Long time no see, Oppo! Summer is approaching so I’ll be posting a little more frequently now that I have time to spend with my MR2. That being said, it started accelerating unevenly yesterday and I’m not sure what’s wrong.

For reference this is a 1991 MR2 (2nd gen) with the stock non-turbo 5S-FE 2.2 liter 4-cylinder and the 5-speed manual transmission.

Such a professional graph!

Under heavier throttle inputs, let’s say 50% throttle or more, the car accelerates unevenly. It seems to alternate between full power and no power about two or three times per second on the gas.

Advertisement

From what I’ve been able to google, this could be one of three things:

-Clutch could be slipping, resulting in uneven acceleration. This could make sense under hard throttle, but the engine isn’t revving higher during the delays in acceleration. I’m fairly sure it’s not this one but I’m including it just in case.

-Something is wrong with the ECU. Maybe a sensor isn’t reading properly.

Advertisement

-Throttle cable or some linkage. It seems to be alternating between wide open throttle and no throttle and that’s what results in the uneven acceleration.

Taking the derivatives of the original graphs I get what I think the throttle position looks like over time. These gaps in power delivery are alarming and I haven’t yet found a conclusive diagnosis.

Any thoughts? Is this an issue I can avoid simply by driving the car gently until I find a fix for it, or is there a risk of greater problems arising if I continue to drive it? Any and all input is greatly appreciated.

Advertisement

Picture of the car for your time: