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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 15181
Experience:  GM Grand Master Technician 2007. 14 years experience.
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It idles rough abd doesnt accelerate good after it starts

Customer Question

it idles rough abd doesnt accelerate good after it starts running rough
JA: Is the rough idle intermittent or consistent?
Customer: it runs good when first starded for a few blocks then when u go to push in the clutch and brake it idles bad sometimes dies and after that it doesnt accelerate hardly at all it falls n its face until you get off the gas
JA: What is the model/year of your Chevy?
Customer: 1991 s10 6 cylender
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: yes changed fuel pump filter and tps
JA: Anything else you think the mechanic should know?
Customer: thats it.. i dnt have the 43 dollars right now to pay to chat with him i get payed next week...
Submitted: 3 months ago.
Category: Chevy
Expert:  kalamykid replied 3 months ago.

When was the last time you had the cap and rotor button replaced on the distributor? I also need to know if you have a cpi fuel injection engine or a throttle body fuel injected engine please?

Customer: replied 3 months ago.
tbi and new cap and rotor and also new plugs and wires
Customer: replied 3 months ago.
i drove to work about 20 miles away and then on the way home it started falling on its face so i shut it off then turned it back on and it did ok for a few minutes then started doing it again
Expert:  kalamykid replied 3 months ago.

Do you have a fuel pressure gauge so you can see how much fuel pressure you have?

Customer: replied 3 months ago.
i do not.
Expert:  kalamykid replied 3 months ago.

You really need to know what the fuel pressure is first. All the other things we can check would be for nothing if the fuel pressure is to low. Can you borrow one in the am?

Customer: replied 3 months ago.
yea but i unpugged the map sensor and it changed nothing could the map sensor have anything to do with it and how much fuel pressure does it need
Expert:  kalamykid replied 3 months ago.

It should have 9 - 13 psi.

Expert:  kalamykid replied 3 months ago.

Do you have a scan tool that will read live data from the ecm?

Customer: replied 3 months ago.
nope it doesnt have any codes no check engine light
Customer: replied 3 months ago.
i had a diagnodtic done today and no codes showed up just the one one two blinks
Expert:  kalamykid replied 3 months ago.

Live data would tell me what the sensors are doing, not just tell me the codes.

Customer: replied 3 months ago.
well im not sure wher i could even go to borrow one
Expert:  kalamykid replied 3 months ago.

With no codes being set I do not think the map sensor will be a problem. It will most likely be low fuel pressure, or a vacuum leak, or the base of the throttle body is gummed up and not letting vacuum get to where it needs to be.

Customer: replied 3 months ago.
the timing chain was just replaced so i doubt its the throttle body being gummed up.. all vaccum lines are on i just dont see why it all of a sudden started doing this
Customer: replied 3 months ago.
makes me think a sensor went bad or something. unless the regulator went bad
Expert:  kalamykid replied 3 months ago.

The throttle body would not have been taken off to do a timing chain. If tit where a bad sensor the computer would have set a code.

Customer: replied 3 months ago.
hmm
Expert:  kalamykid replied 3 months ago.

We really need to know what the fuel pressure is. The pressure regulator could be the problem, but it is best to test then replace parts as needed.

Customer: replied 3 months ago.
ok i will let u kknow in the morning
Expert:  kalamykid replied 3 months ago.

Thank you. That will help me help you much faster.

Customer: replied 3 months ago.
12 pounds of fuel pressure
Expert:  kalamykid replied 3 months ago.

Do you have a helper that can try to start the engine for you?

Customer: replied 3 months ago.
it was started and running when we checked that
Expert:  kalamykid replied 3 months ago.

I need you to pull the air cleaner and spacer off so you can see the injectors. Whit some one turning the engine over watch the injectors and see if they both are spraying fuel out in a nice cone shape.

Customer: replied 3 months ago.
yep their good
Customer: replied 3 months ago.
could it be the coil?
Expert:  kalamykid replied 3 months ago.

It can be the coil, ignition module, or the timing can be off. The vacuum ports on the bottom of the tbi unit can be gummed up as well. Can you unbolt the tbi and look on the bottom and see if the passages in the base plate are stopped up with carbon?

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