Hey guys I'm looking for some advice on an issue I've been having the past 2 days now. It started on the 25th when I was driving to the gym, I was accelerating over a hill when the car started chugging and bucking under roughly half throttle. I glanced at my w/b and the afr's were normal, and just as soon as the issue started it went away, and the car drove like normal from the gym to work and then to home.

The next day I woke up Fired up the cavi and drove straight to work and all was fine, afr's were great passed some slow people under wot and pulled hard like normal. Once I got out of the car ( it was idling fine) punched onto the clock and went back to move the car again it started running like I was on 2 cylinders then bucked and bogged again only this time it didn't go way. I had enough momentum to coast to where I park, and tried restarting the car. Nothing...just chuggged fired up and would die asap. I tried one more time and gave the car maybe 1/3-1/2 throttle and it fired up and ran if I kept the revs up to 2.5-3k rpm's but once I tried to let it idle it would stall out.

So given my past experience with J's and the car chugging like it's on 2 cylinders I figured my ICM or coils took a @!#$ finally. So I went over to Napa before they closed and picked up both parts so I could throw them on the car while I had daylight still at work. ( I work nights 7pm-4am) Once I did that the car fired up normal and I took it for a spin around the block and ran ok. Fast forward to after work when I'm driving home and the same issue is back. The car doesn't want to run below 2k rpm's smoothly, so I just kept the car in 3rd gear @35mph on the way home. Once I got home the car wouldn't idle and just stall out like before.

Now today I woke up, pulled the plugs and looked into the cylinders with a flashlight, and everything looks normal, plugs are all gapped to .032 just like when I installed them, and no signs of detonation at all just a little rich. Now today after looking at the plugs I put the car back together and it fired up didn't want to idle at first but did, it was only after I'd rev it a little and slip the clutch to move the car that it would die out.

I've not scanned the car yet as my friend has my scan tool at the moment, but I also didn't get any flashing cel's or any engine lights popping on or off. Does anyone have any idea's or past experience with a similar problem? I don't have a fuel pressure gauge hooked up but I did press the shrader valve in and it had plenty of pressure. Wouldn't a faulty fuel pressre regulator cause the car to stall out under slight peddle but not when the car is creating boost?

Thanks for any info or advice you have to give.

Not sure by ur registry but I'm assuming ur HP tuned yes?

yes I am, I had Cavattack tune the car over a year ago and have had not a single issue with the tune.

Can't say I can help my issues have been with the reflash. But fueling kinda sounds like the next step.

bad idel air control motor. stuck shut maybe? just a thought.

I have the EXACT same issue with my 02 Ecotec, but it wasnt boosted. Its the IAC. Swap that out, and it will be fine. Its almost textbook for the issues your having. Sounds like its binding up and such. Easy way to see if its that, is to remove the IAC and see if the car runs and idles fine. If it does, which it should, then u got ur problem. ) Goodluck!!

Thatnks for the insight guys I'll try that after work when the sun's out. Otherwise I'll be working on my j this weekend instead of going to the meet saturday.

Could it possibly be bad plug wires or clogged cadillac converter?? i used to have a 94 grand prix and i had some of the same problems so i started trying stuff and those were the 1st 2 things i did and it started running great again

See that doesn't exactly sound like an IAC problem. When he is on the throttle(accelerating over a hill), the IAC doesn't play any part in how the engine runs. Or am I wrong?

However, when you said it was idling and had the problem, THAT sounds like an IAC that is not open, or only open part way.

I would try what sneezy said before I bought any more parts. I would scan it also and check fuel pressure with a guage.

My old Cav with m62 setup did this once in a blue moon, but always went away in less than 5 seconds.

Dan- the eco doesn't have wires, and I've been on a test pipe for a while now

Mr. Choo, You are right about the IAC not playing a part in the throttle hesitation, but that sounds like it was cleared up when he did the coils. Now, with that said, when he presses the throttle, the IAC closes since its not needed, but once the throttle is let off, its suppose to open as needed. If it isnt running lower then 2K then it sounds like the IAC is sticking closed or not moving as fast as it should. The fuel pressure sounds fine (wont really know till he gets a gauge on it) since he is able to romp on the throttle and the car moves, but once he lets off it wants to die. My old J had that exact same issue, if I held it while driving it would run just fine, but the min I tried to let it idle, she died. And the IAC is such a stupid design on the eco's because there is a thin piece of wire that breaks and renders the whole thing useless. It happened to mine. I threw my buddies on it and boom, problem went away. Either way, Im almost sure thats it. Its literally almost text book as to the symptoms of a sticking IAC or a lazy IAC.

for some reason i was thinking u had a 3X00 swap..my bad..lol

Well I still don't have the scanner back yet from my friend but fuel pressure off the port was 55psi @idle and 63psi@ wot or with the reg disconnected. I also checked the IAC and the LS1 IAC is covered in plastic and nothing is visible but I cleaned it off with carb cleaner, lots of dirt came off it.

Last thing I checked was my IAT wires and they were corrosion free and had tight connections still from when I wired up the Tmap sensor. I still don't have an engine light on....

I would tart with scanning it, even if the light isn't in there may be faults, check pending faults in generic OBD as well.

Jeff, did you run the car with the IAC actually removed?? Thats the only way you can see if the IAC is causing a problem or not. At least you cleaned it up, but the car needs to be ran with out it in the TB to see if thats whats causing the car to sputter and stall when idling.

my vote is still with the IAC.

I picked up my scanner, but I'm heading into work now. I'll get it scanned friday when its daylight out.

Mike, I didnt try running the car with it out.

Well, if there is any kind of a MF the scanner wont pick it up, Like i said, even the GM Tech 2 didnt pick up when it was MF'in on my car. But I dont think thats the issue, I think the IAC is screwin up on u. Just pop it out, and run the car and see if it goes away. You can also plug in the IAC and leave it out of the throttle body, hold your finger over the plunger with the car running and it should move back and forth smoothly (dont push on it, let it push your finger), if it just feels like it "bumps" then its not good.

Alright I just woke up and scanned the car, pulled a P0106 from the history-Manifold absolute pressure/baro sensor range performance. So I'm going to pick up some solder and shrink wrap and remove the quick connectors on the Tmap and redo the connection. If the car still acts up I've got a friend with a tmap I can swap out. He also has HPT but had to send his cable in for repair like 2 days ago....

Well I redid my tmap connections and shrink wrapped them, all is fine now. I just got back from a 10mile cruise and didn't get any codes or hickup out of the cav.