Weird idle question

[rsm688]

Okay guys I've noticed every now and then when sitting at a red light or in in my driveway my idle will drop down for like once second and feel a little vibe/shutter come from the motor. It only lasts for a second and just occasionally happens. The H3 runs fine otherwise, its an 2006 with 96k miles. I did notice there was a good bit of black soot in my new exhaust pipes after 1000 miles but it had been sitting for 6 months and I ran some seafoam through it, new plugs, cleaned the MAF, cleaned the throttle body, Air Doc intake, new idler/tensioner pulley/belt, AFE filter, cat back exhaust, new oil with a little Marvel Mystery oil so was thinking that was just carbon buildup blowing out.

I've also noticed if I press the brake pedal hard and hold it for a second it will sometimes idle down a little too for just a second then come back.

And if I hold the power window switch up when the window is all the way rolled up it slightly idles down for a second too then comes back (new optima battery installed)

If it just slightly idled down from the window switch/brake pressing I probably wouldn't think twice about it but the little random sitting at a red light idle drop/vibe/shutter makes me want to look into it a little more.


Anyone have any ideas on what might could cause that?


Thanks,
Spencer

 

[Happy Hummer]

Pretty well got it covered...lol.
Try some techron?
Gf's does similar thing. Techron clears it right up.
Could be intake bolts loose.
Chris

 

[alrock]

See post #8. Same thing. http://www.hummer4x4offroad.com/forum/showthread.php?9066-Headlight-issue&p=160879#post160879

 

[rsm688]

Thanks guys! Alrock, so could that be the same issue with the electronics even when I'm just sitting at a red light slightly holding down the brake pedal?

I didn't realize the H3's had electrical assisted brakes, that makes sense with that now. I've also noticed a whining noise from my master cylinder area when pressing the brake pedal but can't find what's causing it and everything works fine

 

[rascole]

Marvel Mystery Oil, now that's old school. Didn't any one used that anymore. I would just use quality synthetic and ditch the MMO. Because it can actually cause issues with gumming up the throttle body. MMO has a lower boiling point than motor oil so it will vapor off quicker and vent off into the throttle body.

 

[Best4x4]

Yep we have very simular brakes to say a Land Rover. Hit the pedal moderately and it's got plenty of pressure to apply the brakes. Do an emergency stop or hold the pedal at a light and the pump will run causing the engine idle to drop slighlty. Same thing happens when the A/C kicks on before the idle goes up to compensate for the extra load. The 5 cylinder is an inline engine and more sensitive to loads applied to it from stuff like that. In my Alpha I just hear the brake pump vs see or feel any idle change.

Honestly I am very impressed to see that kind of brake setup on our H3's. Way beyond what any Jeep ever came with!!

 

[4speedfunk]

I routinely run Lucas Fuel System Cleaner in all my toys. It keeps em happy.

 

[rsm688]

Marvel Mystery Oil, now that's old school. Didn't any one used that anymore. I would just use quality synthetic and ditch the MMO. Because it can actually cause issues with gumming up the throttle body. MMO has a lower boiling point than motor oil so it will vapor off quicker and vent off into the throttle body.

Lol, I use it in older vehicles every now and then. I just used a little bit mixed in with my fresh oil since the motor had been sitting for a while to help free things up. It is not in the H3 anymore just put some in, drove for two weeks, then changed all the oil again (was trying to flush it all out).

I usually run some Seafoam through my tank every couple of fill ups.


Thanks for the help guys!


Spencer

 

[USMC_TOP]

X2 on the Lucas

 

[USMC_TOP]

And 93 octane

 

[Steve #1]

Also check the battery cables and grounds if this is something you are now noticing, something has probably made it more noticeable than it should be.