Questions and Answers

Supercharged MR-2 Q. I have a 1986 Toyota MR-2. I have replaced the engine with a later model Toyota engine. The original engine was a 1.6 Liter 4A-GE NA throttle body injected straight four. The new engine is a Japanese spec 1.6 Liter 4A-GZE Super Charged engine.

Now I rewired the engine to use US electronics, as they are easier to get. So I am using a US AFM , US Dizzy, and US ECU. Vehicle also is using the stock auto transmission.

I know I have a lot of variables here, however, I feel that my problem should be symptomatic to some situation or circumstances that can be fixed.

The car starts fine. Idles smooth. but will not rev. It seems to rev say 90% when first started. Will rev to redline, but seems kind of sluggish to do so. But once warmed up to operating temperature, it stops revving. If I open the throttle slowly, I can get it to rev to about 4,000 RPM, but it will not rev past that, as I think the ECU engaged the Super Charger (electo clutch).

If I go to Wide Open Throttle the engine hovers around what ever RPM it is at, usually 2,000 RPM or so. It will not stall or back of the revs. Simply stays at 2,000 ish and will not climb, kind of sputters and complains though. As a result it does not produce any power when driven.

I have verified that timing is set correctly. The AFM is within spec according to the test I have run as recommended by the shop manual. I have set and verified the Throttle Position Sensor settings.

Here is one thing I have done that seems to work, but is not a viable solution. I have opened the AFM so that I can watch the actuation of the electronic swing arm. If I manually operate the flapper, and the throttle at the same time, the engine revs perfectly. I have spent an exhaustive amount of time searching for vacuum leaks, but have had little success.

Thank you very much for any help you may be able to provide.
Raymond

A. The big question in my mind is what ECU are you using? It looks to me that you are in a Catch-22 here. If you are using your original ECU, the new engine will be operating outside of its parameters and if you are using the ECU from the replacement engine it will also be operating outside its parameters.

But I think your primary problem is the Air Flow Meter (AFM). Not that it's bad, but that it's not designed with a supercharged engine. The supercharger is stuffing the intake manifold with compressed air and none is being drawn in through the AFM. Consequently you have tons of unmetered air coming into the engine. If the air is unmetered the computer can't adjust the fuel mixture accordingly.

The air the supercharger is drawing in must go through the AFM in order to solve your problem.