Cleaned My Throttle Body

[CosmosC4S]

I've been having a problem with my 02 C4S lately.

When I start the car for the first time, it idles weak, stumbles and seems like it's gonna stall...but it doesn't.

This would go for like 10 - 20secs, then suddenly it "catches" and the rpm goes up to normal,

from then on eveything is fine, and for the rest of the day it starts fine, until it sits again for a long period of time.

At the time during the weak idling, if I step on the gas, it will stumble.

I've tried tapping gently on the gas, and it could, most of the time, help coax it to "catch" and go to normal idling.

Well, the symptom got worse, and the engine did stall for the first time the other day.

I started it again, and it did start, and did the regular weak idling routine, then got back on track after a few seconds.

Also, I didn't mention that during the weak idling, the "Battery/Generator" warning light would come on,

but would go away immediately as soon as the idling catches on to normal and the voltmeter shows about 14v.

I figured that the alternator didn't get a chance to power up any juice with the low rpm when the idling was struggling,

and as soon as the idling was normal, the alternator was able to get to work and the Battery/Generator light went away.

Anyway, after reading up on the many common issues with the throttle body being dirty and thus affecting idling,

I decided I had to look into that area.

It was a pretty easy job, removing the air-intake box and getting to the throttle body took about 10 mins.

I was about to remove the throttle body, as suggested by some here, to clean both the front and back of it as well.

Then I saw that the throttle body itself is not that deep, and the plenum was right there behind it.

I didn't see any need to remove the whole throttle body, as there wasn't really anything to clean behind it, it was kinda flushed with the plenum.

Unless I'm missing something here? Can someone please elaborate or explain why or if the throttle body should be removed for cleaning?

Anyway, there was some carbon buildup around the butterfly, but not as bad as I had expected, judging from the symptoms it was causing.

The inside looked a little dirty as well, but nothing shocking.

I was relieved not to find any oil in or around there, as I've had pretty frequent brief "white-smoke" startups lately with the poor idling.

That would eliminate a possible Air/Oil Separator issue.

So, after the cleaning around the butterfly area with a Throttle Body cleaner, and the inside with a clean rag (using a wooden dowel)

I put everything back, and performed the ritual for the throttle body adaptation.

Started the car and.....one crank...the engine jumped to life at full-speed idle! (after a split-sec hesitation)

Something I have not seen in about a month of two!

It is simply amazing how such little carbon buildup on the throttle body could make such a big difference in the startup idling.

However...I'm not jumping to conclusions just yet. After the initial cold start, the car usually starts and idle fine after that.

As such, I couldn't re-test the car to confirm the fix. I'd have to wait till tomorrow morning to do the startup test again.

Thanks to everyone and Loren for the tips!

Here are some before and after pics of the throttle body:

BEFORE:

AFTER:

Edited July 26, 2007 by CosmosC4S

[GranburyChuck]

I've been having a problem with my 02 C4S lately.

When I start the car for the first time, it idles weak, stumbles and seems like it's gonna stall...but it doesn't.

This would go for like 10 - 20secs, then suddenly it "catches" and the rpm goes up to normal,

from then on eveything is fine, and for the rest of the day it starts fine, until it sits again for a long period of time.

At the time during the weak idling, if I step on the gas, it will stumble.

I've tried tapping gently on the gas, and it could, most of the time, help coax it to "catch" and go to normal idling.

Well, the symptom got worse, and the engine did stall for the first time the other day.

I started it again, and it did start, and did the regular weak idling routine, then got back on track after a few seconds.

Also, I didn't mention that during the weak idling, the "Battery/Generator" warning light would come on,

but would go away immediately as soon as the idling catches on to normal and the voltmeter shows about 14v.

I figured that the alternator didn't get a chance to power up any juice with the low rpm when the idling was struggling,

and as soon as the idling was normal, the alternator was able to get to work and the Battery/Generator light went away.

Anyway, after reading up on the many common issues with the throttle body being dirty and thus affecting idling,

I decided I had to look into that area.

It was a pretty easy job, removing the air-intake box and getting to the throttle body took about 10 mins.

I was about to remove the throttle body, as suggested by some here, to clean both the front and back of it as well.

Then I saw that the throttle body itself is not that deep, and the plenum was right there behind it.

I didn't see any need to remove the whole throttle body, as there wasn't really anything to clean behind it, it was kinda flushed with the plenum.

Unless I'm missing something here? Can someone please elaborate or explain why or if the throttle body should be removed for cleaning?

Anyway, there was some carbon buildup around the butterfly, but not as bad as I had expected, judging from the symptoms it was causing.

The inside looked a little dirty as well, but nothing shocking.

I was relieved not to find any oil in or around there, as I've had pretty frequent brief "white-smoke" startups lately with the poor idling.

That would eliminate a possible Air/Oil Separator issue.

So, after the cleaning around the butterfly area with a Throttle Body cleaner, and the inside with a clean rag (using a wooden dowel)

I put everything back, and performed the ritual for the throttle body adaptation.

Started the car and.....one crank...the engine jumped to life at full-speed idle! (after a split-sec hesitation)

Something I have not seen in about a month of two!

It is simply amazing how such little carbon buildup on the throttle body could make such a big difference in the startup idling.

However...I'm not jumping to conclusions just yet. After the initial cold start, the car usually starts and idle fine after that.

As such, I couldn't re-test the car to confirm the fix. I'd have to wait till tomorrow morning to do the startup test again.

Thanks to everyone and Loren for the tips!

Here are some before and after pics of the throttle body:

BEFORE:

AFTER:

I noticed my TB looking like that on the last air fulter change. I was thinking of cleaning but was concerned about which solvent to use that wouldn't mess up the electronics downstream. I have gumout carb cleaner. I started to open the butterfly by hand and noticed the tension so I didn't push it any further. Di dyou just push yours open by hand?

[Loren]

You can likely get it pretty clean by holding the butterfly open and spraying behind it.

I like to remove the throttle body because it is not hat hard and then you can see the back side of the butterfly (without forcing it open) and make sure that the small idle holes at the edges are clean.

[CosmosC4S]

I noticed my TB looking like that on the last air fulter change. I was thinking of cleaning but was concerned about which solvent to use that wouldn't mess up the electronics downstream. I have gumout carb cleaner. I started to open the butterfly by hand and noticed the tension so I didn't push it any further. Did you just push yours open by hand?

Yes, I pushed the butterfly with my hands, and gently rocked it back and forth to clean the part where it hinges on the body.

Also pushed it all the way open to clean the inside and way into the plenum with a clean rag to clean the layer of oily mist.

I would think carb cleaner is fine and would do no harm, that's what everyone here recommends.

But when I was at the auto-parts store, I saw this, and that's what I used.

You can likely get it pretty clean by holding the butterfly open and spraying behind it.

I like to remove the throttle body because it is not hat hard and then you can see the back side of the butterfly (without forcing it open) and make sure that the small idle holes at the edges are clean.

Oh Ok, thanks Loren. That explains why the throttle body would be removed.

I figured I could clean thoroughly inside, and even spray behind the butterfly, so I skipped the step.

Also, when I sized my socket onto the bolts, I noticed (just as I was warned before in previous posts)

that the socket would not completely fit into the lower right bolt. I would need an open-end wrench to loosen that bolt, right?

Also, I saw that the bolts were blue color-marked, which could mean it's one of those bolts that need to be replaced with new ones after removal.

So I thought I'd skip the step and save myself the hassle.

OH! And I'm glad to confirm that it has resolved the issue. I started the car this morning, and it started with perfect idling right away.

What an easy fix, you just gotta know the tricks! And Thanks to you guys, :cheers:

Edited July 26, 2007 by CosmosC4S