Disgusted With How My 81 Runs arrrggghhh!

[Wajulia]

Is it only the idle that is of concern at this point -- it runs fine off idle -- no black smoke -- no 6MPG? if so -- focus on the idle circuit

The idle circuit on the e4me is controlled by the computer using a the Mixture solenoid and the idle air bleed plunger. You can see the plunger adjustment from the top of the carb -- it is the large brass screw right in front of the primaries looking straight down.

There is a very precise adjustment procedure for it in the service manual, I will try to send it to you tonight. But this is my poor mans version is below, you need to have a dwell meter. You can do it without out one but you need a little luck, and you learn a lot about the computer/carb interaction if you have one.

Gently screw it in until it bottoms out , it is very fragile, just barely bottom it out. back it out 4 full turns. Connect a dwell meter to the green connector that is just sitting in front of the carb somewhere -- normally it is not connected and just sitting on top of the engine.
With the dwell meter on the 6 cylinder setting, it should be reading 30. Adjust the screw in small increments (1/8 turn, letting the engine stabilize) until you get the reading. Without a dwell meter, turn-wait-turn-wait - after about a turn or so something is not working. I have seen cars come alive doing this when the carb and computer start working together -- it makes you wanna cry!

This will tell you if the computer is controlling the carb properly. if it does not work, there may be a few other things that can be checked
1) Adjust the idle mixture screws in the front of the carb. Baseline at 3 turns out from the bottom, adjust 1 turn out at a time on both screws. looking to see if the dwell begins to change. (this usually has much less effect on the carb than the idle air bleed valve)
2) the carb needs to be cleaned and rebuilt -- While this is not a big deal and can be done with some simple research -- it is probably not necessary
3) the carb has nothing to do with the idle problem. Check all other emmision controls -- EGR?

Good luck

 

[Peer81]

With the engine running disconnect a sensor (TPS or something like that) and see if then the ECM is throwing you a code (check you're light is still working). When the engine is running very very very poor the service light will come on but that is only when you think it's running like a 3 cylinder diesel!

I really think a dwell meter and the discription will get you back on track.
If you want to change everything to pre ECM things, that is your call but to be honest. A dwell meter and a couple of houres to try are alot cheaper then changing everything.

Greetings Peter

 

[damoroso]

Are you sure you don't have a bad plug wire??

 

[KANE]

There is a really nice gent from Florida that does work with the L81 carbs. His name is Sensei.

Reach out to him (if you haven't done so before ) with a PM and let him know what is going on. He might have some ideas.

Hope that helps!

 

[Wajulia]

I sent you the adjustment procedures. As I have already said, focus on the idle air bleed valve adjustment abd the idle mixture screws. I have heard a lot of people say that the idle mixture screws do very little onthe e4me. I never adusted them, just bring them 3.5 turns out from bottom and let the computer do the rest. But the computer can not adjust the idle if the idle air bleed valve is adjusted incorrectly.

Cliffs comments -- not trying to know more than cliff -- I dont -- but trying to keep it simple. The slotted adjustment he describes is the Idle air bleed valve adjustment, this is most likely where the issue lies.
The other two adjustments that he mentions are also on the top of the carb (the ones that need the tool) and adjust the lean and rich stops on the mixture control solenoid. THESE HAVE NOTHING TO DO WITH IDLE. They contol the maximum rich and minimum lean that the computer can drive the carb off idle and before secondaries kick in. So my suggestion would be to leave those alone if off idle is ok. I have also provided the adjustment procedures for the mixture control solenoid, but you also have my warnings.

Another thought, you said there is a driveability problem when you let off the gas -- that may be a sign of a faulty EGR Valve. I have included procedures for the EGR and PCV testing.

Good luck

 

[HammerDown]

Are you sure you don't have a bad plug wire??

Wires not that old, new cap/rotor last summer. If a plug wire was faulty it would certainly show off idle, it's smooth as silk there.
Thanks, Ray

 

[HammerDown]

I sent you the adjustment procedures. As I have already said, focus on the idle air bleed valve adjustment abd the idle mixture screws. I have heard a lot of people say that the idle mixture screws do very little onthe e4me. I never adusted them, just bring them 3.5 turns out from bottom and let the computer do the rest. But the computer can not adjust the idle if the idle air bleed valve is adjusted incorrectly.

Cliffs comments -- not trying to know more than cliff -- I dont -- but trying to keep it simple. The slotted adjustment he describes is the Idle air bleed valve adjustment, this is most likely where the issue lies.
The other two adjustments that he mentions are also on the top of the carb (the ones that need the tool) and adjust the lean and rich stops on the mixture control solenoid. THESE HAVE NOTHING TO DO WITH IDLE. They contol the maximum rich and minimum lean that the computer can drive the carb off idle and before secondaries kick in. So my suggestion would be to leave those alone if off idle is ok. I have also provided the adjustment procedures for the mixture control solenoid, but you also have my warnings.

Another thought, you said there is a driveability problem when you let off the gas -- that may be a sign of a faulty EGR Valve. I have included procedures for the EGR and PCV testing.

Good luck

Not when I let of the throttle...only a rough idle and mostly noticeable when it's in drive/reverse >idling.
No surging, hunting of the engine off idle.
Thanks for the info and all the suggestions from everyone.

 

[damoroso]

Wires not that old, new cap/rotor last summer. If a plug wire was faulty it would certainly show off idle, it's smooth as silk there.
Thanks, Ray

Not necessrily, a bad wire (not broken) can short easily at slow/idle speeds, but when you increase speed it still hits the plug with enough energy to spark it. But if you're convinced they're good thats okay, one more thing off the list. Hopefully the Idle Air Bleed Valve adjustment will take care of the problem. Like has been described before, you can adjust it using a dwell meter connected to the green connector that should be near your choke. The dwell meter will also tell you if the M/C Selonoid is working correctly. If you need the exact procedure out of the manual, let me know, I'd be happy to get it to you.

 

[procketus]

Could it be a wiped out cam lobe?

Had a Camaro that acted similar, ran great down the road, but when idling in gear sounded like it had thumper of a cam in it. Started out so gradual it took quite a while until I figured out what it was.