Voidance

Hey all, I bought my 240 with a stock KA24DE about a month ago with a blown head gasket. We had started the car beforehand to get it onto a car tote, and it was running perfectly normal.

We re-did the head gasket, removed all the EGR crap, and removed all vac lines except the FPR, SCV, BB, and IACV/AAV. Put everything back together, time it to 20btdc and I have an inconsistent misfire that's mostly noticeable at idle. It will run fine for about 10 seconds on first start-up, then as the rpms drop, it misfires worse and worse.

It will idle at ~850rpms at 14.5-15.7 a/f with very minimal misfires, but then randomly drops to ~700rpms with the a/f at over 18:1 and misfires horribly. If I push the gas about 5-10%, it will stay all the way lean and slowly rise the rpms. Once it reaches about 1700rpms, a/f returns to normal and rpms jump to 2800.

If I floor it from idle, or anything under 1500rpms, it will flood itself out. If I'm cruising in town at anything under 2000rpms, it will lean itself all the way out and misfire horribly. Over 2000rpms, a/f stays consistent with a normal but quite jumpy reading. Half throttle accel from 2k rpms+ it will swing constantly from 12.5-16.8 a/f. WOT from 2k will remain around 12.5-13.5.

I also have NO low end power until roughly 3700rpms. From 3700-6500rpms, a/f is fine. Only problem I have in the upper R's is the vibrations, which I mainly feel in the shifter. Makes it feel like I'm taking a grinder to a slab of cement.

So far I have tried to remedy with:
Replaced FPR
Switched to a known working MAF
Swapped knock sensors
Cleaned cap/rotor
Cleaned IACV and AAV
Replaced 2 bad injectors that read 25 and 52 ohms(After that, it ran worse..)
Replaced plugs (All spark is fine)
Replaced CTS
Compression checked out within spec
Checked vac lines for leaks
Fuel pressure is 44psi w/ vac disconnected, 38psi w/ vac connected.
Replaced PCV hose

TPS was set at 2ohm closed, 10ohm WOT. This resulted in "decel" being at 13 a/f, almost like having the cruise on. I do believe that it's now set at 1ohm closed, 9ohm WOT. I had tested this TPS off the car on a different manifold, the OHM change from closed to WOT has no spikes or drops.

Also, the IACV screw doesn't affect idle as it should, which leads me to a vac leak. Though I don't see how. When the idle screw is backed out, the idle will jump to 1,100rpms, then stumble to 400rpms and try and stall out. With the idle screw almost all the way in, it will sit and idle at 750rpms in timing mode. Also, while in timing mode, it still leans itself out. But when it does, it only drops about 50rpms with a lot fewer misfires than normal operation.

I don't know if I can explain this any better. I've gone over almost everything I could think of with this car without having the use of a consult. The only other culprit I could think of is the intake mani gaskets. I bought Beck/Arnley from RockAuto, and they were about as thin as a piece of paper.

Much thanks in advance.

Walperstyle

Could be IACV still, try cracking your intake a little so it gets more air at idle. Or replace IACV with a different one.

I had a similar issue that was electrical. Whenever i was at an idle, and operated the windows in my car, or anything that drew current, it would missfire a little. Could be a bad ground.

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Voidance

I was thinking that it may also be the IACV still as well. I do know that the throttle plate was cracked a tad. Though when it was, the idle was horribly jumpy. Like 2k rpms that plummeted to 500rpms without the ability to change it. I closed the plate and the idle is as it is now.

I'm thinking that I may just take the other full intake that I have and block off the IACV, AAV, PCV, and remove all unnecessary crap. Then run the idle off only the throttle plate/TPS. That ALMOST seems easier than trying to just pull off the IACV, lool.