Hello Folks,

My 1994 2.3 standard transmission has failed an emissions test. It has a roughness at fast idle that disappears under load. We have a 2 speed idle test here with no load on the engine which has given an excessive HC and CO reading.

The vacuum lines appear intact. A guage test shows no leaks.

The EGR seems to work when a vacuum source is attached to it while the engine is running, slows to a stall almost.

The EGR solenoid seems to be switching when the engine is revved up as witnessed by the vacuum guage at the EGR end.

The DPFE has 5 volt reference voltage and sends a switching signal voltage of 0.6-0.7 volts at idle to about 2.77 volts for a rapid throttle opening.

I haven't checked the fuel pressure yet as I will have to borrow a friend's guage kit for that. I did notice that removing the vacuum line while plugging it, to the fuel pressure regulator makes no difference in engine speed.

The other thing that seems a little amiss is the timing on the crankshaft harmonic balancer with the engine running and a timing light on the front intake spark plug is showing about 30 degrees advance at idle jumping past scale to maybe 35 degrees as the engine is revved up. Is this normal?

Any suggestions?

 

When was the last tune up?

 

I couldn't tell you. This was a recent purchase which had failed an E test with the owner unwilling to spend time and money on it.

Some vacuum checks revealed that the EGR was getting vacuum at idle which was opening the EGR enough to cause a rough idle and a rich condition. Taking the vacuum line off the EGR and plugging the line smoothed out the system. The EGR solenoid has been replaced for the same effect.

The truck needs brake work to pass a fitness test before licensing and at that point it is off for another E test which hopefully it can pass this time.