rmadursk

A little history may be in order...

I have a1991 NA. Replaced blown motor with known good running motor. The car starts up no problems, will rev unloaded to at least 6500 but has a stumble off idle. The car bucks and kicks terribly under a load, will barely go up a gentle hill but smooths out perfectly as soon as the load goes away coming down the other side.

I'm pretty sure I do not have any vacuum leaks. I found a couple early on after assembly was complete and I checked again this weekend to make sure none had developed. I use a tube stuck in my ear and moved around the manifold to hear them.

I have not adjusted the timing but the CAS has not been moved.

The car idles smoothly at 800 RPM and will do so all day long.

The ECU is spitting codes 18 and 28. Both ranges of the TPS. I have the TPS adjusted about as perfectly as it can be (I think). I tried a bunch of the different methods posted here. This is what has worked for me. I used the FSM method using a digital multi-meter (DMM) to check for voltage at the green 3-pin connector. I would adjust the screw until the resistance on the 6-wire plug was in spec between both A-B and D-E contacts for both closed and open throttle, plug it back in and adjust tha same screw to get 1.000V on the G/R wire and check the 3-pin again to make sure it was still OK. I can hear the relief solenoid and the other one (I forget what it is called) actuating as I move the narrow range plunger in/out.

Using this method I am able to get the resistances right in the middle of the range specified, exactly 1.000V on the G/R wire, and the test light functioning perfectly. All of this is being done with the engine at normal operating temperature.

Disconnect the battery ground, go grab another beer, hook it back up and the ECU is still spitting out 18 and 28.

What am I doing wrong?

Any clues for other problems might I have once I get the TPS issue worked out?

Thanks,

Ron

rmadursk

No clues on this one?

I may have mis-typed the codes. I think the TPS codes are 12 and 18.

Help me out here guys...

Ron

satch

iTrader: (1)

Have you tried to drive the car with the TPS disconnected to see if the same symptoms occur? Checking the voltage at the ECU might give you a different reading then at the sensor itself (possible wiring issues). You can measure the narrow range where at the idle setting it reads 1 volt and at 30% or so throttle the voltage increases to 4.5 volts and the increase needs to be smooth w/o jumps.

rmadursk

I was able to pull the car out last night and it still has the same symptoms without the TPS connected.

Thanks,

Ron

rmadursk

I removed the intake to check to make sure the movable ports were installed correctly. They were in the correct orientation. However, I did find a couple of other problems in the vacuum system. There are check valves under the UIM and 2 of them were damaged. One split at the seam and the other was cracked at the stem that goes into the vacuum line.

Where do I get these?

Also, since I have it apart I am going to repair/replace the injectors since a lot of the posts I found during my searches mentioned this as a maintenance step. Who currently is doing this kind of work and doing it quickly and well?

One thing I was glad to see was oil coming from the oil injectors.

Thanks,

Ron