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Chris (aka-Moose)
Chris (aka-Moose), Technician
Category: Car
Satisfied Customers: 1176
Experience:  16 years of experience
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Has trouble starting when cold and when in drive and idling

Customer Question

Has trouble starting when cold and when in drive and idling idle drops down periodically
JA: How many miles are on the car? What size is the engine?
Customer: 94 silverado 305 v8 177
JA: Are you fixing your Silverado yourself? What have you tried so far?
Customer: Distributor cap rotor plugs wires fuel filter
JA: Anything else you want the mechanic to know before I connect you?
Customer: Nope
Submitted: 6 months ago.
Category: Car
Expert:  david craig replied 6 months ago.

Hi Im David, pull the IAC and EGR valves. clean all the carbon out of them with brake parts cleaner and a brush and rag. clean them good and clean the passages where they mount. reinstall them. it should make a difference for sure.

Customer: replied 6 months ago.
Would that also cause it to hesitate when you're first trying to accelerate it's like it almost stalls when I first give it gas
Customer: replied 6 months ago.
When I'm stopped in and drive the idle drops down and the engine makes like a knocking sound and then picks back up and then knocks again over and over again but when I'm on the gas it seems to run great
Expert:  david craig replied 6 months ago.

yes, those would cause problems like that. is the check engine light on?

Customer: replied 6 months ago.
No no engine lights are on what so ever
Expert:  david craig replied 6 months ago.

ok, yea then try that. let me know how much improvement you get.

Customer: replied 6 months ago.
Ok thanks
Expert:  david craig replied 6 months ago.

keep me posted..please.

Customer: replied 6 months ago.
One other thing when it's been sitting for a couple of hours and I go to start it it usually won't start right up unless I cycle the key a couple of times
Expert:  david craig replied 6 months ago.

fuel pump............

Expert:  david craig replied 6 months ago.

or the fuel pressure regulator. it should not take 3 times to build up the right pressure.

Customer: replied 6 months ago.
Yah when it sits a couple hours
Customer: replied 6 months ago.
I also replaced the fuel filter
Expert:  david craig replied 6 months ago.

fuel filters rarely cause problems anymore. its either a weak pump or fpr. have a fuel pressure test done.

Customer: replied 6 months ago.
What pressure should it be stabilized to have when running
Expert:  david craig replied 6 months ago.

i wil send you the spec. allow me a sec

Expert:  david craig replied 6 months ago.
Customer: replied 6 months ago.
Just getting to my truck now I took off my IAC and cleaned it thoroughly it was kind of dirty but I don't seem to see an EGR on my engine
Expert:  david craig replied 6 months ago.

standby a minute, i send you a pic

Expert:  david craig replied 6 months ago.

its a solenoid, not a valve

Expert:  david craig replied 6 months ago.

electronic vacuum regulator valve

Customer: replied 6 months ago.
I found it cleaned it and the IAC I also bought a rebuild kit for the pressure regulator valve and rebuilt that starting it up now I'll update you in a few minutes
Expert:  david craig replied 6 months ago.

i really hope its clears everything up for you!

Customer: replied 6 months ago.
On the IAC is the spring inside supposed to have a decent amount of resistance because mine was fairly soft. And the truck still hesitates and stumbles and ever built the fuel pressure regulator
Expert:  david craig replied 6 months ago.

the pintle on the inside should not be able to hardly move unless electrically actuated

Customer: replied 6 months ago.
Ok I did find the PCV valve hose headache rack and the other breather hose going from the carburetor to the other side valve cover also had a crack so I temporarily take them up but still runs the same the only thing I really have left is the fuel pump
Expert:  david craig replied 6 months ago.

check the fuel pressure before replacing the pump.

Customer: replied 6 months ago.
I don't have a gauge to check it but I found a new pump online for fifty bucks. What really else could it be
Expert:  david craig replied 6 months ago.

fuel injectors not getting pulse from the computer, clogged fuel injectors...

Customer: replied 6 months ago.
But if that was the case wouldn't do it even when the engine is cold. Because if I shut the truck off and then started back up again it idles and runs fine for about 5 minutes and then starts doing it again
Expert:  david craig replied 6 months ago.

I suppose it would, but I would run to harbor freight, but a fuel pressure guase for cheap and test it before replacing the pump. because if its the pump,why would it wait 5 minutes? something is dropping out and overheating. and it may be the pump, but i would want to be sure.

Expert:  david craig replied 6 months ago.

do you still need assistance?