idle problem
03-03-2007, 02:00 AM
#1
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idle problem
k i need some advice on what to check next.
car drives great. strong as hell. startup is a little laggy. not as prompt as it usually is. it idles okay until you drive it for awhile. then when you come to a stop it misses bad. idles really really rough. it has come up with a few codes almost on a daily basis.
not only does the SES light flash at idle sometimes but its had codes for misfire #1 and lean bank 1. to me those dont correlate. if its misfiring shouldnt it be rich? ive changed all 8 plugs and just changed the fuel filter. i give up already.
im thinking maybe cap/rotor and wires, but im also starting to think its mechanical. if maybe the pushrod on #1 intake is bent its not opening that valve all the way, and so its not getting the fuel in there, hence the lean code, and its also not getting the right mixture in there to properly ignite, so thats the misfire.
anyone shed some light on this one?
car drives great. strong as hell. startup is a little laggy. not as prompt as it usually is. it idles okay until you drive it for awhile. then when you come to a stop it misses bad. idles really really rough. it has come up with a few codes almost on a daily basis.
not only does the SES light flash at idle sometimes but its had codes for misfire #1 and lean bank 1. to me those dont correlate. if its misfiring shouldnt it be rich? ive changed all 8 plugs and just changed the fuel filter. i give up already.
im thinking maybe cap/rotor and wires, but im also starting to think its mechanical. if maybe the pushrod on #1 intake is bent its not opening that valve all the way, and so its not getting the fuel in there, hence the lean code, and its also not getting the right mixture in there to properly ignite, so thats the misfire.
anyone shed some light on this one?
03-03-2007, 09:14 AM
#4
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give it some shakedown runs with a scanner hooked to it and see where all your engine management peices are at, compared to where they should be, like the IAC, TPS sensor, Map, MAF. make sure that the engine is in good condition electronically and then move on. when i took my car to speed INC for what i beleive now is a piston slap problem, he was able to tell me that i had a misfire on cylinder number 5. get some codes read and see where all your sensors check out then move on to the basic things like wire and distributor. you dont wanna be changing that stufff when you can change a 25 dollar sensor in 3 minutes.
03-05-2007, 10:58 PM
#5
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ok new developments. im no longer getting a #1 misfire, its down to just a random misfire. and today i scanned it and i have both bank 1 and 2 are too lean. so now im suspecting my rail/injectors.
03-05-2007, 11:07 PM
#6
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take them off and you can get them hooked up to a battery and make em spray. you will be able to see if they can physically spray well or if one/some are clogged. fuel pressure is good to the rails ya?
03-06-2007, 12:58 AM
#7
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cant check. my fuel pressure gauge is broken.
so i can take the rail off the intake and just point the injectors to a cup or something and apply a ground and then power? it cant be 12 volts. i need resistance right? i probably need a power probe.
so i can take the rail off the intake and just point the injectors to a cup or something and apply a ground and then power? it cant be 12 volts. i need resistance right? i probably need a power probe.
03-06-2007, 09:11 AM
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actually the way we did it with my Z28s motor a few weeks ago, it wouldnt start so we wanted to check the injectors. we did this:
bleed fuel line pressure, take off fuel rails and pope the injectors out of the intake. leave them in the rails and then we put a flat but big enough tupperware top under the injectors and on top of the intake to catch all the fuel. then hook up the injector wires again(this is where its tricky to get enough room to get something to catch the fuel but still small enough so you can keep the injectors plugged in) then we primed the pump and gave it a few cranks and watched the fuel squirt out. that was the very simple deedeedee way, but it worked and we knew that wasnt the problem.
bleed fuel line pressure, take off fuel rails and pope the injectors out of the intake. leave them in the rails and then we put a flat but big enough tupperware top under the injectors and on top of the intake to catch all the fuel. then hook up the injector wires again(this is where its tricky to get enough room to get something to catch the fuel but still small enough so you can keep the injectors plugged in) then we primed the pump and gave it a few cranks and watched the fuel squirt out. that was the very simple deedeedee way, but it worked and we knew that wasnt the problem.
03-06-2007, 11:05 PM
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yeah i just need a second guy to check the spray, make sure its good. and no one say just check if theres fuel in the tupperware top. cuz it could be dribbling.
i brought home my fuel pressure gauge, and an multimeter to test my IACV and my crank sensor. i'll tinker with it tomorrow.
i brought home my fuel pressure gauge, and an multimeter to test my IACV and my crank sensor. i'll tinker with it tomorrow.
03-07-2007, 07:35 AM
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It could be your rotor starting to arc out. It did that once to me on a different f-body. Would idle fine until it was hot but it would stumble a little bit once it got up to operating temp. It would run great under full throttle but would also stumble some on part throttle.
It doesn't take much to arc inside that distributor to make an issue. It another thing to think about-
It doesn't take much to arc inside that distributor to make an issue. It another thing to think about-
03-07-2007, 02:11 PM
#13
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yeah if i had to do that i might as well get the MSD cap and rotor kit. its just the labor to do that. pain in the ***. but here i am again throwing parts at it.
and if this is from a bad rotor how could the mixture be lean? since its gotta misfire it should be rich, but its lean both banks. so i think its either a vacuum leak, fuel issure, or sensor issue. ima get under my hood today and look into it...after my job interview at 1
and if this is from a bad rotor how could the mixture be lean? since its gotta misfire it should be rich, but its lean both banks. so i think its either a vacuum leak, fuel issure, or sensor issue. ima get under my hood today and look into it...after my job interview at 1
03-07-2007, 09:28 PM
#14
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ok well i tinkered with it today. fuel pressure at idle is 36 lbs and when i unplug the FPR it goes to 43 lbs. i ran the gauge to my windshield and went for a drive. the pressure stayed good at idle, various throttle positions it did as expected. so its not that. i let the motor run and i unplugged each injector one at a time. each one gave a momentary drop in rpm. so there isnt a bad injector. i checked for spark from the coil. strong spark. i checked a few of the plug wires for spark, really strong, especially #1, which had a misfire code for that cylinder.
i then checked the MAF, IACV, and MAP sensors for anything suspicious, and they all appeared functional and sound. no vacuum leaks were detected anywhere. as i unplugged a few hoses, like the brake booster, the engine stumbled as expected. i checked the EGR. i manually applied it at idle. it stumbled. i checked all other sensors, theyre all plugged in. then i unplugged my crank sensor, and drove it. it still had the idle and miss problem, but it wasnt as severe. also it didnt lack power like it did when it was plugged in. so im leaning toward the crank sensor being bad.
i then checked the MAF, IACV, and MAP sensors for anything suspicious, and they all appeared functional and sound. no vacuum leaks were detected anywhere. as i unplugged a few hoses, like the brake booster, the engine stumbled as expected. i checked the EGR. i manually applied it at idle. it stumbled. i checked all other sensors, theyre all plugged in. then i unplugged my crank sensor, and drove it. it still had the idle and miss problem, but it wasnt as severe. also it didnt lack power like it did when it was plugged in. so im leaning toward the crank sensor being bad.