85 s10 carb refuses to adjust
dragon_kin01
01-23-2011, 12:46 AM
85 s10 1.9l isuzu motor with the DCH 340 2 bbl carb.
heres the problem. old carb was shot beyond repair. new carb on it and tried to adjust fuel mixture and idle speed. it just plain refuses to adjust proporly. what is happening is the truck, after it heats up to get off the fast idle cam, idles out (dies). i refire the motor and it will idle at 800-850 (like its supposed to). after coming off of any load (neutral or moving load) the idle will do 1 of 2 things: 1. die or 2. rpms will drop to about 500, shoot to 1000, then come slowly back to 800-850.
also found out that my vacuum is not steady. i got a reading of 15-21 in hg (the needle on the gage was bouncing). did a compression test, both wet and dry, and these are the results form that:
1 2 3 4
dry 111 108 110 101
wet 120 115 120 110
Next thing, the truck pasted emissions. heres a list of things ive replace or did, thinking this was causing my idle problem: new carb, new fuel pump, fuel line flush, fuel filter, intake manifold gasket, EGR valve, igntion timing, valve lash adjustment, igntion tune up. after doing the first 6, the carb adjusted PERFECTLY. needle on the tach was dead nuts at 800. after a week, it started with the idle fuckuation.
im going to be picking up a leak down tester to find out if i need to do a head job or motor rebuild
my biggest question is, for the 1.9 4 banger, what is my compression psi specs (acceptable and minimum)? next question (lets go off the assumtion that i dont need a head job or motor rebuild) what the fudge would be causing my idle to be a troubled child on crack? (i have been fighting with this idle problem for about 2 years now.) also, from what i can tell, the motor has never been rebuilt and the truck has 156k+ miles.
heres the problem. old carb was shot beyond repair. new carb on it and tried to adjust fuel mixture and idle speed. it just plain refuses to adjust proporly. what is happening is the truck, after it heats up to get off the fast idle cam, idles out (dies). i refire the motor and it will idle at 800-850 (like its supposed to). after coming off of any load (neutral or moving load) the idle will do 1 of 2 things: 1. die or 2. rpms will drop to about 500, shoot to 1000, then come slowly back to 800-850.
also found out that my vacuum is not steady. i got a reading of 15-21 in hg (the needle on the gage was bouncing). did a compression test, both wet and dry, and these are the results form that:
1 2 3 4
dry 111 108 110 101
wet 120 115 120 110
Next thing, the truck pasted emissions. heres a list of things ive replace or did, thinking this was causing my idle problem: new carb, new fuel pump, fuel line flush, fuel filter, intake manifold gasket, EGR valve, igntion timing, valve lash adjustment, igntion tune up. after doing the first 6, the carb adjusted PERFECTLY. needle on the tach was dead nuts at 800. after a week, it started with the idle fuckuation.
im going to be picking up a leak down tester to find out if i need to do a head job or motor rebuild
my biggest question is, for the 1.9 4 banger, what is my compression psi specs (acceptable and minimum)? next question (lets go off the assumtion that i dont need a head job or motor rebuild) what the fudge would be causing my idle to be a troubled child on crack? (i have been fighting with this idle problem for about 2 years now.) also, from what i can tell, the motor has never been rebuilt and the truck has 156k+ miles.
Rick Norwood
01-28-2011, 05:29 PM
Vacuum Leak? Try spraying the vacuum hoses and fittings with Carb cleaner or WD-40 while the truck is running and see if the rpm's jump.
dragon_kin01
01-29-2011, 01:00 PM
theres no vacuum leaks. im thinking the truck needs eithr a head job (ran a leak down, cyl 4 exhaust leaking), or a new timing set.
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