Need Help Badly!

[TriTown]

Can anyone help me locate a guy that REALLY KNOWS how to work on tune port injection? I'm located in the Milford, Massachusetts area...I've been told more times that I want to hear, "The car is too old to fix".

My problem is that my 85 coupe has a wicked stumble off a stop light. So bad it will stall if you don't nurse the fuel and clutch to get going (replaced the throttle switch, set at .54) The car has all the get-up and go I think an 85 should have and runs great if you keep the pedal on the floor. As for the driveability in traffic it's just the worst! Say in 3rd or 4th gear with rpms steady and appropriate for that gear in traffic the car is not smooth it is serging and bucking. If I'm reading the service manual correctly the book referes to this as Chuggling.

What I've done so far besides spend money on repairs at shops that have had no luck or cure is replace the IAC valve, O2 sensor, set the timing, cleaned the throttle body. Who knows what the shops really did.

I'd really apreciate any feed back on who to go see with this problem.

Thanks,
Joe
PS... I was told by one shop that the PROM is the original. GM was supposed to have had an up grade or two somewhere along the line. Can't find any info and Superchips has never returned my email or call.

 

[The Car Whisperer]

The first thing I would do is clean the throttle body, then I would check for vacuum leaks.

 

[rrubel]

I second checking for vacuum leaks. Buy a decent gauge, attach it to the back of the plenum (one of the two ports on the right side) and you should have a fairly steady 20 inches of mercury when revving the engine. If it drops, or if it bounces around a lot at idle then you've got a vac leak. Given the age of the car, it's not surprising - after all this time, the plastic lines get so brittle from heat that they fall apart if you look at them funny. Fortunately, you can get rolls of line at any auto parts store and make your own tubing because GM doesn't have all of them available any longer.

Also, if there's a leak between the manifold and intake runners, you'll get really poor running. A mechanic with a smoke-test kit can find that.

May want to check the MAF, if you haven't. If the car doesn't know how much air is coming in, it can't regulate the fuel properly.

Finally, have someone check the signals to the fuel injectors. I had a problem with my ECM (not the chip, but the computer itself) where the signals were being sent to the fuel injectors at the wrong time so it stumbled, had really bad off-idle hesitation, and would stall if I didn't nurse it at idle.

[RICHR]

 

[jmccloud]

Chuggling

The symtoms you describe are classic vacuum leak indicators. With a car of that age, check the PCV valve and EGR early in your diagnostics. The PCV is often overlooked but is so cheap that it should be replaced rather than evaluated (really iffy chore). Vacuum hoses are suspect of course. The EGR can usually be evaluated 'visually' by providing artificial vacuum (get a new clean hose on the actuator and suck on it) while watching for movement. I don't know whether your year has an EGR solenoid, but they fail too.
Hope this helps

 

[milehigreg]

Amazing!

Once again I am amazed at the depth and breadth of the helpful information available on the forum. I have read a little lately on the TPI in both Lingenfelter's book and there is a current series on it in Chevy High Tech Performance magazine. I don't think there is a thing wrong with the TPI. It was apparently a big breakthrough when it came out. Try the suggestions these guys have given you. Too old to fix? Poppycock!:L

Can anyone help me locate a guy that REALLY KNOWS how to work on tune port injection? I'm located in the Milford, Massachusetts area...I've been told more times that I want to hear, "The car is too old to fix".

My problem is that my 85 coupe has a wicked stumble off a stop light. So bad it will stall if you don't nurse the fuel and clutch to get going (replaced the throttle switch, set at .54) The car has all the get-up and go I think an 85 should have and runs great if you keep the pedal on the floor. As for the driveability in traffic it's just the worst! Say in 3rd or 4th gear with rpms steady and appropriate for that gear in traffic the car is not smooth it is serging and bucking. If I'm reading the service manual correctly the book referes to this as Chuggling.

What I've done so far besides spend money on repairs at shops that have had no luck or cure is replace the IAC valve, O2 sensor, set the timing, cleaned the throttle body. Who knows what the shops really did.

I'd really apreciate any feed back on who to go see with this problem.

Thanks,
Joe
PS... I was told by one shop that the PROM is the original. GM was supposed to have had an up grade or two somewhere along the line. Can't find any info and Superchips has never returned my email or call.

 

[87blackroxi]

I found these 2 shops you may want to check out. I haven't had any experience with either but they are reputable from I hear. They made the 100 most reputable corvette shops list. If it's worth anything, my mechanic in Tampa is on that list and he knows his stuff! Hope it helps in the future!

Corvettes & Classics
Michael Barrows
44 Winthrop St.
Taunton, MA 29780
(508) 823-6150

Ron’s Auto Restoration and Sales
Ron Bunnell
21 Willow St.
Fitchburg, MA 01420
(978) 345-6159

 

[Edmond]

Too old to fix? What a load of BS.:L:L:L TPI is easy to fix, it's an old fashioned SBC.

 

[TriTown]

Need help badly!

Thanks for the help! I knew someone could! Sorry for the time it took to get back to all of you! I work way too much truck driving!!!!

This week end I'll check out all your suggestions and let you know how I make out.

Again THANKS!!!!!!!!!!

 

[TriTown]

Well I'm a week late leting you all know the out come of your help. I just can't put a finger on the problem...Thanks to 87blackroxi I now have an appointment with Ron's Auto Restoration shop in Fitchburg, MA. After talking to him for a while I feel like this might be the guy who will fix the car, FINALLY!
I look forward to driving it without the annoying bucking and stalling at lights. It goes into the body shop for paint at the end of the month. After that it's tires and a 4 wheel alignment. It should be a great fair weather driver!

Thanks again for all the help! Your all a great bunch!!

 

[TriTown]

Well it took me a month to get back to you all on the outcome of my running problem. 87blackroxi had found several shops in my area to take the car to. I contacted on and had a appointment. Before I got to take the car to the guy a friend ran into the former instructor for Chevrolet. He taught at the GM training center in Dedham, MA while these cars were new. What a find he is. He has all the tricks and fixes.


My cars running problem was nothing more than being grossly out of adjustment. The last guy that had it had bumped the timing 20 degrees. The throttle plates were set wrong and needless to say the TPI switch was set wrong. The computer was confused. It runs great now!

It goes to the body shop in two weeks for a repaint.

Thanks again for all the help and suggestions!

 

[rrubel]

That wouldn't have been Gordon Killebrew, would it? The man's a walking C4-clopedia.
[RICHR]

 

[Edmond]

You spent a minimal amount of money to fix a big problem. What more could you ask for?

Please do a write up when you get that paint job done. I'd be interested to see how things work out on that.