Well guys its been a while since my last post, so hear is the problem. For a while i have been trying to figure out what the problem is and i have even took it to a mechanic and he told me to change out the IAC. so i did, at first it was ok but then it the rpm's shot up between 1000 to 1500 and i even disconnected the battery to clear the codes. With the old IAC it would do that shoot up to 1000-1500 rpms and would not go down and for a while the rpms would not do down so i would have to throw it into neutral to slow down. So what i did was i took off the new IAC and put the old one back on cuz it seemed the old one worked better. So i dont think the IAC is not the problem. Can anyone help me out.

 

Goat,

You disconnected the battery to clear the error codes, but exactly what error codes were you getting?

Have you checked the CTS resistance at various temperatures? A CTS that intermittently goes open-circuit as the temperature changes could cause the target idle to climb to 1500 - the RPM level it should be at when a cold engine is first started.

Just curious about the codes...

 

yes, i have checked it and i have changed it twice cuz at first I thought that was the problem. as for codes i think it gave a 15,21, 32, 36,44

 

Hello Greygoat,

Your code 15 is for the coolant temp sensor circuit and it is possible that the sensor is not the problem, but the wire harness somewhere. Code 21 is the throttle position sensor. Code 32 is the EGR. code 36 is the MAF burn-off circuit. Just a thought!!!!!!!

The Trickster!!!!!!!!!!!!

 

dont know i have to check again to make sure what are the codes

 

Vacuum leak after the TB maybe?

 

Check the throttle body gasket or intake gasket. TBI cars idle extremely high with a bad gasket.

 

I had a similar problem, especially at start-up. Sometimes it would idle down, but most of the time it would go back to fast idle. I hear ya about having to throw it into N to slow down. Coincidently, my front right caliper was sticking. I scorched both front rotors beyond repair. I took it to my mechanic and he got his buddy from the shop nextdoor who knew more about the Q-jets. Turns out that it WAS switching back to fast idle while the engine was already warmed up. A new choke thermostat cleared it right up. I'm assuming yours is carbed. I got mine for $50, but I needed a quick fix. If I had the luxury of parts searching I probably could've found a better price. The odd thing though is that the old choke thermostat didn't look broken or anything. But, enough said, that fixed it. Hope it helps.

 

The same thing will happen with an incorrect PCV valve.

 

Well, I did check the TBI gasket when i took off the IAC and it was still good. What i notices was that in warm temp. it would idle high and the check engine lite turned on. Now that the weather is cooler the Idle has gone down to normal sometimes. So what sensor is causing it to do that.

 

possibly the engine coolant temp sensor

 

I have changed the coolant sensor twice and im not sure what the problem is. Im confused

 

any suggetions

 

have you swapped in another computer? If you have tried most of the sensors, checked for vacuum leaks and such, thats where i would go next. There are so many things that will make an engine run bad/strange. It's just basic mechanics, after that you have to look at the computer and 2ndry components.
Jason

 

I have changed the computer once before, could it have messed up again?

 

Why did you change it before? Did it run any different/better after you changed it?

 

I went and reread your original post. Have you cleaned the throttle body? I mean have you taken it off the car, took throttle body cleaner and blew through all the holes? With TBI, as with any other fuel injection system, there is whats called a minmum airflow requirement. The engine needs so much air with the throttle shut, then if it needs more, say when its cold the IAC motor should take care of it. If the throttle body, around the blades, is all gunked up, the computer will compinsate and kick the IAC motor up a little to get the air. After you put the IAC motor on, did you go and drive it about 45mph for 3-4 miles? This resets the IAC motor. It still sounds like a bad vacuum leak, but without being there I can't tell. Also, this happened to me a few weeks ago on a truck with TBI. It idled really high. It ended up being the EGR gasket, it was sucking air in through that. Also a bad EGR valve will do that, disconnect and plug the vacuum line and see if that changes it. It is the car burning any oil? If so it is possible the it's sucking air through the bottom of the intake and not the top. Does it always idle up that high? Also, has the throttle linkage been bent? You might want to take the throttle off at the TBI and see if its holding it open some, thats happened to me before too. These are just some idea's I thought of, maybe one of them will help.
Jason

 

yes i have taken off the TB and cleaned it out and blew air through it and i the linkage is not bent. I will check the egr and intake for any leaks, thanks i will let u know what happens