The dreaded high idle issue - D1

[Knightspirit]

I have researched this - and have about 10 different possible causes. At first - I thought I fixed it by resetting the adaptive values - which worked for about 5 seconds. I reset them and started it - and the idle was normal - so I shut it off thinking DONE! Then the next time I drove it it went right back again to about 1500-2000 rpm.

Now I am on to vacuum leaks - and I don't see any problems with the lines - they all look good. Not sure the best way to test that though.

Next on the list is:

Idle control valve
ECU
Closed throttle position
MAF sensor

Meanwhile if you have had this issue and fixed it - please share what your problem was. Thanks!

 

[robertf]

check tps values, see if its linear from open to close

 

[LRDONE]

Any Codes?

 

[HughLouisDewey]

I had the same high idle, so the first thing I did was replace the idle air control valve with this compatible Mopar part for a Jeep (Link) (I had to cut a new gasket since the old one was shredded), which didn't solve the problem. Then I learned about adaptive values and was able to reset them using RobertF's GEMS ECU Utility app on Android, which immediately lowered the idle to just below 700, and it's stayed that way for about four months now.

If I were you I'd go ahead and change the IACV, since it's cheap enough, and then reset the adaptive values again and see if there's any change. If not, I'd check for any vacuum leaks, which I do by sticking a long piece of flexible tubing in my ear then moving the other end of the tube all around the engine bay when it's running; it amplifies the sound and helps to hear if there's any leaks. There's also a way to do it with smoke I think, but I never got that far.

Good Luck.

 

[Knightspirit]

check tps values, see if its linear from open to close

OK - that went right over my head. What are the TPS values? How do I check them? What's opening and what is closing?

Not getting codes on this.

 

[Knightspirit]

I had the same high idle, so the first thing I did was replace the idle air control valve with this compatible Mopar part for a Jeep (Link) (I had to cut a new gasket since the old one was shredded), which didn't solve the problem. Then I learned about adaptive values and was able to reset them using RobertF's GEMS ECU Utility app on Android, which immediately lowered the idle to just below 700, and it's stayed that way for about four months now.

If I were you I'd go ahead and change the IACV, since it's cheap enough, and then reset the adaptive values again and see if there's any change. If not, I'd check for any vacuum leaks, which I do by sticking a long piece of flexible tubing in my ear then moving the other end of the tube all around the engine bay when it's running; it amplifies the sound and helps to hear if there's any leaks. There's also a way to do it with smoke I think, but I never got that far.

Good Luck.

Just purchased from your link - I will definitely do that and see what happens - thanks for that! I saw the mod for creating a smoke machine to feed into the vacuum system on youtube - kind of crazy - but I guess it works. I was really hoping the adaptive value reset would have fixed it!

 

[Gordo]

I’m my case, 96 gems, it was the tps. I have nanocom so that helped but the actual reading and expected reading on the tps at idle were not matching up on the nanocom. I ended up elongating the holes in the tps and turned it a little to “fix” the problem and it’s been fixed for 1.5 yrs. Not saying it’s the right way but both my tps were causing the same issue. Oh yeah and check the throttle body at the butterfly for carbon. It can cause a similar issue if it gets thick. Gordo

 

[discostew]

I’m my case, 96 gems, it was the tps. I have nanocom so that helped but the actual reading and expected reading on the tps at idle were not matching up on the nanocom. I ended up elongating the holes in the tps and turned it a little to “fix” the problem and it’s been fixed for 1.5 yrs. Not saying it’s the right way but both my tps were causing the same issue. Oh yeah and check the throttle body at the butterfly for carbon. It can cause a similar issue if it gets thick. Gordo

Theres a function on the old T4 laptops that's called reset closed throttle position. I used to run that ater reset adaptions. You would think resetting the adaptions would include relearn closed throttle. But it doesn't seem like it does.

 

[discostew]

I have researched this - and have about 10 different possible causes. At first - I thought I fixed it by resetting the adaptive values - which worked for about 5 seconds. I reset them and started it - and the idle was normal - so I shut it off thinking DONE! Then the next time I drove it it went right back again to about 1500-2000 rpm.

Now I am on to vacuum leaks - and I don't see any problems with the lines - they all look good. Not sure the best way to test that though.

Next on the list is:

Idle control valve
ECU
Closed throttle position
MAF sensor

Meanwhile if you have had this issue and fixed it - please share what your problem was. Thanks!

I think your on the right track with the vacuum leak idea. The best way to find vacuum leak is pressurized smoke from a smoke machine. But since you don't have one of those you could get a spray bottle and start spaying a heavy stream of water at the intake gagets and the upper plenum. If you find a vacuum leak the water will fill the leak temporarily and the idle will change a little. Also make sure your throttle is really closed. That black thumb wheel near your throttle is for turning up the idle when winching or running a PTO. Make sure that thumb wheel isn't holding the throttle open a little.

 

[terryjm1]

What about if the issue is not going into high idle? I have reset the adaptive values and replaced the IACV.

Before I replaced the IACV it was hard to start cold. It would take, every time, three starting attempts. It would start and almost run the first two times. The third time it would barely start and idle at 300ish RPM and after 5 seconds or so idle up to 700-800. But, if you pressed the accelerator it would die. If I let it run a few minutes it would not die when pressing the accelerator but struggle/stumble until warmed up. After warm up, no problems.

After IACV replacement it starts right up, idles up to to about 1100 but only for about 5 to 10 seconds. Then, it goes back to stumbling when given any accelerator pedal action until warmed up.

If it was an old carburetor with manual choke, I’d say it acts like I forgot to set the choke. (Like not enough fuel or too much air for cold running conditions.)

The IACV I installed is a used one I pulled from a spare engine. i thoroughly cleaned it before installing it. I do wonder if it is also misbehaving but in the opposite way as the one I removed.

The D1 I am having this problem with is one I bought with a locked up engine. So, I have no idea if the problem existed before I installed the replacement engine. Aside from the cold start / no high idle issue it runs like new.. There are no codes or unwelcome engine noises. However, the engine and all accessories, while very low mileage, sat for over a decade unused. I did replace all the injectors. Aside from the the injectors and things like hoses, gaskets, and spark plugs/wires, everything is original.

If I let it warm up for 5 minutes before driving, there are no issues with driving. It just doesn’t hold high idle when cold.

 

[boxster]

You could try propane gas bottle with a hose around any air intake areas for vacuum leaks.

 

[Jimmy]

What about if the issue is not going into high idle? I have reset the adaptive values and replaced the IACV.

Before I replaced the IACV it was hard to start cold. It would take, every time, three starting attempts. It would start and almost run the first two times. The third time it would barely start and idle at 300ish RPM and after 5 seconds or so idle up to 700-800. But, if you pressed the accelerator it would die. If I let it run a few minutes it would not die when pressing the accelerator but struggle/stumble until warmed up. After warm up, no problems.

After IACV replacement it starts right up, idles up to to about 1100 but only for about 5 to 10 seconds. Then, it goes back to stumbling when given any accelerator pedal action until warmed up.

If it was an old carburetor with manual choke, I’d say it acts like I forgot to set the choke. (Like not enough fuel or too much air for cold running conditions.)

The IACV I installed is a used one I pulled from a spare engine. i thoroughly cleaned it before installing it. I do wonder if it is also misbehaving but in the opposite way as the one I removed.

The D1 I am having this problem with is one I bought with a locked up engine. So, I have no idea if the problem existed before I installed the replacement engine. Aside from the cold start / no high idle issue it runs like new.. There are no codes or unwelcome engine noises. However, the engine and all accessories, while very low mileage, sat for over a decade unused. I did replace all the injectors. Aside from the the injectors and things like hoses, gaskets, and spark plugs/wires, everything is original.

If I let it warm up for 5 minutes before driving, there are no issues with driving. It just doesn’t hold high idle when cold.

Since this thread is about going into high idle, you should start your own thread.

 

[Knightspirit]

OK- so I have figured out that the TPS is the throttle position sensor - so if resetting the adaptive values do not reset the throttle position with the ECU - and assuming most people don't have an old T4 laptop - what is the method for resetting the position sensor with the ECU? And what is used to assess the values? I have a bluetooth OBDii plug and a generic app on the iPhone - maybe that will show something.

 

[jymmiejamz]

I just had one yesterday that was the throttle position sensor causing the issue. Typically when the TPS is the issue you can temporarily resolve it by resetting the closed throttle position, but the issue always come back

 

[robertf]

resetting the adaptive values does reset the tps value

if you look at the before and after value it should change

 

[robertf]

so gems seems to actively change the tps to whatever minimum value it measures in operation and set that as its closed value. Ive seen a bad tps that had a dip in reported values between open and closed substitute the actual closed value for the dropped value so when the throttle was closed the ecu saw a reported val over the recorded min. this sticks it in some power enrich strategy thinking its accelerating and opens up the iac while it should really be idling

this is why the reset works until you drive it around a bit

 

[terryjm1]

Since this thread is about going into high idle, you should start your own thread.

That would make it easier to search for others later on. Half the time I end up answering my own questions after later diagnosing them. The great thing about reading a post like this is it helps me connect the dots as I think about similar issues leading me to figure things out. I will start a new one.

 

[Knightspirit]

Great info - thanks everyone. I will wait for the air control valve to arrive - replace that and then reset the values again - and if it continues, I think I might spring for a new TPS (after vacuum leak check...)

 

[best4x4]

I use the IAC from a 4.0L I6 Jeep Cherokee

 

[Gordo]

To me the easiest way to find a vac leak is spraying some carb cleaner around the connections, hoses, intake etc and listening for an increase in rpm’s. Maybe someone mentioned that already. Another thing to check is the wiring to the crank position sensor. They can create issues when they dry out and crack, in our case the truck wouldn’t rev past 2500rpm. May want to reset base idle too. Good luck it can be a pita to figure it out. Even with nanocom/t4 etc
Here is a link to my post if it helps

High idle drama 1996 D1 nanocom question/idle reference speed

Hey guys, Just wanted to see if someone can help me understand what is going on with my gems 96 disco. Its been having intermittent high idle issues for a couple months. I changed the IACV with a jeep one (rotating back to the old one does the same), a used known good TPS, a new MAF, vacuum...

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