1989 MR2 hesitates

Possibly an air leak?

Kurt, 82K 89 MK1 SC..Care to sell it? =) Some shops wont want to work on a rear engine car, but some will. I would not hesitate taking it to a local garage. I would say that either its a Coil, bad ground or unlikely bad injectors.

If you want more help try the MR2 Board

Yeah, that's what I was thinking. Look for leaks in the air tube from the filter to the plenum. The MAF is metering the air from the airbox, and extra air getting in the tube stumbles the engine.

Something else I found on my '85 Celica (2.4L 22RE) is that there is a connector right at the entrance to the plenum. I patched my tube and it ran well for a while, but after a time I tried to check the timing and it kept moving. We replaced the engine with a truck 2.4; kept the same intake, etc and it still does it. I found if I wiggle the wiring to this connector the idle will smooth out without stumbling. I wonder what it connects to?

Intake air temp?

:> Possibly an air leak?

: Yeah, that's what I was thinking. Look for leaks in the air tube from the : filter to the plenum. The MAF is metering the air from the airbox, and : extra air getting in the tube stumbles the engine.

: Something else I found on my '85 Celica (2.4L 22RE) is that there is a : connector right at the entrance to the plenum. I patched my tube and it : ran well for a while, but after a time I tried to check the timing and it : kept moving. We replaced the engine with a truck 2.4; kept the same : intake, etc and it still does it. I found if I wiggle the wiring to this : connector the idle will smooth out without stumbling. I wonder what it : connects to?

You're talking about the tube from the air filter in the trunk and then downstream from there? How do I check for leaks? Just visual inspection?

I'll have to look at the car because I can't remember, but isn't the air flow meter (MAF? definition please) downstream of the filter? It seems that you would have to have a leak after the meter to effect the engine.

I'll also check the resistance of the ignition coil windings

The tube from the air filter to the intake can develop cracks, fixable with duct tape. If you can, remove the tube from the engine compartment and check the entire length and circumference.

MAF stands for Mass Air Flow. The leaks generally occur between the air flow meter and intake plenum.

I don't remember which type of air flow meter you have. Earlier ones were a hinged flap attached to a potentiometer. As air flow increased, the flap was opened more, and the more the flap opened, the more voltage was sent to the Electronic Control Unit. On this type, make sure the flap moves smoothly.

Some air flow meters were basically a small mirror mounted on a wire that was stretched across an opening. An LED light was projected on the mirror and as more and more air flowed past the mirror, it would oscillate more quickly and the sensor picking up the reflection from the LED would know how much air was going past the meter.

Yet another type is a hot wire. A wire's resistance changes with temperature, and as more air flows past the wire, it is cooled, changing its resistance. The meter measures the varying volage from the varying resistance.

I didn't notice the leaks until I took it off and flexed it a little bit. Then I found a bunch, in between the 'flutes'. I patched them with Duct tape.

The air filter is in it's little home, OK? Now right after the airbox you will see a gadget that has a Toy P/N with a connector going to it. That's the Mass Air Flow sensor. It meters the air from the filter to the engine, through the tube. That's why, if there is a leak in the tube the engine runs rough, because the engine is getting more air than the MAF is telling the computer.