Question after doing DIY throttle body cleaning

[rasank]

Hi Folks,

Thank you very much for this great site. I have been having a slightly erratic idle on my 2001 coupe. The high idle is fine but when it drops down to 800 rpm, the needle quivers around that and jumps from around 775 to 825 approximately. You could also hear the slight change in engine note. There was quite a lot of carbon around the throttle body and I cleaned it all out today. It's much better now but the needle is still not steady. Now its at 800 but oscillates within the painted line, if you know what I mean. I am expecting the needle not to move at all. Should I not worry about this any more or should I clean the MAF? From what I read, it seems like the MAF doesn't really come into play below 3000 rpm? Also, since I bought the car two months ago, I have been running 91 octane and not 94. The car was previously used by a gentleman that garaged it for the entire winter. I don't think he drove it too much this summer either.

Any suggestions? Apart from this, I had an O2 sensor fail and it was replaced a few weeks ago. Also all coil packs, spark plugs, spark plug tubes and air filter were replaced a couple of weeks ago as part of the 30k mile service.

Thank you.

[Loren]

The MAF does almost nothing at idle. If the MAF was a problem then you would notice issues above 4000 RPM.

Did you clean behind the throttle butterfly? I have seen a number of these where they are so gummed up the butterfly does not close properly and the small air ports are clogged. So I would make sure both side are clean - even if you need to remove it to do that.

A bottle of Techron would not hurt either and always use the highest octane gas you can get. Remember your engine costs more than than $32,000 new - and more than $17,000 for an exchange factory rebuilt.

[logray]

Searching idle could also be from plugs or intake leaks.

[rasank]

Loren, 94 is what its going to be from now. I tried to clean it as best I could but it was at lunch hour in the parking garage at the office. I certainly tried to do it on both sides. There is nothing past the butterfly right? I only cleaned the butterfly and tried to push it horizontal so I could get both sides.

Plugs were replaced 2 weeks ago along with tubes and coil packs.

[rasank]

Also want to add that I was having this issue even before the oxygen sensor warning. The shop said it might be due to the failing sensor Nd replacing it would sort out the issue. I will reopen it and clean the throttle body again more thoroughly. Add some techron and lets see what happens.

[Loren]

What were the fault codes?

[rasank]

fault codes were P1117 and P0139, this was before O2 sensor replacement

I am getting a durametric soon.

[Loren]

If those are the only two codes then I think it best to work on the throttle body some more.

Any look for any damaged vacuum hose or other leaks.

[rasank]

Thanks Loren. Can you advise how to look for leaks? I assume the vacuum hoses are not anywhere close to the main intake tube? THe intake tube is in good shape supple and soft. The only other place where there is a smear of oil is on the hose clamp on the plenum behind the throttle body. The indy tells me it's normal for some vapor inside the plenum and can smear that clamp.