Rough idle, EA82T, looking for easy fix ;-)

[S]

Hi All!

I have an '85 GL turbo that I just got running after a loooong (14yr)
rest . . .
Runs great, passed emissions just fine, but it has a stubborn miss at
idle. I have replaced _all_ of the fuel hardware; gas tank, fuel pump,
injectors, injector rail (whatever ya call it), pressure regulator,
filter, etc. (Had to; worst case of "varnish" I've ever seen . . .)
Also replaced the plugs, plug wires, cap, and rotor. As such, I have
had the engine down to basically a long block and back; The intake
plumbing is intact and tightened, and all of the vacuum lines are
good, and presumably in the correct locations. But the roughness at
idle remains.
The emissions tech (surprised that it passed) said that he thought it
was a "lean mis-fire", caused by the ECU trying to minimize CO (O2)
readings at the oxygen sensor. While I've never heard of this before,
it seems at least possible; certainly it gets _worse_ as the engine
warms, which would seem consistent with his diagnosis. BTW, this car
has an automatic tranny.
I have another EA82T car (MT) that doesn't have the rough idle issue,
and am planning on swapping parts in an effort to isolate the problem.
Before I do, tho, I thought I'd ask to see if anyone in the group has
experienced this sort of problem, and if there is an easy fix.
Any thoughts on this greatly appreciated. TIA!


PS: The AT car only has 67,000 miles on it. 4sale if anyone's
interested; $1000, $1200 after I (hopefully) fix the idle and replace
the windshield. Very clean little car; the missus sez it has to go :-(

ByeBye! S.

Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

 

[johninKY]

Did you replace the injector seals when you replaced the injectors? Just as
a test, disconnect and plug the vacuum line that goes to the transmission.
See if the engine idles differently. I would inspect all the engine
harness connections for corrosion. Also would clean the idle circuit in
the throttle body along with the IAS. Lastly, check/clean all the engine
grounding points.

Thinking the model also has an injector dropping resistor over by the RF
strut. may want to also take a look at it.

 

[S]

Hi John!

Did you replace the injector seals when you replaced the injectors? Just as
a test, disconnect and plug the vacuum line that goes to the transmission.

Yep, new injector seals. And I tried pinching off the vacuum line to
the AT; no change. Also checked the brake booster vacuum, and the
canister purge. The canister _did_ have a suspicious connection; the
actuator line fitting/nipple was cracked. Replaced the canister, no
change, Sigh.

I would inspect all the engine
harness connections for corrosion.

Nice and clean.

Also would clean the idle circuit in
the throttle body along with the IAS. Lastly, check/clean all the engine
grounding points.

That I _haven't_ done. I have someone looking at the car this morning,
but if they don't drive it away, I will work on it some more this
afternoon. My plan of attack (based on ease of implementation more
than anything else) looks like: AFM, O2 sensor (whole down pipe assy),
throttle body/TPS.
If that doesn't get it, perhaps the ECU (will they swap AT vs MT? Same
year car; '85), or maybe that anti-knock thingie . . .

Thinking the model also has an injector dropping resistor over by the RF
strut. may want to also take a look at it.

If it does, I'll try swapping that as well. Thanx for the input.

ByeBye! S.


Steve Jernigan KG0MB
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101