91 Escort transmission problems?

[ILuvCelicas]

My girlfriend's 91 Escort LX wagon 1.9 has had a couple major problems recently and I can't tell what's going on with it. At first, it would jerk after heating up. It was like the throttle position sensor signal was going in and out, so I replaced it and the problem was still there, but it didn't get worse for a while. Then it seemed to be just on hills that it would not even go up them. RPMs would go really low and it could only crawl up even the slightest incline at about 5 mph. Then it was taken to their mechanics, who have not been very good/honest from what I can tell, and they changed the fuel filter. After that the car was doing the same hesitation/jerking thing that it was doing before, but now it will only shift from 1st to 3rd at 35 mph, completely skipping second. Obviously the mechanics screwed it up somehow, but can anyone help me out as far as these two problems? I would hate to have to junk the car but it's completely undriveable. Thanks in advance for the help.

[A. Souphound]

Originally Posted by ILuvCelicas

My girlfriend's 91 Escort LX wagon 1.9 has had a couple major problems recently and I can't tell what's going on with it. At first, it would jerk after heating up. It was like the throttle position sensor signal was going in and out, so I replaced it and the problem was still there, but it didn't get worse for a while. Then it seemed to be just on hills that it would not even go up them. RPMs would go really low and it could only crawl up even the slightest incline at about 5 mph. Then it was taken to their mechanics, who have not been very good/honest from what I can tell, and they changed the fuel filter. After that the car was doing the same hesitation/jerking thing that it was doing before, but now it will only shift from 1st to 3rd at 35 mph, completely skipping second. Obviously the mechanics screwed it up somehow, but can anyone help me out as far as these two problems? I would hate to have to junk the car but it's completely undriveable. Thanks in advance for the help.

Have you tried to read the trouble codes? There are Self-test connectors under the hood on the passenger side for a scanner hook-up. Autozone or Advance Auto Parts will read out the ECC and tell you the codes. This would be a good starting point. Another alternative is to buy a scanner for about $30 at these stores and do it yourself. Complete instructions are furnished with the scanner.
The complaint of bucking and jerking is common on this forum, and it's cause has been identified as different things, but generally speaking I think it fair to say the biggest cause was poor maintenance. If this car has not been tuned-up with plugs, wires, distributor cap rotor etc. I would look at their condition very carefully, and replace if necessary. Since changing the fuel filter did help, I would put some fuel injector cleaner in the tank, the problem could be a sticking injector/s.

[ILuvCelicas]

Thanks for the advice about the scanner. I bought one and I think I need to get one for all my cars. The codes came up as the throttle position sensor voltage being off and two for the idle: engine speed unable to go past normal idle, and normal idle being uncontrollable or high (I don't have the book with me, sorry). For some reason I removed the TPS and replaced it and it worked fine. It's happened before but I can't figure out why. It will work for a while, then mess up maybe then you slam on it, take it off, put it on, good as new. So the not shifting problem is solved. As far as the other two codes and the jerking, could it be maybe the IAC valve not working right? Is there a way to test it and can cleaning it help? Thanks for any and all replies.

[ILuvCelicas]

The codes were 12 and 13: cannot control RPM during KOER self-test high rpm check and cannot control RPM during KOER self-test low rpm check. And all the routine maintenance is up to date with the car. About 7,000 miles ago it underwent EVERYTHING, tune-up, timing belt, brakes all around, so I think it's probably something that normally doesn't go bad over time. So I'm at a loss unless it is an IAC valve.

[A. Souphound]

Originally Posted by ILuvCelicas

Thanks for the advice about the scanner. I bought one and I think I need to get one for all my cars. The codes came up as the throttle position sensor voltage being off and two for the idle: engine speed unable to go past normal idle, and normal idle being uncontrollable or high (I don't have the book with me, sorry). For some reason I removed the TPS and replaced it and it worked fine. It's happened before but I can't figure out why. It will work for a while, then mess up maybe then you slam on it, take it off, put it on, good as new. So the not shifting problem is solved. As far as the other two codes and the jerking, could it be maybe the IAC valve not working right? Is there a way to test it and can cleaning it help? Thanks for any and all replies.

Yes, the scanner's have saved me a lot of time and money, and glad you are pleased with it.
I'm concerned over the TPS voltage being off. Most of the manual's suggest R & R and say words like checking it is beyond the home mechanic and needs to be calibrated...etc. .The TPS is nothing but a wirewound potentiometer and can be checked with an ohm meter. If you have a VOM you can check the TPS as follows: Engine off, key off, disconnect the TPS connector. There are three wires going to the TPS the black wire (-) the center wire is the signal wire and the other outside wire is the reference voltage (+) wire. Hook-up your VOM leads and read the resistance (ohms) with throttle closed (*should be 0), and start opening the throttle. The resistance should increase smoothly if it doesn't or the needle jumps, the TPS should be replaced.
By monitoring the TPS voltage the onboard computer can determine fuel delivery based on throttle angle (driver demand). A faulty TPS can cause intermittent bursts of fuel from the injector and an unstable idle or hesitation because the computer thinks the throttle is moving.
*Note: With throttle closed, if the resistance is not 0 loosen the TPS and rotate until it reads 0.
You are saying IAC valve, do you mean the Idle speed control valve (ISC)? Do you have Mult-point fuel injection?
Let me know your progress. Great news it wasn't a transmission problem.

[ILuvCelicas]

It is multi-port fuel injection. I meant the IAC valve because in the Haynes manual it described the sensor's function as increasing airflow when the car's engine is under load. That's why I'm thinking it is malfunctioning because when the car is under load (hill?) it seems like it reverts back to idle and creeps up the hill at 2 mph.

[A. Souphound]

Originally Posted by ILuvCelicas

It is multi-port fuel injection. I meant the IAC valve because in the Haynes manual it described the sensor's function as increasing airflow when the car's engine is under load. That's why I'm thinking it is malfunctioning because when the car is under load (hill?) it seems like it reverts back to idle and creeps up the hill at 2 mph.

There are a number of things that could cause this condition.....fuel pressure regulator, fuel pump/low pressure, insufficent volume, EEC, etc.
The computer codes indicate a TPS voltage problem, and throttle response problems....
I found the meaning of the IAC acronym = Idle Air Control and ISC = Idle air speed Control, basically they perform the same function. (The valve looks like a motor located on the throttle body.) Sometimes they stick, and you can remove, clean and re-install. There is a tube which binds and a little oil or WD40 will help.
Let us know what you discover.

[old409]

I had the same exact trouble with my Escort 1.9. The code identified the TPS as the culprit but changing it did nothing. I took the car to an honest mechanic and he found that the keyway on the balancer that also has the crank timing device mounted to it was worn and the crank balancer assy was bouncing around causing the timing to jump all over and drive the computer nuts. The car wouldn't go up hills and at times you could floor it and it wouldn't rev up.

As crazy as this sounds, it fixed the car.