Idle and backfire/rich

Asked by skyward Aug 06, 2016 at 08:50 PM about the 1995 Chevrolet C/K 1500 Silverado RWD

Question type: Maintenance & Repair

I have a 95 silverado with a fresh built 355 (350
bored .030 over). Its a stock tbi motor except for a
performance timing chain set, high volume oil
pump and shorty headers all from summit racing.
The truck was running great until a week ago
when I took an hour and a half drive and on the
way back the power started cutting out under
acceleration. We thought it was bad gas. Ruled
that out after pumping the tank and putting 100%
87 in it still ran choppy and idle surged from as
low as 700 to 1200. Replaced fuel filter, map, icm,
iac, fuel relay, rebuilt top portion of throttle body
with new fuel regulator, cleaned grounds, cleaned
egr w/new gasket. I'm not hearing any hissing
from anywhere on vacuum lines and intake gasket
is brand new plenty of silicone on fromt and back
not leaking any fluids. I'm a little lost, it will start
but wont idle, dies immidiately.

3 Answers

skyward answered 7 years ago

The fuel pump is getting more than enough fuel to the throttle body, so much that its running rich. Idk if its a computer or sensor problem. Anywhere I read if a fuel pump is going out it wont get enough fuel to the throttle body. Instead of a mist from the injectors im getting an occasional dribble.

Mark helpful

Austinc12 answered 3 years ago

Same thing here. I have a 94. Bored it 30 over and put a small cam in it. I’ve replaced, fuel pressure reg., egr, egr sensor, distributer (just the shaft and sensor) new wires and plugs tbi gaskets, coil,map sensor, iac valve, tps, coolant temp sensor, computer, and even a new alternator. Fuel pump has got plenty of pressure it runs rich. Timing was retarding until I unplugged the 02 sensor. Now you can set it at zero and advances to around 20 degrees it only runs bad win it retards. It runs ok when it’s cold but when it warms up you can gas on it and it’ll back fire through the intake. I believe something is retarding my timing. But what could it be??????

Mark helpful

Your Answer:

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