4.3 problem

I have a 1990 4.3 van that when you start it you must push the gas pedal and when it starts its very rough and has black smoke. After a few seconds it will smooth out but it still smells very rich and if you mash the pedal you will get more black smoke. Any help please!:banghead:

possible coolant sensor on the fritz. you can check it with ohm meter roughly 3500 ohms at 70f. if its open you found the problem.

Is this a TBI engine or CPI system?

I think the 90 has TBI. Checked the air filter lately?

It has TBI and the air filter is new. We just replaced the motor in the van because the old one had alot of knocking in the bottom. We didnt have this problem with the old motor but once we put everything on the new one and installed it into the van now we are getting the rough start-up and the black smoke.

Did you use the original throttle body and injectors, or the parts from the replacement engine?

Wanted to give an update on this problem.

The van wont start at all now...........

Has fire and gas

Replaced map, oil, coolant sensors. New coil and pick-up coil.


We had it running sunday night and now it wont start. We even shot starting fluid in the intake and it wont start.

Please help!

I am to the point of setting this thing on fire.:banghead: :banghead: :banghead: :banghead: :banghead:

You sure that engine is any good? Is it used? Maybe the timing chain gave up or the distributor shaft/gear broke. A compression test sould rule out the chain..

compression is fine and distributor is working fine and we purchased a new one today and dropped it in and got the same thing.

If you're getting excessive fuel, the plugs may be wet by now.

Thanks for the help. After way to much $$$$$$$$ we had it towed off today to see if another shop could figure this out. It realy sucks to have all that money in new parts you know it didnt need but replaced anyway just in case and it still wont run.

Last night we put on a new TBI and still got the same thing.

If the shop can find out what the hell is going on I will update this and let you know what they have found. Everything is working and firing fine but it still will not start back up. All electronics have been replaced and tested and re-tested.

Im sure someone will find some stupid @ss little thing we over looked and have it running in 2 seconds.:banghead:

• Recheck the ground wires on the bell housing bolt
• Replace the wire harness between the distributor and coil, GM upgraded this short wire harness about 1994, it will have a larger wire in it
• Replace the ignition coil if it is loose in the frame, also upgraded by GM about 1994
• Can you see that one injector is spraying full force compared to the other? Disconnect the harness to the over fueling injector and you will probably be able to start and run on 3cyls. A defective ECM causes one injector to over fuel, (possibly always the passenger side injector), the ECM damage may be caused by a bad alternator producing AC. Do a diode charging test rather than relying on volt-meter alone

• Replace the ignition coil if it is loose in the frame,


Are you sure? I have an aftermarket coil, and it was semi-loose in its housing since new- Now its fairly loose.

regards

If the coil has been replaced recently it should be OK. The aftermarket coil may be the same as the first run GM part. They used them for 4 years. Upgraded coils may be the same except for a little epoxy to stop the movement and possibly grounding out on the frame. The wire harness is inexpensive and more likely to have an intermitent connection that is certain to fail eventually and will stop spark and the engine. The loose ground wires are very common when the bellhousing bolts have been removed during trans or engine replacement. Check out the injector spray. Inspect the charcoal canister and all the evap hoses.