Hayk

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175,600 on the clock.

My engine vibrates at idle (~700 rpm) like it's constantly trying to stall and then recovers from it. It only happens after the car has been warmed up and after it sits for a while before I restart it. So far, I only experienced it three times. One time was in a parking lot after I got out of a store. Second time was at a stop light, after getting out of a store. And the final time was today, after I moved the car in my driveway. This final time, I noticed the CEL flashing on and off. I revved up the engne for a few seconds, which seemed to have solved the issue.

When I was doing the Valve Cover gaskets, I noticed the intake plenum was full of carbon and the throttle body was dirty as well, but I wiped it down around the butterfly valve. Do you think I should go back and clean out the IAC valve?

EEngineer

for the 1MZ the IAC is built into the throttle body I believe. if you are having idling problems, you should just take off the TB and give it a good clean inside out.
and then seafoam the car twice or something.
you might want to take a look at your EGR piping as well. might be clogged as well

Hayk

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I remember when I was learning about the EGR system, it said that the EGR only kicks in when you're cruising on the highway, and it turns off at idle and WOT because those situations need as much air as possible. So why would it cause an erratic idle? When I took off the intake plenum, the EGR valve didn't look too bad, but the EGR piping I can't really comment on because it's almost impossible to remove.

mdbrown

It's possible for the EGR system to coke up and stay partially open creating a vacuum leak, the valve can possibly stick intermittently creating an intermittent vacuum leak. Clean your throttle body and the IAC valve. You can check for an intake leak by using throttle body cleaner. While the engine is idling, spray around the intake manifold area, air intake boot, throttle body and injectors. If you are spraying an area and the idle speed consistently picks up at that area then you have found a leak. Your sympton sounds more like a sticking IAC valve though. 700 rpm is normal idle speed but it should choke up like that.

yeldogt

Whenever you get a flashing CEL light the car is warning you that you have a serious enough misfire that raw fuel will be expelled into the exhaust system -- this gas will then ignite in the catalytic converter and overheat it. Its important not to drive a car under these conditions.

Did you get the codes ?


The best way to start is to read the codes and then clear them - and see what comes back first. Many times misfires can cause many codes to eventually come up -- so you need to catch the first one.

The first thing to look at is a failing coil -- they can be sneaky. Although you have done a fair amount of work around the engine recently ... correct? Was it running correctly prior to the work? Then checking all the vacuum lines would be prudent.

donbryce

Be careful cleaning that IAC valve and throttle body. I screwed my valve up trying to clean it without removing it, as several threads recommended. I ended up buying a good replacement off EBay, got lucky I guess. Take the time to remove everything and do a careful cleaning on the bench, instead of just spraying TB cleaner into the plenum. Also, if you have a high idle condition after reassembling everything, as I did, check the throttle position sensor. I had to adjust mine so it would close enough to allow the IAC valve to meter the idle air properly.

Hayk

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It vibrated today when I cold started the engine and shifted into Drive (the revs dropped below 1k). As a result I got an CEL - I couldn't scan it because I had to get to work, but I'll do it when I come back.

Actually when I cleaned the throttle body, I used some brake cleaner and I squirted it down into the IAC. So hopefully that's the issue.

EEngineer

^please do not ever use brake cleaner again for any intake/throttle body parts when they are on the car. it's called brake cleaner for a reason.

brake cleaners have water content. TB cleaner do not.

Hayk

iTrader: (1)

Yeah I figured that was stupid to do.

Also my ignition coil electrical connectors' plastic clips have broken off. I gotta replace them.

Hayk

iTrader: (1)

Just scanned the CEL.

p0300 random misfire
p0302 cylinder 2 misfire
p0304 cylinder 4 misfire
p0306 cylinder 6 misfire

Those are all in the front, so maybe it is my bad electrical connectors.

Strangely, the engine runs strong without any hick-ups when I'm driving around. It's very smooth. So this issue happens randomly, and it hasn't happened since I set off in the morning. I had a check engine light for one of the A/F sensors last week, but it hasn't repeated itself since I cleared the code. And my fuel economy seems to be average (I'm going to calculate it).