Question
1991 Acclaim 3.0 liter V6 - auto/ac - miles unknown -probably 90,000+
Engine may be from a '94. I bought a TPS but the book part doesn't match the actual part. We traced the part number from the actual part and found that it was a TPS for a '94.
During an incident, the engine will not respond the the accelerator, then it will hesitate, stumble, and sometimes surge but sometimes not surge. When it surges into recovery, it runs smoothly with good power. It may go a day or three between incidents then have several incidents in a day. Each incident may last from a few minutes to an hour or so. I use this car 4 or 5 hours a day doing stop and go driving at speeds mostly under 40 mph. The problem went on for several days without throwing engine codes. During one incident, I pumped the gas repeatedly and got a check engine light with code 21 - O2 sensor. I think it threw the O2 code because I exceeded the O2 sensors ability to respond. I have some suspicion the the fuel pump or fuel pickup may be the problem but the hesitation/stumble is pronounced and doesn't act to me like fuel starvation. I've recently replaced the fuel filter and the TPS but I wonder is there is some congealed gasoline in the tank blocking the fuel pickup. I can turn wrenches and I don't mind following the steps. I just don't want to replace a bunch of parts because I don't know what steps to take in what order. ** An update on the TPS. The car ran great for 30 minutes then the stumbling got much worse and threw a code (24 I think) that indicates the TPS put out voltage over 5 volts so I put the old TPS back on. Your answer will be appreciated. And I'll say thank you very much for any help you give now just in case I can't find my way back later
AnswerHi Don,
You can cancel all the stale codes by disconnecting the battery for a few minutes, then all that will be there is a 12 code. And you can reread the codes as often as you like. So why not recheck that again.
I would not dismiss a 21 code, which indicates the sensor either stays at center voltage or is shorted to voltage supply; I don't believe the malfunction of the engine would cause it.
Check the wiring harness for the TPS, it could be shorting out. Also, use an ohmmeter on the throttle body measuring between the center pin and either side pin. Move the valve slowly through the whole range of motion looking for any discontinuities in the resistance readings. If it is smooth, then it should be OK? Have you cleaned both sides of the throttle plate and the by-pass idle passageway?
The other thing to check is the egr valve, if you have one. That is used on the '94 engine, but only used on '91 cars that were sold in California. It is mounted in the exhaust pipe that crosses over from the front manifold to the rear, underneath the throttle body. Find its stem, if you do have an egr, which is in the flange area between the round top and body of the valve. The stem has a slot into which the tip of a screwdriver can be inserted to move the stem back and forth against spring-action in one direction. Make sure that the spring moves the stem to a dead stop, and that it moves freely back and forth. If not, then spray the stem where it enters the valve body with WD-40 and move it some more to free up the action.
Let me know what sort of fresh codes you readout.
Roland
