Stumble Just off Idle
#21
Team Owner
I was wondering the same thing.
Any reading I have done on the tps is that it supposed to be set at .54
I have also read (it might not be right) that if it is set too high it messes with the ecu because you are telling the ecu your foot is depressing the pedal. personally i'd be getting an adjustable tps and putting it at .54
i suppose its possible that the 90 L98 does not have that requirement whereas my 85 and 87 do.
Any reading I have done on the tps is that it supposed to be set at .54
I have also read (it might not be right) that if it is set too high it messes with the ecu because you are telling the ecu your foot is depressing the pedal. personally i'd be getting an adjustable tps and putting it at .54
i suppose its possible that the 90 L98 does not have that requirement whereas my 85 and 87 do.
#22
Team Owner
But the car is how old again? You have no idea what fuel was going through it. Yes, we all have gotten a batch of bad fuel or so so fuel. It isn't horribly expensive and probably should be changed after 5 to 10 years at the outside. Even fine wine goes bad after a bunch of years.
#23
Racer
Thread Starter
I was wondering the same thing.
Any reading I have done on the tps is that it supposed to be set at .54
I have also read (it might not be right) that if it is set too high it messes with the ecu because you are telling the ecu your foot is depressing the pedal. personally i'd be getting an adjustable tps and putting it at .54
i suppose its possible that the 90 L98 does not have that requirement whereas my 85 and 87 do.
Any reading I have done on the tps is that it supposed to be set at .54
I have also read (it might not be right) that if it is set too high it messes with the ecu because you are telling the ecu your foot is depressing the pedal. personally i'd be getting an adjustable tps and putting it at .54
i suppose its possible that the 90 L98 does not have that requirement whereas my 85 and 87 do.
go to the garage, hook-up my scanner and write down the acceptable idle voltage range, I 'think' it's around 0.65 to 0.96V but I will check.
UPDATE: The acceptable range for closed throttle is 0.36V to 0.96V
Mick
Last edited by QZRBLU; 09-23-2016 at 04:03 PM.
#24
#25
Racer
Thread Starter
I just hooked up the scanner (Snap-On MT2500) and warmed the engine up and watched it go closed loop. O2 mv reading in closed loop is 105mv and it jumps instantly to 805mv when I blip the throttle and make it rich. Idle IAC is 69 and Learned IAC is 65. Desired idle (warmed in the garage) is 738 and actual idle is 750. The acceptable closed throttle TPS range is 0.36V to 0.96V, actual closed throttle is 0.80V and WOT is 4.42V It did NOT stumble today.
#26
Racer
Thread Starter
#27
Racer
Thread Starter
Every drop of fuel through this engine was pumped by me and until I moved to AZ, every drop was Shell premium and we just got a new Shell station 1/2mile from the house. Over here in AZ I've been using Quick Trip Premium (Tier 1 fuels). I ordered a new Delco O2 sensor just because of the age, even though the original responds instantly.
Mick
Mick
#28
Team Owner
Every drop of fuel through this engine was pumped by me and until I moved to AZ, every drop was Shell premium and we just got a new Shell station 1/2mile from the house. Over here in AZ I've been using Quick Trip Premium (Tier 1 fuels). I ordered a new Delco O2 sensor just because of the age, even though the original responds instantly.
Mick
Mick
#29
Safety Car
I just hooked up the scanner (Snap-On MT2500) and warmed the engine up and watched it go closed loop. O2 mv reading in closed loop is 105mv and it jumps instantly to 805mv when I blip the throttle and make it rich. Idle IAC is 69 and Learned IAC is 65. Desired idle (warmed in the garage) is 738 and actual idle is 750. The acceptable closed throttle TPS range is 0.36V to 0.96V, actual closed throttle is 0.80V and WOT is 4.42V It did NOT stumble today.
#30
Racer
Thread Starter
I do not watch the distillation process but I DO buy top tier fuel.
I had the car out for a short trip this morning, no stumble even after it got warmed-up in closed loop. I have a new O2 sensor coming tomorrow and the car is up on the lift until I get that replaced. I will also pull the IAC to see if there is any carbon build-up.
Mick
Last edited by QZRBLU; 09-24-2016 at 04:14 PM.
#31
Racer
Thread Starter
You're running rich for the o2 to be at 800. It should be flagging back and forth which indicates the computer is making corrections to keep it at the correct air/fuel ratio. Your IAC is trying to compensate by opening up to allow more air in. You need to find out WHY it's dumping fuel. TPS setting for my 86 is .54 at idle.
It is constantly switching rich/lean while it is warm. I can cause it to go Rich blipping the throttle. Your TPS is different and NOT auto-calibrating like my '90. L98's with a MAF sensor like yours have an an adjustable TPS, I don't.
MIck
Last edited by QZRBLU; 09-24-2016 at 05:41 PM.
#33
Team Owner
No AK,
I do not watch the distillation process but I DO buy top tier fuel.
I had the car out for a short trip this morning, no stumble even after it got warmed-up in closed loop. I have a new O2 sensor coming tomorrow and the car is up on the lift until I get that replaced. I will also pull the IAC to see if there is any carbon build-up.
Mick
I do not watch the distillation process but I DO buy top tier fuel.
I had the car out for a short trip this morning, no stumble even after it got warmed-up in closed loop. I have a new O2 sensor coming tomorrow and the car is up on the lift until I get that replaced. I will also pull the IAC to see if there is any carbon build-up.
Mick
#34
Racer
Thread Starter
UPDATE: I've had the car out several times between storms and I noticed
no hesitation or stumbling. It MAY be fixed, we will see.
Mick
Last edited by QZRBLU; 05-09-2017 at 09:34 PM.
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antfarmer2 (09-26-2016)
#35
UPDATE: New O2 sensor installed and IAC motor removed to check for build-up on pintle. Pintle was dark but had no build-up, all throttle passages were clean, even under the top cover. It's been raining here most of the day, so no test drive today. I will hook-up my scanner and do a test when this rain blows out of the area, maybe tomorrow.
Mick
Mick
#36
Team Owner
#37
Racer
Thread Starter
#38
Team Owner
But if you sprayed carpet shampoo and drove around, it might clean out your inside too.
#39
Team Owner
After seeing that C4 last week driving in the storm with the top down, I kinda got addicted to seeing things like that. Don't ask me why he did it. If I were driving, regardless of what the weatherman says, I will have my top on and if I took it off, it will be in the back. This guy was driving down the highway with the top off in the storm. Even the bikers have enough sense to hide under a bridge or pull off somewhere dry.