I have been dealing with a rough idle when hot issue for a while now. After numerous trips to the dealer with reflashes, #1 and #4 injector replacements, new valves on #1, and two sets of sealing washers, and ECM I still have not been able to get this fixed.

So based on another post here on DTR, as a last resort I decided to borrow my buddy's laser thermometer to measure each cylinder temp at idle to see if I could come up with anything before I make my next trip in for regular service on Friday. Here are my first measurements taken tonight after a short drive home and a couple minutes of idling:

Outside temp=64F
Thermostat housing=183.5F

At top of exhaust manifold flanges:
#1=178.5
#2=178.5
#3=180.5
#4=187.0
#5=194.0
#6=182.0

At flat spot on head over exhaust ports:
#1=181.5
#2=182.5
#3=184.0
#4=188.0
#5=192.0
#6=185.5

I took two sets of measurements and both sets were within 1-2 degrees. It appears to me that #5 might have an issue (overfueling?). Are there any holes in my theory? I plan on taking more measurements throughout the week to see if it is consistent after different driving conditions.

Also if any members here have a laser thermometer and wouldn't mind taking some measurements to compare, I would like that information. The absolute temperature doesn't matter to me but I would like to see if there is any difference between cylinders.

Thanks in advance for any advise or help.

 

BigHorn-I'm sure there's an allowed tolerance for differences in the amount of fuel that each injector sprays for a given throttle position. You'd just have to find it somewhere. As it stands, though, your EGTs differ by less than 10% from each other (the greatest temp difference being from 1 or 2 and 5). The other thing to try to find is if there's a tolerance range for injectors not only at idle, but at 25% load, 50% load, full load, etc. That means you'd need to look at individual EGTs per cylinder in order to figure that out. I've got the factory service manual here on my computer-if I find anything out, I'll let you know.

I've seen some buildups on gassers where they put an O2 sensor in each header at the exhaust port for each cylinder, in order to get the A/F ratio perfect. You'd almost have to do something like that in order to see how the injectors are working under load (since you can't very well use an IR thermometer while the truck is moving).

Fitz

 

BigHorn-

Here are some things from the FSM to consider:

Just some things to consider. If I find anything more, I'll let you know.

 

Thanks for the reply. They have had all 6 injectors out a couple times already, and installed new sealing washers, so it could be a deformed connector due to torquing. That is one reason why I am trying this to determine if I can isolate a certain cylinder. So far they have been unable to correctly diagnose this problem, so I am taking things into my own hands so to speak.

The first set of readings above is just a start. It was somewhat cool and idling relatively smooth when I took them, so I need to get it good and hot to get the rough idle going and see if there are any more drastic temperature differences.

 

Yeah, you might want to go hot lap it, come back, let it cool for a couple/few seconds, take some readings then.

 

Maybe you are refering to an EGT probe in each header tube at the exhaust port? And one O2 sensor at each COLLECTOR maybe, for a total of 2 Oxygen sensors (one for each side of the motor)

They would not run 8 Oxygen sensors, but they do run 8 EGT probe's. Is that what you meant?

 

Here are my readings from tonight. I drove about 15 miles home before taking these so there is a little more heat than the last set.

Ex. Man.
1=203.5
2=201.5
3=199.0
4=203.0
5=220.5
6=198.5

Head:
1=185.0
2=186.0
3=186.5
4=187.5
5=196.0
6=188.0

Still looks to me like something is up with #5. It is definately hotter than the rest. I tried to get the temps immediately after pulling off the highway, but they were cooling down too fast to compare to each other, so I had to let it stabilize a minute or two. Tomorrow I am headed out of town over a mountain pass so I am going to stop at the top and see if I can quickly stab some temps to compare for some higher readings.

I also have a buddy with a stock '05 that I should be able to get some readings on next week to compare to mine. Hopefully when I take this information to the dealer they will believe me and try replacing #5. I am crossing my fingers this will be fixed for good.

 

Not sure if you want to do this, BUT:

Swap injector #5 for #1. It seems #1 is the coolest. So, pop #1 in #5 place an vice versa. Drive it, take readings. If teh hot spot MOVED to teh the #1 location, then you know it is an injector. If no, then obviously something else

 

I did temp guage reading I was gettin aroung 180. The cool ones were number two and number 5. I thought my prob was # 2 but then noticed 5 was not heating fast either. Decided I could not make Diagnosis with laser temp. Took to dealer he replaced #5 truck did not make it home. Towed back to dealer - now says high pres bump is out ***** 3k - siad he was nuts towed truck home . I paid 800 for one stupid (me) injector. Who tatoed sucker on my head!!! Dealer - Dealer always lose, but I wasnt sure how to diagnos. I know they can cut out individual injectors with computer to search for bad injector. Bad tes. They did not first check fuel presure. I think fuel presure pump problem may cause injector to trip?

 

Need better diagnosis procedures because we are gettin hosed. I don't believe so much about cascading problems. I belive some is bad diagnosis.

How does bad pump harm injector. How does bad injector damage pump? How does lift pump damage high pressure pump?

I just don't know - please post your best educated gueses

 

Whe low pressure pump (lift pump or LP or low pressure pump) goes bad, doesnot provide pressure or proper amount of fuel to the CP3 (Injector Pump or IP or high pressure pump) and when that happens, teh CP3 starves,is not properly lubricated, and goes bad.

The LP is NOTORIUS on our trucks at going bad. Poor design, poor pump. The CP3 is a good pump, just goes bad when teh LP goes bad.

Injector can notdamage a pump ( in a conventional way) I would need someone to explain WHY they said that to answer that more completely.

 

I thought about that, but seeing as how it is still under warranty and I have never done injector work before, I will let them decide what to do. At this point I am just trying to help figure this out since it has been an ongoing problem.

Thanks for the help though!

 

Keep in mind that they will likely try to discredit any info you give them that is generated on your own. We have to keep in mind that we are (said sarcastically) stupid truck owners, and that the factory knows it all!

You may also want to reference another truck or 3 to get a sample of the readings so you can show that yours is outside the trend.

on edit: you may be seeing normal distribution, with just a small outlier. The only way around the imbalance may be to go to aftermarket injectors.

Any change in oil level? That's usually the strongest indicator of a bad injector. You could also send an oil sample out to analyze & specifically ask for fuel dilution. It should be REALLY low ~<0.1% for a normal engine. There are several posted on this site you should be able to reference too.



HTH

Tony

 

Hey no prob. Maybe you can talk THEM into doing that

I can understand your frustration, and if there is a problem with ECM controlled vehicles these days, is that. The little problem, that seemed to elude everyone. With a carb, you had fuel and fire, and if you did not have one of them, your car did not run. And tryng to find why you did not have one, was usually quite simple. NOW, so many wires/sensors/programming it can take forever trying to diagnose a problem like what you are describing. Bad fuel? Dirty injector? Bad ECM ground? Malfunctiong/faulty_________(fill in the blank with appropriate sensor)

 

Oh I am sure there will be some explanation from them about what I am seeing. I will get some readings from my buddy's '05 to compare and hopefully discredit any of their discredit. It is definately an outlier, but there is a good chance it is causing my idle, smoke and light surging problems.

I have not seen any rise in oil, in fact if anything my oil has dropped a bit.