Ok, after the latest tranny swap, my car was running great but not boosting. I limited the problem to the stock boost controller, since I had used my Profec-B since I got the car, and took it out to de-tune the car. Well, I found my spair, and threw it on, and it was much better. Well, of course I went out and played a bit, and it ran fine untill last night. Now it has a mis I can't seem to find. I swapped the o2 with a brand new one I had, changed plugs, checked the wires, coils, and module was swapped with a spair. The x-over is no worse than it has been. IT's mostly under light throttle and while decelerating, but it does miss a bit on the higway cruising(although not much). For instance, while decelertaing down a shallow incline it will buck and miss like crazy, go back up the other side and it hardly misses at all.

Any ideas guys?

Decelerating sounds like torque converter clutch engaging and disengaging. Try running in d or second gear an see if it still does it.

Jud

It's engine related, I can hear it. TC and trans are perfect(re: brand new).

Did you use a adjustable spark tester set to t he spec recommended by the GM Manuals?... Sometimes a coils will be weak, and spark, but not have enough juice for the correct volts spark... The gap on the adjustable spark tester will find a weak but not BAD coil.

I bought brand new coils and module. I also switched them around with the old coils to see if anything improved and nothing. All the new stuff is on now. I'm starting to lean a bit towards the fuel system.

Stumbling/bucking on deceleration can sometimes be an indicator of an improperly functioning EGR(usually when this occurs, the car will stall at lower speeds), I guess it couldn't hurt to buy a cheap gasket for it and take it off/clean it to see if that helps.

I never thought about the EGR. It does stall at lower speeds(mostly when stopping at intersections while cold, or trying to crawl down the alley behind my house). It also has a low throttle stumble, but as soon as you punch it, it seems ok. Albeit there is a loss of power but it's not missing when you nail it. Fuel milage also decreased.

sounds like you and I have the exact same problems.... could a bad crossover pipe cause the issue with the EGR?

DAMN!, yeah I got that "exact" same problem. And I also have replaced tha plugs, plug wires(complete tune up), module, coils, and rebuilt tha crossover pipe with JCW flex joints. Tho there is still a very tiny leak on it, around tha welded area(would that do anything). but yeah, after all the above was replaced it ran a little bit better but still misses. My car pritty much runs exactly like you explained. Only that when I floor it, it putters rapidly well the boost elivates. I would really like to find out whats wrong with my car. I already have it in tha local auto trader, maybe if i fix'd it I wouldn't have to sell it...

Mine has gotten worse, and the rapid flutter under hard acceleration has started as well. It still boosts and pulls, but not like it should.

It's fixed! I put another set of new plugs in, changd the wires again, checked and celaned all of the injectors, checked and reran all the vacuum lines, and it still ran like crap. Changed the IAC and TPS, and it runs like a champ! I thought both of those would set off codes though, so i never though to check them before. It was kind of a last resort and I had a set laying around.

Quote from: maximageIt's fixed! I put another set of new plugs in, changd the wires again, checked and celaned all of the injectors, checked and reran all the vacuum lines, and it still ran like crap. Changed the IAC and TPS, and it runs like a champ! I thought both of those would set off codes though, so i never though to check them before. It was kind of a last resort and I had a set laying around.

Hey, THANKS for the update!!!  AND SHARING THE GOOD NEWS!!!!!  Now we are talking, I mean it was designed to run right one time, should be able to get there again, took a while and had a few curves thrown at you, but you persisted and it paid off.  After all this work done to you car with all this, you are now a pro at ripping through a W-Body car getting her fixed, just don't let the W-Body guys knows this or you will adopt a ton of used cars to fix  :lol:   Anyways, super good news, the rest of what you did will just eliminate a ton of chances for your baby to complain for a long time to come, and if it every does, you know your way around it no problem now!

Jeff M

This is interesting..As I thought a bad TPS would always set a code........ It could've been there was carbon tracking on the TPS causing slight voltage flunctions not enough to throw a code but enough to throw the ECM off...

:idea:

Quote from: Jeff M

Quote from: maximageIt's fixed! I put another set of new plugs in, changd the wires again, checked and celaned all of the injectors, checked and reran all the vacuum lines, and it still ran like crap. Changed the IAC and TPS, and it runs like a champ! I thought both of those would set off codes though, so i never though to check them before. It was kind of a last resort and I had a set laying around.

Hey, THANKS for the update!!!  AND SHARING THE GOOD NEWS!!!!!  Now we are talking, I mean it was designed to run right one time, should be able to get there again, took a while and had a few curves thrown at you, but you persisted and it paid off.  After all this work done to you car with all this, you are now a pro at ripping through a W-Body car getting her fixed, just don't let the W-Body guys knows this or you will adopt a ton of used cars to fix  :lol:   Anyways, super good news, the rest of what you did will just eliminate a ton of chances for your baby to complain for a long time to come, and if it every does, you know your way around it no problem now!

Jeff M

I've been a pro for a while. Ripping out trannies and putting in new ones, on top of the never ending battle to finish the cars build(it's never reallly finished, I always find SOMETHING...)... It's a love/hate relationship my car and I have. I love it, it hates me... j/k   :twisted:

I think most of the time a sensor will throw a code.  In my other car, the O2 was causing a misfire, but the code didn't show up for 3 weeks.