Help: Engine falls on its face during acceleration, NOT turbo lag!

[carcrafter22]

Bad hesitation on acceleration, NOT turbo lag!

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I have a 2006 LBZ that is starting to give me problems, I have 122,000 miles on it and it is very well maintained. The engine is all stock except for efilive DSP5 tuning, I have ran a nicktane 2 micron fuel filter since the truck was bought new.

For some reason for the past 2,000 miles (only took a month to get those miles)I have been getting a very bad hesitation sometimes when I acclerate. The hesitation doesnt always happen but it does happen often and it does it at different throttle positions, never at the same exact rpm range.

I can accelerate normally when merging into highway traffic and it will go fine for the first few seconds then it feels like the engine falls on its face, then it will take off I can help it come back to life faster by pushing the accelerator more. When I do get the hesitation and push on the throttle harder it will still hesitate for a second or two then come back to life and take off again blowing out white/grey smoke.

The truck idles fine just like it always has and drives good for the most part its just this new hesitation and lack of power, sadly I cant even beat the wifes 09 camry V6 anymore.

I have checked the balance rates but everything I have read says they are fine. I will check them again tomorrow along with turbo vanes, injection pressures and TPS using EFIlive, any other suggestions? Any idea what may be wrong? sounds like fuel to me but I would love to hear opinions.

Balance rates

min max avg

1 -1.09 .17 .50
2 1.84 3.13 2.57
3 .5 .79 .23
4 -2.64 -2.27 -2.49
5 1.34 2.34 1.83
6 -1.63 -.33 -1.05
7 -.61 .41 -.10
8 -1.63 -.73 -1.16

I highligted the worse ones but they seem to be within spec still. could these two injectors be causing a problem?

 

[JoshH]

Balance rates look fine. I would look at the WIF sensor. I worked on a truck a few weeks ago that had similar symptoms. It turned out the sensor wasn't sealing correctly, and it was sucking air under high fuel demand situations.

 

[wes06dmax]

Whats your rail pressure showing it may be running your rail dry of fuel

 

[68skylark455]

If you can access a scope check for glitches in the accel pedal sensor, we had some issues with them both gas and diesel.

 

[BlkMax]

Whats your rail pressure showing it may be running your rail dry of fuel

X2, check your rail pressure

That sounds like what I had going last spring (at 130k miles)....it turned out to be a bad FPR (and a couple of marginal injectors were not helping). I ended up doing a new CP3 and injectors. Problem solved.

 

[TheBac]

Sounds like a typical clogged filter to me.

 

[Killerbee]

ditto Tom's assessment. Change the fuel filter. Technology is great, but makes us overlook the usual suspects.

 

[carcrafter22]

X2, check your rail pressure

That sounds like what I had going last spring (at 130k miles)....it turned out to be a bad FPR (and a couple of marginal injectors were not helping). I ended up doing a new CP3 and injectors. Problem solved.

Thats what I am thinking it might be right now but I wont know till I check rail pressure with efilive.



The fuel filter is fresh, both the CAT 2 micron and factory filters along with a new ($70 freakin dollar) WIF sensor since my last one was cracked. I fill up with the same fuel from the same place and never had a problem with them, (they are a major truck stop with a good reputation for fuel).

Does anyone think the DSP5 tuning could be causing this? I know it does it in all 5 positions just with varying levels of hesitation and punchiness if I lean into the throttle with its hesitating, thats another reason why I am thinking injection pump. dumb thinking?

I will recheck the WIF sensor to see if its come loose somehow, check all the fuel lines for any leaks, look at my lift pump to see if its working (would a bad lift pump cause this? TTS dual pump setup.) check the rail pressure, etc.

I am thinking of checking compression, I guess after a couple small nitrous shots :rofl: and 122,000 miles it couldnt hurt anyway to know what it is.


Any other ideas guys? great suggestions so far. Really appreciate it.

I sure hope I'm not in the market for a new injection pump soon.

 

[carcrafter22]

Ok rail pressure seems to be ok.

Here is part of a log of rail pressure.

Desired Actual RPM

25949 26282.34 2692
25988 26353.4 2708
26005 26105.39 2731
26026 25716.69 2745
26080 25008.9 2788
26098 23735.47 2804
26107 21333.64 2805
26107 18876.7 2827
26107 16875.17 2845
26107 14944.71 2854
26107 12627.01 2865
26107 10380.37 2872
26107 9643.58 2887
26107 8344.04 2882
26107 7106.86 2882
26107 5520.15 2879
26107 5663.73 2926
26107 6024.88 2909
26107 5772.51 2879
26107 5772.51 2830
25277 6963.27 2432
25392 9748 2414
25217 11714.72 2371
25082 13294.18 2324
22990 16981.05 2251
19569 24195.24 2106
15218 19121.81 2109
10503 13294.18 2090
8699 10415.18 2089
8699 9713.19 2076
8699 9115.64 1970
9252 9853.88 1797
9178 9502.89 1779
8969 9327.39 1794
8699 8413.65 1763
8699 8554.34 1784
8699 8554.34 1785
8699 8625.41 1774


Seems more like defuel to me than the hesitation I am feeling since its at higher rpm. I think the injection pump is good. Might be the TTS lift pumps not working and causing some sort of restriction, although I thought they were flow through pumps.

 

[TheBac]

No need to get defensive about the filters. 99% of the time thats what it is. Yes, the WIF sensors are not cheap. Damn gourmet diesel parts.

Id check both fuel pumps to see if they're working. IIRC, I've read in the past that if one of the TTS/Kennedy pumps stops working the loner wont be able to keep up and draws down to 0 under load.

 

[dmaxfireman]

unless you recently changed your tune i'm betting you have a clogged filter / lift pump not working properly / or drawing air in somewhere. basically a issue in the fuel system.

 

[LBZrcks]

unless you recently changed your tune i'm betting you have a clogged filter / lift pump not working properly / or drawing air in somewhere. basically a issue in the fuel system.

X2, your rail drops A LOT!

 

[carcrafter22]

No need to get defensive about the filters. 99% of the time thats what it is. Yes, the WIF sensors are not cheap. Damn gourmet diesel parts.

Id check both fuel pumps to see if they're working. IIRC, I've read in the past that if one of the TTS/Kennedy pumps stops working the loner wont be able to keep up and draws down to 0 under load.

Sorry, not getting defensive just stating a fact.:thumb:

Good point on the lif pump failing, I was afraid that could be a possibility. I havent had time to check them and now I have to go out of town again today, just found out. GGRRR!!!

 

[Bako_Dmax]

Have you checked to see if your MAF is dirty? I had a similar issue with my LBZ thought it was fuel related but turned out my MAF was dirty sprayed it with some cleaner problem went away.

 

[S Phinney]

From the log I would drop the tank and check for algae clogging the pickup. First change your fuel filter to see if it stops first.

 

[jc1843]

I suggest you do this-

Remove the hose coming out of the filter - attach a long hose-- turn on the fuel pumps and see how the flow is-- that will test everything,-- tank pick-up, pumps and filters. If the hose is long enough, you can just direct it right back in the tank.

 

[fishsmith]

I vote lift pumps. Mine was doing the same thing when my tts pumps were going out. The lift pumps were making pressure but when you went over half throttle rail pressure would bottom out just like yours. I only had 6 months of use on mine also and not daily driving.

 

[Big Block 88]

have you bottle tested it??

 

[trashygasman]

Has it been using oil? Sounds like the same thing mine has been doing. Turned out to be the seal in the turbo. It was hesitating because it was sucking oil through the turbo. Only did it every once in a while. I thought it was the fuel filter too, till it starting dumping oil out the tailpipe.

 

[Kdromo]

I'm having same problem started today,when I went to pass fell on its face.my fuel filter percent gauge shows 10 per cent I hope it's that