Greets,

Okay first the back story. '93 ES300, failed state emissions test. So after checking under the hood I noticed the pcv valve didn't have a rubber grommet to plug it into. Fixed that and right away both oxygen sensors light up the check engine light. Swapped them out for new ones. Next I changed the spark plugs, which of course involved removing the intake plenum for access. Put it all back together and started it up, no problems. Two days later car is started and instead of exhaust sounding like rmmmmmmmmm it goes puttputtputt. First thought was vacuum leak so I tried tightening the four bolts on the plenum a little tighter. Car started up fine again, after which I took it back for inspection and it passed. One week goes by and then it went back to puttputtputt. Took it all apart again, replaced the plenum gasket again but still...puttputtputt. So now I'm looking for other problems and one of the things I want too check is the timing. Problem is when I put the jumper on E1 to TE1 on the DCL1 the idle jumps up to about 1050rpm but to check the timing it has to be at 700rpm. So how do I check the timing? I really don't think this is the problem but I want to rule out all the cheap/easy stuff first.

Also, I'm looking down the checklist of things that can cause this behavior (according to the service manual) and I see one of the first things it lists as being a culprit is the Engine coolant temp. sensor circuit. Anyone here can tell me how that would affect the idle?


DJSG3

 

Check your IAC valve.

 

^I would check that for sure. You removed the intake manifold and all that? I didnt remove a thing when I did my spark plugs. I have a 93 as well. But I also replaced my sparklugs just a week or so ago becuase the engine was "bucking" sort off. It was real weird and happened only when it was over half a tank of gas. Once it was below it didnt seem to do it. But bought NGK OEM spark plug wire set and fixed it! Dont think thats the problem with yours but I would change them too if your doing plugs. Always a good thing to do if you havnt. I had no record of when it was done since I just bought my car. Has 241k on it and figured it would be good to do. Good luck with ur car. Hope you can figure it out.

 

Thanks for the input and yes I will check the IAC as its #9 on the checklist but what I want to know about is how to check the timing. If I do it the way it says in the manual the idle goes up around 1000rpm but the check is at 700+/-50.
On a different note, you folks know any online sellers that might have reasonable prices for things like an IAC? Prices I've been seeing are way too expensive to justify putting them into a 17year old car.

 

I just finished (or rather, suspended working on) fixing my high idle issues, documented elsewhere here. From what I could gather from the forum and service manual, the coolant temperature sensor tells the ECU when to adjust down the idle speed, which means, send pulses to the IAC valve to gradually close it as the coolant temp. rises.
I found a used, 'guaranteed to work' IAC off EBay for about $60.00, shipped. I ended up adjusting the TPS a miniscule amount CCW to get the values specified in the manual. After this adjustment, and the replacement IAC, the idle quieted right down to about 700rpm.
The old IAC, strangely, does test within all the parameters in the manual, and is perfectly clean, so I don't know why it wouldn't work as it should've
Now, I just finished a 500km drive, furthest the car has gone since I got it, and find the idle really rough when the engine is hot. It's a bit choppy when cold too. I'm trying to figure out why and continue the 'idle from hell' fix.