Car Revs In Neutral(Auto) While In Motion

[stretcha]

Ba mk2 xr6t, rough idle and revs in neutral

Hey guys, I need some help, advice with my xr6t ba mk2 auto with 140000kms. Just recently I did some work on it. Cleaned my throttle body, changed one coil and tightened a loose turbo stud. But since doing this, when my car is in motion, the throttle doesn't fully close when I back off. If I put it into neutral when moving, eg. down a hill, it revs up to between 2000 & 3000rpm, but it idles fine at rest. Also an idle and when warm, the car has a shake to it, but it's not a miss. Another strange thing I found was the short term fuel trim( not sure but think sft1) is up between 30 & 40% nearly all the time. Any help would be great. Thanks

[Ralph Wiggum]

You got yourself a vacum leak. Did you disturb and hoses when cleaning the tb?

Start the car and let it idle, spray tb cleaner around the tb mounting gasket, manifold vacum lines etc. The engines not will change if you spray the leak.

[discostig]

Note*

[stretcha]

I'm pretty sure it hasn't got an intake leak, I checked that with water a few weeks ago. But convinced myself to reach for the carby cleaner sat night. No leaks. Today I noticed that the problem became intermittent and when it was playing up it wasn't revving as hard. Only noticed because when I backed off for the turn off. Drove it again tonight and it's doing it all the time again. You can be going along at 50 or 60, back off and it will pretty much maintain speed.

Also another thing, it's only happened 4 times, but twice this week, when I've started the car, after letting it sit for an hour, hour half, it misses it's ass off, kind of similar to when traction control kicks in. It throws an engine light too. I turn it off, think hmmm, then restart it and it starts fine and the eng light has gone out. Also, when I cleaned my tbody, I pushed the tplate in so I could wipe it with a rag. I thought they closed hard and always reset their position just before start up.(I was always taught to be careful with fingers around them when turning the key). Could I have some how damaged the tps or tbody motor? Is the throttle body or plate Teflon coated and I've rubbed it off? Maybe I've pushed a heap of carbon into the throttle shaft and its sticking? Might give it another clean. Do they have idle bypass ports that could be at fault? Hmmmm...

I'm pretty sure it hasn't got an intake leak, I checked that with water a few weeks ago. But convinced myself to reach for the carby cleaner sat night. No leaks. Today I noticed that the problem became intermittent and when it was playing up it wasn't revving as hard. Only noticed because when I backed off for the turn off. Drove it again tonight and it's doing it all the time again. You can be going along at 50 or 60, back off and it will pretty much maintain speed.

Also another thing, it's only happened 4 times, but twice this week, when I've started the car, after letting it sit for an hour, hour half, it misses it's ass off, kind of similar to when traction control kicks in. It throws an engine light too. I turn it off, think hmmm, then restart it and it starts fine and the eng light has gone out. Also, when I cleaned my tbody, I pushed the tplate in so I could wipe it with a rag. I thought they closed hard and always reset their position just before start up.(I was always taught to be careful with fingers around them when turning the key). Could I have some how damaged the tps or tbody motor? Is the throttle body or plate Teflon coated and I've rubbed it off? Do they have idle bypass ports that could be at fault? Hmmmm...

Edited 29/06/13 03:57 PM by stretcha

[discostig]

Are you saying the butterfly does not swing shut on its own? They should do so fairly strongly when the car is off.

[stretcha]

It looked like it was working fine when I was spraying it and revving it. But it returns to idle at rest ok so I don't think that's the issue

[rockafellqeinstien]

my car had the same issue (manual fg turbo).

when rolling in nutral or with the clutch down it would rev high but as soon as I stoped it would drop down.

It was a manifold leak (gasket blown) . there must have been a special idle control or something that was able to over come the extra air from the leak but it only activated when the car was stationary.

as soon as I fixed the leak it was all good.

do a pressure test (preferably with smoke) on your intake all the way from the turbo to the engine. (presure and some soap suds also work - that's how I found mine)

[stretcha]

Here we go again... I was driving tonight, the first time in a week at night, and I noticed that my lights were on but my dash lights weren't on. It was like it wasn't switching over to night mode. Same goes for the audio unit, still on day display. But it gets better... On my way home from a bit of pier fishing, at about 2.30am and bam, the cops pull me over thinking I was someone pissed from the clubs. They said everything was all good and that my tail lights were dull. I turned my lights off when I got pulled over, so I turn them on and check for myself, couldn't tell, so I got the officers to turn off there party lights and well f*ck me, I have no tail lights. Haven't had a chance to look at it, but could it be a Lighting Control Module? The lights had been flickering before, but I haven't payed attention to it lately. Could it be alternator related? Hmmm

[stretcha]

Oh, I forgot to mention that before, at night I've noticed that with the car idling, the interior lights and also headlights slightly flicker. Seemed to go away when the revs were raised. I want to get it fixed and sorted once and for all, but the way I'm going ands the price of fuel, I might have to sell it :(

[Paulie2256]

Sounds like batt or alternator related problem