LBZ: Engine Surge???

[trashygasman]

When running down the highway, my motor has a small surge that shows up as about a +/-1 lb in boost. It does it more when going up a slight hill that puts a liitle bit of load on the motor. I have changed out the vane pos. sensor, cleaned the MAF sensor, and changed tunes around. I went back to my stock tune and it still does it. I have tried it with and without cruise control. Does it both ways. Any ideas or suggestions on what else to check?

 

[TeaBagger2006]

might me the torque converter.....or a dirty fuel filter

 

[RedDmaxLBZ07]

Does it do it when you're stopped and in gear?

 

[dmaxfireman]

white smoke?

 

[PAT]

Maf, fuel filter or, if it does it as soon as you put it in drive, could be your FPR. My truck used to do that up to 25 mph because of a horribly worn out FPR. Owner before never had a lift pump and ran large tunes. Killed my CP3.

 

[DMAXchris]

Sounds like you might have a cracked bellow on an up pipe. Mine would do the same thing and it would get worse at WOT. The fluctuation in boost is the vanes trying to compensate.

 

[trashygasman]

It doesn't do it sitting still. I mainly notice it going down the interstate running 70 to75. I have changed the FF since it has started doing it also. No smoke. I first thought it was the cruise trying to hold speed, but its not that.

Sounds like you might have a cracked bellow on an up pipe. Mine would do the same thing and it would get worse at WOT. The fluctuation in boost is the vanes trying to compensate.

Wouldn't you hear it if it was a leak?

 

[x MadMAX DIESEL]

Okay, wth he a surge?? I think people use that term too loosey, which makes it confusing for people like me who don't know what it is.

 

[DMAXchris]

It doesn't do it sitting still. I mainly notice it going down the interstate running 70 to75. I have changed the FF since it has started doing it also. No smoke. I first thought it was the cruise trying to hold speed, but its not that.



Wouldn't you hear it if it was a leak?

I couldn't hear mine leaking over the roar of the engine. I think I started a thread about it as well.
I didn't know until I sent it to Tony B and they called back and told me there was a big crack in it. I'm not saying that its 100% the up pipe, but it sounds alot like what I was experiencing.

 

[trashygasman]

Okay, wth he a surge?? I think people use that term too loosey, which makes it confusing for people like me who don't know what it is.

It just feels like you are pushing on the go pedal then letting off ever so slightly...but I'm not:cool2:

I couldn't hear mine leaking over the roar of the engine. I think I started a thread about it as well.
I didn't know until I sent it to Tony B and they called back and told me there was a big crack in it. I'm not saying that its 100% the up pipe, but it sounds alot like what I was experiencing.

Hmmm...I'll look at that and see, thanks.

 

[PAT]

Do the RPM's jump at All?

 

[trashygasman]

I haven't noticed that. LOL I'm always watching the boost. It may be too small to notice on the gauge. I'm going to try to log it tomorrow. You should be able to see it on it.

 

[PAT]

Well hopefully you can get it figured out and it's just something small.

 

[trashygasman]

I did a full reflash with my stock tune per JoshH. I thought at first that that fixed it, but it is still doing it. It is more intermittent now. I still haven't gotten to log it yet. Also, it did feel like you were just barely pushing on the gas pedal, but now it sometimes feels like you are letting off a little sometimes. I pulled it down into 5th today and it did it worse, like +3 lbs boost. I'll just slowly try to keep diagnosing it as I go.

 

[PAT]

Mine would do that up to about 30 mph or so. I could even pit it in cruise and I could feel it. Ended up being the FPR.

 

[trashygasman]

I could see it being that by the way it acts. Almost like the fuel pressure changes so it is trying to compensate? What do I need to check to find out if that is what it is?

 

[JoshH]

I don't remember fuel pressure fluctuating on the one log you sent me a while back.

 

[dmaxfireman]

log injector balance rates and look for white smoke when you feel your "surge"