The Wok

Ok, I've got an 87 MR2 with a JDM 4A-GE, what appears to be a 2nd gen 4a. I drove it for a couple days after I got it (this week) and it ran fine. Now it has suddenly spawned a hideous mis-fire.

So first I replaced the spark plug wires; no fix. Spark plugs; no fix. I pulled the distributor apart and there was oil in it. I cleaned it out thoroughly and put it back together (the rotor looked ok), still missing.

The car wasn't driven for a few months before I got it. The day before the problems started I replaced the air filter (he has a cone filter hooked up "short ram" style) and filled the gas tank. Tommorrow I'm going to replace the fuel filter and check the compression. I'll be checking timing Monday.

Any other ideas on what this could be? I've heard something about the MKI mr2's cooling system making the engine run like hell when there's air in it; how could I check this?

ToyotaTechGeek

you don't check it, you bleed it. if you have air in the system, then you had better bleed it as per the Toyota factory specifications, if not, then you run the chance of blowing the head gasket. further, what is a JDM 4AG-E? just curious, i mean, are you speaking of a high compression 4AG-E? or something else?
you need to check base timing (aka cam timing). you also need to check spark plugs and get a 'read' off of those.

The Wok

I was wondering how long it would take you to see this.

I have no idea, the guy told me it was a JDM 4a from Rising Sun motors on california.

Do you think air in the cooling system could be it? It doesn't run hot which makes me think it's something else...

The Wok

Also, the "miss" starts to get really bad around 3.5-4k rpm and up. Perhaps it could be the TVIS?

I'm just throwing ideas around at this point.

PJ2

The TVIS won't make it miss fire it will just have no power on the lower rpm, it sounds like you may have a vacuum leak somewhere, if you/he replaced the air filter tubing with a cone, did you plug the A/C idle up hose back in or did you cap it?? You didn't advance the timing did you?

The Wok

I did nothing to the timing and the A/C idle line is hooked up.

ToyotaTechGeek

i still say check base timing. the second thing to do is check timing with a timing light (don't forget to short the service terminals!). if there is still trouble, then it's a bitch, but you may have to check to make sure the dizzy is installed properly. without any more description of the 'misfire' it would be diffucult to try to guess what might be causing the trouble. does the misfire occur and then suddenly disappear? or does it still stumble throught the rest of the rpm range? what kind of plugs did you use? what kind of plug wires? why didn't you change the dizzy cap and rotor? you should, even if it 'looks' fine. what did the old plugs that came out of it look like? burnt? white? bronze? this will also give you some clue as to what is going-on.

The Wok

It stumbles from about 3k on up, and after a while driving it under load will do it at idle; like stumbling from 1k to 500 rpm, it almost wants to turn off.

The old plugs looked burnt; i replaced them with some bosch plugs. The wires are just the ones that they sell at Advance (Xact? I was just trying to get it running right at this point.) I really thought the oil in the dist. was causing it but I guess not.

I was planning on changing the cap/rotor today with the fuel filter. Also checking compression. When i go back to work tommorrow I'll have one of the master-techs look at it (I work at a toyota dealer.)

It should also be said that I have little to no experience with distributors; the first car I really dug into was my SHO which is distributorless.

ToyotaTechGeek

burnt? black? then they would have been rich. bosch plugs...yech! in a Toyota?!?!? NGK or Denso only!

The Wok

i had them already so I went ahead and stuck them in there (they are the correct ones.)

Beats spending another 30-40 on plugs I didn't NEED.