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Cranks then shuts off, idle not smooth, Yes new plugs/wires,

Customer Question
Cranks then shuts off...

Cranks then shuts off, idle not smooth

Mechanic's Assistant: Have you checked the fuel supply? And are all the spark plugs working?

Yes new plugs/wires, new fuel pump and filter. Getting gas to carburator just erratic spray from injectors

Mechanic's Assistant: What is the model/year of your Chevy?

1989 s10 blazer v6 4.3L

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

Yes, replaced fuel pump & filter. Plugs/wires, pcv valve, blew out fuel line, added injector cleaner, replaced fuel pump relays. Taking off distributor cap now and cleaning prongs. Getting fire but seems like maybe not enough gas.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Had trash/mud like stuff in tank before cleaned and truck was sitting for a while before got it running. Ran good yesterday but cut off. Replaced filter again today after blew out the line.

Submitted: 9 months ago.Category: Chevy
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Answered in 18 minutes by:
9/17/2017
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago
Tim's Auto Repair
Category: Chevy
Satisfied Customers: 16,246
Experience: Have owned a repair shop for 25 yrs.
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Hi, My name is ***** ***** for the delay.
I will do my best to assist you.

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Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

does the engine light stay on?if so,can you give me the trouble codes?

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Customer reply replied 9 months ago
Engine light does not stay on
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

hi

ok.

does it always start up with a prime?starting fluid or a little fuel into the throttle body?

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Customer reply replied 9 months ago
but can start without but after a minute or two it shuts off. Injectors are spraying fuel. Just took injectors out to try and clean to see if wasnt getting enough fuel. If work throttle back and forth to simulate pumping pedal, can keep running for munute or two. But if hold open or leave closed it shuts off.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

ok

a few things could do this.

1-the map sensor may be bad causing the weak flow through the injectors.

2-the distributor,check to make sure the distributor isnt worn and has play

3-the ignition module,even if it does have a good spark it may be killing the injector pulse

4-the pick-up coil in the distributor,if this is the problem you may as well replace the distributor with a new rebuilt distributor unit.

i would think the distributor is the problem

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Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

If you are satisfied with my answer, Please Rate my answer by clicking the rating button so I can get credit for my work. I’m not always going to be giving you good news, so please don't let this stand in the way of you accepting my answer. .it does not cost you more money and we will still be able to communicate, ,.please understand, i can not see, hear or touch the vehicle and only know what you tell me. Bonuses and positive feedback are appreciated.. if you are not satisfied with my answer, please do not leave bad feedback ,i will gladly opt out and let another expert handle the question. .if i have sent any diagrams, please print them. .sometimes you may need to right click the image [,then save picture as]to save it to your computer so you can open it with your picture program...Please ask if you need more help.

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Customer reply replied 9 months ago
I do appreciate any information given and even bad news wont hender my decision on a good rating. Those are some options i can look into and will check them out tomorrow and will let you know my results to see if that is the problem. I do understand you dont have hands on to determine the issue. Im not a machanic, but know my way around engine a little, so i will try my best to describe in detail the symptoms the best i can.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

please do

thanks

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Customer reply replied 9 months ago
I changed the distributor cap and cranks up right away as well as seems to run longer but when go to press the gas it wants to bog down and shut off, any suggestions? The idle sounds good, no shakes or rumbles, just steady.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

two things

1-you need to test the fuel pressure,,it must have no less than 9psi regulated.

2-the tps[throttle position sensor .

again,you may need to replace the complete distributer if it is worn of the pick-up coil is bad

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Customer reply replied 9 months ago
If i do replace distributor, will that require retiming engine or can it be done without? In my Haynes manuel it talked about checking fuel pressure from bleed off valve behind rear air intake plenum, but i couldnt find it. Could it be located else where?
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

this engine doesnt have a test port,,to test the pressure on this one you got to disonnect one side of the fuel filter then put in a "T" then reconnect the filter then connect the test gauge to the t.

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Customer reply replied 9 months ago
Oh ok, that makes sense then. I will give your suggestions a try and see what the results are.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

ok

thanks

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Customer reply replied 9 months ago
Hey Tim, changed the distributer with brand new one. Also replaced tps and map sensor. Still same issue, it cranks up and idles fine. When try to drive and press gas it shuts off. Crank back up the shuts back off. After few tries cranks and idles but if try to give gas wants to bog down and shut off. Not sure what to even try next, any suggestions?
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

HOW MUCH FUEL PRESSURE DOES IT HAVE NOW?..I KNOW YOU REPLACED THE PUMP,BUT WHAT IS THE REGULATED PRESSURE?

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Customer reply replied 9 months ago
I havent checked that yet, will check in the morning and let you know.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

ok

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Customer reply replied 9 months ago
The pressure seems to be reading about 10.5 to 11 on guage i rented from autozone.
Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

if that is the case,the pressure is good

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Chevy Mechanic: Tim's Auto Repair, mechanic replied 9 months ago

please stand by. perhaps one of the other guys has a better idea of what is going on here.

someone will be right with you.

thanks

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Customer reply replied 9 months ago
Thank you
Chevy Mechanic: Jerry Newton, Chevy Technician replied 9 months ago
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,666
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
Verified

I would be testing for a restricted exhaust. Use an exhaust back pressure gauge, you can usually borrow this gauge for free at popular parts stores, like AutoZone, Advance, etc. This attaches to the exhaust in place of the oxygen sensor. It sounds like you have a plugged up catalytic converter, and this test will pinpoint it. Allowable pressure is 1psi, if the gauge starts going way up, you'll need to address the exhaust issue.

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Customer reply replied 9 months ago
Took catalytic converter off but no change, after 5-10 mins or so still stumbles on idle and cuts off.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 9 months ago

OK, I understand.

Common problems with these: MAP sensor vacuum port in the throttle body gets clogged up and will cause this issue exactly. Even though you have vacuum, the port can be so plugged up that only a tiny pinhole exists, causing the vacuum response to be very delayed or even missing altogether at the MAP sensor. Remove throttle body, flip it over, and clean carbon out of passage. Use a new throttle body gasket.

Engine coolant temp sensor issues, a false high or low reading affects fueling dramatically.

Ignition timing is critical, must be set exactly as specified on the underhood label.

It's a pretty simple system, I would have a scan tool on it to see what's going on as it stalls. It would be worth finding an old scan tool to get a look at this.

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Customer reply replied 8 months ago
Ok i have replaced vac lines to tbi and map as well as replaced coolant sensor and oil pressure sensor. Still no change, cranks and idles fine you can mash gas and revs good but after 20 mins or so when warms up idle starts to drop off. If mash gas wants to bogg down and have to keep pumping to keep running. Put a scan tool on just to see if would read but blinks once with pause then two blinks which from book indicates system pass. Not sure where the problem is. Took tbi off and didnt notice any carbon.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 8 months ago

Have you replaced the coil?

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Customer reply replied 8 months ago
replaced the coil, still not runnng. Talked to a guy that use to work at GM and he suggested that it could be the computer. I took the tbi off and cleaned and replaced all the gaskets and o-rings. It is at the point now where engine doesnt have to warm up where it idles and shuts off. The engine surges when pressing gas, not steady run.
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