Matt16

Over the last couple months, the warm idle has crept up from ~750rpm to 1500. I'm almost certain that the adjuster screw hasn't turned itself (too much resistance for vibrations to turn it). My throttle body was clean the whole time period between when it was idling at 750 and when it was at 1500- so its that some big gob of crud was plugging the idle air control valve. The engine runs fine aside from that. Just find the creeping idle a little strange. Any ideas what's up?

I can think of a lot of reasons why the idle speed would drop from where you set it (vacuum leak, crap plugging the IAC etc., but aside from a screwed up TPS, I can't think why it would climb.

I know that its climbed as the engine does that loping idle thing when the idle is set too high and that just started the other day- today I dialed the idle down and it stopped the loping.

abecedarian

step back from your engine and think... what can change within the engine that you can't test from outside of the engine? I mean, vacuum leaks, etc... can be tested externally, so... what can affect your idle? And don't rule out the obvious.

... and no I'm not trying to help... yet. Just trying to get you to think about your engine.

abecedarian

you could have something as simple as a leak around the PCV or related systems, a valve cover leak, malfuntioning TPS, a/c idle up valve...

abecedarian

I know you don't like me but it doesn't matter. Whatever makes you think, no?

Matt16

Pretty certain there are no vacuum leaks- I redid all the seals, gaskets etc and there aren't any oil leaks and the hoses are in good condition too. I'd be confident ruling out vacuum leaks- besides vacuum leaks cause a low idle- my issue is with idle climbing ~500 rpm over 6 months maybe.

Other possibilities:

• Maybe a sticking throttle cable- don't think so, but I'll check.
• Maybe the Auxiliary Air Valve is not closing properly- crud in the cooling system blocking it?
• Maybe the thermostat not opening enough. BUT but the engine temps are fine even climbing a 3 mile long hill at 4500rpm daily. Its never overheated. Its not like the radiator is cooling too effectively due to air temp, its around 5*C (40*C).

Perplexed by this one.

abecedarian

I'd still theck the IAV/AAV- it's not exactly in a 'high flow coolant zone', and it's in a 'low spot' as well: it's inlet and outlet are higher than the valve itself leaving the possibility for deposits to settle.

Matt16

I've poked around in there before, it was clean last year, but I've got lots of little bits floating around the cooling system so some my have built up.

Strangely, today I drove about 10mi, the idle dropped to 1100rpm, then i parked, left the engine running and it jumped to 1500 where it stayed for a bit, then I punched the gas, and it went down to 1100rpm.

Jay351

Its a long shot, but test your TPS wiring. I have been having a similar issue for years now. Traced it down to a bad wire... havnt brought myself to pull the upper intake off to find the short though....

abecedarian

could be TPS, can't argue that.
Not sure the TPS will raise your idle 300+ rpm though.

like I said the IAV/AAV is a 'low volume flow' area- it gets its coolant from where?... and returns it right back where it got it from, no? (seems to me to be a zero-net flow).

Jay351

Mine goes down 5-600rpm if I spend a ton of time idling... I guess it might be a combined problem

Matt16

Well, after re-adjusting the idle, its idles great. Maybe the harsh vibrations from the York compressor pulley did shake the idle crew enough to loosen it.

muddpigg

iTrader: (1)

Possibly the little o-ring on the idle adj screw is old and letting extra air by or less resistance to turning.. I had to buy a five pack to replace mine would offer you one but after another move I have no earthly idea where they are.

Matt16

I appreciate your generosity, I'm in BC, but I'm sure OEM O-rings are fairly cheap. I hadn't thought about that. I wonder if TB intake cleaner (for FI) eats the o-rings? I cleaned out the TB with cleaner less than a week ago, and the idle acted all weird a couple days later. There wasn't much to clean out, its only been a year since the last time. I'll have a look tonight.