You can not do this with EFI fuel injected systems without having to change out the injectors for a higher PSI rating and, even if you were to do so, that would cause another problem: higher PSI = higher rate of flow thus, leading to too much fuel thus leading to a rich condition.

The PCM fuel trims will not be able to trim it down to the proper flow rate to achieve the proper A/F ratio thus tripping the ASD relay in attempt to alleviate the over-pressure condition by means of failsafe mechanism at the ASD relay level.

Onto the original problem:

We know you have misfires and, it's across both banks and, it's random.

So, we ask the question: what would cause that to occur?

We list that out as follows with the most common first to the less common:

-Bad Ignition wires: I HATE MSD Ignition wires with a passion. I had nothing but issues (MISFIRES) with them regardless of routing. I ran TWO sets of their 8.5 Super Conductors and, both sets- had MFG issues. Finally, I took them off and began to test them. I had one wire that was dead / OPEN and, three or four more that showed breaks in continuity under flex-testing. I wouldn't be surprised at all if that's the root problem to be honest. If your looking to run THE BEST wires, go to www.magnecor.com and get yourself some top quality wires. IF you've got all the coil packs and a CAP based system, I highly recommend throwing those MSD wires into the trash because, in my tests- they prove to be nothing but rubbish. I've pulled them apart finding failure after failure with their wires. The ends bend, the boots are the wrong material thus sticking to the plug, the fiber inside is cheap, standard junk that most other wire companies use etc etc. There's a whole material science to ignition wires and, most of the companies out there are making rubbish.

Spark Plugs wrong temp rated plugs / cheap or bad plugs / incorrect gap will also induce misfires like mad.

- Bad COIL -OEM: bad coil / aftermarket CAP based system that is NOT Properly installed will trip a misfire across the board as well as an OEM coils that are faulty- same fault is produced- multiple misfires on both banks. Make sure that the MSD ignition system is properly installed.

- FAULT: COIL DRIVER CKT at the PCM level: will also cause the same exact fault- misfires across both banks. This resides inside the PCM and is NOT user serviceable or user repairable unless- you've got the skill set to take it apart, scope it, replace the fried diodes, and resistor cap network etc. You will need a new PCM if that's fried as a result of the MSD ignition system backfeeding into the PCM.

-Faulty fuel pump, bad gas cap, bad overflow / vent tube or filler tube = loss of pressure.

-Faulty Fuel Pump relay: high contact resistance = low pressure

-wiring harness issueVoltage drop across the wiring harness that feeds the fuel pump. High resistance= V drop again. Check all the connections for corrosion etc.

-FAULT: injector coil driver CKT: This controls the EFI injector pulse. If faulty, new PCM is needed. Would produce misfires across both banks.

-CPS: found inside the dizzy. If the Hall sensor is out of whack, the timing will also go out of whack. This CKT in conjunction with the CKPS controls the timing. if it's faulting, misfire across all banks will occur.

-Fuel leak: loss of PSI= misfires due to lean running condition

-Ground fault from the COIL to the PCM- open / intermittent

-Clogged CAT / Partially restricted CAT will also induce misfires but, usually, it's isolated to the rear two (7&8) cylinders due to the heat backing up into those first.

-Problem at head, intake level where, either oil or fluid is being drawn into the chamber thus fouling the fuel mixture. Blown head gasket, blown intake gasket, plenum gasket etc.

-FAULT: CKPS- bad / intermittent crankshaft position sensor. Will also induce misfires across both banks. It is the MASTER sensor for the entire EFI system so, if it's out, everything else is also going to be out of whack.

In order to narrow it down, the history would need to be reviewed. I would ask: when did this START to occur? Pre or Post MSD ignition install etc etc. Explain it out in more detail as to when this started happening.

CM

 

Even if theyre not stock wires, cross talk can still happen between 5 and 7.

Your wires should be routed whether it solves the problem or not. Runs smoother.

 

Not the case. Only junk wires need to be routed per the TSB as a workaround.

I run Magnecors and, I've got no issues with induction cross-fire with a nice straight setup. It happens with cheaper ignition wires due to the dielectric properties allow the 30-40Kv to pass through at either the boot level or somewhere along the cable length.

Get good wires, alleviates the need for wiring per TSB. I even run the coil wire next to adjacent wire in the loom and, it's a non-issue when running wires that are designed and made to spec vs. the junk that they toss on the shelves at the local auto parts stores.

CM

 

I believe your problem is simple...your using ngk spark plugs. THOSE ARE FOR IMPORTS! Honda, nissan, ect... my truck had three misfires from crap spark plugs before, just put in a new set of copper tip champion plugs and it should be fine.

 

how expensive are the mag wires?

 

I can't recall. You'd have to call them and obtain a quote. I think (please don't quote me on this) they were 130.00 shipped to my door ready to go.

CM

 

No no no. NGK makes THE best standard plug out there. Highest quality materials and super reliability from set to set. I ran NGKs V-powers FOR YEARS and, I still have a spare set of those. Champions are the ones you've got to watch out for as they are not made like they were in their heyday. The name is still there but, the quality control is not. Again, we had to go through an entire box just to make a set of eight that were good. I wouldn't consider them to be a top quality plug at current. Autolite 3924s and NGK -V power are the only two that are worth installing with the edge going to NGK for higher quality and better design.

You most certainly can use NGKs without issue. Just get the correct model and gap them accordingly and you'll be fine.

CM

 

To answer the last question: YES. Your going to want to fix that exhaust leak ASAP. Here's why:

When there's a leak there, it ends up drawing cold air through that leak over the valve on the intake stroke thus allowing UN-monitored air flow into the combustion chamber thus inducing a lean condition in that chamber thus, leading to a misfire or, actually a NO-burn condition.

In the winter / cold weather, this is extremely problematic. If cold air is drawn over a hot valve just right, the valve can end up cracking thus causing some valvetrain issues that will screw with the timing, A/F ratio, compression, possible valve seat cracks etc.

Fix that as soon as you can.

As to those NGK cold plugs, what is the model No on those and, what is the reach length on those? I seem to recall a long-ago story involving cold plugs. I can't remember what the issue was at the moment but, it'll come to me later on.

I have some questions for you:

Question: what is the peak voltage output of your MSD ignition system? This is the amount of voltage measured in Kv.

Question: what is the plug gap set to at current?

Question: Did you reset the sync value after you changed your CPS? Where did you buy your CPS- If it's NOT OEM, it's may not work. Here's why:

The sensors at the "stealership" are fully screened for electrical performance characteristics (SINE, PULSE etc) and, they are fully tested to ensure that the voltage output is within a specified range along with meeting a tolerance of MIN and MAX. The ones that DO NOT PASS screening are REJECTED by OEM dealers and are not bought. Those rejects vary in terms of characteristics and performance. They are sold to brokers and other third parties that turn around and sell them to certain auto part stores at a signifigantly reduced cost thus, the reason they end up costing a third less than what the dealerships charge. However, this poses a real problem. This is also another reason why they choose to have the NO RETURN on electrical parts. They pay 10.00-20.00 for it, mark it up and, they end up not losing a dime on a part that may not be any good right out of the box.

The real issue is when one puts on an aftermarket CPS and / or CKPS and, the output is way out of tolerance. Well, it throws everything else off in the timing sequence at the PCM level. I went through this last year in fact with not just one but FOUR of those after market sensors. I finally contacted a component engineer friend of mine and he told me why I was having issues with aftermarket sensors and such.

I ended up returning all four of those sensors and replacing them with OEM - dealer parts. It dropped in and worked 100% without having to compensate for it at the PCM level by resetting / programming in new sync values just to get it to work. It would also drift up and down thus making impossible to sync.

My recommendation is this: if your running after market sensors such as the MAP, CPS, CKPS, TPS, IAC and O2 sensors- think about buying them from the dealer instead. I went through three IAC motors only to find one that worked whereas, I could have paid for it once and been done with it. Again, this is only my recommendation based on experience and being educated by an engineer who used to source those parts.

CM

 

I will also vouch for NGK plugs and magnecor wires,

They have run quite well on my truck for the last 3-4 years.

 

I recently put in the autolite plugs suggested by the parts monkey at Jotozone. They didn't have the Champs.Truck ran like crap. went to another loacally owned parts house that had the Champions. Gapped to 40 and she runs great. Threw the autrolites in the trash !