420A Idle climbs when coming to a stop

[rshissler]

Ok the problem im having is when I'm coming to a stop i push the clutch in, doesn't mater at what RPM, the car will go to around 2000rpms untill im completely stopped, then idle normally. Does this everytime. Im lost on this issue. All the sensors are new and have been replaced, twice to make sure, EVAP and EGR are deleted and removed from the car, No vaccum leaks, Only codes are from the EGR and EVAP. i really need this fixed becuase it gets annoying.

 

[Juanpa]

What's the problem? Once your stopped the car idles normally correct? Atleast it doesn't go super low like 400 and then go back up like mine used to.

 

[Absit]

How many steps is your ISC running at idle?

 

[beihl304]

have you tried checking and cleaning your isc? or was that one of the sensors you say you replaced?

edit::: ^^^^ beat me to it!

 

[rshissler]

ISC was one of the sensors that was replaced. I'll have to check on how many steps is at tomorrow. Te problem is that i live in a very hilly area. i normally like coasting down most of the hills to conserve gas well everytime i push the clutch in the car goes right to 2000rpms and its annoying to me and defeats the prupose. also everytime i come up to a red light i get looked at like im an idiot ### the cars movin at 5 or under mph and the cars reved at 2k.

 

[Absit]

Check the tension of your throttle cable as well.

 

[rshissler]

that was also checked. Think i figured out what might be causing the issue. I have a griffen Alumin radator i installed before winter. Well its doing toooo good of a job and the car never reaches its normal temp ( half way up the gauge). the highest it gets is maybe 3/8 the way up the gauge. What im thinkin is that the computer is keepin the idle high to warm up the engine like at start up. this make sense to anyone?

 

[Absit]

What does your logger say your temp is? Your thermostat should close partially if operating temp isn't hit, allowing you to reach operating temp.

 

[Juanpa]

Check your thermostat then. It must not be working efficiently.

 

[bullettdsm]

You have an isc? But....you have a 420a. Let's just leave that alone for semantics (you have an IAC so "step" away from the sensor, ) .

But certainly if your coolant sensor is giving information on the car not being warm yet, then you can fool the ECU into thinking it should give more gas because it thinks it is cold. BUT that could also be just the sender (for the gauge) being incorrect. But the CLT information is certainly a possibility (I put it that way because I know you said you replaced it. What I'm getting at is the fact that the ECU is seeing the coolant temp not going up for what ever reason).

If you have a "turkey" thermometer, you can check the temp by simply putting it in the thermostat housing and seeing how hot you really are by the sender. And yes, the thermostat is a possibility.

Did you rule out your VSS yet?

MB

 

[rshissler]

sorry yes i ment the IAC not ISC (thought they were about the same thing) How do i check the VSS? never thought of that.

 

[Juanpa]

If the vehicle speed sensor fails, the cruise control system will not get a speed signal. If this is the case, most probably, the speedometer will usually stop working as well.

 

[Mike02rt]

To OP: After the vehicle is at a dead stop does the idle "surge" to 2000 rpm every few seconds then drop to normal idle? If so, then it might be a vacuum leak.
I have an 02 Neon R/T (daily) that was misfiring due to a leaking intake manifold and had nearly the same "symptoms" as your vehicle.

 

[necrotopsy]

my 420a avenger did the same thing for awhile. it was a vacuum leak, so check out your vacuum seals.

 

[rshissler]

after driving home from work yesterday i used my scangage to see the live data and it said the ECU was reading 164*... thats low. I'll check everything i can today again to see what i can find. also the idle is normal all the time besides when coming to a stop or coasting with the clutch in. pretty much its whenever the cars moving and not under load.

 

[david-b]

my 420a avenger did the same thing for awhile. it was a vacuum leak, so check out your vacuum seals.

Agreed. My ESi did this from day 1. Just about any light when rolling up out of gear, idle would go up and sit there, no fluctuating or anything. Very persistant and always was there.

Going over every vacuum line, was the smallest vacuum leak, but it did it.

 

[brownfinger]

Replace your thermostat first, and rig up a boost leak tester to check for vacuum leaks.

 

[Juanpa]

Yeah like I said. That thermostat must not be working good.

 

[bullettdsm]

Yup, 164 is a problem. Would probably make you run rich with ECU thinking you are still in warm up.

To test to see if the vss is causing the problem, simply unplug it

MB

 

[Juanpa]

Hey, you fix the problem yet? Get back to us. I'm interested in knowing what it is? If it's the ECU you should consider getting a Super AFC.

 

[rshissler]

not yet today i picked up a thermastate, and was hoping to get it in tomorrow and redo all the vac lines but i wont be able to till next weekend maybe.

 

[Juanpa]

Alright keep us posted.

 

[e96eclipse]

Had this same issue in my old 420a and it was a vac leak.. fixed the leak and fixed the prob... bought a new gst.. and having the same issue on it.. checked the codes and says vac leak. So... sounds like you have a vac leak.