I just had a Flowmaster American Thunder cat-back and Magnaflow Cat put on my 91 TPI. I also replaced cap, rotor, and coil. and now my car likes to die while driving at random times. Scary.

Car drives fine for about 15-20 minutes and then all of a sudden it bogs down during acceleration, back fires, and dies. After it dies, I can start it just fine, and it idles OK in P and D, but when I accelerate to about 25 MPH it craps out again. If I wait a few hours it's fine again, but the issue will happen again after about 15 minutes of driving.

The cat-back was installed by a reputable exhaust shop, so I think it was done right. I had it towed back to them and they couldn't reproduce the problem (what a surprise) but said they couldn't find anything wrong.

Any ideas??

 

sounds like the egr is opening due to the lack of back pressure on the positive back pressure egr.

 

I was thinking EGR as well. I recorded this issue with datamaster and when the car bogs down and backfires the EGR DC flag drops from 100 to 0. Also, the CCP DC goes from 0 to 50. Not really sure what these values represent, but it's the only data that changed significantly right when the car starts acting up.

Think I should just replace EGR? Thanks for the reply by the way, I really appreciate it!

 

I remember a while back you said you had the wrong memcal in the car one from a maf tpi. Hopefully thats resolved. Does this have the original multitech injectors in it? You might want to ohm them when the engine is warm could be a coincidence the injectors are failing after the new exhaust upgrade.

 

Indeed. MEMCAL has been replaced with the correct part AXXB (although, even with the incorrect MEMCAL, the car did not do this backfire and die thing). This problem is new, only after I got new exhaust put on. The car does not have the original injectors, I replaced them with 19LB BOSH III last year from south bay.

I think you were on the right track with the EGR and backpressure...but I don't know enough about it to say for sure. Is there a way to test the EGR? Should I replace it? I gotta figure this out...stalling on the highway is no fun.

 

Also - you sure new cap is locked down properly, and new coil wiring is ok? Just sayin' since you mentioned changing them. My car developed the habit a few months ago, of spitting the power connector off the dist at random times, left me dead on the freeway a couple of times.

 

Sorry, Im not sure the test procedure on the positive back pressure egr. I don't use egr's on my tpi's and delete them in the memcal programing.

 

That's cool. I'll figure it out. I need to do some more datalogging. I don't think I can delete my EGR cause I have to pass emissions every year. "Mile High Country" Does that mean you live in Denver?

 

I have my truck registered at my cabin in cotopaxi, And I also have tpi in my 67 camaro. No smog test on that.

 

The TPI system does not have a positive EGR, only the TBI has that.
I had a similar situation with a bad coil.

 

Im having the same issue right now with my car, the stock cat back was rotted so i cut it off and ran just the cat, and it was broken inside, my car started acting like yours but worse at times. I removed the cat and I have a 24" glass pack in it's place with a spout and the car is doing the same thing, I had ti tuned up and still doing it. Shop thinks my issue is a bad PROM chips as it will not talk to the scan tool and when my PROM is installed in a differant PCM it does the same thing. Once my car is running again and if it's doing the sme thing I will have them look at the EGR valve.

 

Update: just replaced the EGR Valve and EGR Solenoid. Problem still exists. Car Idles great in P and N. Drive it for 15 minutes and it stumbles, backfires, and dies. Have to wait a few hours for it to cool down and then I can drive it home.

I'm thinking Ignition Control Module (never been replaced), Purge Valve (Need to check this with vacuum pump), TPS (Never been replaced, although it tests fine.), or maybe MSD sent me a bad coil..?

 

have you ohmed the injectors while hot, hopefully these are not the mulittecs

 

I will do that when I get home. I don't think that's the issue because I just replaced them last year with 19LB BOSH III from South Bay last year. But you never know.

I know a hot ICM/pickup coil can short out and stall a car if they are faulty. Also, if the vapors aren't being purged properly that can stall a car. So maybe purge valve, charcoal canister, or even gas cap. There's also a solenoid on top of the charcoal canister...need to check that as well.

I hope it's not the fuel pump..that's not something I can do in my little garage.

 

ICM does sound likely, if the problem follows the heat state of the engine, I've had both module and pickup coil do it to me.

 

Hey guy, you have completely ignored other peoples suggestions on this. You need to recheck your rotor and cap, and receck your connections from the spark plug wires, this does not sound like an exhaust issues, make sure your spark plug wires are seated, and not arcing over somewhere, check the cap and rotor again, then check coil.

Did you also replace the spark plugs? Check them at the plugs and make sure they are seated.

 

I installed a cutout after my cat. It drove it with an open cutout for ten miles to a car show. On the way back, about 3 miles down the road, it started sputtering, backfiring and stalling. It even died a couple of times in traffic. It didnt matter wether the cutout was open or closed.

The next day I started it and now the car has been driving perfectly fine since. I'd like to know what causes this too.

 

Thanks for the responses. Killjoy, I have not ignored anyone's advice. I have checked cap/rotor. Plugs are new, wires are new, all good to go. Checked arc, seat, and resistance. Injectors are good as well. Just didn't bother to tell everyone every little thing I checked. My bad.

I will be replacing the ICM and pickup coil today. Will let everyone know if that was the issue. If not, it's gotta be a purge system issue considering my gas tank pressurizes a lot after I drive it (Hisses when gas cap is removed). Buggy, I'll keep you up to date...

 

Have you checked to see if the installers removed the heat shield between the muffler and gas tank? Muffler touching heat shield? Muffler touching gas tank?

 

Check the fuel pimp ? My car did the same thing and it was the fuel pump

 

hope you are making progress mrpink, The springs is a federal disaster hope you doing ok.

 

Yeah, it's a mess. I'm about 20 miles away so I'm fine. My mom was evacuated though, she's about 3 miles away so she should also be fine. I think people might reconsider building mansions next to dead pine trees in the future.

Anyway, to update. The heat shield is still there and I don't think any components are touching. Although, I do think this is the problem: Exhaust is getting too hot and heating up fuel tank messing with the fuel pump, tank pressure, etc and cutting the car out. I bought a Kevlar muffler heat shield and some exhaust wrap for the pipes near the fuel tank. Next weekend's project.

Also, I replaced the pick-up coil and ICM and set timing to 6 deg yesterday. So between all that I should hopefully solve the problem. I'll keep everyone updated. Might just do fuel pump anyway...I'm pretty sure it's 20 years old.

 

glad all is well, I have heard issues with the walbro pump and airtex pumps but ac delco ep241 has allways been a good pump. man sorry to hear your troubles after the exhaust upgrade.

 

Did you notice any tread missing on your rear tires? I wouldn't be surprised if a certain shop went on a joyride and messed something up...

 

lol. no. It's funny you mention that though. Last time I took my car in for something, I gave it to the shop with a mint dash pad. Got it back with a huge crack on it. Looked like someone punched it. They denied it of coarse. I try to do everything I can in-house; I hate letting people touch my car.

Still haven't had time to see if the new parts/exhaust shields fixed my problem. I'll keep you updated. I have a new baby at home, so car is like 6th priority right now.

 

plug the hose going to the EGR, and drive it ,to prove your idea.you might play around with vaccum bleed /delay valves .its a band aid for sure ,but it might buy you time

 

I agree.
If you haven't by now, stop buying parts and put your stock coil back on to eliminate the possibility of a bad "new" MSD coil. I have 2 or 3 bad MSD coils layn around here.

 

Just to let people with similiar problems know,

I fixed my problem by replacing the MAP sensor. It took all of 5 minutes to replace. The car has been driving great for the past two months.

 

I have had the MAP sensor issue as well. Riding down the road, car stumbles and dies...was able to limp home. You will know the MAP is at fault because your CEL will come on and throw the MAP code (forgot which on it is). My issue is totally UN-related. No codes thrown, no CEL comes on. Mine was heat related as I will describe below.

 

Thanks for everyone's help. Solved my issue.

After replacing Ign. Coil/Module, EGR Valve, Charcoal Canister/Control Valve, and Tank Valve to no avail, I decided it was a heat issue.

I installed a Kevlar muffler heat shield from Thermotec and a Flowmaster muffler heat shield (in addition to the stock heat shield) and I have not had my car stall or had any fuel pump noise since. Fuel pump was just getting too hot and acting up (its old and cranky). Although, there's an entire thread of people who have the same issue with new pumps...I'm sure I'll have to replace it one of these days, but I'm out of time/$$ this summer.

Now to try and pass emissions. Keep failing by fractions of a point. My BLMs are way too high, but my mechanic can't find any vacuum leaks. And it goes on...

 

thats good to know cause I have a really free flowing exhaustlive in elizabeth, just down the road and wasn't having that problem but mine comes out the sides no where near the gas tank. Only difference I don't have emmitions

 

That's good. keep exhaust away from the gas tank...it's a disaster waiting to happen.

Yeah Elbert County rocks. I need to find a way to register my car in Elizabeth so I don't have to deal with this emissions garbage anymore. In 5 years it's going to be impossible for any TPI/TBI to pass if they keep lowering the standards.