Not your typical idle problem

[SpecM]

loose valve clearances will not make an m20 idle rough, only be down on power and make a lot of noise!

[eighteight325is]

Subscribed! My car has just started doing EXACTLY what you are describing. All the usual suspects have been checked. Now I'm going back and rechecking...hoping to find a vacuum leak I missed. I feel your pain.

[Collin]

Update:

I checked in the bentley manual; they say the first test for the Idle Air Control Valve is to unplug it with the engine running, and the engine should shoot to 2000 RPM. I perform the check and the engine actually drops RPM and almost dies. This would suggest the valve is bad, but it sounds like it's running and it's resistance tests well within allowed range.

The temp switch appears to be working, but the temp sensor gave me some weird readings. I got 1.409 on the ohm meter, but the book calls for something like 2400, maybe I'm just using the meter wrong, or reading it incorrectly. Does this seem like it may be the cause?

loose valve clearances will not make an m20 idle rough, only be down on power and make a lot of noise!

Thank you for eliminating that! I have a rough idle, but I'm not really down on power or making more than the usual tapping noises.

Thanks to everyone for all your help and advice! I'm going to spend some time under the hood and I'll check back later tonight.

[SpecM]

Thank you for eliminating that! I have a rough idle, but I'm not really down on power or making more than the usual tapping noises.

well... let me qualify that.. if they are TOO TIGHT then you can have idle issues, but if you haven't touched them then that's probably not your problem! btw, my idle drops when I unplug the ICV too... not sure io f that is normal. Did you clean out the ICV + TB?

ALSO: I checked my temp senser today, it read about 240-1000 ohms over time (cooler = more resistance). Hope that helps!

[Collin]

Did you clean out the ICV + TB?

ALSO: I checked my temp senser today, it read about 240-1000 ohms over time (cooler = more resistance). Hope that helps!

I ran some TB cleaner through both, so they should be clean. I do have to replace the TB; I had to bypass the coolant hookup there, as it was leaking.

I tested the temp sensor after the car sat for a few hours, so it should have been about 55 degrees F.

[Atreus]

same problem with my car recently. however its only happened twice now, but it jumps the revs, and then it loses power on me. i'll clean out my icv and tb, hopefully that clears it up..

[Collin]

Great news guys! I replaced the temp sensor for the fuel system and now it idles worse! Woo! I need an exorcism more than I need new parts.

On the plus side when I sell it, I'm going to be able to list a ton of new parts.

Next to check/replace, O-rings for the fuel injectors, I think they may be letting air through. After that I don't know what else to look for, short of ripping the entire engine apart; which isn't really feasible as this is my DD.

Wish me luck.

[pilotskillse30]

I took it to the shop finally after no luck on my own, the tech found my fuel injector seals were the problem...hope this helps you

[SpecM]

Great news guys! I replaced the temp sensor for the fuel system and now it idles worse! Woo! I need an exorcism more than I need new parts.

On the plus side when I sell it, I'm going to be able to list a ton of new parts.

Next to check/replace, O-rings for the fuel injectors, I think they may be letting air through. After that I don't know what else to look for, short of ripping the entire engine apart; which isn't really feasible as this is my DD.

Wish me luck.

get some cheep carb cleaner ans spray it on the backside of the manifold (around the injectors) while its running. If a seal is leaking, the idle will change when you spray it.

[Collin]

The problem has been located, thank you to mike and matt for finding in 30 seconds what I didn't notice for a month (and for making a newb of me).

The verdict:
Loose nuts where the intake plenum connects to the head. Thank you ladies and gentlemen.

/thread

[StereoInstaller1]

Wow...vacuum leak like everyone suspected, or at least several people did.

Glad to hear it.

Did you ever try the old "spray carb cleaner on the spot" kind of test? Smoke machines do not always work for every type of leak.

Oh yeah, the coolant passages are entirely rebuildable on that TB, gaskets are cheap, takes minutes.

Luke

[kswappedE30]

i have a question my civic has a k swap in it and it keeps not breaking down why is that

[TopOfTheLine89]

^Cause its a lame front wheel drive that never has a RWD fun?

[kswappedE30]

yea we do we drive in reverse lol i have many 95 civic ac parts and eagle alloys too and maybe a rod knock from VTEC!!!!!!!

[Spieler209]

I think it might be the MAF--at least thats whats going on with mine.. Sounds identitical to my issues..