Well, I finally have had a chance to work some more on my 94 11.9 Escort
That Refuses To Hold an Idle.
So far, I have replaced the Idle Air Control Valve, O2 Sensor, Throttle
Position Sensor. Have checked for and found no signficant vacuum leaks
anywhere. Based on the erratic idle (it sometimes will but usually won't
once the system goes closed loop) I was thinking sticky EGR valve.
That was ruled out today. I was going to replace the EGR valve, but could
not get the exhaust gas inlet line loose from the exsisting valve. As an
EGR diagnostic, I made up a small blanking plate that I was able to install
between the valve and where it bolts to the intake runner. The blamk made a
tight seal against any EGR leakage into the intake manitold. At the same
time, I was able to blank off the fuel canister purge line that connects to
the underside of the throttle body. I've eliminated all the other vacucum
lines as leakers already.
Well, those two above diagnostics had no significant effect on the poor idle
performance. So it looks like the EGR valve replacment would have been a
waste of time.
I have been focusing on vacuum leaks from such sources since the poor idle
seems to be accompanied by low manifold vacuum. The only relevant OBD code
that I have been seeing is an intermittent 182: Partial throttle rich
adaptive limit, system lean. This comes and goes mainly at speed with no
notable coincident changes in performance.
As always, the car runs very strong once you goose the throttle and never
hesitates or surges under load. Lately the idle stability has gotten worse,
with the engine immeditely going into a stall while at the end of slowing
down to a stop with the clutch disengaged. But at other times it will hold
idle quite well for many throttle up and down cycles. I'm stumped...
Fuel filter? If it is partially clogged, why is only idle affected?
There's no hesitation or surging when the throttle is booted and going
through the gears, or on a steady cruise conditon.
Timing belt a little off tension/timing?
Fuel pressure regulator?
Whatever it is, it's gradually getting worse - I'm thinking its time to
throw in the towel and send it to a shop....