Finally got another 4th gen

[JL8Jeff]

I picked up a 96 SS on Friday and it's pretty clean and pretty much unmodified except for the air filter and stereo. It pops up an SES light and the place I got the car from said the code showed it as a random miss. The car runs and drives fine so it's probably a pretty minor code, but you can't pass inspection in NJ with the SES light. I'm gonna replace the plug wires since the car is at 85K and I'll throw some washers behind the ICM mounting to the head to help keep it cool. Any other thoughts that could cause the random miss other than Opti? Plugs are new.

[Trash man]

ur on njfboa.org arent ya? i thought i saw that car somewhere else. ur one lucky man, i wish i could have a LT1 ss

[JL8Jeff]

Yeah, I jump around njfboa.org, camaross.com, fbody.com but I haven't been on here since last year. I used to have a supercharged 93 Z28 Indy 500 Pace Car and sold it to raise money for my 69 Z28 restoration. My 69 still isn't done but I saw this car for such a good price I jumped on it and financed it. Nothing like being in debt!

[JL8Jeff]

Not sure why this thread was moved because I had some tech questions about the random miss SES light I'm getting.

[Joe 1320]

If the plugs are new, it's likely the wires or opti. there is also the possibility that the metal boot covers are causing the ignition energy to ground. I had to complelty remove mine and use Taylor firesleeves to eliminate the miss yet keep the boots protected.

[Injuneer]

If you know someone with a Tech 2, they can access the misfire count by individual cylinder. That might show you if its possibly an injector, cross-firing on two plug wires, or truely random. A quick check under the hood in the dark might show some arcing, but its hard to see if its back under the exhaust manifolds.

Sounds like you have something you could actually drive to a CJC/FO meeting, if we ever have one again........

[JL8Jeff]

I was looking at the engine last night and it sure looks like somebody did some work to the wiring on the injectors on the passenger side. The tape over the wiring is all new. Will the SES light flash showing which cylinder might be the problem? Because on Sunday it started to flash while I was driving and then went back to staying on. Yesterday the light went back out as I was driving home from work.

As for CJCFO, it would be nice to see a few people show up for another meeting.

[Injuneer]

The blinking SES light means there is a problem that could damage the catalytic converter.... i.e. - misfires dumping unburned fuel on the cat. That gets you P0300 - random misfires. If the misfire was easilly pinned down to a specific cylinder, you would get P0301 for #1, P0302 for #2, etc.

The PCM also keeps a running total of the misfires by cylinder, so even if its seemingly "random", sometimes you can see the problem is worse on one or two cylinders, so it shows you where to look. I think you need a scanner with "GM enhanced parameters" to get the misfire count. I know the enhanced version AutoTap can do it.

You can not get anything specific by "flashing" the SES light, nor does the flashing rate or pattern correlate to anything.

The whole misfire identification is done by the PCM looking at the tiny variations in the crankshaft velocity, and comparing the pattern to a known pattern for the engine. You can even get random misfire codes from a hairy cam, or from a rough road surface. I suspect you can rule both of those out

[RyanB58]

The blinking SES light means there is a problem that could damage the catalytic converter.... i.e. - misfires dumping unburned fuel on the cat. That gets you P0300 - random misfires. If the misfire was easilly pinned down to a specific cylinder, you would get P0301 for #1, P0302 for #2, etc.

The PCM also keeps a running total of the misfires by cylinder, so even if its seemingly "random", sometimes you can see the problem is worse on one or two cylinders, so it shows you where to look. I think you need a scanner with "GM enhanced parameters" to get the misfire count. I know the enhanced version AutoTap can do it.

You can not get anything specific by "flashing" the SES light, nor does the flashing rate or pattern correlate to anything.

The whole misfire identification is done by the PCM looking at the tiny variations in the crankshaft velocity, and comparing the pattern to a known pattern for the engine. You can even get random misfire codes from a hairy cam, or from a rough road surface. I suspect you can rule both of those out

God He knows his stuff!!!!
What do you not know about our cars?

[Injuneer]

Is it "dazzle 'em with brilliance".... or "baffle 'em with bullsh!t"?

[AmericanZ28]

Is it "dazzle 'em with brilliance".... or "baffle 'em with bullsh!t"?

Im Baffled! LOL! Fred never siezes to amaze me with his bullsh!t, I mean brilliance! Honestly though, Fred is a real asset to this site.

[JL8Jeff]

I'm still getting the P0300 random misfire code on my 96 SS I just bought. The plugs look new(I only checked 2) and I just put on new MSD wires(PITA). The SES light will flash before it comes on and stays on. The car runs great with no hesitation and no rough idle or anything. I'm thinking it might be more fuel related(lean causing too high ECT temps that could damage cats) but I'm open to ideas or thoughts. The code will go away and then come back again. I'm trying to get ahold of something to do some drivetime scanning to look at fuel/exhaust.

I just ran the car in the dark to look for any type of spark scatter or weak plug. No sign of any spark problems. This looks like it will be a fun one to troubleshoot. Is there any way to test the crank position sensor?

[Joe 1320]

When you did the wires, by any chance did you install the metal plug boot covers? When I swapped wires, I was getting misfires that I traced back to the boot shields. I had to remove them completely. I hade to install taylor firesleeves to retain some heat protection. Once the metal boot covers were ditched, the misfires were gone. It's worth a look.

[JL8Jeff]

Yes, I put the metal boot protectors back on with the wires. I didn't see any sign of sparking or grounding out when I was running the car in the dark and the misfire was there before doing the wires as well.