peculiar driveability problem

1992 Metro with automatic.
When driving in steady state, engine seems to cut off completely when throttle is lifted slightly. When throttle is again depressed engine runs again. This seems to be what's happening. It sort of feels like a compression brake engaging whenever the throttle is released just a little. It is a royal pain when cruising as you must maintain positive pressure on the throttle to keep it from happening. On the bright side it really seems to piss off tailgaters!

Also the check engine light continually flashes a code 13.

Any ideas comments will be appreciated.

I got te same problem on my 1991 Geo and everybody tells me its the TPS Throttle Posision Sensor so i went and got the new one and i still got the same problem but do me a fav open your air box take the air filter out and look at your Throttle wile you try to keep it at hight rpm and when the problem starts happening see if the fuel cuts off for a sec or so :2cents:

I was thinking tps too, but it would seem that if it were a tps it would always occur at the same exact throttle position, which it does not. I'll look down the throttle bore like you suggested. Did you ever fix yours?

I checked the injector while free-revving. I could not notice any cutting out. Perhaps it needs to be under load.

Check the MAP sensor it might detect no vacum at high RPM, the MAP sensor cuts the fuel to the injector when detects no vacuum or high vacuum I don t remember well, when you rev the engine in park you will see that the injector stops the fuel for a sec til the engine rpm goes down.

can you tell me how to do that? I have a dvom

Well i took my geo to couple of mecanincs and they couldnt find out what the problem is do to the fact that i dont have a obd system wich tells me that they only depend on the scanner tool but no i didnt fix my problem yet i got the map sensor from junk yard last week i put it on still the same problem i just did a conversion on my geo from auto to manual to end up whit the same damn problem , And as for the rev in the park im keeping my throttle in the same posision and the
engine's rpm keep going up and down on it's own whit out me moving the throttle im all out of ideas at the moment but good luck i hope you do fix it

Wow you did an Auto to manual conversion! That certainly rules out the tranny don't it! At any rate the car has other problems, namely burning 1 quart of oil in 150 miles. Just bought the thing sight unseen online and trusted the seller (you know the story "one owner creampuff") boy did I get screwed.
Anyhow I'm going to go ahead and change out the pistons and bearings, all the seals and gaskets and then deal with the driveablility problem later. Do you think there is any chance it is the injector causing this?

About a year ago I put a JDM motor in my 93 metro and have had a very similar problem ever since. I don't get the trouble code though, just a complete shut down each time I ease off the throttle. Starting up cold it doesn't do it, only after it has been driven then shut off and restarted. I have driven it for 4 hrs without shutting it off and it runs perfect, but shut it off for any reason and then the problem begins and doesn't stop no matter how far or how long you drive. The metro has an automatic transmission and whether it is acting up or not the gas mileage doesn't seem to be affected, usually getting around 36mpg.

This morning I pulled all the pistons out, so it will be awhile before I can tackle the driveability problem. I ordered a factory service manual, it should have some pretty detailed troubleshooting sequences I can go through. This problem has got to be solveable. One plus is that there will be no doubt once it is fixed!

So i see you gonna do the hole overhaul of the motor let me know what price is for all of it Couse ATK is asking $1500 for a motor,For the injector i figured if it was that that it would happen all the time,but i did take my Injector and cleand it out still same problem i just wish that the check angine light would stay on so i can read the code but it doesnt. Can you tell me where did you get the Factory service manual,

As far as the overhaul goes. I looked at the bores and they are good no ridge or scoring, the crank looks good. I've ordered 3 pistons & rings for $75.00
a head gasket set with bolts is about $55.00 rod bearings are $24.00. I need to do some head work too. That is kind of unknown right now as to the total amount, but the valves did not pass the leak test (gasoline in the ports with camshaft removed).
I ordered my factory repair manual from http://www.rothautobooks.com/ It was only $50.00 plus $5.00 shipping. I don't know if they have any more. You can get the manual from gm's supplier as well, but it is $109.00

As for the cutting out, check the power wires goin in and coming out of the fusebox under the hood. I've had that happen on one of my metro's before. Those terminals get burnt, and the plugs melt. And they get a bad connection sometimes. You'll notice the check engine light flash right when the engine cuts out usually.

Thanks for the suggestion. However, my problem is much to consistent to be what you said (it seems).
This problems happens every time I relieve pressure on the gas pedal. And only when I slightly relieve pressure. When the pressure is fully releaved the engine continues to run.

Ron, my problem is identical except for the check engine light. Mine doesn't come on. What puzzles me though is why mine runs perfect when started up cold and never acts up until after it is shut off and restarted. Does yours do that, or is it all the time?

Mine does it all the time. the check engine lite won't flash code 13 if I pull the diagnostic fuse out.
You may try installing yours and see if you flash any stored codes. BTW, code 13 is O2 sensor.
I had a dream last night that is was the TPS, I even saw sparks coming out of it in my dream. This may sound silly, but I have solved many diagnostic problems by listening to my dreams! I still have the engine apart so it won't be for awhile before I get an answer.

Ron that is a good dream,
I messed around my tps and found out that some how efects timing how is this possible

Thanks, when time permits I'll check to see what trouble codes are stored. I also want to remove the TPS and make sure it is working and adjusted right. I have the manual to explain how. I'll keep you posted on what I find or if anything I do fixes it. I keep thinking it is electrical or a vacuum switch since it only does it after being shut off and restarted. Something seems to be sticking. Good luck on putting the engine back together. When I put the JDM in, I installed a new water pump and timing belt while I had it out. The water pump is cheap and to change it, the timing belt has to come off. I have put 15,000 miles on the motor since I put it in and it runs fine except for the one problem. If I can't find what is wrong, I'll take it into the shop to be fixed. Anyway, I'll keep you posted. Thanks again.

Hey Ron i hope your build is going as you wanted well i wanted to let you know i got my problem fixed over the weekend and here it is i have a advanced distributor and in side it theres a white wire that got striped so every time the vacum would advance it would move that wire to the wall of the ditributor and make a conection wich made da motor run like crap so i hope this fixes your problem or anybody out there thats has the similar problem

I am now a happy man :cheers:

Congradulations! I'll have to take a look at that. So far my engine is still apart. This is a bit of a back burner project right now. I did order a used throttle body complete with TPS and injector. It was only $30 so I figured it would be worth trying to swap it out & see if there's a change.
It may be a month before I get around to putting the engine together.
Thanks for the info.