When and for how long does the ECU store misfire counts?
03-21-2007, 09:25 PM
#1
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When and for how long does the ECU store misfire counts?
Had a few misfires tonight (stuttering on acceleration in 2nd and 5th gear at WOT) and plugged in the laptop as soon as I got home, without turning the car off, and no misfires were reported. I'd like to catch what cylinder is having problems so I can just swap that plug/coilpack pair. Should I take it out again tomorrow and hammer it to force more misfires or won't it make a difference? Thanks!
03-21-2007, 10:47 PM
#2
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I've had three different coil pac failures. The first showed up under heavy load only
The engine idled and ran normally under light load. Under acceleration or hillclimbing at freeway speed the engine missfired pretty hard. I limped home over 200 miles on interstate 5 because I had no spares with me. The car never CEL'd and logged only once: multi cylinder missfires with no specific cylinder or counts indicated.
The second time, one cylinder was completely gone and it hard missfired continuously, from idle. It Cel'd and coded cylinder #1. This fortunately, happened right in my driveway.
The third matched the second, a dead cylinder. But this time, no CEL or codes. I was 20 miles from home. I chugged it home on 3 cylinders.
Yours sounds like my first case. And the majority that I've heard about are this type. With more driving, it might log a specific cylinder, or not...
Only the guy who wrote this code can answer you question. None of it is documented or in the public domain. This unfortunate set of circumstances, the inability to reliably pinpoint the failing cylinder, has led to the practice of replacing all four pacs to insure that the failing one is truely gone.
The second time, one cylinder was completely gone and it hard missfired continuously, from idle. It Cel'd and coded cylinder #1. This fortunately, happened right in my driveway.
The third matched the second, a dead cylinder. But this time, no CEL or codes. I was 20 miles from home. I chugged it home on 3 cylinders.
Yours sounds like my first case. And the majority that I've heard about are this type. With more driving, it might log a specific cylinder, or not...
Only the guy who wrote this code can answer you question. None of it is documented or in the public domain. This unfortunate set of circumstances, the inability to reliably pinpoint the failing cylinder, has led to the practice of replacing all four pacs to insure that the failing one is truely gone.
03-21-2007, 10:56 PM
#3
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When it rains it pours...
I think there really was something wrong with the coolant temp sensor, the car did start to behave better after it was replaced. The thermostat does appear to stick open, still slow to get up to temp, and now the misfires. Guess it's about time for all the scheduled maintenance... good thing I've got that order om the way from ECS 
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03-22-2007, 09:02 AM
#8
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"Figured it was coil packs.. something else?"
IMO the pacs are the weak link on these cars. They're under-built. OK in unmodified 150-180 horse versions, but the increased heat generated in higher horsepower 225's, especially modified ones, easily pushes them over the edge. The so called upgraded versions, in use have proven to be an expensive joke. I've had them fail in as little as 7k miles. The more horsepower your making through higher boost, chip, big turbos and such, the hotter the engine runs, especially in the immediate environment where the pacs live (in the cylinder head, RIGHT on top of the combustion chambers). Power tweaks to your 225? Keep a set in stock (or in your trunk)...
Guys have spent hundreds of dollars changing out sensors and all of the other parts that can cause missfires in the absence of good, clear failure data, presented in codes. Then attempt a "one pac at a time" strategy in an effort to be precise, and save a buck. All the while the car runs lousy and you don't want to drive it. One car I know of was sick for months. If you're lucky enough to guess right and change only the one bad pac, consider that the other three have accumulated the same number of heat cycles. How much time do they have left? Then it starts again.
So my advice: if the car is missfiring, codes or no codes, change all four packs FIRST (and throw in a set of plugs too if there's any doubt about their condition). It can save you so much grief (and money)...
Guys have spent hundreds of dollars changing out sensors and all of the other parts that can cause missfires in the absence of good, clear failure data, presented in codes. Then attempt a "one pac at a time" strategy in an effort to be precise, and save a buck. All the while the car runs lousy and you don't want to drive it. One car I know of was sick for months. If you're lucky enough to guess right and change only the one bad pac, consider that the other three have accumulated the same number of heat cycles. How much time do they have left? Then it starts again.
So my advice: if the car is missfiring, codes or no codes, change all four packs FIRST (and throw in a set of plugs too if there's any doubt about their condition). It can save you so much grief (and money)...
03-22-2007, 11:32 AM
#10
yup. good advice. difficult to pin down if it misfires under load...better to replace all
and possibly the plugs as well...or do a visual inspection. initial startups in the extreme cold can also damage part of the ceramic insulator in the plugs...thus causing misfires as well.
best bet to change packs and plugs to make sure.
best bet to change packs and plugs to make sure.