jerking, bucking, & stumbling

[oldfrt47]

Hi. My 94 transport (3800) acts like it has a carb with bad choke!! ( I know it's injected) Every time you first crank it after it's been sitting a while, it doesn't want to run. Acts as if it's starving for fuel. Stumbles, jerks, hesitates for a minute, then runs fine. Doesn't matter if it's cold or hot weather. If I let it sit and idle a couple minutes, it runs fine. Check engine light doesn't come on. I replaced plugs, wires, and fuel filter when I first bought it. After the stumble is gone, the thing runs like a champ. Anybody experience anything similar or can offer any suggestions? Thanks.

[GMMerlin]

Could be many things that are causing this. Low fuel pressure or a fuel pump drainback problem.
Possibility of a schewed sensor reading.
First thing I would do is check the fuel pressure and for fuel pressure loss with the engine off.
Fuel pressure should be 41-47 psi and hold steady after the key is turned off.

[sloechli]

I have a 93 transport 3800 with a similar problem at startup.

After the car has set for several days it will sometimes start very hard, backfire, black smoke not idle stall, very had to keep running, I can only keep it running if I hold gas down to about 2500 RPM, After about 5 Min of foot on gas it will smooth out and idle fine. It acts as if the timing is off, but once running it is fine. Once I get it running it will run like a champ the rest of the day with multiple stops starts.

Some days it will start fine.

I have replaced plugs.

[will123345]

I own a 94 transport and have a similar problem as well. So far i have changed plugs, wires, fuel filter, air filter, and egr (which helped on stalling). I have tested my fuel injectors, iac, maf and tps with a digital multimemter to ensure that the electrical components are working corretly. I believe the problem lies within the throttle body. When you unplug your batter from a GM the computer resets thinking your car is new. Therefor it believes that your gunked up throttle body is new, and it will cause the car to run poorly. I have tried to remove my throtle body with no success. If anyone has any further information on this subject please post it.

[will123345]

I also forgot that i changed my o2 sensor and also recently found a vac leak leading to my fuel pressure. After installing a new hose i notice some overall improvement in the cars feel, but my van is still running rough.

[toivo]

if your throttle body keeps acting stupid, spray some card cleaner into your pcv port while you hold the throttle at high idle. if performance improves remove your throttle body and clean out the passages between the venturi passages. toivo

[sloechli]

Originally Posted by sloechli

I have a 93 transport 3800 with a similar problem at startup.

After the car has set for several days it will sometimes start very hard, backfire, black smoke not idle stall, very had to keep running, I can only keep it running if I hold gas down to about 2500 RPM, After about 5 Min of foot on gas it will smooth out and idle fine. It acts as if the timing is off, but once running it is fine. Once I get it running it will run like a champ the rest of the day with multiple stops starts.

Some days it will start fine.

I have replaced plugs.

Anyone with this problem come to resolve, my transport is still showing same problem.

I was driving it every day for a while and the problem only happend about once a week. It is back to every morning again.

[toivo]

unplug your coolant temp sensor by the gooseneck for your thermostat and try to start it. see if it starts up ok, when it is unplugged. toivo

[richtazz]

check the port for the egr in the intake manifold. It may be clogged and not allowing enough flow. Also check the egr control solenoid if your has a vacuum EGR, as this controls the opening and closing of the EGR. One last thing to check, the air intake temp sensor, if the ECM is receiving false info about intake air temp, it can over richen/lean the fuel mixture.