Difference in power

sdeeter19555 · April 11, 2017

Ok, doubt there is an answer for this but it bothers me now...

I have always had a low end surging/chugging, almost a misfire. Never a CEL, no codes stored. I've always thought this 2012 of mine was a slug, thought it was the nature of the beast. Mine is a 2012 2500hd CC, 4wd, 3.73....103k miles.

Fast forward to today, and I had to swap trucks out with a field crew. Took the new-to-this-office company truck on a 50 mile run...no surge, power in reserve, picked up faster in 6th than mine would in 5th on the same road (drove it yesterday in my truck). This truck is a 2012 GMC 2500hd EC, 4wd, 3.73...107k miles.

This company truck would easily out run mine and feels like it would out pull it also...it even has DuraTrac's on it that roll a lot harder than my HT3's. Thing easily pulled on traffic at a redlight not even running it to do so...mine will barely keep up to traffic off a light. It is night and day difference between the two...I mean I do have some extra weight, between the CC, tools, and winch; but not this much!

So the question is, WHY? Why would a seemingly identical truck run so much better? What should I look for as a cause?

This company truck ran better on 87 than mine does on 93 octane...mine is a complete slug on 87. I guess this really bothers me because I know I over maintain mine, and I doubt this company truck has even had basic oil changes done routinely.

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KARNUT · April 11, 2017

Back in the day when my father had his construction co he would buy identical trucks 3or4 for him and his brothers. Of course they would line up, one was always faster sometimes by a lot, he would get that one. Miss those days.

dcheeseman · April 11, 2017

Maybe a good custom tune would help a lot!

Daniel

Formulabruce · April 11, 2017

Before any "mods" are discussed. ( which you really dont want on fleet vehicles), I would consider the following.

1. New iridium plugs ( yes they are expensive) Use COPPER never seize when installing. Make sure your gaps are correct. A worn plug or excessive gap can cause the problems you describe

2. Clean THOROUGHLY the throttle body, the plate and the surrounding area with throttle body cleaner.

3. Clean the MAF and use MAF cleaner, Nothing else.

4. Check and vacuum clean the air filter

It's likely this is a Induction or electrical issue, but at 130K you better be servicing that transmission, T case and rear end as well.

sdeeter19555 · April 11, 2017

Before any "mods" are discussed. ( which you really dont want on fleet vehicles), I would consider the following.

1. New iridium plugs ( yes they are expensive) Use COPPER never seize when installing. Make sure your gaps are correct. A worn plug or excessive gap can cause the problems you describe

2. Clean THOROUGHLY the throttle body, the plate and the surrounding area with throttle body cleaner.

3. Clean the MAF and use MAF cleaner, Nothing else.

4. Check and vacuum clean the air filter

It's likely this is a Induction or electrical issue, but at 130K you better be servicing that transmission, T case and rear end as well.

Already did the plugs, no change...new AC Delco iridium plugs and wire not even 20k miles ago. Surge was there before and after...I did check gaps before installing and they were spot on.

Air filter has been changed twice now, the last was at 95k. There is never really too much in the box.

I can have the MAF and throttle body cleaned this week. It going in for a bad rear ABS sensor, flush coolant, belts, etc..

I've already changed the trans filter twice and fluid every 25k. The differentials and transfercase were done for the third time at 95k.

This is my personal truck, not a fleet. As I said, it's over maintained from a fluid change and PM perspective. I don't have any mods to speak of, and really don't want any.

The surging has been there since new, I just thought it was normal which, based on an abuse company truck, apparently isn't the case

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sdeeter19555 · April 12, 2017

The low power, would that have anything to do with fuel pressure? I'm wondering if I should have that checked while it's at the garage?

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XSKIER · April 13, 2017

On a '12 if you really felt a stumble, there would have to be some stored trouble codes. They don't always illuminate the engine light, but the vcm will store them. One thing that comes to mind is a history of misfires on one or two cylinders. Also, if your engine was running poorly, both traction and stability won't know what to do and display that they need to be serviced. I would start with a scanner that has data logging, and really watch what is happening when you feel the stumble. If you don't have easy access to the scanner, you can start with a $40 compression tester. With all 8 cylinders within 10% of each other, at least you'll know that continuing to throw parts at it is not a waste.

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sdeeter19555 · April 13, 2017

The TC and ABS issue is from a wheel sensor, already sorted that one out.

This stumble or surging at low RPM is noticeable in feel and you can hear it in the exhaust also. To describe it, imaging you're cruising at speed, higher trans gears, rolling along at 1500 or less RPM...and then you encounter a very mild grade that requires just a little more throttle to maintain speed...then you get this surging. I'm hoping that they can see something...in the OPE world, you would guess it's a weak coil by the way it's acting. At WOT, it pulls pretty hard and very smooth...it's only when lugging along that you notice this surging, and it's worse with lower octane gasoline.

Other than this low rpm surging and the noticeable difference in power between my truck and the company truck, mine runs flawlessly and gets really decent fuel mileage (17mpg hand calculated on my last trip)...if I didn't have another truck to compare it to, I wouldn't suspect any issues with mine at all...

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Formulabruce · April 14, 2017

time for a dry compression check. Im betting that one set of rings didnt fully seat when engine was new.

sdeeter19555 · April 14, 2017

time for a dry compression check. Im betting that one set of rings didnt fully seat when engine was new.

Well then it will stay that way... with 100k on the clock, being five years old, and plans to trade in another three; I will live with it if it's that deep.

They finished the truck yesterday, but I haven't picked it up. Belts, coolant, ABS sensor, and cleaned the MAF and throttle body. He said there are no codes stored in any of the modules, they ran it around hooked up and there were no parameters out of range...told me that as far as the computer is concerned; there's nothing wrong with it.

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