Just cleaned out the throttle body (very gunky with 206k miles) and the MAF sensor with the appropriate cleaner solvents. Had the battery disconnected for an hour. At full warmup, the engine IDLES at 1800 rpm. In Drive, it stays at 1100 rpm.

Is there an adjustment? There's slack for the throttle cable, but I'm wondering if there are screw adjustments?

Ideas?

 

Which engine / year?
Yes there will be a screw, but if you didn't touch it, it probably didn't move.

Most likely a vacuum leak, check all the hoses you took off, how did the throttle body gasket look? you probably should have replaced it when you were in there. Check the connection to the air intake after the air flow sensor.

 

8 cylinder for a 98 GS400. I didn't take any hoses off since I have the SRT intake. One screw and I have access to the TB.

 

I find that my car idles high after cleaning up the TB and disconnecting the battery for a long time. Fire it up again to see if anything changes.

Did you happen to touch the throttle position sensor?

 

I don't remember bumping into the tps...black module on the right side of the tb? Doesn't look adjustable...

 

Did this ever get resolved? I'm still searching which is how I came across this, and Percy's scenario sounds identical to mine.

My car is a 99 GS4 with SRT intake

Here's my order of events:
Idle out of gear is within spec, 700-750rpm
Idle in gear is just fine too, but will occasionally dip about 100 rpm low causing the car to idle a liiiitle rougher, but not bad, just noticeable b/c I'm used to the car. That problem has been getting more common so Sunday afternoon when I pulled up to my garage I decided to sit outside a min. and let it idle in drive for a minute or two, I was hoping it would trigger a CEL so I could diag., but it didn't so I pulled in and shut it off.

A few hours later I fired it up and it ran like total garbage immediately triggering a CEL, VSC, and VSC OFF, so I shut it off, fired it up again and it ran fine, but those lights were still on. Yesterday I fired it up, lights still on drove it for about 5 miles and scanned it. The code was a P1121 by itself, not the P1120 I did not clear the code.

I decided to clean the t-body w/ carb cleaner and MAF with CRC MAF cleaner, everything is buttoned up and secure. Throttle cable has some slack so I'm good there, no preload. Then I cranked it up and almost immediately all of the lights turned off on their own and its like nothing ever happened except, just like Percy's, now I have high idle.

And here's the weird one and the reason I'm continuing to search. My t-body has become completely cable operated right now, yet no lights on dash.

Any ideas?

Thanks guys

 

when I cleaned my TB, disconnected the battery it took a few hours of normal driving or overnight for it to find itself back to the correct idle. could be just the computer adjusting.

give it a little time and see what happens..

 

Russom, our cars are drive by wire...the cable is for cruise control. Reset the ecu and see what hapens

 

Yeah I know, thats what has me scratching my head. I read on here that people are explaining their limp mode situation as only having 10-25% power by way of cable operation only at the last bit of pedal travel. I can't attest to this b/c mine has never gone into a limp mode, but last night after I put everything back together one of my co-workers got into crank it up and I'm standing there watching every bit of the throttle movement being controlled by the cable, not just the last little bit of travel like the limp mode stories have explained.

The car drives just fine, only a little higher idle in all circumstances, no lights on the dash, BUT its entirely cable operated right now. I don't get it.

I disconnected the battery this morning we'll see what happens. I'll update this afternoon.

Keep em coming.

Thanks

 

Just hooked the battery back up and no change, no lights, and still cable operated. Fly by wire is not working.

The exact high idle numbers are:
1100 in park
750 in drive

Any ideas?

 

If you hit the pedal ALL the way down, does it respond? The last little bit of travel will indicate "limp home" mode.

For me it was a Throttle Position Sensor adjustment. Sometimes the idle is incredibly low...350 rpm.

If you have a more advanced scan tool, the TPS % should be around 13 to 14 percent at idle.

 

It's your tps. My car idles high everytime I clean my throttle body and it stays high.(can't explain why) The way I have found to fix it is to let the car warm up to normal temp and while the car is idling in park, I loosen the tps screws slightly then lightly tap down on the tps until the idle sounds normal. Once set, the idle remains dead on until the next cleaning.

 

Its like this. My car decided on its own to not be fly by wire yesterday afternoon. After it's decision all of the error lights went off on their own and the car performs perfectly with the exception of a slightly higher idle. BIZARRE!

Anyone seen Christine? lol

 

I'll try that now and report the difference.

Anyone had a APP sensor go out and noticed that the car turned cable only and the CEL.VSC/VSC OFF lights go back out on their own even though its not operating as fly by wire anymore? I'm wondering if this is somewhat common and it goes unnoticed b/c drivabilty doesn't suffer.

 

Yep - had this happen. TPS sensor is intermittent. Keep an eye on it.