Idle issues with v8...

[Teddyzee]

You may have heard I made a solid gasket for the IAC in my Mustang, and just set the idle at 600rpm and it acts exactly as I want!
Doing it "right" may be more appealing to you, though.

Don't overlook the MAF. The MAF caused a mess with the idle on my Ranger until I got it all figured out. My truck is OBDI, Fox Mustang based, and idled much better with the MAF unplugged, solid as a rock. The older stuff will run and drive with the MAF unplugged.

 

[shr3dd3r 09]

Better yet reading closer run it around 2000 rpms and unplug the IAC then set the engine idle You want the IAC all the way closed and unplugged to set the throttle butterfly position, then reset the computer by disconnecting the battery and make sure everything is plugged in when you start the motor.

I'll give it a whirl.

 

[kimcrwbr1]

I had a similar problem with my jeep it ended up being the connector for the TPS was bad. To test the IAC I got one from the bone yard and plugged it in leaving the one in the TB. when you give it gas the plunger should fully extend and when you let it idle the plunger should retract the computer will be looking for a rise in the rpm depending on the inputs as in engine temp, A/C on, gear selection.

 

[kimcrwbr1]

http://www.youtube.com/watch?v=lJEGigONelc
Good stuff

 

[kimcrwbr1]

I prefer using a analog VOM the needle shoul make a nice smooth sweep if it jerks the TPS is suspect.

 

[shr3dd3r 09]

Tried unplugging the IAC with the truck revved to 2000 rpms like you said. It returned to base idle around 1000 rpms. But after a few minutes of idling it dropped to 300 rpms and started chugging just like it always does. The IAC valve works, so I think it is computer related. For some reason after idling for a few minutes the computer is retarding the timing. I have no idea why. Vacuum lines look good, didn't detect any leaks. Everything is going where it's supposed to I think, so I think it must just be in need of an adjustment tune.

 

[aspevacek]

Is the computer getting as knock sensor reading? Are you getitng any codes from the system at all? I know some of the systems if there is no knock sensor reading present the computer will retard the time a pretty good amoun tot protect the engine, but that should be a limp in mode and give a CEL.

 

[RangerSVT]

The timing gets retarded after a few minutes due to the engine reaching operating temp and starts reading the O2 sensors. What handheld did Greg sell you?

SVT

 

[shr3dd3r 09]

The timing gets retarded after a few minutes due to the engine reaching operating temp and starts reading the O2 sensors. What handheld did Greg sell you?

SVT

He did not sell me one. He just installed a chip. I'm on a bit of a budget at this point.

 

[shr3dd3r 09]

Also it is throwing bank 1 and 2 lean codes. Both O2 sensors are brand new.

 

[RangerSVT]

It doesn't make sense why he would chip a flashable ecu, but either way, drop him a line. I'd be willing to bet its in the tune. Rarely is a tune perfect the first time. Mine needs tweaking, but I'm about to make some changes, so I'll wait til I get them done...


SVT

 

[shr3dd3r 09]

Found out the EGR was not functioning properly so the solution was to cut it off and weld the holes shut and remove the EGR function from the tune. Truck runs a little better in terms of power, but the idle issue is still present, even after telling the computer to idle at 750. Even so the idle is still somewhat random and rough.

Did some data logging and sent the info to SCT to see if they can see anything that may have been missed in the tune. Will be in contact with Greg when he hears from SCT. Still stumped.

 

[RangerSVT]

I can't compare anything I've dealt with to that, as I deleted my EGR from the tune from the start. I still have it in place, its just not in the programming. I know I'll be swapping out the exhaust manifolds, so I deleted ahead of time...


SVT

 

[BullFrog13x4]

I would agree that the first thing you should do is consult with your tune guy.

I was thinking about this and considering the comp program has been tuned, i would think it could be possible that it is switching back and forth between open and closed loop. The difference in idle setting/fuel mixture that is programed into the computer for the open/closed loop and a wrong setting could be the source of this problem.

If you need more explanation of the open/closed circuit than you might want to ask some of the other guys her in the forums, as i am a little rusty when it comes to fuel injection programming. I haven't played with any automotive programming in at least 7 years.

Hope you get it fixed before you decide to brake down and go with a carburetor.

Let us know what you end up finding.

 

[shr3dd3r 09]

I would agree that the first thing you should do is consult with your tune guy.

I was thinking about this and considering the comp program has been tuned, i would think it could be possible that it is switching back and forth between open and closed loop. The difference in idle setting/fuel mixture that is programed into the computer for the open/closed loop and a wrong setting could be the source of this problem.

If you need more explanation of the open/closed circuit than you might want to ask some of the other guys her in the forums, as i am a little rusty when it comes to fuel injection programming. I haven't played with any automotive programming in at least 7 years.

Hope you get it fixed before you decide to brake down and go with a carburetor.

Let us know what you end up finding.

Naww, I won't switch it to a carburetor. My tune guy already sent some data to SCT, so I'd think they of all people could figure out what is wrong. I'm supposed to call him on Tuesday to see if SCT has responded with any info. I'll let you all know what the problem was provided it gets figured out.