Misfire Diagnosing/Troubleshooting Advice?

[itzHypn0tic]

Sorry if this has been covered countless times or pinned somewhere, but I'm at a loss with a current misfire problem...

I just bought a used 2000 lightning and it's missing on cylinder#4 and cylinder#6... I've already replaced all the spark plugs with new NGK's TR6's gapped at .42... The truck is stock all around (or to the best of my knowledge).

I've tried swapping the coil packs and injectors around between "good" cylinders and the missing cylinders, but there doesn't seem to be any difference. The misfire stays on the same two cylinders.

I've hooked up a Noid light on both the injector and plug harness, and they both are receiving a current (the injector flash is more dim, but I'm not sure if that matters?)

The resistance at the coil packs and injectors also seemed to be fine...

After driving around the car I did pull the plug again and it seemed a little white, but nothing crazy. The misfire does go away as I accelerate, but it still bogs down a little when shifting. (I'm not sure if this is the Computer performing safety measures)

Below are the current codes I'm receiving... I will be performing a leak down test once I get a new fitting adapter that Is deep enough to thread into the plug threads.

-p0356: ignition coil F Pri/SEC circuit fault
-p0234: turbo overboost condition
-p1746: pressure solenoid circuit open
-p1760: pressure control solenoid A short
-p1124: TP Sensor out of range
-p0300: random misfire detected

My thoughts were that the overboost condition is occuring because there's a misfire and the computer is trying to perform safety measures by turning off the injector, etc...? I also did not think a TP sensor out of range code would cause misfiring in 2 cylinders specifically. The pressure solenoid codes should be irrelevant and I also didn't think I'd get a p035X code if it was a compression issue.


Any suggestions would be greatly appreciated.

 

[Dusten]

Sorry if this has been covered countless times or pinned somewhere, but I'm at a loss with a current misfire problem...

I just bought a used 2000 lightning and it's missing on cylinder#4 and cylinder#6... I've already replaced all the spark plugs with new NGK's TR6's gapped at .42... The truck is stock all around (or to the best of my knowledge).

I've tried swapping the coil packs and injectors around between "good" cylinders and the missing cylinders, but there doesn't seem to be any difference. The misfire stays on the same two cylinders.

I've hooked up a Noid light on both the injector and plug harness, and they both are receiving a current (the injector flash is more dim, but I'm not sure if that matters?)

The resistance at the coil packs and injectors also seemed to be fine...

After driving around the car I did pull the plug again and it seemed a little white, but nothing crazy. The misfire does go away as I accelerate, but it still bogs down a little when shifting. (I'm not sure if this is the Computer performing safety measures)

Below are the current codes I'm receiving... I will be performing a leak down test once I get a new fitting adapter that Is deep enough to thread into the plug threads.

-p0356: ignition coil F Pri/SEC circuit fault
-p0234: turbo overboost condition
-p1746: pressure solenoid circuit open
-p1760: pressure control solenoid A short
-p1124: TP Sensor out of range
-p0300: random misfire detected

My thoughts were that the overboost condition is occuring because there's a misfire and the computer is trying to perform safety measures by turning off the injector, etc...? I also did not think a TP sensor out of range code would cause misfiring in 2 cylinders specifically. The pressure solenoid codes should be irrelevant and I also didn't think I'd get a p035X code if it was a compression issue.


Any suggestions would be greatly appreciated.

1) tr6s are the wrong plugs for a stock truck. They are a heat range to cold.
2) you have a misfire and an ignition code, so I would look harder at the coils and wiring. Since the code doesn't move, so likely wiring. The 0356 code is a complete failure of coil six. Likely wiring related.

The 1746, 1760, and 1124 all lead me to believe you have a shorted harness.


The overboost codes often trips with a misfire.

 

[itzHypn0tic]

1) tr6s are the wrong plugs for a stock truck. They are a heat range to cold.
2) you have a misfire and an ignition code, so I would look harder at the coils and wiring. Since the code doesn't move, so likely wiring. The 0356 code is a complete failure of coil six. Likely wiring related.

The 1746, 1760, and 1124 all lead me to believe you have a shorted harness.


The overboost codes often trips with a misfire.

Can I get away with the spark plugs for now? I just grabbed the first ones I saw because I didn't think about it... Is it possible to have a bad ground/wiring issue while the Noid light or plug still gets a pulse? Is there a specific ground for the injector or plug harness?

 

[Dusten]

Can I get away with the spark plugs for now? I just grabbed the first ones I saw because I didn't think about it... Is it possible to have a bad ground/wiring issue while the Noid light or plug still gets a pulse? Is there a specific ground for the injector or plug harness?

I swore I replied to this.

The plugs steer ok for now but aren't optimal.

The coils need a set voltage to fire. Each coil has a ground at the connector

 

[itzHypn0tic]

I swore I replied to this.

The plugs steer ok for now but aren't optimal.

The coils need a set voltage to fire. Each coil has a ground at the connector

Sorry for the late response here... So I ended up checking all of the wiring between the PCM and the coil packs and everything seemed to check out... I apparently did something to cause the PATS system to trigger and blow the fuse for the PATS/PCM/etc, but fixed that since. That seemed to have occurred with further troubleshooting and I don't think it was related...

I finally ordered a leak down tester adapter and tested the cylinders. It looks like at least my #4 cylinder is leaking and I'll need to pull the heads and possibly an engine rebuild. I did not check my cylinder #6, but I figure I'll have to pull both heads anyway. I checked both TDCs at 90psi and they only held 20psi. It sounded like it was at least leaking out of the intake, but I'm preparing for the worse.

Would a bad cylinder cause the check coil pack check engine light to come on for any reason? I wouldn't think so, but if the bottom end is messed up... Could that then cause the crank to misread and cause it?

Would you also have any good recommendations on what I should do when the engine is apart? If the bottom end is ok, I was probably going to just look into fixing the heads for now. Is there any way to "bullet-proof" the spark plugs and issue or are stock heads worth replacing?

Finally is there any recommended bottom end kit that's typical? If I have to rebuild the bottom end I'd like to do it right, even if I keep stock level horsepower for a little bit...

Thanks and sorry for the novel

 

[hotcobra03]

1st,,suggest you find the factory service manual..

I have it on cd, best tool ever..

it has the PC/EC section for codes.

being,codes are sent over electric, I find laying out all the codes with wiring diagrams..9 out of 10.they cross..which is where problem is..

I feel a lot of these issues are just on main engine harness. which helps for wiring problems..

my last issue..was cam sensor..po340..which was a wire issue,

I found being the location on mine had you pull on wire to get connector off to do other work..instead of movin something to get hand on actual plug.

I found a stretched wire..not completely broken..

using just a multi meter on only engine harness..

these wire's are tiny..

each coil and injector have its own ground signal..

each coil and injector has 12v.

just because the noid lit,doesn't say a wire is hurt..

also..pins and barrels inside connections can move and cause issue.


keep looking..

 

[StrayBullitt]

Good advice above, I would have to say anytime misfire is of concern it is worth checking compression though.

If you clear faults does that ignition coil circuit fault return ? I'd be curious if that was set by trouble shooting.

 

[itzHypn0tic]

Good advice above, I would have to say anytime misfire is of concern it is worth checking compression though.

If you clear faults does that ignition coil circuit fault return ? I'd be curious if that was set by trouble shooting.

I've cleared the codes and they do return, and it looks like I have bad heads/valves on those two cylinders... I'm not sure why the coil pack light is being triggered as I tested the cables with a multimeter and noid light and they seem to have good continuity from the PCM and to the coil packs. The coil packs themselves also seem to be working correctly even though they look rough and have minor cracks..

Pretty sure my intake valves may be burnt or bent as they only held 20psi with a leak down test (it was hard to hear exactly where the air was escaping, but I did not see any bubbling in the coolant...)

I also compression tested the engine to make sure and both cylinders held 0 pressure... I tested another cylinder to verify and it was near 150psi.

I pulled off the supercharger and lower intake last weekend and will be looking at the heads this weekend. The intercooler was disgusting and it looked like the previous owner sucked in tape or a plastic bag (not including the ton of oil).

 

[Dusten]

that tape may be the teflon flaking off the blower rotors. its common. most people will strip it.