AMRAAM

I can't remember the codes I'm getting, but I keep getting a misfire code and an occasional crank sensor code as well.

I believe the flywheel was balanced incorrectly. The weight was not removed before balancing and the machine shop that did the work sai he took a lot out to balance. I think it was like 46g or something.

The CAS has already been replaced. Is it possible that the unbalance could possibly pull the reluctor away from the sensor enough to cause a misfire?

Eric D

What flywheel are you using, stock or aftermarket?

The flywheel imbalance would have to be so bad that you wouldn't dare go over about 3000 rpm, and even than not likely to trigger a misfire. However, bad crank sensor, loose sensor, or bad wiring would. Other factors that can cause misfire codes, a cylinder with lower than the rest in compression, bad plug, bad coil, or bad plug wire.

AMRAAM

Thanks, Eric. I am using the stock flywheel, and what you said is what I've been thinking about, but I can't seem to find anything else. I've had it to two tuners, neither of shich coul dfind the issue. I'm thinking of putting it back to stock.

Sorry for such a late reply, been a busy day at work.

lucky131969

Exactly what work has been done on the car recently before this issue?

It would help if you provided some detailed info. What codes? Are you experiencing a vibration? If so, when i.e. at idle, cruise, etc. Since tuning software has been used, what cylinder(s) are misfiring?

AMRAAM

Sorry, I have posted on this before and just wanted to know if the flywheel could cause my issues.

Below is a cut and paste from another thread. The work was done about 2 years ago, but has been doing it ever since then:

Car - 1997 Coupe

Mods - P1SC procharger, FMIC, blower cam, headers, ported 243 heads, LS6 intake, Lingenfelter FP and Kenne Bell Boost-a-pump. I also have some sort of aftermarket MAF, but not sure where it came from. Tuner installed it and told me about, but I forgot what they told me.

Symptoms - car bucks constantly at constant speed and wideband O2 spikes lean after each buck. It feels like a dead miss. I sporadically get a P0300 code, typically after driving at slower speeds. The codes never indicate a specific cylinder even with an external code reader.


The thread this info came from seemed to indicate this:

The tuner I had taken it to said they adjusted it, but it still does it.

n8dogg

A bad flywheel can definitely cause a misfire condition. If its bad enough that is, it doesn't necessarily mean the cylinder is misfiring, but the imbalance can cause the crack position sensor and/or knock sensor to think there is.

lucky131969

Ok....trying to help here...what about vibration? Do you feel any? Also, tuning software or a Tech II can map the cylinders, and reveal a miss. Has this been done?

AMRAAM

Yeah, I know you're tying to help. Hope I didn't come as not being appreciative, I am. I'm just saying that's why I didn't go in to too much detail on what the problem was.

There is a slight vibration, but not too bad, especially since the car is cammed. i think most of the vibration is from that.

I am unsure what kind of tuning software was used. i can only speculate that the cylinder mapping was done, but unsure. I'll PM the tuner and see if he can step in and clarify some things.

lucky131969

Like Eric already stated, if you did have an imbalance issue, it would certainly be pronounced(to precipitate a misfire)......so much so, I doubt a tuner would run it on the dyno.

DALE C

Sorry it has been a couple years and I dont remember all the details. The thing that stands out the most was the galled rocker bolts one broke when we were taking them loose to do a leak down and we had to pull the head.

I thought we had it straightened out. The car had a card style MAF and a very funky MAF table I remember it was going scary lean.
If it went away and came back I would check the maf and intake tract for oil. I have also had a car with fatigued valve springs that cracked valve seats and set up a reversion in the intake causing the same symptoms Crank sensor codes and random misfire that car had a much larger cam and RPM range. From what I remember the misfire was random we did graph it and it was above the cam overlap range and a true misfire. Which usually leads to a fueling or mechanical problem.
I would check the MAF and check fuel pressure (under load if poss a gauge taped to the windshield while driving). We would be happy to do it but I know it is a long drive into the shop.

Feel free to give me a call.
Thanks, Dale

AMRAAM

Thanks Dale. I knew you would be able to add more on the tech side. It never really did go away. It seemed better when I left your place, but it was still there.

I have a fuel pressure gauge and it seems to be fine. It seem sike we, or maybe you switched out the MAF and didn't make a difference either. ALl I know is when the piping blew off ath the throttle body, it ran like a dream. Doesn't that indicate that it isn't something mechanical?

I'm basically to the point of possibly de-modding, although I hate to.

lucky131969

What "piping" are you referring to?

AMRAAM

The hose that connects the MAF with the throttle body came apart. As i was driving it to a place where I could pull off the road, it appeared to be running great.

I know that counters my flywheel imbalance theory, but it was just that, a theory.

Here are a couple of vids of the WB. 1st one is at idle, 2nd one is cruising. It's hard to see, but you can definitely see the lean spikes.

DALE C

That gauge bouncing around at idle or steady state cruise does not surprise me. The cam does have some overlap and any unburnt mixture will show lean the o2 only reads oxygen so even a super rich mixture without a complete burn will read lean.
I would really check the maf and the air bridge for oil and clean the MAF with MAF cleaner (the cause of the oil in the intake was the mechanical problem I was talking about) oil in the intake will throw off the fueling and cause a knock which will rattle and vibrate the motor.
The car should cruise lean if it is showing lean at tip in or WOT that is another story.
If the Maf is contaminated and the air tube came off causing you lose boost and the maf. It does not surprise me that it would run smoother.

AMRAAM

I can check the MAF and clean, however, the miss has been there since the MAF was installed. I believe the stock MAF was put back on to see if it was a MAF problem as well and it still continued.

DALE C

When we started on the car it had a bad lean missfire. Just changing the Maf without changing the operating system will be very lean due to the operating system I still dont know what that MAF they put on the car is but it is not compatable with a stock file or vise versa.

AMRAAM

I know I brought it up with me at your request. I thought that you had tried to swap out the MAF, but that never happened. I'll try to get it cleaned out in the next couple of days and see what happens.

DALE C

no we were unable to switch it due to the wiring conversion and operating system.

RichAshley-Black99

Check your spark plugs , after my clutch install my headers upon reinstall had hit one of my plugs and cracked it slightly, could barley see it but it was missing and running like shiat was getting the P0300. swapped in a new set of plugs and all was good.

AMRAAM

thanks, but I've changed plugs and wires several times since I did the mods and nothing changed.