throttle sticking when cold?? Need some ideas..

[d1giPhux]

1999 Subaru Legacy GT M/Trans

The throttle on my car seems to stick (car continues to go faster and faster) when you press on the gas pedal. The gas pedal itself is not hard to press, but this is becoming annoying.

I cleaned the throttle body / plate really good the other day, and it seems like its still doing it. But get this, it ONLY does it after sitting overnight in the cold, or during a very cold day.

Symptoms of whats happening:

-When i accelerate on the highway, car will continue to accelerate for an extra 3 seconds or so after taking foot off pedal.
-When shifting gears, I will press in the clutch and the engine will 'rev' as if I was pushing on the gas pedal.

Its weird that its ONLY happening during the cold too. During the day when its warm, everything works fine. After cleaning the throttle body / plate, it didn't seem that much carbon came out. The cables all appear to be functioning properly.. so now I need ideas as to what may be causing the issue. This only recently started to happen.

Any help would be appreciated as to what I should check and do next to eliminate this problem. :smt023

[Huffer]

Did you check vac hoses for any leaks or blockages? If there is a crack or a block in any vac pipe allowing air post-filter it will make the car behave this way... my Honda Accord did this after I pinched a vac line when changing an air filter. It settled down eventually but the symptoms were the same - rising throttle with no pedal input.

Also you might want to see if the throttle plate is greased properly and the throttle cables have sufficient lube - the lube might be old and needs "heating" up before it moves freely.

[d1giPhux]

Wow.. didn't know that about vac hoses post air filter. I will definitely need to check those. Any in particular I should check? Ones running off the intake itself, or?

I will also check / re-grease the throttle cables. They seemed to be fine, and I was thinking that could have been a possibility. Only seems to do it when its really cold out.

Any other things I should check that may cause this? All suggestions are helpful.

Thank you! :smt023

[phi11]

any codes?

[d1giPhux]

Not throwing any codes. Seems to happen randomly, but appears to happen more during the cold hours or after sitting all night in the negative degree weather.

[lord flashheart]

Use the scanner to lookat thelive data. I want to know what the tps is reading. Also how high is it revving.?
If the tps is reading 5% or whatever it could bethe iacv vaccum leak etc. If the tps is reading 30% then you may have a sticky cable or bad tps or whatever.

[d1giPhux]

Unfortunately, I don't have a scanner, let alone one that can do live data. Any you recommend? I'm actually thinking about picking one up in the future.

Here is more info about the symptoms. I notice that when I'm on the gas, when I press the clutch in.. it actually rev's higher a bit without touching the gas pedal at all. So sounds like it MAY in fact be a vacuum leak. It happens at any RPM really, but mostly while driving in the 2k-3k rpm range.

[L.Michael]

There aren't a lot of vacuum lines, so a quick check on all of their ends with a flash light will determine if ones disconnected or not. If one is cracked, you'll typically hear a whistling sound under the hood. Thats a dead give away with vacuum lines.

Did you take off the cables recently? What about the TPS? use a voltmeter for the proper setting on the TPS, and ensure the cables are allowing the valve to close fully on the throttle body.

[danieltrusty]

I've noticed a similar problem when first starting my car and driving it when cold. 1997 LGT 5MT/EJ25D. When I first start driving after the car has been sitting in the cold for awhile, the RPMs will stick when slowing/stopping. For instance, when coming to a stop the RPMs might stick at around 2500(or where ever I had just revved to, usually not much higher than 3000, b/c it seems to warm up before I get far enough for anything more). The RPMs will stick for a couple seconds, then very slowly slow down. This doesnt seem to be hurting anything, but it is annoying.

[lord flashheart]

The reason i think it could be a vacuum leak is because when you start the car you have a warm up inrich ment, the computer gives extra fuel to warm up the motor, and brings ip the idle. If you have a vacuum leak you are allowing un metered air in and ballencing the ratio out which will cause it to idle high when cold.
They dont always make a sound. The quickest and easiest way to check for a leak is brake clean. Spray the vacuum ends. Thr alcohol in the brake clean will cause the idle to change. It could also be a iacv. But tipically that will cause it to die randomly while idling. But on occasion ive seen a high idle problem. they do get sticky and the return spring get weak.

[Huffer]

I've noticed a similar problem when first starting my car and driving it when cold. 1997 LGT 5MT/EJ25D. When I first start driving after the car has been sitting in the cold for awhile, the RPMs will stick when slowing/stopping. For instance, when coming to a stop the RPMs might stick at around 2500(or where ever I had just revved to, usually not much higher than 3000, b/c it seems to warm up before I get far enough for anything more). The RPMs will stick for a couple seconds, then very slowly slow down. This doesnt seem to be hurting anything, but it is annoying.

This is your Intake Temp Sensor... and your overall engine temp/thermostat. The engine will rev higher at colder temps to bring the temperature up quicker. This is normal. If you want it to stop, minimize, install an engine block warmer. The other thing that may be happening is that your throttle cable and throttle plate could be sticking a little.

[1055]

I bet youve got oodles of carbon on your iacv. Have you Pulled it yet? I havent owned a subaru that hasnt had a botched iac at some point. Excessive carbon on the control surface would certainly contribute to the symptoms you're describing.

Sent from my iPhone killer

[1055]

I've noticed a similar problem when first starting my car and driving it when cold. 1997 LGT 5MT/EJ25D. When I first start driving after the car has been sitting in the cold for awhile, the RPMs will stick when slowing/stopping. For instance, when coming to a stop the RPMs might stick at around 2500(or where ever I had just revved to, usually not much higher than 3000, b/c it seems to warm up before I get far enough for anything more). The RPMs will stick for a couple seconds, then very slowly slow down. This doesnt seem to be hurting anything, but it is annoying.

This is your Intake Temp Sensor... and your overall engine temp/thermostat. The engine will rev higher at colder temps to bring the temperature up quicker. This is normal. If you want it to stop, minimize, install an engine block warmer. The other thing that may be happening is that your throttle cable and throttle plate could be sticking a little.

Subaru's warm up strategy is not to exceed 1500 rpm, as you enter a different emissions bracket at that point. Hanging close to 2500-3000 at cold is more indicative of a faulty iac or an intake manifold gasket torn, that is sealing one heatsoaked.

Sent from my iPhone killer

[1055]

The reason i think it could be a vacuum leak is because when you start the car you have a warm up inrich ment, the computer gives extra fuel to warm up the motor, and brings ip the idle. If you have a vacuum leak you are allowing un metered air in and ballencing the ratio out which will cause it to idle high when cold.
They dont always make a sound. The quickest and easiest way to check for a leak is brake clean. Spray the vacuum ends. Thr alcohol in the brake clean will cause the idle to change. It could also be a iacv. But tipically that will cause it to die randomly while idling. But on occasion ive seen a high idle problem. they do get sticky and the return spring get weak.

Carb cleaner will offer a more obvious difference as it displaces the oxygen and offers a less volatile reaction further than brake clean would.

Sent from my iPhone killer

[d1giPhux]

I have not pulled the IACV. Didnt figure it would be that. The problem hasn't been happening lately, and the temperature around here has been warm. So still not sure what the issue is.

All I have done is clean the throttle plate with cleaner.

Seems like this happens only when the engine is cold. Not so sure its a disconnected vacuume hose, as I haven't seen anything.

When you say intake manifold gasket, do you mean on the engine, or the intake itself? The manifold gasket itself should be fine.. hopefully.

[1055]

Yes. The manifold to head gasket. They may be stamped metal composite but they are prone to leaking over time. Its a rare occurence. But not one to rule out. Do you have access to a mechanical vacuum gauge? Easiest way to know right there..

The colder it got, the more my iac acted up till N.O.T.

Sent from my iPhone killer

[lord flashheart]

i dont think i have ever seen MLS intake gaskets on these cars.

[1055]

Dont know why I said mls. Stamped composite is what I meant :lol:

Sent from my iPhone killer

[lord flashheart]

Haha i figured it was a brain fart.

[1055]

Wouldnt you know I found a ripped one yesterday too :lol:

Any updates op?

[d1giPhux]

Yeah, car hasn't really been having the problem at all recently. After I cleaned the throttle plate and such, seems to have gone away. I'm still waiting for the issue to come back, but so far.. nothing.