Troubleshooting Issue - High Idle (2400 RPM) and Rich

[jshilli1]

After a disassemble / reassemble I'm having the following problem-

When I start the car, it idles at 2000 RPM. The RPM's then slowly creep up 25 at a time to 2375-2425 (per scanmaster). IAC moves to 140 after reset. Once the car hits O/L, it spews clouds of black smoke, super rich.

Before this the car was running great and idled at 800-850 with TurboTweak chip. I had the cam sensor out and reset it, I think either the IAC, cam sensor, or the MAF are the problem. Readings are as follows-

TPS- is at .30 with the throttle stop screw backed out completely, the idle was previously setup with the screw in about 1 turn for TPS at .42. I have tried starting at range of TPS from .30 to .60 and the result is te same. The MAF is reading 18 at idle, and previously was 05-06 at idle. I have followed the IAC reset procedure- it still goes back to 140. I checked the throttle linkage for any binding, but if the throttle was "stuck" I would think the TPS should reflect that.

At this point I'm just looking for a little guidance... I'm planning to do the IAC reset and block it off and see if I can get it to idle that way, to rule out the IAC as a possibility. Are there any other tests for the IAC?

Lastly, would the cam sensor being mis-adjusted cause behavior like this? I think the air is coming from somewhere so it must be the IAC or the MAF.

 

[PhilM]

You can unplug cam sensor and ECM will put engine in "batch fire" so you can tell if that is the likely cause. If your sensor isn't set properly, unplugging it will make it run a little better since batch is less discriminate. If it is set properly, then putting into batch would make it run worse. I doubt the cam sensor would cause that bad of a problem, but who knows... I would start with the "variables" that you would have changed since it ran good before. Did you remove/reinstall the chip btw?

Phil

 

[TurboDave]

After a disassemble / reassemble I'm having the following problem-

When I start the car, it idles at 2000 RPM. The RPM's then slowly creep up 25 at a time to 2375-2425 (per scanmaster). IAC moves to 140 after reset. Once the car hits O/L, it spews clouds of black smoke, super rich.

Before this the car was running great and idled at 800-850 with TurboTweak chip. I had the cam sensor out and reset it, I think either the IAC, cam sensor, or the MAF are the problem. Readings are as follows-

TPS- is at .30 with the throttle stop screw backed out completely, the idle was previously setup with the screw in about 1 turn for TPS at .42. I have tried starting at range of TPS from .30 to .60 and the result is te same. The MAF is reading 18 at idle, and previously was 05-06 at idle. I have followed the IAC reset procedure- it still goes back to 140. I checked the throttle linkage for any binding, but if the throttle was "stuck" I would think the TPS should reflect that.

At this point I'm just looking for a little guidance... I'm planning to do the IAC reset and block it off and see if I can get it to idle that way, to rule out the IAC as a possibility. Are there any other tests for the IAC?

Lastly, would the cam sensor being mis-adjusted cause behavior like this? I think the air is coming from somewhere so it must be the IAC or the MAF.

Sounds like you're operating under some serious misconceptions!! The idle stop screw ISN'T. It had nothing what so ever to do with adjusting the tps or idle rpm. It is for setting the minimum air bleed setting, which is a complicated way to say "adjusting IAC number".
You're going to have to start from scratch.

Set the air bleed screw in so that you can only see one thread on the opposite side of the block the screw is in. Savy?
Now, properly adjust the TPS by loosening the two screws that hold it in place, pull it forward (for max WOT setting) tighten both screws just enough to hold it in place, and loose the top screw, adjust the nose of the TPS up or down to achieve a .40 value at closed throttle. Anything below .36, or above .46 are unacceptable.

From this point you can use the bleed screw to achieve suitable IAC numbers at idle, usually 5-30 is best, but if you adjust it, you'll have to go back and readjust the tps, they interact.
"resetting" the IAC accomplishes nothing really, unless it's properly adjust with the air bleed adjustment.

Cam sensor would have nothing to do with this behavior, but a huge air leak would. Everything get tightened down good? LIke the vacuum block on the throttle body? All hoses clamped thight?

 

[jshilli1]

Sounds like you're operating under some serious misconceptions!! The idle stop screw ISN'T. It had nothing what so ever to do with adjusting the tps or idle rpm. It is for setting the minimum air bleed setting, which is a complicated way to say "adjusting IAC number".
You're going to have to start from scratch.

Set the air bleed screw in so that you can only see one thread on the opposite side of the block the screw is in. Savy?
Now, properly adjust the TPS by loosening the two screws that hold it in place, pull it forward (for max WOT setting) tighten both screws just enough to hold it in place, and loose the top screw, adjust the nose of the TPS up or down to achieve a .40 value at closed throttle. Anything below .36, or above .46 are unacceptable.

From this point you can use the bleed screw to achieve suitable IAC numbers at idle, usually 5-30 is best, but if you adjust it, you'll have to go back and readjust the tps, they interact.
"resetting" the IAC accomplishes nothing really, unless it's properly adjust with the air bleed adjustment.

Cam sensor would have nothing to do with this behavior, but a huge air leak would. Everything get tightened down good? LIke the vacuum block on the throttle body? All hoses clamped thight?

I think I was using the wrong terminology. Previously the IAC/TPS were adjusted correctly with the throttle stop/ air bleed screw backed out completely. IAC's were around 25-30 idle and TPS .42 ish. Does IAC at 140 produce a good sized air leak? I'm not sure how much the IAC screws in/out- it looks like it has a fair amount of travel. At zero it should be fully extended into the port in the manifold, correct?

I think everything is tightened down good, or at least it was before. I guess I'll get out the WD 40 and start hunting for leaks-

 

[jshilli1]

You can unplug cam sensor and ECM will put engine in "batch fire" so you can tell if that is the likely cause. If your sensor isn't set properly, unplugging it will make it run a little better since batch is less discriminate. If it is set properly, then putting into batch would make it run worse. I doubt the cam sensor would cause that bad of a problem, but who knows... I would start with the "variables" that you would have changed since it ran good before. Did you remove/reinstall the chip btw?

Phil

Have not removed the chip- its sounding like I have a massive air leak somewhere. I was thinking the air leak is causing the high idle and the cam sensor causing the rich/unburned fuel (pooling due to firing not at 25 BTDC). I'll try putting it in batch fire to remove a variable. Thanks!

 

[PhilM]

Yea, like said before, i dont think cam sensor would cause a problem like this. Test for leaks around intake TB, couplings. You can use ether sprayed around cracks to see a jump in idle if there is a leak, although this sounds like a pretty big leak.

If it is really rich do not continue to run it, it will wash out cylinder walls and thin oil. Be sure to give it a nice oil change when you find the problem.

Phil

 

[jshilli1]

Yea, like said before, i dont think cam sensor would cause a problem like this. Test for leaks around intake TB, couplings. You can use ether sprayed around cracks to see a jump in idle if there is a leak, although this sounds like a pretty big leak.

If it is really rich do not continue to run it, it will wash out cylinder walls and thin oil. Be sure to give it a nice oil change when you find the problem.

Phil

Thanks everyone for your help- turned out to be the IAC was stuck. I picked up a new one for $30. Tested the old one by unscrewing it, plugging it in, grounding ALDL A-B, turned key on, in diagnostic mode it didn't move (it should completely extend the pintle). The new one actually moved when plugged in during diagnostic mode (advice- don't test in diagnostic mode very long- the pintle will completely unscrew itself).