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Lou P.
Lou P., ASE Certified Technician
Category: Chevy
Satisfied Customers: 3739
Experience:  building and driving chevy's since i was in the womb!!!! camaro and corvette enthusiest, access to factory diagrams and tsb's
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92 chevy k1500 4.3 runs rough at idle rpm goes up and down

Customer Question

92 chevy k1500 4.3 runs rough at idle rpm goes up and down sometimes dies no codes here is the weird thing is, when i hook up my scan tool and go into data display it runs fine when i exit data display it runs bad again
Submitted: 1 year ago.
Category: Chevy
Expert:  Lou P. replied 1 year ago.
ok, first , the ecm runs off the scan tool when the tool is hooked up so yes the idle will smooth out, so if there are no codes then you are going to have to go after common issues, throttle body leaks, fuel injectors dripping, idle air control valve sticking, throttle body base gasket, egr sticking, heres what happens, the engine starts , the ecm sees low idle or excessive air, so adds fuel, then the engine smooths out and the o2 sensors see to much fuel, so it lessons the fuel with gives lower rpms, and it keeps doing this trying to find the proper air fuel ratio, so the issue is with fuel or air. hope this helps,Please take a second and click the box and rate my service GOOD OR EXCELLENT SERVICE if you feel I have been helpful and please request me in the future. If you feel I have not been helpful please DO NOT RATE BAD OR POOR AND WASTE YOUR MONEY , I will opt out to see if another expert can provide more or better assistance so you're not wasting your money!!. Thanks for choosing just answer. Lou. also , if you feel i deserve one , BONUSES are GREATLY APPRECIATED ! ūüėČKeep in mind that rating me does not end the chat, it simply credits me for assisting, i will still be here to help if follow up information is needed , Lou.
Customer: replied 1 year ago.
customer already throttle body, 02 sensor, map sensor, ecm, temp sensor, distributor and egr valve, can't get good data when it run right with scan tool hooked up. this one is kicking are butts!!!
Expert:  Lou P. replied 1 year ago.
well the scan tool should do its own tests, there should be a option to test the system, i can t remember the exact verbalige. but how does the spray from the injectors look? nice mist? any drips?>
Customer: replied 1 year ago.
NO DRIPS SPRAY LOOKS FINE RPM GOES UP AND DOWN UNTIL IT FINALLY DIES
Expert:  Lou P. replied 1 year ago.
ok, how is the tune up how many miles on the truck?
Customer: replied 1 year ago.
JUST TUNED UP NEW PLUGS, WIRES, CAP, ROTOR, AND DISTRIBUTOR COMP 160PSI ON ALL CYLS. 192000 MILES
Expert:  Lou P. replied 1 year ago.
Ok try this. Take off the distributor cap, turn the engine by hand until you see the rotor move , then mark the crank to the engine. Now turn the engine back and see how far it moved before the rotor starts to turn. That will check the timing chain
Customer: replied 1 year ago.
I WILL CHECK THAT BUT REMEMBER WITH SCAN TOOL HOOKED UP IT RUNS FINE
Expert:  Lou P. replied 1 year ago.
I understand. With the scan tool like I said the car will Always run fine. I wish I had remembered why. I'll see if I can find out why. But I do know that the scanner controls the car at a baseline.
Customer: replied 1 year ago.
NO PLAY IN CHAIN
Expert:  Lou P. replied 1 year ago.
ok, i will opt out to see if another expert can help. sorry.
Expert:  Lou P. replied 1 year ago.
i have released your question so other experts can assist. hope it works out for you.
Customer: replied 1 year ago.
THANK YOU
Expert:  Lou P. replied 1 year ago.
no problem
Customer: replied 1 year ago.
?????? any info yet?

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