Hi All,

I recently bought an 89 corvette but have been having engine problems.  I was driving the car to work about two weeks ago and I noticed the car had problems going up a very slight gradient at 65mph.  Progressively this became worse to the point I was giving this car everything it had to get 45mph on a flat section of freeway.  It sounded like the engine was operating properly, it just lacked power.  I also noticed the check engine light kept coming on and the engine was heating up very quickly.

After this incident I limped the car over to the mechanic and by the time I made it over there the engine had severe spark knock.  All engine fluids were normal, oil pressure was normal.  

The mechanic changed the gas filter, engine oil and transmission oil and then suggested I possibly had contaminated fuel.  I pumped the tank and replaced all the fuel. As a temporary measure, the mechanic also retarded the timing by six degrees to help reduce any spark knock.  I limped the car from the mechanic back to my house but it was flat out doing 10mph and eventually to the point were I couldn't even release the clutch into first gear.  

I understand that retarding the timing will dramatically reduce power, but there is still spark knock.  The engine is now very hard to start and when it does run, the engine surges at idle.  If you put your foot down it sounds like the engine is choking and it will stall out.  From the exhaust it smells very rich probably almost to the point of flooding.

I've looked in a Haynes manual but I cannot diagnose what the problem might be.  These are the things that I thought it could be:

Deteriorating coil on distributor
A faulty sensor of some kind?
Vacuum leak?
Faulty ECM?
 
I don't quite understand if it is running rich then why is there spark knock?

If someone has any ideas your help would be greatly appreciated.

Thank you    

Just had a  problem just as bad, change mass flow after code 32 finally showed up,change EGR, fuel reg, man tepm switch, no change, the problem was the right cat came apart and clogged the main cat, had all 3 replace and runs like new gas mileage back to 24-26mpg.  

I experienced a similar problem on my 1987 Corvette. After installing new custom made header's. A few days had pass when I heard the engine suddenly sound off. I too noticed a decrease in power. One note here I do not have the Pre-Cats on the front Y pipe. But the main Cat had crumbled apart. This during my DMV Smog test requirement. I ordered a new main Cat by MagnaFlow from Mid-America. Not waiting the shipping time I gutted my now defunct Cat. Runs like a dream again. I liked this performance with a 2.2 mpg increase so well I have yet to put on the MagnaFlow. You do not mention how many miles you have but a good investment may be new injector's at some point. I understand that after 120,000 they can start to fail. At least run poorly.  

Thanks everyone for your advice.  I took the car over to an exhaust specialists and too my suprise the car had three catalytic converters. The front left hand side converter had totally broken down into what looked like lumps of charcoal.  This had blown down into the back converter and clogged it.  

I've now had the new exhaust & cats fitted. It's truly amazing the amount of power I am now getting. My economy has also improved to just under 25mpg.

However... I noticed that a couple of new problems have arisen.  Firstly I can't get the alam to turn off.  I've tried locking the car from the inside then using a key to unlock the door, but it doesn't stop.  Also I've tried the key in the ignition but that doesn't kill it either. It sounds like a relay is going off in the cab.  I can see a red and green flashing light through one of the vents.

Initially all of the lights would flash, but now it is just the relay.

Everytime I finish driving the car I have to disconnect the battery as it will drain it.  I can't find any wiring schematics on the anti-theft module, maybe this is something very simple.


Plus on top of this I've also noticed that when the car is stationary with the engine running, there is no resistance on the brake pedal. I can push it all the way down, however when I am driving the resistance returns and the brake feels normal.  From what I remember there was always resistance in the pedal.  Could it be a leak in the break booster line from the intake manifold? I tried reving the engine to improve pressure in the manifold but still the brake feels the same.

I would appreciate any suggestions you might have.

Thanks again for you advice, I'm now back on the open road road enjoying my vette.  

Have the PCM looked over, you may need some reprogramming.  Also, have the vacuum on the fuel injectors tested.  

Do they normally put in new injectors when an engine is rebuilt? I have had my 1989 for about a month, and it is hard to start, runs rich, but is strong and smooth once it gets going. I am wondering if my injectors may be going?