Car can't drive when cold. only once warmed up. Misfiring when Warm....

[Ryann]

I'd say swap the AFM with known good unit. 2K-4.5K would be the most used/worn out range of the AFM contacts. Maybe the chipped DME is more sensitive to AFM input, idk.

If I were there I'd swap every damn component out of mine until we figured this out.

[fiftytakedowns]

I had a couple of AFMS and tried swappin them a while back with no avail. I have a narrowband and can have someone swing the barn door and see if it is changing the AFR

[Ryann]

I'm way behind you, aren't I?

WHAT ELSE IS LEFT?? Wiring..

[fiftytakedowns]

Literally, I think I have gone over every sensor in this fucking car. I even put in new upgraded injectors a while back. including 02 sensor.

[Kershaw]

i had a problem very similar to this in my eta. it was my o2 sensor. (i know you just said you replaced yours.)

try unhooking your o2 sensor and driving around. does it change anything?

[fiftytakedowns]

Will do, Thanks a bunch.

[fiftytakedowns]

I replaced one of the relay boxes, actually pulled it out by accident, and it seemed to fix my problem for the most part the hesitation comes and goes much less.. I did find a vacuum leak though, which I think is causing occasional missing, not sure
and I can not FIGURE OUT WHERE IT IS. If I cover the intake so I create a vacuum you can hear the whistle, sounds like its coming from lower intake rail.
I took it all apart, and to no avail not fixing it or aynthign. sprayed some WD poured water, nothing cant find the fucking leak.

[dkbmxer002]

what do you mean exactly when you say you cover the intake so you create a vacuum?

also how hard was it to replace the relay box? or do you mean you pulled one of the relays?

[fiftytakedowns]

what do you mean exactly when you say you cover the intake so you create a vacuum?

also how hard was it to replace the relay box? or do you mean you pulled one of the relays?

I pulled one of the Relays that sit next the fuse box. the three up top that are covered by the plastic harness cover.


I create a vacuum by putting my hand over the front of the AFM. then opening hte throttle with the other hand. you can see the intake bellow collapsing, and the noise of a leak near the intake. I cant find it.

Here are Some driving symptoms:

occasionally the stuttering will start occuring between 2-3K rpm, and when It does, here is wat the car does when that happens:
IF I floor it I can sort of stutter through the missfire until i get out of the zone, then past 3k rpm and then pulls hard to redline. If I pull off the gas, but downshift back into the zone without letting the car cruise at a lower rpm for a bit it will stutter if I get back into that zone.
If I put it in nuetral and let the car idle for a second, or two, I can slowly (without any load) accelerate through that zone, and then it goes away and I can drive normally until it shows up again, usually within 5 minutes.

the event only shows up UNDER LOAD! or cruising, USUALY cruising. Never at WOT, or SMashing through the gears.

[dkbmxer002]

mine is a little different where mine only shows up when flooring it or under a decent amount of load. but mine does it all the way through rpms.

i will check my relays too, i have tried swapping them around in the past to see if anything changes.

[fiftytakedowns]

mine is a little different where mine only shows up when flooring it or under a decent amount of load. but mine does it all the way through rpms.

i will check my relays too, i have tried swapping them around in the past to see if anything changes.

Probably 02 sensor or relay issue like mine, it was amazing how much of a difference it makes, however the problem still persists, just not as often or as hardcore. still makes driving unreliable.

[fiftytakedowns]

also, after letting the car cool down completley, It still has the cold start problem, where it is impossible to drive when cold, It will only idle. merely bogs down off the bat

[fiftytakedowns]

don't quit on me now eveyone!

[fiftytakedowns]

Did some more thinking, hopefully it can help us all figure it out.

Cold start -> cuts fuel when attempting to rev up, only can idle until reaches operating temp.

When driving --> occasional misfire most likely due to fuel cut or loss at 2k-3k Rpm

Which sensors would affect a fuel cut misfire during that revband no matter how hard pedal is pressed, could it be pair of injectors causing the jerking?

Vacuum leak would cause a leAn condition not sure if it would be so violent and rpm specific.

An erratic icv signal would cause an interesting shift in air , however it would tell the afm to enrich mixture. What would cause an erratic signal possibly?
Should I plug all possible vacuum lines Adjust the throttle to supplement for icv blocking?

Can relays switch off and on erratically? Such as the fuel pump relay? Any specific wires I cab check resistance of? What should I look for ? What values?

[Ryann]

Cold start -> cuts fuel when attempting to rev up, only can idle until reaches operating temp.

Okay, let's address one thing at a time here. There are two common things that cause this symptom.

1. Insufficient fuel delivery
2. Unmetered air entering the intake

Rule out the first by connecting a FPG to the supply line and observe the gauge while the engine is running & cold, AND while squeezing the throttle. We know you've already tested for pressure at idle, but if the gauge reading dips when you apply the accelerator then you have a problem.

The only way to completely rule out the second is to disassemble the entire intake and associated hoses from the AFM on. Fully and thoroughly inspect EVERYTHING, including the upper and lower intake manifolds, as they have been known to crack.

I've had success verifying the presence of hidden vacuum leaks by driving the car down to my local DIY car wash: use the wand to lightly mist water in and around the intake area. When your leak sucks in some mist you'll hear your idle dip.

Be thorough and rule these things out, then move on.