81 Rough idle and surging

[Bills money pit]

Recently while driving the 81, it started to idle rough and would surge about 100 rpm. I checked for codes, none saved. I plugged all the vacuum ports, the rough condition continued. I checked the EGR, it is free and opens and closed as it should. Checked the carb fuel filter, it is like new. I can hear the M/C solenoid clicking and now I am out of ideas.

I bought this car three year ago and have battled the ECM system on a regular basis. I am now tired of the whole mess. I have asked two local mechanics to work on the vette and they do not want to work on the car stating the electronics carb and components are a nightmare and they are not interested.

I am considering removing the electronic quad and distributor. Please tell me what year carb and distributor I should get and what other parts of the electronic system will need to be deactivated or should I just drive the car as is ignoring the idle issues.

Thanks for your opinions.;help

Bill

 

[LT4man]

How many miles do you drive the Vette in a year? If it is less than 10,000 miles, I would start with a container of Techron Fuel System Cleaner.

Go to your friendly, neighborhood Auto Zone, Pep Boys, Advance, NAPA or whatever :L and pick up a bottle. It comes in a black, plastic bottle. Put one in with your next tank of gas.

The stuff works wonders and I swear by it. I would not use any other!

Then just take the Vette out and drive!!!

Let us know how it goes!

SAVE THE

 

[Bills money pit]

Thanks for the advise

I will try a can, but I will surprised if the contents of a can will fix a mechanical problem.

 

[22229stingray81]

I know you said it checked out okay, but I had the exact same symptoms when my EGR went south. Got a new one in (along with a new TPS) and it ran smooth as ever.


-Tatortot

 

[vmrod]

Keep looking for a mechanic. Most mechanics these days are merely 'part changers'. If a computer does not tell them exactly what to do, they are at a loss.

 

[HammerDown]

When mine ran rough etc it turned out to be a vacuum leak at one headlight actuator and also a small vacuum leak at the trany module line.

 

[GerryLP]

Bill,

One simple way to re-boot the computer is to disconnect the battery and wait about 5 minutes.

When you reconnect, it will take a new set of numbers, and if it runs well, then we got lucky, but we'll have to wait until it happens again (if it ever does), and we'll take it from there.

GerryLP:cool

p.s. of course, this will also do away with your radio pre-sets...

 

[Bills money pit]

Gerry:
Nothing seemed to be wrong (no codes or vaccume leaks)but still ran rough and surged. I became very frustrated and removed the carb. I disassembled it and found that one of the brass fuel tubes (one of the four that attach to the horn or top) had come loose and fallen into the bowl area. I tapped it back in and hope that is the cause. I am not sure if the tube having fallen out would cause the rough idle and surging. Also, I noticed the plastic sleeve or cup under the M/C solenoid connector was missing. Again I do not know if this has any effect on how the carb performs. Finally, I noticed there is slop where the throttle shaft goes through the plate. Its loose enough to allow air to be drawn in and would effect the idle, I presume. I have ordered a bushing kit to repair the problem. Also I ordered a new TPI (throttle position sensor) and new M/C solenoid. I thought they should be replaced while the carb was disassembled.
I believe this should fix the problem. If the problem continues, at least I can eliminate the carb.
Thanks for you interest.
Bill

 

[LT4man]

You are correct about the throttle shaft. Any kind of play or clearance will have a direct effect on idling and off-idle hesitation.

Sounds to me like you have pinpointed the source of your problems.

Let us know how you progress!

SAVE THE

 

[GerryLP]

Gerry:
Nothing seemed to be wrong (no codes or vaccume leaks)but still ran rough and surged. I became very frustrated and removed the carb. I disassembled it and found that one of the brass fuel tubes (one of the four that attach to the horn or top) had come loose and fallen into the bowl area. I tapped it back in and hope that is the cause. I am not sure if the tube having fallen out would cause the rough idle and surging. Also, I noticed the plastic sleeve or cup under the M/C solenoid connector was missing. Again I do not know if this has any effect on how the carb performs. Finally, I noticed there is slop where the throttle shaft goes through the plate. Its loose enough to allow air to be drawn in and would effect the idle, I presume. I have ordered a bushing kit to repair the problem. Also I ordered a new TPI (throttle position sensor) and new M/C solenoid. I thought they should be replaced while the carb was disassembled.
I believe this should fix the problem. If the problem continues, at least I can eliminate the carb.
Thanks for you interest.
Bill

Bill, that is great news! The carb is not really that difficult to overhaul. One does need some special tools. I believe that Big2Bird started a couple of threads which evolved into good informational postings about E4ME carb repair.

http://www.corvetteactioncenter.com/forums/showthread.php?t=98279&highlight=E4ME

GerryLP:cool

 

[Bills money pit]

I do not have any special tools, how can I set the carb without them? Also, what tools are they?
Thanks!
Bill

 

[GerryLP]

Thexton 362 and Thexton 370 will give you all the necessary tools, but they are discontinued by Thexton; however, with a little bit of patience one can find them. In that link I posted, I posted the company from which I bought the Thexton 362. The large socket-like tool is for removing the needle seats (I believe), and the skinny one is for adjusting the TPS to the correct voltage.

I have not heard from Big2Bird in a while, but perhaps you can send him an e-mail.

GerryLP:cool

 

[LT4man]

A simple Dwell Meter will allow you to adjust the idle mixture.

SAVE THE

 

[petes74ttop]

On my 74 I set the idle mixture in drive with a vacuum guage, is an 81 a different type of carb? PG.

 

[LT4man]

Yes, an '81 has an electronic carb. Trying to set the mixture with a vacuum gauge will not get you close enough to the proper setting.

SAVE THE

 

[Bills money pit]

I made a tool to adjust the mc/solenoid. I grounded out a s;ot in a small screwdriver. It works well. For the life of me, I could not remove the plug to the TPS. I will not be able to set it. I hope the factory set is close enough. Finally, where do I connect the dwell meter? I could not find a green wire some articles mention.
Thanks for your help..
Bill

 

[GerryLP]

There should be a green wire and connector near the air switching valve for the smog pump (or RH engine harness).

When you connect to it, always remember to connect the ground last when the green wire/connector is connected to the green dwell wire, and it should be disconnected FIRST before disconnecting the dwell Green wire from the green wire/connector on the harness.

I find it useful to clip the Dwell ground wire on a rubber hose to prevent it from grounding on another part of the engine.

Use the 6-cylinder scale on the Dwell!!!

Make small air valve adjustments (1/8 of a turn), and this is a pain to wait on, and this is what I meant by having patience.

On the TPS cannon plug, spray some WD-40, so that it can penetrate the rubber seal. Remember that there is a plastic latch that keeps it from disconnecting.

 

[LT4man]

I would start with a base adjustment of the idle mixture screws in the front base of the carb.

Turn them each in until they lightly seat, then turn them out a full two (2) turns.

Run engine till warm, so computer will be in closed loop.

Set the Dwell Meter to the 6-cylinder scale. You want to adjust each mixture screw to obtain a 30degree dwell reading. Use 1/8th increments and let engine idle at least 1-2 minutes between each adjustment.

When you finally reach the 30degree dwell reading for each side, take the car out for a test drive. You should have absolutely no off-idle hesitation or part-throttle hesitation. If you do, then something else is not working properly.

SAVE THE

 

[Bills money pit]

Gerry:
Sorry for being such a DA, but I do not find the wire you are describing. Some wires are bluegreen in color. Maybe they were green to start with. Could you give me another description or maybe a photo. Your help is most appreciated. Also, do I disconnect it from the connector and stick a wire in the connector?
Bill

 

[Bills money pit]

Gerry: No can do on the TPS plug. I can see the top of the adjusting screw and thats it. there is metal around the screw and nothing to pry against. I worked on it for a long time with no results..... I must hope it is within range by the factory settings...
Bill