Hi Guys

My 86 TPI Roc, which i bought new needs some help. It longer starts or run smoothly when cold.. its a total chugging pig! When i start it, it wants to stall and is running very rough. I have to keep giving it gas to keep it going, no check engine light

I have new plugs cap rotor wires on it, a new tps sensor set correctly, new relays on firewall for maf sensor (2) Tried 2 different mafs, and cleaned one out with crc maf cleaner. the cat is clear and the air pump disconnected. It ran the same way before i disconnected it so its not that I have also ran FI injector cleaner through it Dont think it the IAC because it runs rough also

After you drive it a while, it smooths out and will idle when warm. If i shut it off and restart it it will idle and run better

so Oxygen sensor? Its old. What else can it be? Im Stuck

Thanks

 

anybody?

 

o sensor?

 

Probably not o2 sensor. You can drive it without one. You check for any codes?

 

Check your fuel injectors too, very common for one or two to go bad. Ohm them out and report back what you get.

 

ok No codes found yet does a bad o2 make a car rough while cold?

 

I don't think so, but i could be wrong. I think in open loop you are only running on a default setting in your ecm, thus no sensors are really being used.

 

A shorted O2 will cause the engine to run very rich. But it will be worse when warm. Look at the CTS. I recommend using a scan tool to check this out but you can use an ohmmeter too. the CTS should read 3,400 ohms at 70 degrees and 180 ohms at 220 degrees. Definitely check injectors as well.

 

coolant temp sensor? I will check. See first post, why wont it idle when cold? If it was the IAC that was bad, then it would stay running when i put foot on gas, But now i have to race motor (rev) to keep from stalling till warm

If injectors, then y does it run good when warmed up?

 

Coolant temp sensor. The ECM uses it to monitor coolant temperature and it has a dramtic effect on fuel delivery. It's located at the front of the intake. It has one yellow and one black wire to it.

 

I am having a similar problem. It starts like an untuned carb but once warmed up it runs ok. it does need a tune up just finances are extremely tight. I got a lean o2 code that comes and goes when I am driving and gas mileage is horrible 11mpg and I have to drive 55 on the highway to get it.

 

Does anyone have any expireince with incar injector cleaning?

 

lucas injector cleaner. I have always had good results. Pour in the tank.

 

You will be surprised at the mileage difference.

 

Lucas injector cleaner, or some prefer Seafoam, is probably just as good as any in car injector service. For best results, repeat the treatment for two tanks of fuel and then every oil change. Running top teir fuel, such as Chevron or Union 76 is almost as good.

 

well i used seafoam ran smoother when warm but when cold start it wont idle for a while and i just have to keep feathering gas

 

You may want to remove the injectors and have them serviced and flowed.

 

Almost sounds like you are not going into open loop immediately like it is supposed to. Open loop is like a carb car with the choke on. I would suspect a bad ecm, but still look into fuel injectors too. Ohm them with a multimeter. It's easy.

 

Its easy? gimme details how to do it plz...

 

To ohm injectors, simply disconnect each one and use an ohmmeter to measure resistance across the terminals of the injector.

BTW, I would not say that open loop is like a carb with the choke on. On a properly functioning system, the switch between open and closed loop is seamless as the two are indistinguishable to the driver. In fact, due to the single wire(unheated) O2 sensor. It's not uncommon for these early systems to fall out of closed loop after extended idling, due to the O2 sensor cooling.

 

ok checked injectors, they are good changed CTS , seafoamed and redeline sl1 cars runs ok warm but terrible from a cold start. O sensor? ECM?

 

how many ohms am i looking for?

It could be your MAF sensor. Thats what mine was when it was running like that. I changed it and it ran great for a few months, now it wont start... boo. Anyway, the way to check that is to disconnect the MAF and start and run it like that. If it works ok, then thats probably the problem.

 

You can disconnect the MAF and the car will still run? How?

 

With the MAF disconnected, the ECM runs on a default fuel map designed to keep the car going in the event of a MAF failure. Unfortunately, the MAF often fails within range and the ECM doesn't realize that the MAF is reading incorrectly. Therefore it continues to follow the MAF and the car runs like crap.

 

ok i will try this later. I will get to see if this stop the cold star running rough and stalling too. i didd spray the maf with proper cleaner, but if it was dead anyways.....

 

i had a friend at work recently with a tpi 350 in a suburban, which chugged and ran rough when they could get it started, it turned out to be the IAT sensor, have you checked into that yet?

 

iat sensor?

 

its the Intake Air Temperature sensor, my friend said it made her truck run like it was -100* so it was starving, but they changed that and its been running fine ever since