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I had the same problem and it turned out to be a plugg cat. My car had the originial cat on it and it was bad. happend very quickly just like you described. I had a different problem before that. went to work 50 mile run one way and it ran fine got back in it to go home and it started to change rpms I could not keep it running or get it to go to WOT. Turned out to be bad fuel pump. Changed fuel pump like Jim said and it ran fine for quite awhile, Then I had a probelm were it would not go to WOT would idle ok , turned out cat was bad. Disconnected cat and it ran fine.replaced cat and everything checked good
No. Just for that 2 seconds. You shouldn't hear the buzz after that. If the pump is going it will continue to buzz. I've never hear the fuel running back to the tank. I'll go out and listen to make sure.
Jim, In one of your first post's you said that the fuel pump should run for 2 seconds then shut off. If I listen with the gas tank cap off, I can hear fuel running back in to the tank so if the pump is suppose to shut off, I wonder if there is a split in pump assembly. Is that possible? I think I will try to pinch off the return line to see if the noise in the tank stops and also check fuel pressure with a gauge. What are your thoughts?
3 lines. One supplies the fuel. One returns the fuel. The other goes to the charcoal canister. The TBI's are different. Once has a pressure regulator and the other has a compensator. The pump charges the system. The regulator and compensator make sure there is a minimum of 9 psi supplied to the injectors. If the fuel pump is weak the ECM will sense that and turn on the pump until there is sufficient fuel to compess the spring in the regulator.
I had a similar problem running rich and no idle and it was the EGR stuck open just a little bit. Try and work the plunger from underneath and maybe it will seat? KEEP TRING we all been there!
I found the problem!
It was the rubber fuel line connecter between the fuel pump and the steel fuel line in the fuel tank.
Thanks for the help.
Ron
yep..I have heard that story a few times. The rubber hose will rot away over the years. I would go ahead and put a new fuel pump in while you have the sending unit out.
check the plunger where the wires conect to the top of that unit. I forget,its either 2 or 3 screws,triangle shape. A rubber o ring like deal might be bad.
yep..I have heard that story a few times. The rubber hose will rot away over the years. I would go ahead and put a new fuel pump in while you have the sending unit out.
it would be a good time for the 85 fuel pump upgrade.
I am starting the restoration of my '82, and definitely can use all the tips and tricks out there to tune it properly.
The car hasn't been run in about a decade, so there are a lot of things I have to check out. It runs and drives, but not well. It looks like the fuel pump and filter will be the first thing, then the O2 sensor and the coolant temp sensor. Not to mention, I will be replacing all the vacuum lines and rubber fuel lines.
Any more great articles out there, please post them.
i have a 1982 vette it has been running fine all of a sudden it started loping at idle it will go from 600to 1500 rpms back and forth has 82000 miles never had any problems can any one help thanks
i have a 1982 vette it has been running fine all of a sudden it started loping at idle it will go from 600to 1500 rpms back and forth has 82000 miles never had any problems can any one help thanks
I have to ask a few questions first. Is it constantly going up and down or you stop at a light and it jumps up for no reason?
Have you replaced the plenum silicon with the newer felpro gasket?
Has the car been sitting for a long time?
I have to ask a few questions first. Is it constantly going up and down or you stop at a light and it jumps up for no reason?
Have you replaced the plenum silicon with the newer felpro gasket?
Has the car been sitting for a long time?
sits alot just got it out have not did any motor work yet constantly going up and down thanks
Last edited by 6682danny; Aug 4, 2015 at 01:12 PM.
I have a 1982 with the cross still intact (except missing the smog pump) I was having trouble with the motor idiling down correctly, sometimes it would go down to around 600 RPM and some times around 1000 RPM. Yesterday, while driving it began to run very bad. It would only run if I kept feathering the throttle.(kept pumping) When I was able to get it home to inspect I found that the injectors seamed very lean not allowing enough fuel to keep the motor running. I unpluged the vacuum from the MAP's sensor and the injectors went rich allowing the motor to run, but rich. I replaced the MAP' sensor with a new one but still does the same thing. There does not seam to be any vacuum leaks on the intake anywhere (TBI base or base to intake plate)
ANY IDEAS ON WHAT I CAN CHECK ?
The 1982's have a frame-mounted fuel filter directly under the passenger's feet and that filter needs to be changed every 25,000 miles. As that filter is a 25 micron filter it plugs easily and that is likely your problem. Its a common filter that most every auto parts store will stock and less than $10.
sits alot just got it out have not did any motor work yet constantly going up and down thanks
checked fuel filer it was ok checked fuel pressure first problem only had 4lbs of pressure pulled pump pump was fine the hose that connects the fuel pump to the supply tube was very soft and had a crack in it did a fuel pump upgrade runs great idles better than it has in a long time thanks for your help
This is what I did to lower my rpms on an 82 vette.
1. Repaired all vacuum leaks.
2. Readjusted the timing.
3. Readjusted the minimum air adjustment screw at the rear of the driver's side throttle body.
4. Balanced both throttle bodies.
5. Readjusted the throttle position sensor.
Put a vacuum gauge on the intake and check for vacuum leak. Isolate each and every vacuum port, find the vacuum circuit that is leaking and repair.
There is a connector on the driver's side firewall thats close to the oil pressure switch. Disconnect it and set the timing and reconnect.
Make sure both throttle bodies are balanced, if not balance them. If you readjust the minimum idle air screw your throttle position sensor gets affected, readjust it.
When I performed these steps my idle went from 1600 rpms in park to 700 rpms in drive.