ruff idle at start up

[joshwilson3]

I have an 89 auto. A couple of times. Once was from a cold start, and the other was when it had sat for 30 minutes. I start it and it idled real ruff dying or trying to die. So, I had to raise the RPM's to keep it from dying for like 10-15 seconds, then all was fine.

It has just done this twice. Any ideas on what could/would cause that?

I've replaced the spark plugs last year. The wires, cap, and rotor have been replaced by the PO. Last year I pulled the throttle body off to clean it. And I think the IAC had been replaced by the PO because it was very clean. I reset the TPS when I put the throttle body back on. The PO also had the injectors replaced and the FPR. I've replaced the PVC, knock sensor, and 3-way check valve. The timing has been checked.

 

[aklim]

Did you take off the IAC housing to clean it?

Did you reset the IAC? You can use the FSM method but I am not sure how it works with modified motors. I turn off all devices and leave the engine run. When it is in closed loop, I hook up the scantool and adjust the min idle. Target IAC count is 15-20 counts. If the IAC counts are higher than target, it indicates that there isn't enough air coming in and the IAC is compensating. That means I turn the screw in. Then I rev it up and see what it comes to when it settles down. If it is low, I close the screw.

If the timing is spot on and the IAC housing is clean then I would reset the IAC and then check the TPS. With the engine off, I would see what it reads at on the scantool. Increase throttle pressure slowly and evenly and watch. There should be NO dead spots. The TPS voltage must rise slowly and evenly.

What injectors were used and what fuel pressure? Has the chip been reset for the new injectors?

 

[joshwilson3]

Did you take off the IAC housing to clean it?

Did you reset the IAC? You can use the FSM method but I am not sure how it works with modified motors. I turn off all devices and leave the engine run. When it is in closed loop, I hook up the scantool and adjust the min idle. Target IAC count is 15-20 counts. If the IAC counts are higher than target, it indicates that there isn't enough air coming in and the IAC is compensating. That means I turn the screw in. Then I rev it up and see what it comes to when it settles down. If it is low, I close the screw.

If the timing is spot on and the IAC housing is clean then I would reset the IAC and then check the TPS. With the engine off, I would see what it reads at on the scantool. Increase throttle pressure slowly and evenly and watch. There should be NO dead spots. The TPS voltage must rise slowly and evenly.

What injectors were used and what fuel pressure? Has the chip been reset for the new injectors?

Yes, I had the IAC out when I pulled the throttle body off. The IAC was clean like brand new. But I cleaned it anyways while it was out.

I thought the IAC reset itself?

The TPS should be fine when I checked it last. This engine is stock. And I don't have access to a scantool.

The PO has messed with the minimum idle screw as the plate has been removed. But I've had it for 3 years no problems. Just at the end of last year, after it sat for a little while it was a hard start. Then several months later, it happened once after it had sat for 30 minutes.

The PO put in Accel injectors. And I believe last I checked the fuel pressure, it was 34. Which is supposed to be in the normal range 34-39. I doubt a chip has been reset, I've never heard of people resetting the chip when they replace the injectors.

 

[aklim]

Yes, I had the IAC out when I pulled the throttle body off. The IAC was clean like brand new. But I cleaned it anyways while it was out.

I thought the IAC reset itself?

The TPS should be fine when I checked it last. This engine is stock. And I don't have access to a scantool.

The PO has messed with the minimum idle screw as the plate has been removed. But I've had it for 3 years no problems. Just at the end of last year, after it sat for a little while it was a hard start. Then several months later, it happened once after it had sat for 30 minutes.

The PO put in Accel injectors. And I believe last I checked the fuel pressure, it was 34. Which is supposed to be in the normal range 34-39. I doubt a chip has been reset, I've never heard of people resetting the chip when they replace the injectors.

You should also remove the housing to make sure all the passages are clean.

Not sure about that. Depending on how far off it might be able to compensate or not

Autozone might

Hard to say. It might just happen to find the right conditions to cause the problem. Have you checked for a vacuum leak by spraying the hoses with brake cleaner?

Should be 45 with the hose off. Yes you have to reprogram the chip if the injector size changes.

 

[joshwilson3]

You should also remove the housing to make sure all the passages are clean.

Not sure about that. Depending on how far off it might be able to compensate or not

Autozone might

Hard to say. It might just happen to find the right conditions to cause the problem. Have you checked for a vacuum leak by spraying the hoses with brake cleaner?

Should be 45 with the hose off. Yes you have to reprogram the chip if the injector size changes.

What housing are you referring to? I had the throttle body all apart last year when I cleaned it.

How are you supposed to reset the IAC? All I did was rock the needle back in all the way. Bolt it down. Put the throttle body back on. Then I think I just put it to run, then shut it off. Then I reset the TPS.

I haven't checked for a vacuum leak with brake cleaner.

I don't think I'm gonna buy a scan tool.

 

[aklim]

What housing are you referring to? I had the throttle body all apart last year when I cleaned it.

How are you supposed to reset the IAC? All I did was rock the needle back in all the way. Bolt it down. Put the throttle body back on. Then I think I just put it to run, then shut it off. Then I reset the TPS.

I haven't checked for a vacuum leak with brake cleaner.

I don't think I'm gonna buy a scan tool.

The TB has a housing below where the IAC screws into. I take that out and clean it.

I wouldn't have rocked it back in. When I clean my TB, I take the bottom housing off. 5 or 6 torx bolts. That way I can get to clean more passages.

You should do that.

They might lend you one

 

[joshwilson3]

The TB has a housing below where the IAC screws into. I take that out and clean it.

I wouldn't have rocked it back in. When I clean my TB, I take the bottom housing off. 5 or 6 torx bolts. That way I can get to clean more passages.

You should do that.

They might lend you one

Like I said, I had the throttle body all apart and cleaned it. So, that has been done.

Everyone says to rock the needle back in. They say that is how you are supposed to put the needle back into the IAC or you will tear something up.