surging at idle need help, cant find whats wrong!

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Nov 10, 2004 | 01:02 AM

redrocketls1

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surging at idle need help, cant find whats wrong!

surging at idle... seems like its missing.. kinda jumps from 350-750 rpms at idle... doens't always do it.. just when i slow down really quick or kinda give it a lil gas then back off.. doesn't seem to be able to catch up with the inputs or something.. cuts off from time to time.. have msd wires fairly new, changed plugs, checked coil packs, nothing helps.. unplugged maf, nothing changed at all.. old plugs i pulled out were kind of a browing red burnt lookin color.. i have no idea whats wrong, im thinking its the mass air flow sensor, but i really have no clue, car has a 3000 stall, i dunno if that could be causing it somehow.. any ideas?

Nov 10, 2004 | 01:03 AM

CamTom12

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From: Clarksville, TN

O2's maybe?

this is more for an idea than an answer, I don't know for sure what it might be...

Nov 10, 2004 | 01:09 AM

redrocketls1

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i replaced them about 6 months ago... id like to think there not messed up

Nov 10, 2004 | 01:30 AM

Need2gofaster

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From: North Carolina

It's the converter man...mine did the same thing untill i changed my idle speed. did you just change your converter?

Nov 10, 2004 | 02:34 AM

strokedls1

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The car is too rich at idle. Try opening up the throttle blade a little with the adjustment screw. If you have edit you can tune it out on the main ve table.

Nov 10, 2004 | 11:47 AM

redrocketls1

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ok.. yea i put a converter in and it did this... but it got worse after i changed the plugs last nite???

Nov 10, 2004 | 04:18 PM

Another_User

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I have seen the same thing on my car with the O2s each around 100 while cold. Still, I doubt that there was too much fuel. I added fuel and it actually seemed better. There needs to be more info on these idle issues...

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Nov 10, 2004 | 05:46 PM

Another_User

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Quote:

Originally Posted by WILWAXU

Have you unplugged the battery?

Could be that the car hasn't completed an idle re-learn.

I did the full re-learn. Can adjusting the idle timing affect the learned idle that much? All I have done lately is mess with it trying to get everything working right. I can't figure it out. I don't think it is all ignition timing, because I get the same problems if I lock the timing (thanks HPTuners!). Adding to my VE table smoothed out my surging idle, but didn't do crap for my bucking. Plus I ended up with -15+ trims at idle. When I touch the throttle my IAC doesn't dip, so I don't see how that can be contributing. Ugh.

Nov 10, 2004 | 09:14 PM

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TheBowtieboy

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From: DFW

Really hard to say, but another suggestion to throw out there.....
Have you checked all you vaccuum lines ?

Nov 10, 2004 | 09:41 PM

#11

Another_User

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Quote:

Originally Posted by TheBowtieboy

Really hard to say, but another suggestion to throw out there.....
Have you checked all you vaccuum lines ?

Yep. Many times.

Nov 10, 2004 | 10:42 PM

#12

SidewayzOZ

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From: Easley, SC

Back to Redrocket's car...I logged it tonight with hptuners and this was what I gathered. O2's look excellent, fueling looks great. Fuel trims look fine, no vacuum leaks. The car seems to misfire like its going to cut off (lights flicker rpms drop) about every 10 seconds or so. Misfires dont seem to increase with rpms, but Cylinder 4 had a really large misfire history compared to the other cylinders. Doesn't seem to be a fueling issue to me at all, seems to be spark related.

Nov 10, 2004 | 10:57 PM

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ArKay99

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Quote:

Originally Posted by Another_User

Yep. Many times.

Well, I have gotten my idle to stop dipping too much since you last helped me. However, I haven't been able to stop the bucking either. One thing I noticed while logging was at idle my MAP is around 53kpa and when it is in idle and gear and hopping all over the parking lot the map is oscillating between 25kpa and and 85kpa. I logged some of this stuff before the h/c and it stayed right at 30kpa before. I know the oscillating is caused by the load on the engine going up and down but I'm wondering if the throttle blade is servoing in sync rather than opposite to cancel it. Since it's happening at speeds > 1mph I increased the values in the throttle follower decay about 20%. This will cause the blade to open and close a little faster. I'm about to play with this on Saturday. It's been so cold here this week I havn't had the inclination to go out and sit in a freezing car for an hour.
One last thing I saw was the spark tables, both base in drive and and high octane had a spread of from -11 degress to +18 degrees in the area of where this oscillation is taking effect. Since you disproved that as being a factor by locking your timing I would assume it's an out of sync servo at the intake until I try that and it doesn't work