1984 Celebrity stumbles under acceleration.

[PeteCal]

1984 Celebrity with the 2.8L V6 engine. It idles fine and accelerates fine
when cold but as the engine warms up it begins to stumble. Just cruising, it seems to miss now and then. Maybe once every few seconds you can feel a miss. If I try to accelerate it will really stumble. Sometimes so bad that it pauses and backfires through the carb.

I had a problem a few years ago where the engine "throbbed" once a second. I found that if I disconnected the EGR solenoid connector the throb went away. I have been running this way for a few years. (At the time I didn't know what the connector was for, I just knew it made the problem go away.)

Last August (2004) it started to run roughly as the engine warmed up. It was OK when cold and when up to temperature. In between, it would not idle or pull out from a start. I concluded the ECM (computer) was going into closed loop mode at too low a temperature. The temperature sensor seemed to act correctly so I mounted a switch under the dash. With it, I could make the computer think the engine was cold so it stayed in open loop mode. Then, when the engine warms up, I flip the switch so it goes into closed loop mode.

A few weeks ago, the condition in the first paragraph started. It seems to act the same in either open loop or closed loop (My switch open or closed). Since I was still running with the EGR valve disabled, I did some checking and concluded the EGR valve was bad. What I found was if I sucked on the vacuum tube to the EGR, I could draw air through the valve. I took it off and the valve doesn't move when I suck on the tube and air comes through. I think that means the EGR valve is leaking.

As a test, in case the EGR valve was passing exhaust all the time, I fashioned a plate to put in place of the EGR valve so both paths are
blocked. This didn't have any effect. Still the problem in the first
paragraph.

I also replaced the fuel filter.

Currently I get the three error codes:

22 Throttle Position Sensor (TPS) - signal voltage is low during engine idle
OR Fuel cutoff relay circuit - open or shorted to ground
23 Manifold Air Temperature (MAT) Sensor - signal voltage is low
OR Throttle Position Sensor (TPS) error
45 Rich exhaust indication - Oxygen (O2) Sensor voltage stays high after one minute of engine run.

I got these code definitions off the net so I don't know how right they are.

I measured the TPS on pin 2 of the ECM and it changed as I moved the gas pedal.

I don't know where to go next. I don't think it is ignition related because it runs fine when cold. I might think the backfires are a timing problem but why is the timing OK when cold?

Any ideas?

Thanks in Advance

PeteCal

[My Wifes Honda]

did you ever find out what the problem was because I have the same problem

[PeteCal]

Short answer, NO.
I found:
Three broken/leaky vacuum lines,
One crushed vacuum line,
TPS may have been out of adjustment, I readjusted,

It still ran very badly. I disconnected the vacuum line to the ERG valve and plugged it. I also disconnected the Blue connector to the carburetor. This is the one that the computer uses to control the carburetor. Now it runs pretty good. Some stumbling during acceleration but quite drivable. I will continue to drive it and ignore the stumble.

One point, with the blue connector off, the Check Engine light comes on. If you don't want to keep seeing that light, you can put a piece of masking tape over it (just kidding) or put a 2200 ohm resistor across the two terminals of the blue connector. This seems to satisfy the computer that it is controlling the carburetor even though it really isn't.

PeteCal