[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.

 

[bboyalan]

Does anybody have an idea that they would like to share? =/ I'm going to try and pick up a coilpack and isc from the junkyard tomorrow after class, so I'll be able to check here beforehand. [sorry for the bump!]

 

[silver bullit]

Well give it a try and let us know...

 

[Artago]

Hey. I got the same problem as you. I haven't been able to figure it out but I haven't tried to replace the coils yet.

I thought I had it when I replaced the Transistor pack and MDP (Manifold Density Pressure) sensor, but the code came back. Not as frequent but still there. Which leads me to believe that the problem is else where. I was going to try coils (mine are slightly out of spec) and then the MAS.

If any of those work for me then I'll let you know.

In the mean time here are a few threads I've subscribed to regarding P0300:

http://www.dsmtuners.com/forums/newbie-forum/285625-resolved-multiple-cylinder-misfire.html

http://www.dsmtuners.com/forums/problem-diagnosis/233241-p0300-cel-multiple-misfire-detected.html\

http://www.dsmtuners.com/forums/problem-diagnosis/241406-my-p0300-fix.html

If you do manage to solve this then please post the solution, there is no definitive fix to this problem that I've found.

Good luck,

Tom

PS: PieEyedPiper has been trying to solve this for a while. Chances are he'll spot this thread and post something.

 

[bboyalan]

silver bullit - Will do!

Tom - Thanks for the input. After reading a bit of those links you posted, I went ahead and checked the honeycombs of my MAS. Everything seemed straight. I was thinking though... would the high-flow cat install or downpipe being ungrounded contribute to this? I read a lot on this, but never really saw a grounding wire attached nor a CEL. Besides, my o2 sensors have 4 wires so I'm assuming they're already grounded? It's pretty contradictory because the car ran FINE after the install. My guess is that my stupidity with the drilling of those wires somehow shorted my ignition components. Nonetheless, I'll be checking on here when I get back from class and before I see what the junkyard has to offer [one of them has a few DSMs!!]. Just keeping my fingers crossed that they won't $$ rape me =X

I shall keep posted though.

//edit// This is irrelevant, but I forgot to include in my original post that I purchased a higher cranking Duralast battery from Autozone.

 

[Artago]

I doubt the DP/cat/exhaust being ungrounded would cause this but it's worth checking. I'm also ungrounded so if that solves it then great. Let me know what you check and what you replace and if it does or does not have an effect.

Tom

 

[97GSRyan]

Granted I'm rocking a non-turbo, but I had the same CEL a few months ago. I know the Camshaft Position Sensor and Crank Angle Sensor can cause misfire codes, which were the solutions for a lot of people. Mine personally turned out to be the Crank Angle Sensor, haven't had a problem with it yet If you replace the coil pack and that doesn't help, I would definitely recommend checking into the Cam and Crank Sensor. They're fairly inexpensive to buy. Good luck with it, and let us know how it goes.

EDIT: I just re-read your last post, and the 4 wires for the O2 sensor are for the actual sensor circuit (2) and the heater (2). I don't recall the colors of the wires, but if any of them are damaged you'll have issues. The heater coil in my old O2 sensor was going bad, which was throwing off my mixture. Key word there being <b>going</b> bad; I didn't get a CEL for the heater circuit but it <b>was</b> causing issues. Also, a question about your resistance tests - Were you using a Haynes manual for your tolerances? I had an experience when I was testing my coil pack where the Haynes manual actually had incorrect resistance numbers.

 

[bboyalan]

Thanks for the replies again. The trip to the junkyards was more of a hassle than I had anticipated, but MAN... so many parts! I ended up shelling $75 for a 97 GSX's coilpack, but definitely refused to pay $60 for a damn ISC.... they kept on insisting on buying the entire TB assembly . HOW DO THEY SLEEP AT NIGHT?!

To answer your question, I've been using a Chilton manual [previous owner gave it to me]. I'll swap the coil packs after lunch and post results... might try grounding the exhaust too... whatever will make her run again

 

[Artago]

Keep us updated.

 

[bboyalan]

so the results are in... and as this is one difficult DSM... still no go

what was done:
-swapped in a '97 GSX's coilpack
-cleaned PCV valve
-cleaned MAS
-cleaned TB elbow and a little bit of the TB itself

I sat in the car w/ the keys, put my hands together, and made a prayer full of promises if this would work. Started her up with a little roughness. She settled at ~500RPM WITHOUT the bogging and shaking engine and chassis this time [that's an improvement]. As for the test drive... backed her out of the driveway and shortly after the first corner [we ARE the corner house...........] the CEL made its presence known again. The clutching in isn't AS bad, but it's still noticeable that it's close to dying and hard to balance the gas and clutch. Scanner showed P0300 still

soooo disappointed. I felt so good putting everything back together too! I guess next on the list are the CPS AND CAS ughhhh. LUCKILY, I just started spring break so there's a good 10 days to fix this beauty. I'll probably order the ISC while I'm at it [there goes more modding money haha].

 

[turbosax2]

I'm slightly confused. What did you set your idle at when you adjusted the biss? You should have it set at 750 rpm.

 

[bboyalan]

turbosax2: For my odd, special situation, adjusting the BISS didn't reflect much at all in the idle. The ONLY way I was able to adjust the idle was through the fixed SAS [screw thing].

UPDATE:
-as if things couldn't get worse, my dad pointed out that the RPMs would drop 100 when my headlights are turned on [wtf??]
-I finally figured out how to remove the TPS harness and tested it
-TPS pin 1 to 4 checked out fine [5k ohm]
-TPS pin 2 to 4 w/ degrees of open throttle = FAILED [5k when closed; nothing when open]

The TPS would explain why idle adjustment and acceleration are severely affected. It isn't reading the various throttle positions correctly. I was wondering though, would my ECU be taking a crap on me too? I can take it out, but how exactly would I test it besides observing? IF it turns out it has "expired", which would be better: having it rebuilt or replacing it with a used one?

 

[turbosax2]

Don't worry about the ecu just yet. Save that as your last option because it will undoubtedly be the most expensive part to fix/replace. Get a new tps to replace yours - they can be found used for pretty cheap. Also get a new ISC. You know both of those parts are out of spec so replace them first.

Do you have a friend with a 2g? You could always borrow parts from his car and swap them to yours to help pinpoint your problem.

Don't get frustrated. Just take this all one step at a time

 

[bboyalan]

UPDATE:

I went to Ecology's import junkyard this morning and snagged the TPS from a 94 non-turbo Eclipse. I searched on here when I came home and found out the 3-pin connector wouldn't work with my 4-pin setup. After that, i just retested my TPS and discovered it was working fine and that I had tested the wrong pin for progressive open throttle.

SOOO... this afternoon my friend and I headed over to a different junkyard in search of a used ISC. I took one off of a 2000 Mirage that APPEARED to be the same, but it was shorter. We walked to a neighboring junkyard and was able to get one from a '99 Eclipse GS-T/X [w/ that lower portion of the TB assembly]. The small pos costed $65. I just swapped the ISCs w/o the lower halves, reconnected everything, and started her up. The result.... tachometer reports ZERO RPM and the car sounds worse w/ the shakes. In fact, she sounds better w/ the ISC unplugged....

I'm so depressed over this situation........ any more ideas? I don't understand what else could be causing my car to run like crap now. I did notice that the connecting end of the 99 was slightly different and BARELY shorter than mine, but I just crossed my fingers that it would be compatible when inserted.

 

[turbosax2]

Did you test the new isc before putting it in?

Screw your biss screw out most of the way. This should raise your idle up the highest it will go for now. Have you done a boost leak test recently?

 

[bboyalan]

Hey. Yes, I did test the pins beforehand. Interestingly, this page from DSMISC.com #9 says the readings SHOULD be ~40 ohms which are what both my ISC and the 99's that I purchased read. ALSO, they were both encased in the new black plastic housing.... which means I've been wasting my money yet again

I've tested for vacuum and boost leaks already. Kind of funny, but I've managed to drive MUCH better w/ couplers and clamps undone once in the past compared to now. I'll try out unscrewing the BISS, but I'll most likely return the old ISC, replace the O-ring, and take comparison pictures to show the differences I noted.

Any other ideas guys? I feel so close, yet so far.... I don't suppose the CAS or CPS can contribute that much to this can it? Still kind of worried about the ECU now w/ choices being narrowed down.

 

[bboyalan]

UPDATE:

I reinstalled the "original" ISC and opened up the BISS a bit, bit more. The idle sits at 700 +/- 50 RPMs now, however, acceleration is still pretty sappy. I was able to test drive around my neighborhood for much longer where the P0300 code was only thrown once I sat back outside of my garage door and driveway. My dad volunteered to try and find an inexpensive ECU replacement at the junkyards later on.

Also, here are some comparison pictures of the 99 turbo ISC

and my ISC

. Notice that they're both encased within the newer black plastic, but the connecting ends are different.

//edit// My boost/vac gauge reads 18-19 in/HG @ idle. I MIGHT try out changing the transistor and MAS - running out of extra funds though...​

 

[bboyalan]

UPDATE:

Sorry for another update once again, but we've pinpointed a major cause in my random misfire code. It turns out my TRANSISTOR UNIT [part# J722T] was shot. My dad and I tested for both pairs of cylinders [1&4 and 2&3] and the results showed NO continuity once the 1.5v battery's positive side was added.

We managed to get a hold of a transistor from a Diamante/Galant V6, but it's part#J723T with 9 pins instead of 7. I was thinking about just wiring the corresponding required pins to my car, but I'm going to call around tomorrow and try to find an actual used one since a new unit from Autozone runs $109. The same transistor unit can be found in an Eagle Talon and Chrysler Sebring [fyi for people who don't know].

Anyway, I'll provide an update tomorrow assuming I manage to get the part. HOPEFULLY *crosses fingers* this will resolve my problem. Until my next post.

~AL

 

[Artago]

UPDATE:

Sorry for another update once again, but we've pinpointed a major cause in my random misfire code. It turns out my TRANSISTOR UNIT [part# J722T] was shot. My dad and I tested for both pairs of cylinders [1&4 and 2&3] and the results showed NO continuity once the 1.5v battery's positive side was added.

We managed to get a hold of a transistor from a Diamante/Galant V6, but it's part#J723T with 9 pins instead of 7. I was thinking about just wiring the corresponding required pins to my car, but I'm going to call around tomorrow and try to find an actual used one since a new unit from Autozone runs $109. The same transistor unit can be found in an Eagle Talon and Chrysler Sebring [fyi for people who don't know].

Anyway, I'll provide an update tomorrow assuming I manage to get the part. HOPEFULLY *crosses fingers* this will resolve my problem. Until my next post.

~AL

That is probably a good start. I've replaced the Transistor Pack and MDP on my car and it's gone from throwing the code 4-5 times a day to 1 every 2 days. So it did help but did not solve my problem fully. I think it's a combination of factors that cause the P0300 and one the factors is the Transistor Pack. I think (stress the word think) that the MAS might be the other piece of the puzzle.

Anyways, go ahead and replace the transistor unit and let us know if it helps solve your problem or makes it slightly better.

Good luck,

Tom

 

[bboyalan]

Thanks Tom.

Out of 3 Ecology junkyards, we managed to find a matching transistor from a 93 4G63 Eclipse. The car idles very well that it's not even an issue anymore. The issue has moved towards the acceleration and timing where the P0300 code still arises, but after much driving now. The car won't boost passed 5psi atm. We're looking into the timing belt area with the sensor to see what's up, but losing the motivation to continue going on.....

Where the car SHOULD be shifting at 2.5-3.5k the tachometer shows 1-2k RPMs.
"So close, yet so far"

 

[Artago]

You mentioned the cam and crank shaft sensors. Have you checked yours yet? The reason I'm asking is because the shop the put my motor in had to replace the crank sensor and "adjust" the cam shaft sensor. At least that's what they told me.

So it might be possible that they screwed up one of these 2 sensor (maybe even both) and that may be contributing to the misfire code.

I think I'm going to do some research and I'm going to try to find a way to test these 2 sensors so I can verify they are working correctly.

Tom

 

[PieEyedPiper]

Wow, what a headache!
Thanks for the heads up, Tom.

I follow these such issues very closely. Your specific case is considerably different than any of the others I've encountered but lets try and solve it all the same.

You've made good progress and tried many good ideas. The only problem is that we may have skipped more simple steps and hurried into replacing sensors before boost leak tests and using the correct spark plugs.

Your first post indicates that you've been using platinum and iridium spark plugs. Our cars don't like these and while you mentioned your idle is under control now, your plugs probably contributed to that situation. They are also a possible contributor to the P0300 misfire.

Change your plugs to NGK BPR6ES or Autolite Copper 63. These both provide consistent performance and driveability for our cars, proven by the community.

Secondly, please perform a proper boost leak test and report back how long it took your intake tract to depressurize 20psi.

A bad TPS sensor is suspect to this kind of phenomenon. Be sure yours really did test out fine.

Ditto for your coils and transistor, but you can probably cross those off the list too now.

Also, when I replaced my CAS (Cam Angle Sensor), my misfires became much much more infrequent. Like Artago, I used to suffer from this code 4-5 times in a day.

The CPS (Crank Position Sensor) can also be held suspect. I've yet to replace mine.

And lastly, can you tell us a little more about the exact circumstances that bring about your P0300 code?

At what RPM does this happen?
Does it ever happen at or near idle?
Does it only occur on the highway, say cruising at 3krpm? (Most people experience this)

Your circumstances, like I mentioned, are slightly different than others with this issue. So these questions may be important to differentiate between different sources of the same ailment.

Oo, one last one. Do you have an aftermarket clutch/flywheel? When was it installed?

 

[super97gst]

this is the EXACT problem i have been dealing with for a month on my gst. this is the only thread i have read that was exactly like mine. i have a thread right below this one on the same thing. i just replaced the coil pack today with a new oem one and it didnt make a difference. mine throws the po300 code at all times. its got that really really low idle, like so low the motor looks like its fixing to shake out of the car. haha. i know waht your goin through man. i have done all the tests and checks said previously with no effect. hope you figure out whats wrong with your's. since it is exactly the same maybe it'll be the same fix. good luck

 

[bboyalan]

Thanks for the replies again. The car feels as if the timing is more "retarded" than it should be [no pun intended ]. I wanted to adjust and advance the timing, but soon realized it was only allowed for 90-94 [correct me if I'm wrong]. To answer you questions, the car atm can't really go passed 2k rpm. At THAT point, it feels it's nearing 4.5k+ or so. The CEL comes on only after driving for a few minutes, but never at idle. I've yet to go on the freeway, and don't intend on trying until this is fixed hahaha.

I wanted to get the NGK BPR6ES plugs last week, but I just needed a quick, temporary substitute that I could buy locally even though the Iridiums were $7/ea . I WANT to try testing the CAS and CPS, but this whole conundrum [!] is just so energy and enthusiasm draining. Also, before I forget, the clutch/flywheel are both stock so nothing on that. I've retightened and checked ALL I/C clamps and vacuum lines and VAC always reads at 18-19 in/HG.

How difficult is it to test/replace the CAS and CPS?

 

[super97gst]

Thanks for the replies again. The car feels as if the timing is more "retarded" than it should be [no pun intended ]. I wanted to adjust and advance the timing, but soon realized it was only allowed for 90-94 [correct me if I'm wrong]. To answer you questions, the car atm can't really go passed 2k rpm. At THAT point, it feels it's nearing 4.5k+ or so. The CEL comes on only after driving for a few minutes, but never at idle. I've yet to go on the freeway, and don't intend on trying until this is fixed hahaha.

I wanted to get the NGK BPR6ES plugs last week, but I just needed a quick, temporary substitute that I could buy locally even though the Iridiums were $7/ea . I WANT to try testing the CAS and CPS, but this whole conundrum [!] is just so energy and enthusiasm draining. Also, before I forget, the clutch/flywheel are both stock so nothing on that. I've retightened and checked ALL I/C clamps and vacuum lines and VAC always reads at 18-19 in/HG.

How difficult is it to test/replace the CAS and CPS?

i've never installed a cas, but a cps is quite a job. or at least the way i did one it was. the motor mount has to come off just like you would for a timing belt job. i would definitely make sure its bad before swapping.