Can someone help me with some troubleshooting on an 87 Gm 350 tbi??

Question

Best answers?!!?!?

1987 GMV v-1500 with the 350 tbi.New engine and trans and every sensor replaced.When i start the truck in the morning it runs great.When i park the truck for an hour or so,the engine kinda bogs down when i give it gas until the temp of the motor is completely back to 195deg.After reaching this temp is runs fine.It only does this after i've ran it and then parked it for an hour.Why does it do this??It doesnt do it when its freshly started in the morning when its cold.I replaced all sensors.Whats next??Any help??Yes the coolant sending unit for the computer has been replaced twice.Whats the problem??

This has been happening since the engine replacement a year ago.Doubt if its bad gas since ive probably ran over 100 tanks through it already.Fuel filter was replaced about 1000 miles ago.

This is only a 350 tbi.It is not multi port with a fuel rail.The throttle body was completely rebulit(with 2 new injectors).The engine did the same thing before the throttle body was rebuilt.

Answer 1

I had this problem my self once before. I know this is going to sound stupid but with all thoes upgrades did you install a new chip in the computer??? after i lifted my truck and beafed up the motor i had the same problem. After replacing everything there was to replace a friend said get a different chip for the computer. The stock chip runs the truck fin stock but with more power and bigger tires you need more fuel. its hard to explain on here to much typing but i would go to www.summitracing.com and get a beffier chip for the computer. or yours could just be wore out. thats what fiked mine. good luck.

Answer 2

My first thought is a faulty fuel injector is leaking gas into the cylinder while its parked. That would cause an overly rich air/fuel mixture and make it hard to start. To test whether this could be the problem, the next time you attempt a hot start, push the accelerator pedal all the way to the floor and hold it there while you crank for 10 seconds or so. If it starts better, you need to hook up a fuel pressure gauge to the TBI fuel rail and see if the pressure is bleeding off too rapidly when you turn the engine off. It might also be a fuel pump related problem that causes the loss of fuel pressure. Try turning the key on and off at 5 second intervals for 3 or 4 times to force your fuel pump to run and build up fuel pressure before you actually crank the engine and start the car.

Answer 3

If you're sure all of the sensors/sending units are fine (including temperature), then it could be the radiator valve maybe. If the engine runs fine at 195 constantly, then it has to be in the electronics somewhere (the brain perhaps). If it has to GET to 195, then it goes back down and runs right, its mechanical. Check all of the radiator valves, flush the coolant, and check for cracks in either the block or radiator. I'm assuming you checked for leaks and the water pump is running fine. I say it's a radiator valve issue.

This is out there, but it may be a fuel issue. Sediment could settle, and when you run it a while it could slosh around and clog things up. Replace the fuel filters and drain the gas tank (I think it's easy in a pickup, otherwise I wouldnt have you do it).

Answer 4

Sounds like the fuel filter or tank strainer. When you start it in the morning or cold, it's been sitting all night and all the trash has settled to the bottom of the tank. After you drive it and then park it the trash has been stirred up in the tank and is clogging the filter or strainer. Have you ever gotten bad gas before? It could also be water in the fuel tank.

Answer 5

A bad O2 sensor will do that. It makes the engine run way too lean, and bogs it down when it's half warmed up. The choke, or computer adds extra gas when it's cold, and it's OK when it's hot, but when it's in between it's a pig.