Misfire under idle

[xLeGeNDx]

The car is a 3.4L DOHC Swapped car with a coil pack relocation.

The car has a slight jerk under idle and a misfire but its extremely faint. the car is also getting extrmely piss poor fuel economy. now once it gets up into the the rpm range even like at 1200 or so it completely disapears and is perfectly fine. upon idle how ever the car actually kept stalling after sitting there for a good 15 minutes or so AFTER the vehicle has warmed up. what could be the possible suspects?

The spark plug and wires are BRAND NEW and the problem still persists.

EDIT: So i figured out the miles per gallon i was getting, and its not good, using 4 gallons of gas and the car has only been driven 34 miles I got 8.5 MPG which is way from being what it should, and that's not even being hard on it. infact i have been driving it like an old timer and its getting 8.5 MPG.

[Schurkey]

The car has a slight jerk under idle and a misfire but its extremely faint. the car is also getting extrmely piss poor fuel economy. now once it gets up into the the rpm range even like at 1200 or so it completely disapears and is perfectly fine. upon idle how ever the car actually kept stalling after sitting there for a good 15 minutes or so AFTER the vehicle has warmed up. what could be the possible suspects?

The spark plug and wires are BRAND NEW and the problem still persists.

What is cranking compression of all six, and what is cylinder leak-down test results of all six?

What is manifold vacuum at idle? Steady, or bouncing?

What is fuel pressure at idle, with and without the vacuum connected to the regulator?

Are the cams timed properly?

EDIT: So i figured out the miles per gallon i was getting, and its not good, using 4 gallons of gas and the car has only been driven 34 miles I got 8.5 MPG which is way from being what it should, and that's not even being hard on it. infact i have been driving it like an old timer and its getting 8.5 MPG.

How much idle time does this include?

First Guess: It is not possible to push that much fuel into the engine and still have it run nice and not set a "rich" code. You're not measuring the fuel consumed properly; or you've driven farther than you think; or you've got an external leak so fuel used isn't all going down the injectors.

[xLeGeNDx]

When I can dig up the tools I can do all the tests again, Just got situation with a brand new 500 piece set so still getting things organized and what not.

Idle time between times have been low i would let it idle for no more then a minute to 2 minutes. except for this last time when i was bleeding out the cooling system. I know im not measuring properly but for the sake of simplifying things i had a half tank of gas which is at the 8 gallon mark (little bit more since its a 16.5 gallon tank) and after the driving was 34 miles drove on it exactly and its on quarter of a tank. so 34/4 = 8.5 closer to 9 though since the original fuel capacity of the tank is 16.5

[Schurkey]

First half of the tank always lasts longer than the second half. When full, is the gauge way past the full mark? Mine are.

Using the gas gauge to decide how many gallons have been used is futile.

[xLeGeNDx]

Last time I had it filled it did, I used the marks on the gauge just for a quick reference.

[xLeGeNDx]

Looking like its the spark plug wires, did some of my 5AM tinkering while it was still dark.

I started the car, and started pulling the wires one by one to see if there was any change of rpm from any of the cylinders. Cylinders 2, 3, 4, 5, & 6 all produced a rpm drop like it should, went to do cylinder 1 and I get a nice shock after grabbing the base of the wire (was no RPM drop on cylinder 1), grabbed a pair of plyers and took the wire and held it closer to the intake and the entire wire lit up like a christmas tree with blue arcs running the entire path of the wire.

Also pulled the plug from that cylinder as well and smells of unburnt fuel. Continued to test things and did a Ohm test on that wire and it was in the upper range of 15k ohms by itself where the other wires tested in about the 10k range.

And also a small question about the DIS, now you got the coils, DIS module, then back plate. Is the back plate grounding the DIS to the engine block on the original spot? Since I have relocated coils and DIS im thinking about adding an additional grounding point in IF that plate is being grounded to begin with that is.

[pocket-rocket]

I would imagine it is. Grounding it certainly won't hurt. I would give the oil the sniff test since #1 wasn't firing so well to make sure it isn't contaminated and thinned out from unburned fuel.

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[xLeGeNDx]

Ended up picking up a new car. Sorry for not updating for anyone who was interested,. The problem was head gasket, the rear head gasket had let go and was dumping raw coolant through the exhaust. I had cut out the cat to eliminate a plugged cat, well made the cut after the cat and coolant poured out. Decided to run the car like that and you could just watch coolant coming out of it. the weird part of it was my coolant level never changed, and no indication of a failed head gasket. I appreciate all the help on this.

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