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Discussion Starter #1
Hey everyone, longtime lurker, 1st time poster. I've long benefited from info gleaned from this site, but now I've got a headscratcher that I'm stuck on and wondering if I can get any insight.

I have a 4AGZE swapped '86 that is about 95% complete, I'm just trying to iron out the last remaining bugs. I had it running pretty good; I just hadn't checked timing yet. Well anyways, when I checked it, I found it was a bit advanced, so I adjusted it back to the proper position according to the manual. Well, since then, it hasn't been running right.

When you first start it up from cold, it seems to run good for about 30 seconds (probably due to the cold start sequence), but after this period, the idle revs start dropping lower and lower, and if you blip the throttle, the revs will drop down to 400 or 500 rpm before recovering. Sometimes the engine will even die. The idle will often get very rough, and the engine will struggle to stay running. If the engine really gets warmed up, it seems to idle slightly better. That's only half of it.

When it comes to actually driving it, the power delivery is way off the mark. It used to get that trademark power surge once the sc engaged, but now that power delivery is way lagged and uneven. It almost feels like it's not making boost, but as far as I can tell the sc is engaging as it should and there are no leaks. If you slowly roll into the throttle, the power will eventually come, though it still doesn't feel as strong as it should.

Now, I should say that I'm not 100% this was caused by adjusting the timing, or its just a coincidence. I should mention that the car was acting a bit screwy when I was trying to adjust timing. When you put it in diagnostic mode, it's supposed to retard the timing so you can make your exact adjustments. It seemed to do this sometimes, and other times it wouldn't. But after several attempts, I got it timed as it was supposed to be (at least according to the marks on my main pulley).

In any case, a friend with good 4AG knowledge is theorizing that something is up with the air-fuel mixture, and I suspect he's right. The other possibility is that its running in some f'd up mode due to the ECU getting bad data perhaps? I'm not a good enough mechanic to pinpoint it down, and i don't want to go around trying to fiddle with every little thing, so any advice would be appreciated. Thank you

Some other data: the car is running in regular fuel mode, and O2 sensor is not in place. Using stock 86 fuel pump, fuel injectors are freshly rebuilt 4AGZE units. The car ran fine in this state before I made the timing adjustment.
 

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I had the same type of problem with a NA 4AGE. The outer ring on the engine damper had moved, relative the inner ring, so the timing was off by about 20*. Pull the number one plug, and put a screw driver, rod, or dowel, in the plug hole and slowly turn the engine over by hand until it's at TDC. Then verify that you timing marks are correct. davew
 

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If you got the 4AGZE from a different model, then the timing marks may be wrong. The MR2 has a different timing marker than the FWD cars. I think that the problem was that the standard timing marks just were not visible in the rear mounted application.
 

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Discussion Starter #4
I had the same type of problem with a NA 4AGE. The outer ring on the engine damper had moved, relative the inner ring, so the timing was off by about 20*. Pull the number one plug, and put a screw driver, rod, or dowel, in the plug hole and slowly turn the engine over by hand until it's at TDC. Then verify that you timing marks are correct. davew
I'll check this out; its pretty easy to verify after all.

If you got the 4AGZE from a different model, then the timing marks may be wrong. The MR2 has a different timing marker than the FWD cars. I think that the problem was that the standard timing marks just were not visible in the rear mounted application.
I believe the pulley came with the engine. If I check TDC it should let me know if its correct or not.
 

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Discussion Starter #5
Checked the position of #1 cyl TDC and confirmed that the timing marks are pretty much where they should be. I suppose I could try advancing the timing back to where it was before I adjusted it in the first place to see if it ran better, but i'd be more or less ballparking it.
 
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