So my viii has been sitting on jack stands for almost 3 months getting worked on. I did all the belts and water pump. New bosch o2 sensor, buschur tbe exhaust, ets intercooler and piping. Replaced the throttle body shaft seals and cleaned. New battery, both sets of shifter bushing and some other minor things.

I did remove the turbo when I was working on the car and had to replace the hot side because the studs got messed up. I replaced it with a used viii hotside. My o2 is connected into my aem series 1 as thats how the old one was. I had to reuse the old wiring becasue the aem uego wires do not connect the way my old setup did. I check and the harness fits and the wires match up the way the old o2 did.

So today I finally got the car started and on the first start up it had an idle of 2500rpms. So I shut the car off and checked a few things. Nothing looked wrong. So I started it again and same thing. I let it run for awhile and the rpms went down to 2k. If I give it some gas it will rev up like normal but drop back to the 2k rpm.

Is there something I should do besides a boost leak test? I need to make one (I know they need to be done when replaces all the piping like I did) When I took the throttle body off I removed the tps, could that be backwards?? How to I know which position it should be in?

Does the ecu take awhile to "relearn" since I had replaced the o2 and had the battery disconnected?

The car ran fine before I started to work on it, except that the o2 was shot and it was telling the ecu to shut the car down.

All help and advise would be great. Thanks evoM

 

When I replaced my tps I used my scan tool to set it to zero at idle, otherwise it would read something like 6% or 10% at idle. A lot of people have suggested using a pencil mark to record the original position of the tps, but the potentiometer inside the tps is quite sensitive, so even that strategy wouldn't be accurate. If I remember correctly it did not make my idle jump up or down at all, so I believe your problem may be elsewhere.

 

Did you adjust the throttle cable by any chance? check it and see if its in tension pulling on the butterfly causing it to open more?
Also, at idle what's evoscan reading as far as tb position?

 

All I did with the throttle cable was un hook it from the throttle body. I dont know what and how to use evo scan. I do have the cable I think so I may look into that. I may also try and mess with the tps.

Any other ideas???

 

while the car is idling could you unhook the cable and try to close the butterfly for a test and see what rpm it idles at? if the rpm drops, then adjust the cable to be slightly longer to allow for closure.

 

How did you "clean" your throttle body? If you scrubbed the butterfly valve in the throttle body, there's your culprit. There is a light film of sealant on the butterfly valve. Once people scrub it off it looses it's seat/ seal against the bore of the TB. And consequently for those people who have done this unknowingly, experience the same high idle issues your describing. A lot of members have accidentally done this, while cleaning the TB too aggressively.

 

I had cleaned the butterfly by itself when I had it apart to replace the shaft seals. Im going to try and mess with it tomorrow and see what I can figure out.

 

yeah when I got my milspec 65mm TB back it had a sealant all around the throttle plate to make it seal properly. It's not aesthetically pleasing, but it's functional

 

I cleaned the black stuff off the butterfly valve on 2 cars but don't experience a high idle. Maybe it was just luck but I doubt that is your issue. A note on the TPS%, you want it to be around 13% at idle, not at 0%.

Check the hose that connect the the nipple near the throttle body for cracks/dry rotting or if you have the EGR deleted then check the vacuum cap for dry rotting. I had the same symptoms as you on my car and another local car, I replaced the vacuum cap and fixed the idle on both cars.

Good luck!

 

Im going to do all of the above as I am assuming my high idle problem has to do with the throttle body somehow. All I did was take the two screws off the shaft and clean the plate and replace the shaft seals. I had also removed the tps because I was having a hard time disconnecting the harness.

I have the aem series 1 and I just downloaded the software as I did not get it when I bought the car. I need to go buy the cable to connect to my laptop and I am going to try and see if I can figure out the software and see what the tps is set at and go from there.

If anybody has any experience with this could you please post how to check and adjust the tps in the aem software. Thanks guys for all the input so far

 

Well I got the idle down. I had to recalibrate my tps via aem, which meant i had to download the software and buy a new cable but the care seems to idle fine.

I do have one question though and cant seem to find the answer at all. Can someone tell me where in the aem pro software I can see what my tps value or percentage is set at so that I know its not reading 0% or 100%.

 

Bump anybody