Random drivability issue getting much worse, need help with diagnosis.
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Supreme Member
iTrader: (9)
Joined: Sep 2001
Posts: 2,984
Likes: 37
From: North Central Indiana
Car: 86 IROC
Engine: 383
Transmission: TKO 600
Axle/Gears: 3.54 Dana 44 IRS
Random drivability issue getting much worse, need help with diagnosis.
Hey guys, need some suggestions here. I’m having a problem that normally should probably go to the TPI board, but since I’m using TunerPro to datalog during the problem, I think it applies here. I also have questions relating to what TunerPro is showing me.
I’ve put tons of miles on my car this summer and it always runs great. I’ve done the tuning myself and I’ve been happy with the car where it is for 2 months now.
Last night the car started to start harder than normal and it didn’t want to pull out like it normally does (stick shift car). As the night went on and I went home from my friends house the problem got worse. The car ran fine, then out of the blue (steady state 35mph low load) my wideband shows an AFR of 11 and the car starts to hesitate, then it will snap out of it after 2-3 seconds. As I got on the highway to go home more issues arose. At first it would go into highway mode and be fine, then it would randomly peg the WB lean, then go back to normal (16.3 for highway mode) then it would go way fat, up to 10:1. As I got closer to home it would not go into highway mode at all, it would just stay at 14.7, then go way rich, then return to 14.7.
Once I got home I hooked up my laptop with TunerPro and datalogged it. I can watch the O2 values go all over the place, but I can’t find any other sensor input that would cause it. The TPS, CTS, MAF, all appear normal. When the wideband goes nuts, it does not seem to be caused by any of the other sensors.
The only “fishy” things I can find is that during highway when I was datalogging, it said the target AFR was 15.6, which is not specified anywhere in my .bin. I have no idea where it is getting that number.
I thought about doing a free air calibration on my WB, but the car will barely start and idle now, so I know its not the wideband, it has to be something the ECM uses to run the car in open loop like the MAF, TPS, CTS, what else am I forgetting about? The next thing I’ll do is clean the MAF and see if that helps. If that doesn’t fix it I don’t know what else to do. Just for giggles this morning I re-burnt the program to a different chip and tried starting the car. It would barely start, and was slobbering at an AFR of 11.5 and filled my garage with a fuel haze because it was so rich.
I was banking on my datalogs showing something and they didn’t. I’ll look over them again at lunch today and see if I can find anything.
I’ve put tons of miles on my car this summer and it always runs great. I’ve done the tuning myself and I’ve been happy with the car where it is for 2 months now.
Last night the car started to start harder than normal and it didn’t want to pull out like it normally does (stick shift car). As the night went on and I went home from my friends house the problem got worse. The car ran fine, then out of the blue (steady state 35mph low load) my wideband shows an AFR of 11 and the car starts to hesitate, then it will snap out of it after 2-3 seconds. As I got on the highway to go home more issues arose. At first it would go into highway mode and be fine, then it would randomly peg the WB lean, then go back to normal (16.3 for highway mode) then it would go way fat, up to 10:1. As I got closer to home it would not go into highway mode at all, it would just stay at 14.7, then go way rich, then return to 14.7.
Once I got home I hooked up my laptop with TunerPro and datalogged it. I can watch the O2 values go all over the place, but I can’t find any other sensor input that would cause it. The TPS, CTS, MAF, all appear normal. When the wideband goes nuts, it does not seem to be caused by any of the other sensors.
The only “fishy” things I can find is that during highway when I was datalogging, it said the target AFR was 15.6, which is not specified anywhere in my .bin. I have no idea where it is getting that number.
I thought about doing a free air calibration on my WB, but the car will barely start and idle now, so I know its not the wideband, it has to be something the ECM uses to run the car in open loop like the MAF, TPS, CTS, what else am I forgetting about? The next thing I’ll do is clean the MAF and see if that helps. If that doesn’t fix it I don’t know what else to do. Just for giggles this morning I re-burnt the program to a different chip and tried starting the car. It would barely start, and was slobbering at an AFR of 11.5 and filled my garage with a fuel haze because it was so rich.
I was banking on my datalogs showing something and they didn’t. I’ll look over them again at lunch today and see if I can find anything.
Thread Starter
Supreme Member
iTrader: (9)
Joined: Sep 2001
Posts: 2,984
Likes: 37
From: North Central Indiana
Car: 86 IROC
Engine: 383
Transmission: TKO 600
Axle/Gears: 3.54 Dana 44 IRS
Re: Random drivability issue getting much worse, need help with diagnosis.
I found the problem tonight. The diaphram on my fuel pressure regulator ruptured and was dumping fuel into my intake plenum via the vaccum line.
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