[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.

 

[cavillac]

just tuning into this thread..

Wow, tons of money wasted throwing parts at this thing.

And your reputable repair shop isnt good by any means. Everything you replaced could have been tested with an oscilliscope.. even the misfire can be seen with an osilliscope.

An easy way to look for vacumn leaks is to spray the motors vac lines down with brake clean and notice a change in RPM's.

 

[Artago]

just tuning into this thread..

Wow, tons of money wasted throwing parts at this thing.

And your reputable repair shop isnt good by any means. Everything you replaced could have been tested with an oscilliscope.. even the misfire can be seen with an osilliscope.

An easy way to look for vacumn leaks is to spray the motors vac lines down with brake clean and notice a change in RPM's.

Yes an oscilloscope can see a misfire but I don't have one, and even if I did I'd have to hook it up and drive the car around with the scope in the car all the while having someone watch the scope for signs of misfire. And even if the misfire was detected it wouldn't do me much good to diagnose it as the car would be moving down the road too fast for me to pop the hood and start inspecting components. (while the car was moving mind you). It's a good suggestion but has no practical benefit because the car does not misfire under idle (at least mine doesn't).

The brake cleaner on vac hose has been tried already with no results. My vac leaks are under the IM somewhere where I can't spray and even if I could it would help me again because the car has some idle surge and idle lope (BC 272/272 cams).

We all appreciate suggestion but lets try to keep them useful

PS: If I seem a bit bitchy, it's only because this issue has been pissing me off for months.

 

[cavillac]

Yes an oscilloscope can see a misfire but I don't have one, and even if I did I'd have to hook it up and drive the car around with the scope in the car all the while having someone watch the scope for signs of misfire. And even if the misfire was detected it wouldn't do me much good to diagnose it as the car would be moving down the road too fast for me to pop the hood and start inspecting components. (while the car was moving mind you). It's a good suggestion but has no practical benefit because the car does not misfire under idle (at least mine doesn't).

The brake cleaner on vac hose has been tried already with no results. My vac leaks are under the IM somewhere where I can't spray and even if I could it would help me again because the car has some idle surge and idle lope (BC 272/272 cams).

We all appreciate suggestion but lets try to keep them useful

PS: If I seem a bit bitchy, it's only because this issue has been pissing me off for months.

Contare, you do not need anyone to ride around with you as most scopes have a glitch feature which will record any abnomality in waveform for a set amount of time.. this isnt directed at you as I'm sure most people dont have the resources to buy a 4000$ peice of equipment that you will rarely if ever use.

And yes the scope WOULD help you track down where the misfire is coming because you can hook leads into cam/crank/ignition/oxygen sensor/fuel pump all at the same time and wait for the misfire to happen, then it just a matter of looking at waveforms.
Basically what I'm distrot at is you looked for what you thought was a reputable shop and they couldnt provide results.

 

[bboyalan]

Yeah, I know it was a waste of $75 and I'm still kicking dirt about it too. I guess you have to understand that I didn't want to "try this or that" anymore. They seemed to be great seeing as they've been at that same location for 50 years since the beginning of that area's development. In the end, I'm honestly glad I DID go there because they do the ATK engine rebuilds that I was actually looking for [my 3000GT had one and it was wonderful ]. I mean $75 really isn't that bad for a diagnosis on a car that can ACTUALLY have answers yielded. In my case, however, it was just stupid and pointless.

There's no doubt that the scope would've worked right off the bat, but just as you two have mentioned, it's unlikely to be able to attain one hahaha.

In the end, everything still worked out fine. I replaced some older sensors, belts, and ignition components, and the car runs kick ass. It's true that I probably spent money on parts that weren't necessary, but the hands-on experience cannot have a price put on it. Assuming she continues being healthy, I'm actually hoping on visiting a dyno after the semester is over just to see how close I am to my small goal of 250whp. I'm going to try for a MBC @ 14psi.

 

[super97gst]

Yeah, I know it was a waste of $75 and I'm still kicking dirt about it too. I guess you have to understand that I didn't want to "try this or that" anymore. They seemed to be great seeing as they've been at that same location for 50 years since the beginning of that area's development. In the end, I'm honestly glad I DID go there because they do the ATK engine rebuilds that I was actually looking for [my 3000GT had one and it was wonderful ]. I mean $75 really isn't that bad for a diagnosis on a car that can ACTUALLY have answers yielded. In my case, however, it was just stupid and pointless.

There's no doubt that the scope would've worked right off the bat, but just as you two have mentioned, it's unlikely to be able to attain one hahaha.

In the end, everything still worked out fine. I replaced some older sensors, belts, and ignition components, and the car runs kick ass. It's true that I probably spent money on parts that weren't necessary, but the hands-on experience cannot have a price put on it. Assuming she continues being healthy, I'm actually hoping on visiting a dyno after the semester is over just to see how close I am to my small goal of 250whp. I'm going to try for a MBC @ 14psi.

I think we all did the only thing we could do at the time. Not that it was the best thing, but hey, what else can you do. At least we've both got several new sensors and a new alternator for me that probably won't be going out anytime soon.

Why not just crank that MBC up to 15 or 16 once you get it on there?? I cranked my EBC up to 16 when I was still on the 1st stage upgrades without a pump. It worked pretty well. Actually I was running 18 psi before I installed the EBC though. After my full exhaust setup it upped the psi that much without anything to turn it down.