1990 c/k 1500 305 tumble, missing, surge ?

[coleman]

I just got the truck and the guy I bought it from said that he had taken it to a shop, but the problem was not fixed, it has new cap, rotor, wires, plugs, fuel pump, the tank was empty I put new gas in and dry gas.

its fuel injected tbi, when you start it, it will rev then stall, not every time. start it the second time it idles fine but if you rev it up a little and let off it stays and then comes down slow. when you go to take off it stubles and skips.

no codes in the computer, checked the tps good, checked the map sensor it good. could not fine any vac leaks. standard transmision.

anyone have any help?

[rpreston]

You might want to look at the Idle Air Control valve in the throttle body. It's got a motor connected to a valve that the ECM uses to control the the amount of air in the TBI during idle, cold or hot. I'd also check the timing.

[coleman]

ok I will try that

[gyoung3]

Check the gasket under the valve body. When I bought the 90 that I have now the gasket was sucked in. If you remove the air filter and open the throttle you may be able to see the broken gasket.

[Rbraczyk]

I have a similar problem with a 94 350 tbi
Rev to 2500 slowly and let off, motor stumbles to a near stall then comes back to idle.
Rev it fast, comes back to idle. Fucked up huh.

[burnM]

Definately check the IAC, and torque down the TB bolts. Why not soak the TB in cleaner? Gm is known for carbon build up in throttle bodies. In extreme cases, it can cause things like that to happen. Wouldn't hurt to check the injectors and make sure that the fuel filter is clean.

[rayb]

my truck was doin the same thing.I tested the Egr valve and it showed to be working right.I then talked to a mechanic and he told me to pull the vacuum hose loose from the Egr valve and plug it up and try it.I plugged it up, and now it runs perfect!!! Ya might wanna try it.