Help - running rough, new plugs, wires, cap and rotor

[SunlitComet]

I am still racking my brain and tech info still but when the fuel spider was replaced the pressure regulator should have been eliminated as the culprit and I would believe that if there were frayed wires by now something would show up as an computer error. The computer is capable of alot of detailed info. And without the software and interface to access it it will be that much more difficult.

Gully could you possiblly post all known codes you had pulled in case you missed any on previous posts as well as anything else that may seem wierd with your truck even if it does not sound engine related?

---------- Post added at 07:53 AM ---------- Previous post was at 07:43 AM ----------

Including anything installed before it happened.

 

[95TwinTT]

If we are talking hypothetical, any restriction of the return line from the fuel pressure regulator to the tank, will cause fuel pressure to rise proportionate to the blockage……. Does not have to be a malfunction of the regulator itself.

 

[SunlitComet]

Do you not think that would caused the computer to run codes for a rich banks 1&2 condition? Hypothetically.

 

[95TwinTT]

I guess from what I have read in this thread, it’s time to start thinking outside of the box.

This is probably way off base, but let’s talk hypothetically.

If the fuel pressure were 90psi instead of 55psi, the amount of fuel passing the injectors would be considerably more. The O2 sensors would see this and try to compensate on the injector pulse. The program in the ECM has levels of authorization given to various controls.

The O2 sensors in my truck are set to be able to override the program by 25% to correct for rich or lean. If it needs to go to 45% to correct the problem it can’t get there.

I don’t know what percentage of authority is programmed into this OBD2, but if it can’t cut the pulse width down enough, it would still be rich.

These ECM’s are very sophisticated but they are not crystal balls. They can’t know if there is wire harness damage from a accident or corrosion. They are programmed to see “expected problems”, dreamed up by the factory software group.

High mileage vehicles can have a multitude of issues that were never thought about for error codes. Look at how many trucks have been screwed up electrically by improper installation of a remote starting system. The list goes on.

I’m suggesting mostly taking some test meter readings of the components are could affect mixture. MAF, MAP, IAT and a simple check of the fuel pressure to answer the that question.

Also the comment that this all started intermittently should be analyzed further.
Just sayin………………

 

[SunlitComet]

O2 sensors should be able to be backprobed to read voltage so doing that could help decide a fork in the road as far as the other sensors go.

I just eliminated the pressure as a probibility because the old regulator went out with the old spider.

I would eliminate any alarm/starter modules if running rough while truck is not moving or the if the modules are reoriented in axis only.

Maf, Map and Tps can be tracked to what is known as performane or range problems when they don't coincide.

The Iat and Engine coolant temp. (ECT) sensor does not have such a direct error code.

There is a code for insufficient coolant temperature for closed loop ops that would eliminate the ECT in my opinion as if was given feedback for a hot engine or a direct high or low stalled reading.

A malfuntioning Iat does not have a performance variable code but under obd2 can be diagnosed with the help of monitoring egr activity and feedback voltage.

So that is likely a candidate for backprobing based on that the others could report performance problems and up to now haven't.

As far as the inability to cut the pulse width I will for now side with rich bank codes indicating that for now.

I do believe that there is more then just"expected problems".

If you really get into the data and understand theories of operation of the components used and how they interact with other known givens you can extract unexpected problems not dreamed up as well.

I believe the answer is in the data I just can't see his data other than what he reports.

I hate the fact that I am broke right now and can't get the interface and software I want for my own truck right now. I can work on stuff like this for at least a full day or longer and forget to eat or sleep.

I will break for a moment.

Gully, do you know if if the cam correlation error showed before or after the crank sensor was replaced?

 

[95TwinTT]

Thanks Jonathan, great OBD2 info. I only do Tec3, so I can only guess.

I totally agree. It’s hard to diagnose a truck with a unknown history, that has gone through three sets of plugs and wires and distributor caps in a short time.

I understand the FPR's were changed with the injectors, but I would still check the fuel pressure just in case the return line is plugged down stream.

The error codes need some interpretation sometimes. Like a miss in certain cylinders does not exactly say, your wires are crossed, even though that is what was wrong.

I think the intermittent occurrence during the onset is still one of the big clues.

There is likely to be more than one component contributing to this mystery.

Can a loose timing chain or skipping a tooth cause late firing which would not totally burn the fuel, leaving the plugs fouled?

It would be nice to have a wide band sniff the tail pipe……………

 

[SunlitComet]

Can a loose timing chain or skipping a tooth cause late firing which would not totally burn the fuel, leaving the plugs fouled?

That is why I was asking about when the cam/crank corellation problem showed. You can get false misfire codes after replacing the crank sensor. I am kind of leaning to a problem in the drivetrain. I would have thought Gully would have picked up on a unusual noise from there by now.

 

[95TwinTT]

Well then, it looks like it’s time for Shane to step up and do some more testing and get back to us with the results…………….

 

[bass1775]

Check that ECT sensor. My truck started running really rough and began stalling while idling. It actually threw a fault code specifically for the ECT. I would have never guessed that but, the ECM needs that input to properly meter the fuel for proper operation. I didn't check the sensor, I just replaced it ($12.00) and all is well. I'm not saying this is it but, it's worth a try. Like you I initially thought it was ignition related, ie; cap rotor etc. Just my 2cents!

 

[SunlitComet]

The ECT can throw a indirect fault code that a sufficient temperature could not be reach for closed loop ops. or direct one for a short or open circuit but he has not reported one yet.