My car idles perfect when its first started up but once it runs for a few minutes it starts to idle high, right around 1250 RPM's. It doesnt surge, just idles high and the throttle stop screw is all the way backed out. Any clues?
High Idle When Hot
- Thread starter GearHd6
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Vacuum leak.
See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first most contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.
See the sticky "Help me create the Surging Idle Checklist" at the top of the forum for help with your idle problems. The first most contains all the updates to the fixes. I continue to update it as more people post fixes or ask questions.
Ok, heres the deal. I replaced a ton of vacuum lines today and sprayed around with brake cleaner and found no vacuum leaks. If the engine is off but the engine is hot it will start and idle fine, right about 750-800 rpms but then after about 45 seconds it seems like the computer makes an adjustment and then the idle bumps up to about 1000 rpms. If I shut the car back off and restart it then it'll do the same thing as I stated above. Also in order for it to idle as low as it does the throttle stop screw is backed all the way off. Timing is also set at 10*
Its the IAC ive had this problem with my car for years. The only way I could fix it was by taking off the IAC and making the holes smaller by fabricating a small aluminum piece so less air gets by. This allows me to have much more control with my idle screw.. Yes its a redneck way of doing things but oh well!!
I swapped out the TPS with a known good one and still had the same exact thing happen. I also tried a friends brand new IAC and that dropped my idle about 400 RPM's so I KNOW I need a new one of those. Its still right around 1000 RPM's and still does what I mentioned above. The car smells like its running real rich to me but its not tripping a check engine light. Possible bad 02's?
emagdnim said:
I installed a solid IAC gasket so it couldnt get any air through it and it still was at 1000 RPM's just like it was with the known good IAC I borrowed from a friends car. So I dont think I need to add the plate with drilled holes like you did.
The voltage actually seemed to work backwards, it has more volts in idle position and when I increase the throttle the voltage goes down. Then I put another known good TPS on and it ran and idled exactly the same.
How are the 3 TPS wires testing with your meter? That certainly seems like an issue that needs addressing (to me). The inverse-function TPS's dont work as well as the conventional versions.GearHd6 said:
Good luck.
I used the orange and the green wire to do the testing. I set my digital meter on the 20 volt setting and it showed about 4.5 volts at idle.
And another thing, if I take the TPS off the TB while the car is running and then max the TPS out like if it were at WOT the car seems to idle fine. All the wires look fine but it seems like the orange and green wires are backwards or something.
You used the wrong wires.GearHd6 said:
orange - 5 volt reference from the computer
green - TPS signal output
black/white - TPS signal ground
Use the black/white wire for ground and the green wire for the TPS signal.
Try this... Currently there is some dispute about setting it at .99 volts being worth the effort, but anything less is probably OK. All you need is less than 1.0 volt at idle and more than 4.25 at Wide Open Throttle (WOT). You'll need a Digital Voltmeter (DVM) to do the job.
Here’s a TPS tip I got from NoGo50
When you installed the sensor make sure you place it on the peg right and then tighten it down properly. Loosen the back screw a tiny bit so the sensor can pivot and loosen the front screw enough so you can move it just a little in very small increments. I wouldn’t try to adjust it using marks. Set it at .97v-.99v, the closer to .99v the better.
(copied from MustangMax, Glendale AZ)
1. Always adjust the TPS and Idle with the engine at operating temp. Dive it around for a bit if you can and get it nice and warm.
2. When you probe the leads of the TPS, do not use an engine ground, put the ground probe into the lead of the TPS. You should be connecting both meter probes to the TPS and not one to the TPS and the other to ground.
3. Always reset the computer whenever you adjust the TPS or clean/change any sensors. I just pull the battery lead for 10 minutes.
4. Check the procedure for your year, on my 90 I have to turn the idle screw until it just touches the tab, then insert a .010 feeler gauge and give it about one more turn. Then you adjust the TPS voltage to .98v, reset the computer. Start it up, if the idle is to low then turn the screw in until it is just right, then readjust the TPS voltage to .98v and reset the computer and start it up. The key is to adjust the TPS voltage and reset the computer whenever the idle screw is changed.
jrichker.. you're right, I did use the wrong wires. I havent yet checked it with the correct wires yet. Over the weekend i'll get back to rechecking it. I believe the oxygen sensors are the culprit along with the IAC which I KNOW is bad. One 02 sensor is all smashed up like someone banged it around installing the mid pipe. No codes are tripping but I guess they just havent totally failed. The car smells real rich even after its warmed up. I think when the car is first started up and running open loop its fine, as soon as it goes closed loop the 02's are saying its lean so the ECM is richening it up.
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