Hesitation, misfire when warm

[rknorr]

Problem: Have an '89 Cavalier with 2.0 engine and an auto trans. Car has 46,000 miles (original). Starting about a month ago and getting progressively worse, car has developed a hesitation and misfire when trying to accelerate, also service engine light was coming on. This only occurs when the car is warm. These problems were accompanied with a reluctance to upshift or downshift when problem is occuring but this seems to have gone away with the new throttle position sensor. Additionally the service engine light now does not come on but the car still runs just as badly when warm. Car has had new spark plugs installed 6 months ago, otherwise no changes. Any help troubleshooting would be appreciated.

[wcamaddox]

When was the last time it had a complete tune up? Plugs, wires, O2 sensor, fuel filter , pcv, etc....?

[rknorr]

Maybe never, when I bought this car last year it had 30,000 miles and the original tires still. I really can't afford to replace everything right now so I was hoping for more specific suggestions. I saw in another post that someone suggested spraying water on the plug wires at night to expose leaky wires, I think I'll try that one. Car had new sparkplugs about 6 months ago. Thanks for the reply.

[Cavalier2000]

Start with wires, they are cheap, but it is an 89 so eventually you are gonna wanna repalce the rest of the stuff

[wcamaddox]

I wouldnt suggest water especially in large amounts you might end up with a worse problem than you have now (cracked head, exhaust manifold) if the plugs are leaking at night you will be able to tell without the water. But the first and probably cheapest thing I would replace is the fuel filter and pcv both are relatively cheap probably 10 bucks or so then progress to the next thing you can afford o2 sensor is about 20 bucks wires about the same. But I would definately start at fuel filter&pcv.

Bill

[Cavalier2000]

what was your code saying?

[rknorr]

What code? I'm not aware of how to pull codes out of a car this old. I have an OBD II code reader but nothing for this car. How do you read any codes for an '89?

[wcamaddox]

I use a wire non-coated paperclip bent into a "U" shape the aldl will be under the dash on the drivers side. plug the bent up paperclip into the two top right hand side holes. Turn the key to the "RUN" position but dont start the car. The check engine light should start flashing 13 which tells you its diognosing. The flashes will be 1 flash short pause 3 flashes pause and will repeat a couple of times. If it flashes a code other than 13 say like 3flashes pause 4 flashes your code is 34. You should be able to call your local parts store and the=y can tell you what they mean or if you have a repair manual it will tell you. If you dont have a manual post what codes you get I have a manual for that car because my cavalier is an 89 z-24 and it has the codes in it.

[rknorr]

Originally Posted by wcamaddox

I use a wire non-coated paperclip bent into a "U" shape the aldl will be under the dash on the drivers side. plug the bent up paperclip into the two top right hand side holes. Turn the key to the "RUN" position but dont start the car. The check engine light should start flashing 13 which tells you its diognosing. The flashes will be 1 flash short pause 3 flashes pause and will repeat a couple of times. If it flashes a code other than 13 say like 3flashes pause 4 flashes your code is 34. You should be able to call your local parts store and the=y can tell you what they mean or if you have a repair manual it will tell you. If you dont have a manual post what codes you get I have a manual for that car because my cavalier is an 89 z-24 and it has the codes in it.

Thanks, I didn't realise that this car had the ability to store and display codes. I pulled the codes and here is what I get.

1-3: O2 sensor circuit
2-1: TPS circuit
3-3: MAP sensor
4-5: rich system indication

Just today I have replaced the TPS and repaired a broken vacuum line to the MAP sensor. The car runs way better but is now hard to start. The car was not hard to start after replacing the TPS but only became hard to start after fixing the vacuum leak to the MAP sensor. The service engine soon light came back on after fixing the MAP sensor leak.
Question is should I reset the ECM (unplug the fuse) and then take it out for a drive and then see what the codes are?

[rknorr]

Update: I went out and unplugged the ECM fuse (looks like a relay) for about 2 minutes then plugged it back in. The car was then started after 4 or 5 tries and let run for about 30 seconds. The service engine light came on after about 10 seconds. I shut off the car and checked the codes and got the exact same 13,21,33 and 45 codes. Did the ECM actually reset?

[wcamaddox]

Probably not, when I "taught" my computer that it had a new TPS I had to unplug the battery for at least one minute. I dont know if your car needs to be taught it has a new TPS or not but someone else may know. As for the O2 sensor circuit code and the rich condition code they could both be a bad O2 sensor. Idont know what type of auto parts stores you have around you but at my local Autozone it was about $20. Also most parts stores can check if your map sensor is bad. I know Autozone checked mine for me. As far as the TPS circuit code it may need to learn the new sensor. If so I know a way to do that also. I posted it in another thread under 3.1 stalling under braking I believe is what it is called. Good luck and let us know how it works out.

[wcamaddox]

p.s. most times in order to get new codes you need to drive the car a few miles (like 10 or so) between 45 & 60mph when its warmed up. Thats when the computer will start a self diagnostic check.

[rknorr]

I did the TPS learn process then I went out and drove the car for about 10 miles varying speed up to 65mph. Car is hard to start and hesitates everytime the throttle is depressed. The service engine soon light comes on about 5 seconds after the car starts. I pulled the codes after I came back from the drive and guess what; the only code that comes up is for the TPS circuit. What gives? I replaced that yesterday and it made a huge improvement in driveability. Is the new one bad or is there something else I need to do?

[wcamaddox]

Is there a way to set the timing on your car I knoow on my 2.8 its all computer regulated but if I recall correctly your 4cyl can have the timing set. Check your manual. In mine the first six things l;isted for this problem are fuel filter, wires,plugs,fuel pressure & pump,and timing. As for the TPS code still coming up inspect the wires to the plug and away from the plug. Check the plug its self for corrosion.

P.S. I forgot to tell you to try to drive the car at a constant speed for ten or so miles for the self-diagnostic no hard acceleration and no braking I know some areas of the country its tough to do this but in Indiana we have lots of wide open flat roads and I have an Interstate close also. I appologize for not telling you that earlier.
Bill

[rknorr]

Thanks for the quick reply. I will go inspect the TPS plug and wires. The ignition timing is not adjustable, it has no distributor just one coil for every two cylinders. I'm going to try the TPS learn thing again too. I can't figure out why the car started to be hard to start after I replaced the broken vacuum hose to the MAP sensor, the hose I replace was broken 2/3rds of the circumference. I can't imagine it was working. Time to replace the fuel filter I guess.