bad idle

65ugot8up

65ugot8up

New member
Re: bad idle

powercat6 said:
What brand and type of spark plugs and wires did you install? And what spark gap?
Click to expand...

always run AC delco's. they are factory spec. gapped to factory spec as well. this thing is making me want to beat my head off the wall.....
 
SY-1193

SY-1193

Active member
Re: bad idle

...ALSO clean around the throttle blades inside your throttle body. It gets dirty there and can alter your idle.
 
65ugot8up

65ugot8up

New member
Re: bad idle

Typhoon #2131 said:
I feel your pain. I have the same exact problem with mine. Please let me know if you figure it out. Mine dose it bad only when its hot.
Click to expand...

yep sounds like mine. please do the same if you find a fix. was just reading that it mite be in the chip... but looking into that a little more.
 
Six-is-Enough

Six-is-Enough

Use to do a little Boost
Re: bad idle

65ugot8up said:
already did that.. thanks. any other ideas?
Click to expand...


I see in your sig that you have 50 injectors........They are a B!tch to tune for a good Idle period! Whether it is the ultimate or custum tune. I have a couple of possible things to do though.

Low timing can cause a bad Idle. Pull the Brown wire(try search "brown wire'/ "checking timing") and check your timing that it is not off. Particularly on the low side.

Second Idea and this is more of a band aid than fix is to raise the Fuel pressure. Our trucks love to be rich at Idle. It really smoothes out when rich. Just start adding fuel pressure and it should get somewhat better, but be aware it might mess up the tune in other areas.:2cents:
 
The_Bronze

The_Bronze

Donating Member
Re: bad idle

My idle troubleshooting:

First is maintenance. Clean the IAC and throttleplates and housing. Verify correct PCV operation as it will cause a surging idle. Vacuum leaks also aa previously posted.

Check the scantool and verify warm idle counts are over 10 and lower than 30. Usually GMs run over 15 counts. I didn't see where you checked the counts. Next verify the throttle is closed (0% throttle) also look at fuel trim if in closed loop and verify o2 operation. Super lean will cause idle surge but typically I see rich keeps a steady idle.

With the scan tool connected, look to see if the idle counts and spark timing is following the idle. Steady data without changes usually indicates an input problem, although if it's a PCM issue it will most likely be a IAC driver output problem. You can pull the IAC plug the bypass port and with the IAC plugged in watch for pintle movement in an attempt to control idle. No movement with scantool showing the change is a good indication of a bad IAC regardless of ohms test.

Check and adjust base timing. Timing is a major tool for idle correction. Timing that is over or much lower than BMT will prevent the PCM from being able to add or remove enough timing to control idle rpm. Being a degree or two off won't be the problem but more definitely will.

Typically it's easier to just install a new IAC or borrow a known good one. I tell my buddies the above info and it almost always is cured by the above steps.
 
The_Bronze

The_Bronze

Donating Member
Re: bad idle

Page 2 due to iPhone blunder.

Poor cylinder power balance will also cause these problems at idle. Things like partially shorted or dirty injectors, carbon build-ups on valves can cause the same issues, but typically less severe idle variations.
 
cloneman315

cloneman315

Active member
Re: bad idle

If that ultimate is the standard 50 version that tune plan sucks!!Phill turbo 6 has sent me most of his bin files,I will tell you his 50 tune is very very close!It very well could be that chip.In open loop the idle is rock solid!!
 
Typhoon #2131

Typhoon #2131

SAVE THE TA-TAS
Re: bad idle

I have new stock injectors and had the heads fully rebuilt when I rebuilt the motor 1000 miles ago. The timing is at 2 advanced I didn't think that was a huge deal. If I stab the throttle by hand under the hood I can see the EGR moving but if I stab it 2 or 3 time in a row the motor will die sometimes. I also change fuel pump and filter this last weekend and nothing changed.
 
The_Bronze

The_Bronze

Donating Member
Re: bad idle

Typhoon #2131 said:
. If I stab the throttle by hand under the hood I can see the EGR moving
Click to expand...

The PCM will see the throttle move via TPS and the MAP rise and energize the EGR solenoid briefly. If the EGR is okay, then it shuts immediately back off and EGR closes. If the valve is weak it can stay on even after the initial vacuum signal is removed from the valve and cause a very rough idle or stall. Simply removing vacuum to the EGR will determine if it is a problem. Stable idle and no stall indicates the valve is probably bad, assuming the solenoid is not sticking open. Since you have changed both, it is not likely a problem.

Are you sure your timing mark is correct?
 
65ugot8up

65ugot8up

New member
Re: bad idle

Six-is-Enough said:
I see in your sig that you have 50 injectors........They are a B!tch to tune for a good Idle period! Whether it is the ultimate or custum tune. I have a couple of possible things to do though.

Low timing can cause a bad Idle. Pull the Brown wire(try search "brown wire'/ "checking timing") and check your timing that it is not off. Particularly on the low side.

Second Idea and this is more of a band aid than fix is to raise the Fuel pressure. Our trucks love to be rich at Idle. It really smoothes out when rich. Just start adding fuel pressure and it should get somewhat better, but be aware it might mess up the tune in other areas.:2cents:
Click to expand...

thanks. where should i be running my timing at? ill check the today.
 
65ugot8up

65ugot8up

New member
Re: bad idle

cloneman315 said:
If that ultimate is the standard 50 version that tune plan sucks!!Phill turbo 6 has sent me most of his bin files,I will tell you his 50 tune is very very close!It very well could be that chip.In open loop the idle is rock solid!!
Click to expand...

i did have an ultimate an it didnt run that good(but did idle). it would run really rich an almost load up. so i got a diff chip off of someone for it. i mite just need to have a new chip made for my Ty. idk.... im tryin not get to pissed, its just to nice to leave sitting in the garage. thanks for ur input!
 
65ugot8up

65ugot8up

New member
Re: bad idle

The_Bronze said:
My idle troubleshooting:

First is maintenance. Clean the IAC and throttleplates and housing. Verify correct PCV operation as it will cause a surging idle. Vacuum leaks also aa previously posted.

Check the scantool and verify warm idle counts are over 10 and lower than 30. Usually GMs run over 15 counts. I didn't see where you checked the counts. Next verify the throttle is closed (0% throttle) also look at fuel trim if in closed loop and verify o2 operation. Super lean will cause idle surge but typically I see rich keeps a steady idle.

With the scan tool connected, look to see if the idle counts and spark timing is following the idle. Steady data without changes usually indicates an input problem, although if it's a PCM issue it will most likely be a IAC driver output problem. You can pull the IAC plug the bypass port and with the IAC plugged in watch for pintle movement in an attempt to control idle. No movement with scantool showing the change is a good indication of a bad IAC regardless of ohms test.

Check and adjust base timing. Timing is a major tool for idle correction. Timing that is over or much lower than BMT will prevent the PCM from being able to add or remove enough timing to control idle rpm. Being a degree or two off won't be the problem but more definitely will.

Typically it's easier to just install a new IAC or borrow a known good one. I tell my buddies the above info and it almost always is cured by the above steps.
Click to expand...

im tryin to get a scan tool. if i cant find one ill just buy my own. ill check this stuff out an keep you posted. thanks.
 
S

Syclone #1721

I LOVE 4UM SUPERSTARS
Re: bad idle

Not sure if anyone mentioned this or not but my truck idled bad and I checked out everything to no avail until I found the intake gaskets were leaking. I replaced them and the idle smoothed out.
 
65ugot8up

65ugot8up

New member
Re: bad idle

might have found the problem. then when i start the ty fuel press is good but the more i drive it the lower it goes. so idk if it the fuel pump os the fuel press reg. both are about 3 year old and aftermarket. anyone have any ideas? i found out the hard way. i was in the middle of my 3an half hour drive back from truck carlise when i noticed the fuel press started droping then it wouldnt stay running. after sitting for 30 min it started back up. then rite away it started to lose press again.
 
MRKING

MRKING

New Parts for Old Trucks
Re: bad idle

Your not going to get the all around performance you want without a custom tune . Datamaster and tunerpro are free , you just need a aldl cable . Get some wideband 02 datalogs done to see whats really going on .

Every modded syty needs to be datalogged showing wb02 data , otherwise your just taking stabs with whats really going on . Save the time , money , and headaches by doing it right the first time . Post up that log when avail .
 
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