Im new to the forum and hoping to find some advice on my 86 vette woes from some of you tech savvy members on here. I'm about at my wit's end with this car. I replaced a leaky intake gasket, water pump and thermostat, radiator and hoses. It ran fine for a while then it began to stumble and lose power so i changed the wires, plugs, cap and rotor to stock including a brand new stock distributer and it still stumbles and has no power. It always starts right up and idles great hot or cold but when I drive around it stumbles pretty bad and has no power. I was thinking it may be the fuel filter is blocked actually I'm hoping it's the fuel filter because my budget is almost gone and I can't afford another big problem.
just wondering if anyone else has experienced a similar problem.

Thanks in advance.
Vic.

 

Where do you live?
Iron or Al heads?
Manual or Auto trans?
How old is the gas?
How many miles on the odometer?
How long has it been sitting before you took on the challenge?
Fuel filter is easy to pull and check if its clogged. Just messy.
Air cleaner filter checked?
Do you know where the MAF sensor is located?
Have you checked the fuel pressure?

Sounds like you know your way around the engine compartment. (distributor and wires)
So if your planning on trouble shooting here there will be a lot of questions to answer.

Your best friend will be Cliff Harris. He IS the 86 expert among the gurus.

 

You need to check for codes and do some diagnostics instead of throwing parts at it. These are computer controlled engines and rely on many different sensors to run properly. Also get a fuel pressure guage on it and see where youre at with fuel pressure.

Almost forgot, welcome to the forum!

 

Thanks for the prompt replies!

I love in London ontario canada,
1986 corvette
Alluminum heads
manual 4+3
Gas is new
78,000 miles on odometer
air filter is new
MAF sensor is located under the air intake hose to the throttle body
Not setting any codes.

Replaced leaky intake gasket
water pump
rad
hoses
plugs
wires
distributer
cap and rotor

bought the car two years ago it was running ok, drove it all last summer and from April to October. I took it out in May of this year and it was running fine before I did the work and it was running fine after i dd the work. it wasn't until after I had dropped it of and had it painted a few weeks ago that the problems started after i picked it up.they had removed the hood to paint the headlight housings and the engine was pretty dusty. I had put on a set of MSD wires and one wire got cut on the plenum and was sparking something awful against the rear of the plenum. So I bought a set of stock wires and put them on replaced the entire distributer, cap and rotor at the same time due to some nasty looking rotten wires coming of the distributer.
I'm not sure if they left the gas cap off when they prepped and painted the car and debris or dust got into the gas tank but it was running fine when I dropped it off and of course no one at the paint shop knows what happened.
I don't have a fuel pressure gauge so I'll have to bring it into a shop to have it done.

Were is the fuel filter located on this car?

Thanks again in advance.

 

You really need to check the fuel pressure to see if it's good and to see if it holds when you shut it off. Are the fuel injectors original? In the U.S. most parts store have tools to lend (for free, just need to leave a deposit).

 

Thanks JV I will bring it in tomorrow and have them check the fuel pressure. As far as I know the injectors are original.

Thanks.

 

Underneath and behind the front right frame rail almost straight down from the firewall.
Follow the fuel lines from the intake manifold aft or forward from the tank.

Maybe a vacuum line to the FPR that boosts FP when rolling in throttle.
Running fine then not?? I'm betting it's something simple.
It'll just be a bitch to find it.

 

Sounds like crossed spark plug wires. The engine will run surprisingly well on 6 cylinders...

 

I ran into a situation VERY similar to yours...I replaced all of the upper engine gaskets on my 87. Car was running fine before I worked on it. Ran fine immediately after too. Then suddenly, it began bogging, stumbling and performing horribly...it would come and go without warning. I found one of the rubber PCV couplers would intermittently collapse under high vacuum. To fix it I eliminated the original aluminum pipe elbow-laden PCV hookup and replaced it with a straight rubber line from the valve to plenum and have never had a problem since.

Look to the simplest things first, in the areas you were working. 99.9% of the time you will find your problem there.

 

Fuel pressure should be at the top of your check list. I suggest buying a gauge you'll use it more than once, I guaranty.

If your injectors are original, most assuredly they're junk by now. The "ohm" check gives you some indication. Shop around, most of us buy from FIC for injectors. The ECM will shut off a bank of injectors is the the resistance is too low (shorted), this commonly happens once the injector warms up.

 

Well it was as simple as they get. Three of my plug wires were burnt through causing a bad misfire on three cylinders. The wires had been against the exhaust manifold and burnt right through the insolation. The other problem was when the shop did my intake gasket they forgot to install the vacuum hose back on the egr valve. I ordered a new set of wires and will install them on monday.

Thank you very much for all the replies I'm sure I will be on this forum alot looking for advice from the you good people.

Cheers
Vic

 

It's always nice when it's an easy fix. Glad to hear, now enjoy it!

 

Have a new problem. I have bad lifter noise now it just started after I had the timing setup. The shop that did it used the proper method but now the lifters are chattering something awful after the engine gets hot. It won't chatter when it's cold. Also my rad sprung a leak I shut it down but not before the engine had overheated, not sure if this has a bearing on the lifter noise because it ran fine for over two weeks after the overheat. The first shop that setup my timing (GM dealership) set it up all wrong so had to bring it to a speed shop to get it set properly. Not sure if any of these problems are related to the lifter noise.. PLEASE HELP!
Also what viscosity of oil should I be using in this engine? I think the dealership used 5w20 but I was told it should be 10w30 or40. ??

Thank you!

 

That can happen if the proper preload was not applied to the lifters when they were adjusted. The FSM recommends one full turn down from zero lash but an old time drag racer trick of only going down 1/4 or 1/2 turn to prevent lifter pump up at very high RPMs has become "standard procedure" for a lot of tuners "just because that's the way it's always done".

 

Just got a call from the shop and they tell me they think the tapping sound is coming from the bottom of the engine. Does a bad bearing make a tapping sound? At my wit's end with this car one problem after another it seems. Oil pressure is great temp is good. It only starts knocking when It reaches operating temp,,it doesn't do it when it's cold..

I just got the car to run well and now this. When you open the hood It sounds like noisy lifters but when they put it up on the hoist he hears a knocking on the bottom.. If i get them to go any farther it's tons of money and if it's something catastrophic it's major coin that I don't have. Damn damn damn!