'97 GA idle and misfirer probs.

[Makenzie]

Well, I've changed the bad injectors, and there are no vacuum leaks, I replaced the IAC and MAP, new plugs. And I'm still getting reandom misfirers? It can't be the fuel system. Could it have anything to do with the ignition, coil packs or ICM? I measure the resistance across the coil pack and they are all opened. I measured the resistance across all the terminals on the ICM, and compared them to a brand new one, the only difference was the new one was opened across all terminals and mine had a small short, like 1.5Mohm where the #2 and #5 coil pack goes. The car starts right up now, before I used to have to haold the gas to the floor, now, I can just turn the key, but the idle is still up and down, like 500 RPM's to 1000RPM's and it keeps giving me the random misfire code P0300, I think.

Where to start now, I have not replaced the wires, but when I use my inductive timing light to see the spark, the misfire stays with the cyclinder, when I swap wires around?

[carlover626]

I am picking through the clues, but is this the V-6 or the 2.4?

[Makenzie]

sorry. 3.1L It does run better then it did, but. Still not as it should.

[rixGAphx]

As I recall, your previous thread indicated that plugs/coil 2,5 were the *possible* source and location of the P0300's.

Well, those sockets are the primary voltage going to the coil; so even a minor short or other fault can easily result in a spark that's so weak it can't ignite the AF-mixture.

Interestingly, your present testing indicates a 'minor' short on those SAME sockets.
I don't know what the test values should be, but that evidence seems fairly conclusive to me.
Personally, I think you've found the source of the problem.

While a new module isn't the cheapest thing ($98 - $267, depending on brands), here:
http://www.partsamerica.com/ProductList.aspx?parttype=194&ptset=A&searchfor=Ignition+Module%2fControl+Unit ,
perhaps a 'guaranteed' junkyard or Ebay module might be available.

Good luck,
-Rick

[Makenzie]

Alright here's the run down:

By hooking up a inductive timing light and seeing how steady the spark is. I keep getting P0300 and P0305, Random and #5 misfire. but:

#5 fire's steady and constant
#2 Misses, not very constant miss
#3,6,1,4 All fire steady and constant.

So, I swapped #2 and #4 wires, and the miss stayed with #2 cyclinder? I just put new plugs in. I'm sure it's not the plug. The next step is that I'm going to swap the coil packs around and see if the problem goes with that coil pack or stays with the cyclinder. I'm assuming that if it stays with the cyclinder it's probably the ICM?

I also don't understand why I keep getting the P0305 when I just changed the injector on that cyclinder twice. I know that #2 and #5 are on the same coil pack, could the PCM just scerw up and think that #2 is #5? does that make sence at all?

Thanks,
J

[rixGAphx]

Originally posted by Makenzie
...I know that #2 and #5 are on the same coil pack, could the PCM just screw up and think that #2 is #5?
...does that make sense at all?
It makes sense to me.

But then, I don't know how the PCM differentiates which cylinder has actually misfired.

-Rick

[Makenzie]

Well, I went out today and swapped around the coil packs, and I got the same code P0305. And the #2, by an inductive timing light is the one missing not #5? So I lead to believe that it is the ICM. But I was wondering if there was any way that if the valves were sticking shut, or not seating all the way would give me a misfire code like that also? If that is not the case then I'm going to replace the ICM and see what happens

[rixGAphx]

Originally posted by Makenzie
Well, I went out today and swapped around the coil packs, and I got the same code P0305. And the #2, by an inductive timing light is the one missing not #5? So I lead to believe that it is the ICM.Either the ICM itself, or some corrosion or such on the little plug pins/sockets of the ICM.

:puzzled: about P0305 code being set, when #2 is showing the actual lack of spark.
Tho mebbe the #2 'no-spark' is its 'waste spark' (at TDC of its exhaust stroke), in which case it isn't truly misfiring.
Still doesn't explain why the PCM thinks that #5 IS misfiring, when you're getting a good indication that it's sparking (from the inductive tool).

But I was wondering if there was any way that if the valves were sticking shut, or not seating all the way, it would give me a misfire code like that also?1. I'm not sure how the PCM determines 'misfire', other than knowing a spark didn't occur.

2. You mean intake / exhaust valves?
They can't 'stick open'.
Exhaust valves can 'burn' (actually, just pit severly from extreme heat), causing a poor seal and bad compression/combustion. A compression test is used to check for this.
But you would also get other symptoms such as rough running; *mebbe* the misfire you're experience.

Personally, I think this is quite a stretch, since the V6 is basically VERY dependable in terms of mechanical operation.
If that is not the case, then I'm going to replace the ICM and see what happens

Good luck as always,
-Rick

[HeyDace]

Youv'e swapped coils and the miss remains. Have you swapped wires? Try swapping the plugs out, it wouldn't be the first time I have had a bad plug right out of the box.