. Could it be a coincidence? Or better yet, if it is related to the hydraulic system from the clutch then how can we check it? How do we verify that the system is putting out the correct electrical signal?

Tomas