94 Hesitation Problems

[Hardhide]

I've got a 94 with 4.3L V6 that has suddenly started running very rough. From cold start, it idles very rough and hesitates during acceleration. It gets better as the vehicle warms up, but is still has a noticeable hesitation.

I've replaced fuel filter, injectors and O2 sensor. Air cleaner, plugs, wires, dist cap and rotor have all been replaced recently. The check engine light does not come on and there are no codes stored.

Any help would be appreciated.

[horse482]

Check and make sure that the egr valve is not stuck open. It could also be the coolant temp sensor, not the switch for the guage/light. Have seen the sensor go bad and not trip the ses light, but it is telling the computer the incorrect tempature of the engine.

[2000CAYukon]

If the EGR and temp sensor check out ok, I would look at bad cat (or partially restricted exhaust). You can have the exhaust back pressure tested.

//2000CAYukon

[Hardhide]

Thanks for the suggestions. I replaced the coolant sensor a couple of years ago, when it triggered the SES light, but I'll check it again. I'll also check the EGR.

Thanks!

[Hardhide]

Well, after a new EGR valve and coolant sensor, I still had the hesitation problem and it seemed to be getting worse. I rigged up a fuel pressure gauge and hooked it up on the input side of the fuel filter. The gauge indicated that the pump was only building up 3psi and then losing pressure.

I decided to drop the tank and have a look at the fuel pump assembly. When I removed the fuel pump assembly from within the tank, I found that a short 2" piece of rubber hose that connected the fuel pump to the metal fuel line was split and badly deteriated. I replaced the rubber hose with a new piece of fuel line and reinstalled the tank. The truck runs great again.

[horse482]

Glad that you got your problem fixed, would have never thought about that ruber hose causing a problem like this.