I've searched the whole internet and can't find anybody who has had this same issue.

Car runs awesome and pulls hard at all rpm's and throttle positions all the way to red line in all gears. The problem is after WOT runs many times it starts sputtering after I let off the gas and start to slow down. Sometimes it will recover on it's own and sometimes it will sputter out and stall after I stop. After I restart it everything is back to normal and it runs perfect.

A friend hooked his scanner up to it and said the tps sensor readings were off so I got a new tps sensor and installed it and did the reset and it seemed like it was all better. Did a bunch of WOT throttle runs and had no issues. Then after letting it sit for half the day I got it back out and the first WOT run I did it started doing it again.

This is the 4th time now I thought I had it fixed and it keeps coming back.

Replaced O2's, IAC, TPS, plugs, wires, PCV, cleaned MAF. Unplugging the MAF seemed to fix the problem at one time but now it does it whether it's plugged in or not.

Other relevant info. I cleaned the throttle body and changed the water pump last year and have been having idle issues ever since. High idle and the idle is slow to come down after stopping. It wasn't until a couple months later though that this problem came up but my guess is they have to be related. Also, he mentioned that the temps were high when he had the scanner hooked to it but the stock guage was reading normal at 220. The car only gets driven on nice weekends for the most part, hence this year long ordeal.

Also, I'm gonna take it back to him and have him look at it again but he's no expert mechanic, mostly just rebuilds starters and alternators and he used to have a 2000ss with H/C nitrous. Anything in particular I should have him look for on the scan tool?

It's also starting to seem like maybe every time I do a TPS reset it is fine for a few starts and then reverts back.

 

Also, No DTC's other than the secondary AIR. All this time not one. And no vacuum leaks that anybody can find.

 

One other thing that could be relevant is the stft was reading as n/a in one or both banks I think. Neither one of us knew if that was normal or not.

 

the stft's should be reading. It sounds to me like their turned off. My ltft's are turned off and that's the same thing mine says on my scanner.

 

I'm on the original factory tune how could they have gotten turned off? any idea where to start to get them turned back on?

 

Well if your on the factory tune then their not turned off. Maybe his scanner won't read stft's. some of the cheaper ones don't. You can pick up a 0bd2 bluetooth code reader off of fleabay for around 22.00 dollars get the bafx one. and you can use your phone if an android or laptop or tablet if they have bluetooth. and it will read all the parameters that your ecm kicks out. you also need torque pro off of google play. it's only 5.00 dollars. I read all the parameters for my g8 using this setup on a 7" cheap chinese tablet. I always keep an eye on my fuel trims. plus other sensors. Just a thought. And torque pro can read and clear trouble codes. Just a thought. In the meantime, you can probably run to a autoparts store, they will let you use their scanner for free and it will show your stft's if its a decent scanner.

 

I ordered one of those scanners and will start reading up more on how to use it and what to look for until it gets here. I'm guessing the sticky's is the place to go for that but if you have a better suggestion I'm all ears.

The only thing these part stores around here will do for you is pull the codes.

 

I am currently having a similar issue as you. I have a bad injector that isn't working right. I get no DCT's either and went through all the troubleshooting things you did.

Check all of your plugs, look at them closely and see if any seem noticeably different than the others. Here's what I'm getting on my B1 (Driver side). This is what it stays at cruising.

#5 is running rich. I assume after wot pulls it gets bad enough that it makes it difficult for the engine to run, but if I drive it at ~2k or so for a few minutes it clears up.

 

All my plugs looked really good and pretty much identical with a 100k on them. Looked like they could have went another 100k.

As far as those graphs go I don't really have the knowledge yet to know what I'm really looking at it. Where is the problem apparent? At my first glance I would have thought the stft for bank 2 is an issue.

I ran into another thread that leads me to think at least part of my problem has to do with the throttle cracker/follower. Most the time I'm idling about 100 rpm too high. Should be at 550 and it is at 650 in gear. Then when I let off the gas it hangs at about 750-850 until I'm stopped for a second or two then it comes down. Before I cleaned out the throttle body and changed the water pump it never did that. Always came right down to 550.

 

How did you clean the TB/IAC...?

Did you touch any hoses anywhere...?

 

I had the throttle body off when I did the water pump, so I had a bunch of hoses off. Cleaned the throttle body with TB cleaner and the MAF with MAF cleaner.

 

Well I Got my ODB reader and the torque app and think I might have some data to work with.

I actually thought I had the thing fixed again. I disconnected the battery to try to let the PCM relearn with the new TPS sensor and it seemed to have fixed it. Car was running great after several days and many WOT runs and driving at all kinds of speeds and RPM's. Cruise control effect was gone and Idle was really close to 550 for the most part. No sputtering after letting off the gas at all.

One thing that did concern me though was the LTFT's were pretty much always in the +10 to +14 range sometimes they'd come down into the 9's. A little higher at idle and they'd drop a tad while driving at any speed. STFT's were pretty much steady between -3 and +3 no matter how I was driving. The same in both banks for LTFT and STFT. Temps were generally in the 220 range. Also noticed sometime with the foot off the pedal the throttle would read anywhere from 0 to 1.4 occasionally 1.8. Don't know if that is normal for these cars or not.

Then today happened. Getting kind of hot so I started running the a/c for the first time since the battery disconnect and the car was still running great for awhile. If anything even better, idle was holding steady right at 550 where it should be and the LTFT's even dropped a little more down into the 9's for the most part. Even raced a 99Z28 and spanked it pretty easily. Shortly there after I got into some stop and go traffic and the temps climbed up to around 230 and then the idle jumped way up to like 900 and I started getting the cruise control effect and the car started sputtering pretty bad idling or driving. Tried turning it on and off a couple times and even that didn't help it. I think it directly coincided with one of the cooling fans coming on. When this was going on the LTFT's were down in the +2's and +3's for the most part but they would spike quickly up to 18 or 20 hold there for a sec or two and then come back down to 2 or 3 for about 10 seconds then spike again. I also noticed at this time the timing advance was down to 9. STFT's were still in the +-2 or 3 range.

I started a log when this went on but I'm still learning about that and have no idea how to even view it or post yet. I just know there's a log in the app somewhere but I just got home and wanted to get as much info on here as I could before I forget it.

 

One more thing. At one point while it was idling really rough all 4 O2's read 0 for about 5 secs.

 

Update

I think I had two separate problems. First was the throttle plate was adjusted by the dealer when this problem first started with the high idle a year ago. I thought at the time it was odd when they told me they had to adjust the idle screw because I never touched it. They said it wasn't closing all the way. It helped the problem some but it still wasn't normal. Apparently what was happening was that when the throttle body got warm it was expanding and the throttle wouldn't close all the way back to the same spot the TPS was expecting it to. I fixed that by opening it up just a bit and resetting the TPS again. LTFT's down in the +2 to +3 range and the STFT's are as well. Car runs great until the second problem comes into play.

Second problem is something to do with the fans coming on. Right when I hit 228 degrees it starts sputtering. One time it was right as the fan came on and now today it did it again right at 228 and the fan never came on. Seems like something to do with that fan coming on is shorting out the whole ignition system. Is that even possible?

I did see a group of wires that looked like they had melted a tiny bit. Looks like at one point they were exposed against the block. I just noticed today when taking off the throttle body they weren't in the clamp where they should be. Guess I have the dealer to thank for that as well. It's a group that runs out from the injector wiring harness on the passenger side and clamps to the a/c lines and runs down toward the a/c compressor. I'm calling it a day for today and will take a closer look at them on Sunday, I have to go out of town tomorrow. Anybody know if those could possibly be the ones going to the fan?

 

Solved:

It ended up being the MAF sensor. Most the time it was reading fine but occasionally only under certain conditions it would read wrong. Replaced it with a GM one and car is running perfect. Took some time for it to relearn everything under all the different loads and get the idle back down but everything is perfect now except for a radiator crack that just showed up. Now I have to replace that.

 

Was it the original MAF...?

 

Glad it worked out and you updated the thread!

Btw, when you unhooked the MAF and reverted to SD, it should have been okay then?

 

I was still having the issue intermittently with the MAF unhooked. That's what made it so hard to find the cause. I know that's not supposed to be the case but the guy that helped me hunt it down said he's seen it before. Take it for what it's worth. At first when the problem would arise when I unhooked the MAF it would go away but then after doing it for awhile unhooking the MAF didn't help anymore. I was actually on the way to the dealer one day to buy a MAF and it started doing it on the way there and when I unhooked it it still did it so I turned around and went home. Go figure.

 

Yes, original with about 135K on it.