sfc rick

After pulling my hair out and taking the intake on and off so many times I'm better than a NASCAR pit crew, I can't seem to find a hanging idle issue solution. I thought it was an air leak some where and have checked every tube fitting PCV tubing and anything that belches, farts, or wheezes. NO cracks, loose fittings hoses or whatnot.

I can torque an intake down in my sleep, and it even seems like the car knows I'm fixing to pull my toolbox drawer open.

It hangs idle most of the time (but not all the time) and when it does hang, it does for awhile, and then runs perfectly with no hanging idle issues for a few hours, then can start again at anytime.

I hope Megan Fox shows up and wants to play with my toolbox........but that's never gonna happen.

Help!
I listen and listen under the hood for any air leaks...no help!

So is there anything else I'm missing? I've cleaned my MAF and Throttle Body.

I'm fixing to remove the Intake for the umpteenth time and see IF I missed something somewhere. ( I doubt it, but you never know)

Can it be a bad TB? Or maybe a program issue?

I hate it, but Love it when everything works and runs great. I just don't know which way it's going to be whenever I turn the ignition key on. Or how long it's going to run crappy(hanging idle) and then decide to run perfectly.

Anyone with suggestions?

ds98formula

iTrader: (3)

What are the mods on the car? Have you tried spraying starter fluid around the engine to see if the rpms jump so you can narrow down an area to check?

RevGTO

iTrader: (12)

How long has it been since you last disconnected the battery or flashed the PCM? And how much have you driven it since?

NW-99SS

iTrader: (6)

Throttle blade fully closing? This one had me searching for a similar result. Quick check, disconnect throttle cable before cold start - fire it up, monitor idle rpms, give it some revs manually and see if it hangs.

Also what TB? Hole in blade?

Otherwise the suggestions here are good to follow.

JaYZeig

iTrader: (11)

wouldnt by chance have a idle air control motor (iac) you can swap out just to rule that out?

sfc rick

Electric throttle body, no cables, no IAC, Stepper motor.

Just a 98 C5.

I'll try some of the suggestions....

99 2500

Maybe a bad TPS sensor?

baxsom

iTrader: (6)

does your HVAC switch from defrost to middle to floor. very common issue is cracking the hard plastic line coming off the back of the intake that runs the motors that change the hvac output

livewire0201

My car was recently doing this and it turns out the exciter wire to the alternator had a connection issue. It was idling super high trying to pull the amps. Got the connection cleaned up and it idles like it always had.

carguy_24

My engine had idle issues too... Checked all sensors on the intake and it turned out to be a wire that went through the firewall that controlled idle that was grounding on the firewall. Had to pull the PCM, found the wire, electrical taped it up and put some hose pad around it. It has solved my problem so far and this was 15k miles and a few years ago.

chrisfrost

iTrader: (8)

Really it could be anything from a cam pos sens, crank pos sens, thro pos sens, could even be a veh speed sens, dirty inj, fuel filt, feul pump, fuel press regulator, a bad ground anywhere on the car could possibly be a bad spark plug wire (usually 1 end or the other the boot will have spark pass right through it) check at night in the dark and rev pretty good You should see the spark if it's doing this ,,,,,,,,sometimes only under load,,,,,,,,,,,,or any and/or all of the wiring or plug connections . The plugs over time tend to get corroded and can make an intermittent conn. Take the plugs apart and take a dental tool or a eyeglass screw driver and in the female plug tighten the female spade connectors (make sure and tighten them good) re-install even better yet with some ox-gard . And finally yes it could be either a factory program update or a bad PCM ,,,,,,,,,,,,,if no codes ,,,,,really You need a scanner with freeze-frame ..............etc to see what's happening when it switches from idling to not so idling,,,,,,,good luck

usafws6

iTrader: (10)

My tps didthe same thing to me. Drove me nuts for a while.

LS100CAMSS

If I am not mistaken, most drive by wire vehicles do not use a IAC motor since the PCM can control the idle speed by adjusting the angle on the throttle plate. That being said, there are still a ton of possiblities as previousley stated by others. I would also ensure that, while off the intake, you manualy cycle the throttle blade by hand to feel for "stiff spots". Another "old school" idea may be to remove both battery cables & touch them together to erase any history codes & reset fuel trims etc. Best of luck sir.

ls1 1990 VN

Easiest option, take it to a tuner who can hook it up to a diagnostic machine to find what the problem is.

sfc rick

I've got HPTuners and ran a log, so when I get a chance this next couple days I'm going to review it and see what changes are occuring when idling.

sfc rick

Fixed it! Here's how:

Plugged the hole I drilled in the throttle blade. Car runs perfect now. I drilled it last year after the cam install cause it couldn't get enough air to idle(tuner not available at time) quick solution.
Fast forward to now, installed reworked heads by Faerman in Houston, and couldn't get the engine to idle down. Went nuts trying to find an air leak, found one but still had problem. Anyway, turned out that heads must be allowing better flow and pulls more air in at idle than before.......so NO NEED for hole in TB Blade.

FINALLY RUNS LIKE IT'S MADE TOO!

ds98formula

iTrader: (3)

Good to hear

gMAG

iTrader: (1)

Good stuff!
Many people drill the hole, but it is more detrimental, than anything.
My TB came that way, and it caused several issues. I ended the troubles by finding a small screw that would fill the hole!

sfc rick

2 days no problems at all, engine is running like a dream! I went in to Mast Motorsports today and checked out the engine assembly area and talked with the techs and sales staff. I'm interested in dropping a LS3 416 in and was told to offer my 500hp built LS1 for sale while it's in the car and running. I wouldn't know what to expect for it but it's something to consider later this winter. Right now....I love this monster!