Surge after hard excelleration

[Bradleyras]

2006 3500 QC 4x4 short bed.

I just bought this truck. 190K miles, super clean and drives great! BUT....and before someone says SEARCH, because I have read just about every searchable SURGE thread but none of them seem to describe my symptom. When I accelerate rapidly or apply a healthy dose of throttle it almost seems like my throttle is stuck for a second after I let off. Nothing unusual at idle stopped in gear. Nothing unusual when 'pu$$yfooting' the throttle for optimum fuel economy. It happens under hard acceleration. I let off the pedal but it still pulls for a second afterwards.

Throttle position sensor?

 

[Slow Six]

My 03 would do that when I had a "pressure box" on it. I would suspect your mystery tuner.

 

[Bradleyras]

How can I determine what tune is in my truck?

 

[seafish]

Your truck does not necessarily have a problem.
The HPCR engines need a bit of time for the rail to return to lower pressures after high rpm (ie high fuel pressure) acceleration...my 2005 does the same thing with hard accleration above 2800 rpm. That being said, it IS disconcerting when it happens. Like another poster indicated, it IS possible that your "mystery" tuner, which likely increases the rail pressure ramp up, is adding to the symptom.

 

[AH64ID]

How do you know there is a tune on it?

 

[Bradleyras]

It has more UUmmmmmppffff then the stock 5.9s that I drove. A friend who also has a 5.9 (quadzilla, intake, exhaust) seemed to think it was tuned when he drove it. The fuel economy appears to be much better than usual (24-25 highway, 20-22 city). Some minor black smoke under hard acceleration.

 

[AH64ID]

Is that hand calc mileage or overhead? Stock ones can smoke.

If you slowly rev it up to 3,000 rpm, let it sit for 5 seconds and then release the throttle how do the rpms drop? Smooth or steps?

Have you looked underhood to see if there are any fueling modules?

I personally wouldn't drive a truck with a tune I am not familiar with, especially if you ever tow.

 

[Bradleyras]

A mix of hand calculation and the overhead. I'll try the 3K rev drop test tomorrow and report back. I did look over the truck and could not find any modules anywhere under the dash or under the hood.

The overhead is a little optimistic with it's calculations. Despite having bigger tires, the odometer and speedometer are spot on with my GPS which leads me to believe it was recalibrated.

 

[AH64ID]

24-25 highway on any 04.5-07 is going to take driving 55 with a tail wind, especially on a 4wd with larger tires. That generation of motor just isn't that fuel efficient.

Do you know anything on the injectors?

 

[mfurrh55]

I couldn't get that good of mileage even if was being towed, 18 on hiway in Tx. 21 on hiway in Colo. NOT towing anything.

 

[rscurtis]

K&N intake,

JMHO, get rid of that K&N before you end up with a dusted engine.

 

[Bradleyras]

Well, I'm anxiously looking forward to refueling this weekend although the $125 fill up is not something to look forward to....

 

[Bradleyras]

K&N intake,

JMHO, get rid of that K&N before you end up with a dusted engine.

I know right??? I don't know why K&N is still in business....they've been blowing up motors for so many years now....

 

[JJPage]

If you have a leaking injector(s), that can also cause the throttle to "hang", and would also explain "extra" smoke on acceleration. It surely would not help mileage though...

As previous posters have stated, your throttle ramp down sounds normal for the HPCR, I wouldn't borrow trouble at this time, enjoy your new truck!

 

[Bradleyras]

Thanks JJ. How do I diagnose a leaking injector? Can that be done with a scan tool?

 

[JJPage]

Thanks JJ. How do I diagnose a leaking injector? Can that be done with a scan tool?

I wouldn't borrow trouble at this time...

Scan tool may find it, for now I would just monitor crankcase oil level, you do not want to see it rise because of fuel dilution.

 

[cerberusiam]

A scan tool with the correct packages will show contribution percentages that will help diagnose and over fueling injector.

A small hang is not unusual when lifting off the throttle after hard application. The idle drop test from 3k is the best way to see just how good the injectors are working.