Surge, surge, surge... Geo Metro

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HELP!!

Have a '93 2-door Geo Metro Automatic 3 cylinder. We found out after purchase that it has a '90 engine. The car was manufactured in Canada, if that makes any difference. (Don't know where the engine was manufactured.) I only had this car 2 or 3 weeks before this problem started.

Engine begins surging while holding accelerator steady. Doesn't seem to do it until it warms up (A couple of minutes). This is a steady pattern.. up, down, up, down.. about 1 second or a little longer for each cycle.

When you look down the fuel injection port when it's doing it, it doesn't spray during the pulses.

Also, the thermostat for the engine does not kick on the fan. This didn't change after we replaced the thermostat with a new one.

Since buying this, we have replaced the following with new parts:
replaced the thermostat for the antifreeze.
spark plugs & wires
distributer cap and rotor
fuel filter

Also, we replaced antifreeze temperature sensor with a used one. (noticed at the junk yard that there was another sensor right behind that one, which we did not replace).

A lot of repair shops don't want anything to do with this car, because of the body/engine mismatch. No one seems to be able to test the computer except for Chevy, which charges $94 just to diagnose the problem!!

The computer (ECM??) looks like a BITCH to get to, under the dash and behind fuse box and more, if we were going to try to switch it out for one from a junk yard.

Can anyone help, PLEASE! Anyone had this problem themselves?

Thanks so much..

Martha and Mike

posted by  GeoProblems

Where the hell do you people find these cars? I never have these ridiculous problems. Am I lucky or smart?

posted by  What?

You must be lucky, because you sure don't sound smart to us! :mrgreen:

posted by  GeoProblems

Who the f*ck is us?

posted by  What?

Martha and mike obviously...

M&M just hang around for a little while and someone who knows what is happening will chime in. I hear surge and I think of compressor maps and small turbines...

posted by  Zalight

Presumably this is a Jap engine with Denso bits 'n bobs connected to a Denso computer. A fairly common problem with this era engine is they like to hunt when there is an air/steam pocket enveloping the engine coolant temp sensor. Draining the system can lead to this situation, because the makeup tank is lower than the highest point in the system.

You might like to loosen the hose going to the throttle body (it should either have a wax element air valve or de ice circuit) and start the engine. Refix the hose while the engine is running to ensure gravity doesn't undo all the good work.

Make sure you do this while the engine is cold so as not to suffer burns.

posted by  Wally

It debilitates the car, not just when it is idling. Max speed about 5-10 mph.

posted by  GeoProblems

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