anonymousagain

'80 AT: driving ~45 yesterday (constant, but barely on throttle) and felt a slight burble/hesitation. Thought I was out of gas. Pulled out of station after fueling and at very slight throttle - just barely on pedal - the engine cuts out. With slightly more throttle it comes back to life and runs fine; with slightly less throttle (virtually off the pedal) it comes back to life and runs fine.

Simulated it at any speed and it is throttle position related???? Slightly more or less runs fine, but there's one point that just cuts out.

At take off I can get it at the bad spot and if left there it will actually die. At idle I can get it to the bad spot and it will "flatten out" a bit, but won't die. Seems load accentuates it.

Connection to AFM seems clean and throttle linkage operates normal
No fire flies under the hood last night, so it seems wires are okay
Plugs/cap/rotor/fuel and air filter have 1k miles
Tried dusting with carb cleaner while running - didn't hear any vaccume leaks

Any ideas???

animal8526

I still have the same prob with my 81. identical. I will be watching this thread with interest. I can tell you what it isnt though... the brain... I replaced my to no avail.

animal8526

YMMV though.

IcemanG17

Kirt
Odd.....so when its on idle its fine...just off idle its dies & at a more open throttle it runs fine? Really odd.....I'm assuming full throttle is fine....maybe the trap door MAF is acting up...????

anonymousagain

Ya Brian, very odd. Idle is okay and it runs "normal" for all but just slightly on the throttle; WOT still yanks your teeth out when it shifts to 2nd. Cruising at 70 is annoying since you're almost off the pedal --> have to roll into it a tiny bit, then out of it, then in....

MAF trap door... that's what I was thinking since it seems throttle/load dependant. Checked the connector and the door isn't sticking or anything. Is there another way to check it?

I'm figuring it isn't ignition or fuel, since not constant.

Almost like it's tripping a momentary switch or something ???

hacker-pschorr

My 81 was doing something similar - replacing the ECU fixed the problem.

anonymousagain

Hacker, did you check other stuff that lead you to the ECU or other's sent you in the direction and <yippee> it worked for you?

This likely sounds stupid, but any idea how to get a new ECU and/or cost?... I haven't heard much discussion on 16v ECU's or performance related to them.
[assume it's just like changing the chips in my '86]

I'm thinking if it's reasonable $$, it's worth trying. Thanks.

Richard S

I have a spare 80 brain you can try. Problem is, I'm leaving early tomorrow and won't be back until late Sunday night. Can you wait till next week?

Rich

jpitman2

The barn door AFM plate makes fuel pump contacts IIRC, so if these contacts are dodgy somehow....produce the stop symptom, have somebody check for pump running or not?

jp 83 Euro S AT 50k

anonymousagain

Rich - Thanks a bunch. I may take you up on the swap, but no problem to hold off until you return next week some time. Curious, is it the same as the brain on an '84...just swap the big silver box?

JP - fuel pump is running, but it's difficult to tell if it's cutting out briefly while driving under load. It's quite loud though and I haven't recognized it going silent for a few seconds. Nevertheless, the contacts you're refering to, are they just the plug contacts? or are you suggesting inside the little black cover?

neilh

Check the idle switch adjustment on the throttle body, if its way off, the engine will seem like its cutting out when the gas pedal is held in one position.
FSM 1A - 46:

Apoc

Had a similiar prob with my 79, WOT was fine, plant it off the line was fine, but take off gently and it wasn't. Slight hesitation, almost felt like misfiring, some times almost die completely at idle but a quick kick on the accel brought it back. Then one day it started missing consistantly. Turned out to be a distrubutor problem, runs fne now.

Steve

zoltan944

idle and WOT have a switch. The WOT pulls maps from the ecu, and idle can usually be set to idle fine. What happens in between those 2 switches depends what your O2 sensor tells the ECU. My bet is O2 sensor

jpitman2

The pump contacts are inside the AFM...maybe if you uncover the fuse board you might hear the relay dropping out?
jp 83 Euro S AT 50k

anonymousagain

While checking idle switch per neilh's suggestion, it appeared to be at the correct adjustment and funcitoning correctly. BUT, for kicks I ran throttle up a little (off the switch), then triggered the idle switch with my finger and "there she blows!", reproduced the symptom.

Broke out the CAIG cleaner/lubricant and hit the switch thoroughly, while 'popping' the switch arm with my finger to ensure it was well saturated and moved smoothly.

Runs normal again and the cutting out at slight throttle is gone.

Seems the switch was sticking even though the arm was releasing fully, so the transition from idle to throttle was being disturbed. Will keep an eye on it, as I guess it's possible the switch could be showing early signs of failure, but it seems to behave as normal now.

Thank you again for everyone's input and suggestions !!!!