Extremely Rough Idle with Backfire

[89_Corvette]

At the start of the winter my 89 died on the highway and I needed to have it towed home. I determined the fuel injectors went bad so I replaced them with a new set of Bosch. While I had the plenum off, I decided to replace the thermostat. That was the start of my problems. I accidently broke a bolt on the thermostat housing and after numerous attempts at removing it, by drill, I finally bought another intake manifold on ebay and replaced it entirely. When I put it back on it ran terrible. At first I thounght I had the distributor wrong, but it will start and the timing looks to be set a 6 degrees btdc. Next I thought I had a vacuum leak, but I sprayed carb cleaner all aroung the manifold and nothing. I did find a crack in my egr tube, from where I bent it to remove the valve covers. I replaced it, now it really runs horribly, I have no idea where to go from here, any help would be appreciated.

Thanks,
John

[c4c5specialist]

Hi there,

It sounds like there is a pinched wire somewhere.

can you drive it ???

Do you have to hold the gas down to make it idle ????

Allthebest, c4c5

[89_Corvette]

Thanks for the help,

I drove it a 1/4 mile to the gas station the other day and the fluctuating rpms made it jump all over the place.

I don't have to hold the gas for idle. It use to rough idle indefinately, after I replaced the egr tube yesterday, it seems to die after it gets warm. But it will start right back up.

There is also a knock or ping near the distributor, plus smoke comes up from the exhaust manifold near the EGR. I must have a leak there, but I can't understand why.

What is a pinched wire, do you mean a vacuum line?

It has 89K on it.

[c4c5specialist]

HI there,
I would recheck your injectors, to make sure there is 16.5 ohms resistance in each one.

Allthebest, c4c5

[89_Corvette]

injectors check good

[lovehatec4]

Just a thought,This sounds elecrical to me. check the entire ignition system including cap,rotor, coil and the electrical connections to the dist. also check and verify the correct fireing order on the spark plug wires. 1-8-4-3-6-5-7-2 in a clockwise rotation on the dist. 1-3-5-7 left head, front to back and 2-4-6-8 right head, front to back. Even the best of us can make mistakes. I hope your'e not offended if you already knew this but, I thought I would chime in. Let us know..

[89_Corvette]

I am certainly not offended, I appreciate any and all help. I have checked the firing order. It's good. Now, unfortunately, the darn thing won't even start. I have no idea what is going on. No codes are showing, I am not sure what my next move is. Perhaps it will be towed to the shop. I have not take an car to the shop in 20 years.

[lovehatec4]

If it wont start check for spark at the spark plug wires. Pull off a wire and insert a phillips head in it. Then have someone crank engine while you hold the metal shaft of the screwdriver real close to the block..To avoid being shocked, make sure your hand isnt touching the metal part of the screwdriver. You are looking for a very bright and blue spark. This is the shade tree way but what can I say it works and when in doubt, go back to basics. Fuel or fire, fuel or fire. If you have good spark at the wires then check your fuel presure. These to things will lead you in the correct path to diagnosis. Let us know...

[LLC5]

If you have an HEI distributor, check for carbon tracks in the center of the rotor (under the rotor where it bolts to the dist. shaft) and for carbon tracks on the ignition coil (usually from the plastic coil body to the outer corners of the metal mounting points), make sure the coil has the ground strap to it, and that a rubber insulator is installed under the coil for the spring/carbon brush to the rotor.

[89_Corvette]

Thanks for the advice, I just replaced the rotor a few weeks ago. I am not sure why it won't start after I changed the EGR tube, but it has. While trying to turn it over, I get no light on my timing light (connected to #1) and my noid light does not blink also connected to #1 FI. I checked the VATS fuse and the theft fuse, they look okay. Prior to it not starting, it ran very rough. When I tried to adjust the timing, I was getting about 17 lbs of vacuum and when I adjusted the timing to get about 20 lbs of vacuum, I noticed it went to about 12 degrees btdc with the timing light.