Hmmm... sounds like a physical problem... check the sanity of the MAP and MAF sensors (post some logs of the problem happening) .
Hmmm... sounds like a physical problem... check the sanity of the MAP and MAF sensors (post some logs of the problem happening) .
Checked all the header primaries with an infrared thermometer. No signs of dead cylinders.
I added 2% to the ve table in the idle areas, but it still runs high 14s-low15s but then creeps as high as 18:1. I unplugged the MAF and the car runs almost identical to when it's plugged in, but did sound a little healthier and tried to lope some intermittently, but the AFR was still the same and still kept slipping lean every so often. I guess it could just be starving for fuel or air?
Don't want to keep running it tonight and annoy the neighbors so I packed it in for now.
I will catch a log during my lunch break tomorrow and post it up. What PID can I add to catch the wideband O2 sensor so you can see that too?
71 Chevelle, LS1/4l60e, EPS 230/238 113+2, hand ported 799s, ported Fast 90/90, Doug's headers, 3.42 12 bolt
Then that leaves the NBO2's and the MAP... do they produce sane signals...?
GM.EQIVRATIO and EXT.WO2LAM1.
Started the car today (it fired and ran from a cold start even) and it ran better again, a little surge came back though. The AFRs are fatter and do not creep to extreme lean. I guess I will just have to catch it acting up again and log. I did notice the idle sounds stronger when in gear than park even at the same RPMs but that might not mean much.
I put a fuel pressure gauge on so I can keep an eye on that if it starts running poorly again. I will catch a log tomorrow morning either way. But everything on the scantool looked normal to me.
71 Chevelle, LS1/4l60e, EPS 230/238 113+2, hand ported 799s, ported Fast 90/90, Doug's headers, 3.42 12 bolt
Thunder, did you get it sorted out...?
I have not messed with much in a long time. I am having a minor hanging idle problem which I think is the blade in the FAST tb so I need to take some time to see if it's dragging in the bore and if so fix that before I try to tune further.Originally Posted by joecar
Sometimes it hangs at 1200-1400rpm while coasting and others it goes down to normal idle. I've spotted the TP % at .5-1% a couple times so that's making me think it is hanging.
The only other major thing that's still been bugging me is an odd condition where I can start the car cold and let it warm up, but if I try to drive it without first turning it off for 15 seconds and then starting it back up it will surge and hunt for idle. It's much worse if the outside ambient air is colder. On a first start I can drive it for 15-30 minutes (never tried longer) and it will never get better no matter what temp the engine gets up to. However, if I start it and let it warm up just a little (say 160* coolant temp) then turn the car off for 15 seconds then restart it, it will run very well and have no issues. Even more strange it only seems to do this the very first time it is started that day.
The only other tune related hiccup I've noticed is when I start the car warm, the RPMs go up to around 1400rpm or so for about 5 seconds then come down to 1000rpm then back up just a tad before settling at the normal idle I have set. Not a big deal and a friend of mine who has had a few cammed ls1 cars said his all did that too. Is this really normal? It's almost like the PCM is transitioning between some commanded actions and then finally gets to a mode where the IAC corrects the problem.
Other than these idle problems, the car runs beautifully and has been running good at the track. I got a new PB recently of 11.79@114mph and a new PB MPH of 115mph. Fuel economy hovers close to 20mpg highway. The LTFT need a little work at highway cruise, they were -6% to -9% during a long drive yesterday.
Last edited by thunderstruck507; December 31st, 2012 at 11:01 AM.
71 Chevelle, LS1/4l60e, EPS 230/238 113+2, hand ported 799s, ported Fast 90/90, Doug's headers, 3.42 12 bolt
11.79s ET and 20mpg/highway... that's pretty cool
Hmmm, quite a few people have been plagued with airleaks inside their FAST manifolds.
Any idea why the car would run poorly on a cold start even once warmed, but immediately run fine once the ignition is off long enough to reset the PCM?
71 Chevelle, LS1/4l60e, EPS 230/238 113+2, hand ported 799s, ported Fast 90/90, Doug's headers, 3.42 12 bolt
That's a hard one...
you would have to use an oscilloscope to view waveforms of CKP and ignition secondary to see what is really going on.
I thought it was strange. That's honestly the biggest peeve I have right now.
71 Chevelle, LS1/4l60e, EPS 230/238 113+2, hand ported 799s, ported Fast 90/90, Doug's headers, 3.42 12 bolt
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