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#1
DrDomm

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I'll preface this by saying that these symptoms started after the car made significant contact with a guardrail on the passenger side.  The motor mounts broke/subframe was bent.

 

Since then, when I cold start the car the idle is around 2000rpm.  After it warms up, it will come down to 900-950.  Likewise, when cold, if I remove the IAC Valve connector it will drop right down.  If I plug it back in, it STAYS down.  Turn the car off, and then restart...back UP at 2000rpm...until it warms up.

 

Aside from subframe/motor mounts, I've swapped...

- Intake manifold

- IAC valve

- Throttle body

- Camshaft position sensor

 

I found a little vacuum hose under the throttle body unplugged, but reconnected that.  I can't find any other leaks.  Ten-Ground does not affect the idle.

 

Any ideas?


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#2
Martinracing98

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It sounds like a vacuum leak to me. Does the high idle hunt at all? Last time I had something like that I misted water around and found a vacuum leak.



#3
Dave D.

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I would put a scan tool on it to see if the ECM is commanding the idle high or trying to lower it via observing the IAC counts/position and commanded idle. That way You can narrow down if the issue is mechanical(vacuum leak) or electrical( an erroneous data input fooling the ECM into commanding the high idle).



#4
DrDomm

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Hmmm...I've scanned it and didn't get any codes.

 

Hunting?...not sure what you mean.  It will run at different rpm, on different days...but usually stays there.

 

I'm thinking its some kind of leak...but I've tried spraying brake cleaner everywhere...that didn't affect rpm.  I completely taped off the air box inlet...and it ran totally fine...didn't even drop rpm.  That can't be right...can it?


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#5
Dave D.

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If there is and erroneous input (bad sensor, weird reading,etc...), the computer doesn't know there is a problem, so no codes are set. The system in our cars is very simple and dumb, so more often than not, most drivability issues without CELs are caused by bad inputs. Diagnostics should be done the old fashioned way(not just plug in a scanner and look for codes) and use schematic, multimeter, test lights, oscilloscopes,etc and use your knoggin.



#6
Bench Racer

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  I completely taped off the air box inlet...and it ran totally fine...didn't even drop rpm.  That can't be right...can it?

Could that mean a masive air leak after the air box inlet???


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#7
OrangeCrush86

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Block off the coolant bypass valve thing? The thermal activated switch that lets more air in when cold.

 

You could try replacing the temperature sensor the ECU reads as well. That will make the car fast idle if it fails.

 

My car has idle issues as well and I have never solved them after at least 12 hours of troubleshooting. I gave up and figure more air is better and just set fuel pressure to get that extra .1 HP :)


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#8
DrDomm

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If there is and erroneous input (bad sensor, weird reading,etc...), the computer doesn't know there is a problem, so no codes are set. The system in our cars is very simple and dumb, so more often than not, most drivability issues without CELs are caused by bad inputs. Diagnostics should be done the old fashioned way(not just plug in a scanner and look for codes) and use schematic, multimeter, test lights, oscilloscopes,etc and use your knoggin.

 

Bad inputs?  Sensors, connectors, and wires?  Oscilloscopes...this is like science...ugh.  OK.

 

Could that mean a masive air leak after the air box inlet???

 

But there is no massive hole.

 

Block off the coolant bypass valve thing? The thermal activated switch that lets more air in when cold.

 

You could try replacing the temperature sensor the ECU reads as well. That will make the car fast idle if it fails.

 

My car has idle issues as well and I have never solved them after at least 12 hours of troubleshooting. I gave up and figure more air is better and just set fuel pressure to get that extra .1 HP :)

 

The IAC Valve?...I've swapped this thing out, as well as the throttle body.  The temp sensor at the back of the head?...that's different too...as I've put a different head on for another problem (long story).

 

I'll keep trying things when I can, and update as well.  Thanks.


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#9
OrangeCrush86

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Bad inputs?  Sensors, connectors, and wires?  Oscilloscopes...this is like science...ugh.  OK.

 

 

But there is no massive hole.

 

 

The IAC Valve?...I've swapped this thing out, as well as the throttle body.  The temp sensor at the back of the head?...that's different too...as I've put a different head on for another problem (long story).

 

I'll keep trying things when I can, and update as well.  Thanks.

 

 

There is a second air valve that has 2 small coolant hoses running to it.


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#10
speedengineer

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Everything sound on the purge side?  Not sure if this would cause your issue, but it's something to look as it could be a source of vacuum leak.  Purge solenoid is functional and connected?  The hit didn't crack the purge canister, all those vacuum lines hooked up correctly, etc? 


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#11
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Domm, wasn't suggesting a massive hole. If you taped off the air box inlet and it ran fine, seems that's telling something. Is your mass air flow sensor clean and tested? 


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#12
steveracer

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Not all brake cleaners are flammable, try checking with carb cleaner or WD-40. 

 

I've made the same mistake.


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#13
DrDomm

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There is a second air valve that has 2 small coolant hoses running to it.

 

Hmmm...I'll take a look...I thought that was the IAC valve under the throttle body...with the 2 coolant lines.

 

Everything sound on the purge side?  Not sure if this would cause your issue, but it's something to look as it could be a source of vacuum leak.  Purge solenoid is functional and connected?  The hit didn't crack the purge canister, all those vacuum lines hooked up correctly, etc? 

 

The purge canister?  The little black plastic can and all the hoses seem fine.  I will keep looking, though.

 

Domm, wasn't suggesting a massive hole. If you taped off the air box inlet and it ran fine, seems that's telling something. Is your mass air flow sensor clean and tested? 

 

I swapped out the mass air flow sensor with one that worked fine previously.

 

Not all brake cleaners are flammable, try checking with carb cleaner or WD-40. 

 

I've made the same mistake.

 

Good to know...but I'm pretty sure that the one we're using will ignite.  Previous to this little problem, I had a leaky intake manifold (wasn't bolted together correctly/gasket leaked).  It worked then.

 

I'll try to take some videos...thanks for suggestions and patience.


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