hey guys, maybe you help me out. i had the car out the other day and everything seemed fine. i parked it for an hour and had a hard time starting. i had to give it gas to keep it running when just idling. went out this morning and again it was hard to start. it idles rough and i have to give it gas to keep it running. the engine light also came on and stays on. anyone have any ideas? could it be the tps? thanks :aggressive:
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hard start and rough idle
- Thread starter bob89tta
- Start date
When mine did that, it was the MAF sensor. I bought a replacement which worked for about a week - I understand these have a high failure rate. I went with an LT1 style replacement MAF with the translator and have never had another problem.
thanks for the ideas. i just ran the car and looked at the scanmaster. the car is very hard to start and really rough idle. the tps at idle is .08 is there any adjustment on this. i've moved it back and forth and i don't see any difference. could the tps be bad? the scanmaster comes up with trouble code 22 which i believe is bad/misadjusted sensor. any help would be appreciated
thanks for your answers but i have another question. when the car is not running what should the tps be set at when using the scanmaster as a guide. i've pretty much moved the tps all around and nothing seems to change so i have ordered a new tps. i cannot get the car to idle without my foot on the gas. code 22 comes up on the scanmaster which could be a bad tps. i'm new at this turbo game so any and all help is greatly appreciated. i got rid of my big block camaro to get this car but i'm lost with all the sensors and computer stuff
WS6
Stay thirsty my friends
No sweat...we all need to start somewhere and computer controlled cars are your future.
To answer your question directly mine usually sits at .38V engine off-key on. When it's idling it sits at .40V. Anything lower than .42-.44 should be good. any thing over and it may want to to tip in to PE mode.
An indirect answer is you need a crash course on ECM controlled GM cars and a good book is http://www.amazon.com/gp/product/076030422X
Allthough geared primarily towards TBI and TPI N/A engines it will get you familiar with the computer(ECM) and how it uses sensors in GM cars of the era. It will explain closed loop vs. open loop operation and the troubleshooting of the system. Most if not all of it pertains to the turbo V6 as a TPS is TPS and MAF is a MAF in either world,so to speak.
And it's a quick read...second I would advise getting a 1989 TTA service manual supplement book. Usually it can be bought with the complete 1989 F body manual but all you need is the supplement manual. It covers all the stuff the LC2 engine needs.
To answer your question directly mine usually sits at .38V engine off-key on. When it's idling it sits at .40V. Anything lower than .42-.44 should be good. any thing over and it may want to to tip in to PE mode.
An indirect answer is you need a crash course on ECM controlled GM cars and a good book is http://www.amazon.com/gp/product/076030422X
Allthough geared primarily towards TBI and TPI N/A engines it will get you familiar with the computer(ECM) and how it uses sensors in GM cars of the era. It will explain closed loop vs. open loop operation and the troubleshooting of the system. Most if not all of it pertains to the turbo V6 as a TPS is TPS and MAF is a MAF in either world,so to speak.
And it's a quick read...second I would advise getting a 1989 TTA service manual supplement book. Usually it can be bought with the complete 1989 F body manual but all you need is the supplement manual. It covers all the stuff the LC2 engine needs.
thanks for the info on the tps setting. i just set it to .38 key on -engine off. tried to start but still same problems. must give it gas to get it running and keep running. i am going to change tps in a couple of days. when i have someone over who can help me i will check fuel pressure and see what it is reading. i can't keep the car running and check things without a friend to keep his foot on the gas to keep it running. thanks again,Bob
WS6
Stay thirsty my friends
There are 3 things that work together to establish idle(in the simplistic sense) The minimum air setting,the TPS and the IAC (idle air control motor) The minimum air setting is the screw on the left side of the throttle body,opposite the TPS's drift pin.It establishes how far open the throttlevalve (blade) is open, much like the curb idle screw on a carburetor. The TPS which lets the ECM know where the base setting is for idle all the way up through WOT (4.5 ish voltage). The IAC is a stepper motor which regulates how much bypass air to let in around the throttle valve and consequently how much fuel to add too via the ECM.
You kinda have to juggle 3 adjustments at a time,per say, to get the proper IAC counts. First I set the minimum air screw,then check to see how far I've thrown off the TPS base setting. red-adjust the TPS and then check the IAC counts. Then repeat as necessary to regain the ECM's control of the IAC motor.
The IAC is what I use as my targeted sensor to make right and adjust the others to make the IAC counts within a reasonable range. I shoot for 25, but I don't scoff at 40-50 counts as wrong either.
Two things need to happen first before you try adjusting anything. 1, the car needs to be warmed up and 2, you need a scantool,like scanmaster, to see the IAC counts and TPS voltage.
I'm gonna go out on limb here and say you have an IAC problem as it seems that the ECM has lost control of the IAC motor and can't get enough air around the throttle blade...for whatever reason.
The TPS is easy to check as it should base at .38-.42 and wide open at 4.5-4.8V and you can check that with a multimeter...or scanmaster. Of course there maybe a dead spot in it but you won't know till it's out on the road and you incur a whole new set of wierd problems.
The IAC is another story, it's a fragile little devil that steps a pintle in or out a certain number of counts or steps and is made of plastic parts inside. It's a common mistake to pull it out and "clean" it and find that you have manhandled it too much and know it won't step properly. You cannot push the pintle in or pull it out as it strips those gears inside.
Read this http://www.vortexbuicks-etc.com/tuning.htm#IAC (Idle Air Control) Adjustment and have a go at getting your car to start and idle properly. This is a good newbie project and resist,if you can, throwing parts at it.
...
You kinda have to juggle 3 adjustments at a time,per say, to get the proper IAC counts. First I set the minimum air screw,then check to see how far I've thrown off the TPS base setting. red-adjust the TPS and then check the IAC counts. Then repeat as necessary to regain the ECM's control of the IAC motor.
The IAC is what I use as my targeted sensor to make right and adjust the others to make the IAC counts within a reasonable range. I shoot for 25, but I don't scoff at 40-50 counts as wrong either.
Two things need to happen first before you try adjusting anything. 1, the car needs to be warmed up and 2, you need a scantool,like scanmaster, to see the IAC counts and TPS voltage.
I'm gonna go out on limb here and say you have an IAC problem as it seems that the ECM has lost control of the IAC motor and can't get enough air around the throttle blade...for whatever reason.
The TPS is easy to check as it should base at .38-.42 and wide open at 4.5-4.8V and you can check that with a multimeter...or scanmaster. Of course there maybe a dead spot in it but you won't know till it's out on the road and you incur a whole new set of wierd problems.
The IAC is another story, it's a fragile little devil that steps a pintle in or out a certain number of counts or steps and is made of plastic parts inside. It's a common mistake to pull it out and "clean" it and find that you have manhandled it too much and know it won't step properly. You cannot push the pintle in or pull it out as it strips those gears inside.
Read this http://www.vortexbuicks-etc.com/tuning.htm#IAC (Idle Air Control) Adjustment and have a go at getting your car to start and idle properly. This is a good newbie project and resist,if you can, throwing parts at it.
...
just a quick update on the hard start and rough idle problem. i have to thank you guys for some great advice. ws6 showed a lot of patience with me and i really appreciate it. i took your advice and adjusted the tps to 38 and played with the iac a little. running much better(not perfect) and i am able to start without giving it gas and it stays running without keeping my foot on the gas. i think i will put new plugs because i may have fouled them trying to get the car running. i must fine tune the iac setting and then tps, however right now idle is high at 1050 in park. do you know what will lower rpms? thanks for all the great help, Bob
WS6
Stay thirsty my friends
I would try trimming that IAC counts number using the minimum air screw adjustment again.
The ECM controls idle speed (RPM) and for some reason it has either lost control of the IAC or there is a flag set that the ECM is responding to, such as it believes the A/C is on or it isn't seeing the coolant temp up yet.
First though....For shits and giggles, try unhooking the battery for minute or so and thereby forcing the ECM to relearn the IAC and idle speed target RPM.
...
The ECM controls idle speed (RPM) and for some reason it has either lost control of the IAC or there is a flag set that the ECM is responding to, such as it believes the A/C is on or it isn't seeing the coolant temp up yet.
First though....For shits and giggles, try unhooking the battery for minute or so and thereby forcing the ECM to relearn the IAC and idle speed target RPM.
...
