My car has been running awesome, last 2 days it has started to slightly miss under acceleration, almost like its loading up or too rich. Now under hard load it misses and pops out of the exhaust. Has stored a code 42....any ideas?

Opti is 4 mos old and is a gm unit, has been to 6800 rpm MANY times. Car will not idle and spark knocks when you give it gas to help it idle. the code 42 is the only code in the ecm.


Any help appreciated.


David

 

I'm at work and don't have my code list with me. Also, the Opti its self can only generate two codes, one for missing high and one low resolution pulses. If you don't have either of those codes, the internal optical sensor in the Opti isn't the problem.

Based on my Opti experiences (too extensive and very painfull), I'm going to make a guess here. You've got a new build and I bet the rotor screws have gotten loose. I know it is a lot of work to pull the Opti, but that would be my first course of action (I did that four times last summer). And let me know what you find.

WD

 

If you free rev the engine it revs fine, under no load.

You may be right, it has progressively qotten worse and worse. I green loctited the rotor, so it should not have come loose. The green loctite is some bad azz stuff. I will get it off tonight and see. I hope like hell you are right because I have a HOT date this Sunday with my first 10 second timeslip.


David

 

Yes, the green loctite is good stuff and designed for the small machine screws. Also, the GM Optis have really small machine screws (metric I think) for the rotor. The MSD Optis are #6, not too much bigger. Based on the size of the rotor, I think a #10 machine screw would be much more reliable.

Good luck and let me know what you find.

WD

 

I just noticed your sig update, congrats on getting into the 10's, thats AWESOME!

What is your raceweight and rwhp.Transbrake or footbrake?

I am trying to get my 3800lb dragradial car to 60ft like yours on the motor, best so far is a 1.56.


Think O2 sensors can make it run that bad? No ecm codes for O2's.


I am stuck at work until 10 pm, I will get it off when I get home, take about 45 minutes.


David

 

Mine did something similar, a few years ago when it sucked a pushrod in the intake valley..Since its pretty easy, just pull the valve covers and checker' out..Its simple, and free

 

Well, thanks for the input but I dont think thats it. It started a couple of days ago, But wasnt bad. It would clear up almost like it was too rich....but it's not. A pushrod off will have a DEAD miss at all times.

It was due an oil change and valve adjustment, so I did both and it drove ok for few miles, pulled up to a light and it did not want to idle. So when the light turned green I stepped on it a little and it went to popping and banging etc. In neutral it revs good, under load it pops misses and backfires. No codes in ecm other than the 42, no check engine light on.

I will pull the opti and open it up tonight. Hopefully Engineer is right. Would make me VERY happy if he is.

David

 

Hey I just noticed his sig, too! We have similar traps so it is encouraging to think If I whittle down my 60's I could hit 10s with 3600 lbs and a weenie 226/234 cam...Holy crap! Hopefully my Vig 4000 and the new Spohn drag bar will help...

Hey David, did you ever tighten your rear shocks or did I misread your older post about their settings?

--Alan

 

No I left them alone, but if I can get this deal here figured out before Sunday I will try it. Really pisses me off, this car has done VERY well so far, opti has about 2200 miles on it. I want my 10 second slip damnit!

We have a 600ft track here locally, it went a 6.69 with a 1.56 60 ft the other night, the weather was TERRIBLE! fog was so bad you cold not see the scoreboards!
That pass mathwise equates to an 11.04


David

 

I've had two 1.48 60 fts now, but most are 1.50. Also, I'm having valve train issues at upper RPM and I'm replacing my Comp 918 beehives with PAC-1518s and titanium retainers. I have everything, just need to get it done the next few weeks. Weather is really bad here.

Car's weight is currently 3290 and I'm 180, so the race weight is 3470. I weighed it at Tulsa and Ed Wright said the scales were spot on there.

I did several small things to my car through last season and my car really picked-up late season (not just better DA). What was really funny, I bracket race and several poeple who had been spotting me one to two tenths early season, late season I was spotting them a tenth or more.

One of several things that really picked my car up (almost 2 tenths alone), was when I had my MSD apart the last time (when the optical sensor failed in June), I "tweaked" some additional timing advance using the optical sensor timing adjustment. Marked a reference line inside the Opti with a fine point sharpe, then tweaked it a few degrees.

WD

 

A buddy of mine had a problem with symptoms similar to yours. Turned out to be the ICM. And, as I recall, he also had a code 42. Maybe you could borrow one and swap it out before you tear into the optispark?

 

That couldn't hurt and the ICM is easy.

WD

 

LMFAO I thought the same thing AFTER I took the opti off. Rotor screws are fine. BUT the cap has blue(hot) marks inside. No evidence of carbon tracking, but 1/2 way in between each post in the cap there are blue marks.

David

 

Clean it with denatured alcohol! Good to hear the rotor screws were OK.

WD

 

I put a different cap on it that didnt have any blue hot spots in it and it runs great, seems ok.

WHat caused that? ANd can I fix that other cap by cleaning it with alcohol like you said?

David