Would a 1990 L98 have a nylon cam gear? I have read a few articles that said GM stopped using them in the mid 80's but then I have found a few threads in a 3rd Gen forum where people had failures in late 80-early 90's camaros....


I was driving the Vette Saturday evening and it was running fine. I went to accelerate to go up a hill and it developed a miss. About like loosing a cylinder. I started up the hill and it fell flat on its face. No power. I barely made it up the hill and into a parking lot. Car was idling okay but not great. Checked spark plug wires and injector wires all were good.

I was a few minutes from a friends house so I thought I would try and make it there to at least get off the road. Started back out of the parking lot and it got even worse. Car was sputtering and back firing. I pulled into the very next parking lot and now it sounded as though I was running on two cylinders. Car sounded more likely a harley than anything.

I left the car and came back with a trailer. It barely made it onto the trailer and barely made it back off the trailer. The car will start fine but idles very rough and back fires and sputters when given any throttle.

I know older SBC had nylon timing gears that would strip teeth and jump time. I was going to pick up a timing light on my way home from work and check it out but wanted to see if that was even a possibility.

 

The 91 cam I pulled earlier this year did not have a nylon gear. I believe the cam is the same as yours.

 

Time to check fuel pressure.

 

Change the plug wires, plugs, cap, rotor, and maybe the miss will go away. If not, then start diagnosing.

 

sounds like fuel to me...
low pressure results in cylinders dying off and the rest burp and spit..just like low voltage misfiring.
Happening suddenly is a clue. On a L98 its easy enough to yank the dist out and take a look. I've not seen a nylon timing gear since I took apart a Briggs & Stratton...

 

Not the dist. gear, it's the one on the front of the engine under the water pump.

But there is an easy way to tell if the gears are not aligned.
But, there is this disclaimer.........
If the harmonic balancer ring has not moved......

1. put the engine on top dead center according to the crank timing mark.
2. pull the distributor cap, and the rotor should be pointing to #1 spark plug wire.
3. pull the left rocker cover, and the #1 cylinder rockers will be loose, signifying that the #1 cylinder is on top dead center, compression, waiting for the dist. to light off the mixture.

If the harmonic balancer timing mark has moved, just use the last two qualifiers, but now you have to pull the #1 spark plug, get someone to click over the engine till the compression blows your finger out of the hole, check for loose rockers and dist. pointing to #1.

 

ok, I get that,
BUT
if the cam/crank timing gear had slipped he would be walking down the road picking up the pieces of his pistons and valves from the unpleasant meeting they had...

quickest way (some say the ONLY way) to destroy an Accord or Toyota engine is to let the timing belt break....the result is a catastrophic collision of valves and pistons, as would be in this case.

 

Sometimes if the timing gear is worn or a tooth is missing, the timing gear will be off 1 tooth. The motor will run but crappy.

 

Has an accel cap/coil, with wires and plugs all replaced within the past two years....but I will check again.

I'll pick up a fuel pressure guage when I get the timing light from the shop.

Definitely starts and "runs" but not very well.

 

Did you check to see if the distributor hold down clamp has loosened up and allowed the distributor to move?

 

Nylon tooth cam gears normally fail when the engine idles. If it did jump a tooth the motor would still run on 8 cylinders but be down on power.

90's are famous for shorted injectors. The problem you describe could be injectors or possibly a bad ICM in the distributor. Suggest ohm checking each injector.

 

Did a fuel pressure check and I'm running solid at 38psi. I pulled all the plugs on the injectors and OHM'ed them.

Cylinder
1 - 15.8
2 - 16.6
3 - 6.8
4 - 7.9
5 - 15
6 - 5.0
7 - 6.6
8 - 11.3

When I started the car it was running "ok" better than it was but not great. I let it get up to temperature and it started to stumble and misfire. I shut the engine off and re-checked the injectors and several had dropped to 2-3 ohms.

Looks like I found the problem.

Good call Church

 

Time to call Jon at www.fuelinjectorconnection.com