Massive engine problems - need advice
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,023
Likes: 1,181
From: La Mesa CA
Massive engine problems - need advice
I have an 86 with 112k miles that I recently got super cheap. The engine ran well and did not smoke and passed smog here in California.
However, it was consuming about a quart of oil every 500 miles. As the car had been sitting for a year, I have been running Rislone in it in case the rings were sticking.
Yesterday I drove about 300 miles on the freeway. During the trip it started to get hard to start. Instead of catching after the first crank, it cranked many turns without any catching. The exhaust smelled of gas.
Put it up on a lift to see if there were any visible leaks while the car was running, and while it was up there, it really started pumping out a lot of grey smoke, ran rough, and you could smell gas.
At this point I am thinking I need to pull the engine, but I am also concerned something is not working right with the fuel system as well.
Any suggestions would be appreciated. If I do have the engine rebuilt, is there anything tricky about it. The repair shop I go to rebuilds a number of engines, but never has done one of these before.
However, it was consuming about a quart of oil every 500 miles. As the car had been sitting for a year, I have been running Rislone in it in case the rings were sticking.
Yesterday I drove about 300 miles on the freeway. During the trip it started to get hard to start. Instead of catching after the first crank, it cranked many turns without any catching. The exhaust smelled of gas.
Put it up on a lift to see if there were any visible leaks while the car was running, and while it was up there, it really started pumping out a lot of grey smoke, ran rough, and you could smell gas.
At this point I am thinking I need to pull the engine, but I am also concerned something is not working right with the fuel system as well.
Any suggestions would be appreciated. If I do have the engine rebuilt, is there anything tricky about it. The repair shop I go to rebuilds a number of engines, but never has done one of these before.
Pro
Joined: Jun 2004
Posts: 646
Likes: 0
From: Santee Ca
I too picked up a Vette that had been sitting for about a year. I had many of the same problems you have. Most of mine were fixed by replacing the injectors. No amount of cleaner would do the job. Mine was missing though. You might have an injector that is stuck open. I had on stuck closed.
Someone said that sometimes when it gets hard to start and it smells like gas you can hold the throttle open a little bit and the computer will think the car is flooded and cut back on the fuel.
Someone said that sometimes when it gets hard to start and it smells like gas you can hold the throttle open a little bit and the computer will think the car is flooded and cut back on the fuel.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Some thoughts:
1) You have a fuel delivery problem. With that much sitting, check the fuel filter.
2) Sounds like the head gasket went.
3) Working on an L98 is not hard. Very basic SBC.
4) It is not a bad idea to remove the engine and tranny as one assembly... it's only 4 bolts. 2 motor mount, 2 C-beam, out it comes. Reinstall the same way.
Time is a killer with Corvettes. If it sits, just about every gasket and seal becomes a ticking time bomb. This is not surprising to me at all.
I would pull the motor, replace every seal and gasket and go from there. I see no reason to rebuild, unless the oil looks like a milkshake (meaning, oil and coolant have mixed). If they have, then your problem is thus - the cylinders might have gotten washed down, removing the protective layer of oil, damaging the walls and or the rings and making it's way to the bearing surfaces. That's the worst case scenario.
Best case, you turned it off fast enough.
1) You have a fuel delivery problem. With that much sitting, check the fuel filter.
2) Sounds like the head gasket went.
3) Working on an L98 is not hard. Very basic SBC.
4) It is not a bad idea to remove the engine and tranny as one assembly... it's only 4 bolts. 2 motor mount, 2 C-beam, out it comes. Reinstall the same way.
Time is a killer with Corvettes. If it sits, just about every gasket and seal becomes a ticking time bomb. This is not surprising to me at all.
I would pull the motor, replace every seal and gasket and go from there. I see no reason to rebuild, unless the oil looks like a milkshake (meaning, oil and coolant have mixed). If they have, then your problem is thus - the cylinders might have gotten washed down, removing the protective layer of oil, damaging the walls and or the rings and making it's way to the bearing surfaces. That's the worst case scenario.
Best case, you turned it off fast enough.
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,023
Likes: 1,181
From: La Mesa CA
engine problems
The oil is clean, ie no coolant in it.
I thought about the head gasket at first but the smoke looks different than what I have seen blown head gaskets in the past.
I have the 4+3 trans. Does the suggestion to pull the trans with it still apply?
I thought about the head gasket at first but the smoke looks different than what I have seen blown head gaskets in the past.
I have the 4+3 trans. Does the suggestion to pull the trans with it still apply?
Last edited by gleninsandiego; Jul 16, 2004 at 01:43 AM.
Advanced
Joined: Jun 2004
Posts: 50
Likes: 0
From: Redlands CA
Massive engine problems
The only thing I can relate to you is what I just went through. I drove the car on friday and it ran great. Took the car to change oil on saturday and it was having a real hard time starting. I got it home and thought it was starving for fuel and repalced the fuel pump and inline filter. I tried starting it and I smelled a lot of fuel. I checked my dipstick and smelled fuel. I drained my oil pan and it had a lot of fuel. I tested a lot of things with the guys from the forums help, but reached my limit and took it to a mechanic. Turned out to be the brain (computer). It was telling the all injectors to go open before I had even started the engine. I bought a NOID light for $6.00 at the parts store and disconnected the plug from the injector and plugged the light in. I turned the key on and it lit up. This was not good!, but it pulsed when I turned he engine over. Everthing was 180 out. I am not saying this is your problem, but sounds familiar. Try a couple of checks and see what you come up with before you rebuild unless you are lookiing forward to do that
C-YA,
C-YA,
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
Before I thought to seriously about pulling the motor I'd do a compression test. All the above, and what your saying, it's sounds very much like a fuel problem. There's alot of forum members here with considerably higher mileage than yours still running strong.Good luck and let us know what you find. 
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Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
All of the above is good advice. To me it sounds like excess fuel. I would be checking fuel pressire under a variety of conditions. The first being for leak down. If the injectors, even just one, leaks, it will flood the engine and cause hard starting. I think your main clues are in the smell and exhaust smoke color.
RACE ON!!!
RACE ON!!!
Drifting
Joined: Apr 2003
Posts: 1,292
Likes: 2
It may not be a fuel problem. If the coil, say, is faulty, unburnt oxygen will affect the O2 sensor, telling the ECU to add extra fuel. This in turn will foul plugs, more unused O2 ......you see where this is going.
This is not just a theory - I spent a long time chasing this one down on my V8 Range Rover.
I suggest you check you have a strong spark before messing with the fuel system.
This is not just a theory - I spent a long time chasing this one down on my V8 Range Rover.
I suggest you check you have a strong spark before messing with the fuel system.
Instructor
Joined: Jun 2003
Posts: 118
Likes: 0
From: Edmonton_visitor Alberta
unburnt oxygen will affect the O2 sensor, telling the ECU to add extra fuel
Also a cheep solution that might work is injector cleaner.
A word of caution is that rich starts and rich operation will eventually destroy rings and cylinder hones due lack of oil that gets washed off by rich fuel.
Team Owner
Joined: Sep 2001
Posts: 62,155
Likes: 1,731
From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Grey smoke and unburnt gas would indicate a worn O2 sensor, bad injectors, bad fuel filter.
Replacing the filter is cheap, so do that.
A bad O2 wont throw a code all the time, so checking for codes may not work, youll have to hook it up to a tester or just replace it.
Hard starting when hot would be injector(s) stuck open and draining fuel into the cylinder. Hook up a fuel pressure gauge and shut the car off, that pressure should hold for quite awhile.
Replace with the Ford SVO #24 injectors.
If a shop says they dont know how to work on the L98, then theyre scared about the computers. Its just a regular SBC.
Replacing the filter is cheap, so do that.
A bad O2 wont throw a code all the time, so checking for codes may not work, youll have to hook it up to a tester or just replace it.
Hard starting when hot would be injector(s) stuck open and draining fuel into the cylinder. Hook up a fuel pressure gauge and shut the car off, that pressure should hold for quite awhile.
Replace with the Ford SVO #24 injectors.
If a shop says they dont know how to work on the L98, then theyre scared about the computers. Its just a regular SBC.
Thread Starter
Safety Car
Joined: Jun 2004
Posts: 4,023
Likes: 1,181
From: La Mesa CA
running rich
I pulled the plugs and ran a compression test
All the plugs were fouled something horrible. Black as night. Some had oil on the threads. Remember I have yet to do a tune up since I got it.
Did the compression check. All came up to 120-125 psi after several cranks
Put in new plugs. Still hard to start and running rich at idle.
I don't have the test equipment to go much beyond this. It seems as if it is a main sensor or computer issue since all the plugs are fouled, not just one or two.
Is there a way to test the O2 or MAF sensor or do you just buy one and hope for the best?
Thanks for all the advice
All the plugs were fouled something horrible. Black as night. Some had oil on the threads. Remember I have yet to do a tune up since I got it.
Did the compression check. All came up to 120-125 psi after several cranks
Put in new plugs. Still hard to start and running rich at idle.
I don't have the test equipment to go much beyond this. It seems as if it is a main sensor or computer issue since all the plugs are fouled, not just one or two.
Is there a way to test the O2 or MAF sensor or do you just buy one and hope for the best?
Thanks for all the advice
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
Looks like compression is not all that bad. If all your plugs are fouled and compression is good, I would look toward the intake gasket. A bad intake gasket can pull alot of oil. This is not too difficult to replace. Please research the forum on replacing this gasket and "dimpling" the back and front of the block to get the silicone to stick.
I agree with those above about injectors, but injectors will not cause oil consumption.
Good luck.
I agree with those above about injectors, but injectors will not cause oil consumption.
Good luck.
Le Mans Master
Joined: Mar 2004
Posts: 8,700
Likes: 298
From: Ft. Lauderdale Fl
engine problem
Just a guess but I think many of the signs sound like you might start
at the fuel filter. Its an easy and cheap start and when any car sits
for a year, carbs and fuel inj. always seem to get clogged.
at the fuel filter. Its an easy and cheap start and when any car sits
for a year, carbs and fuel inj. always seem to get clogged.