Engine surging above 3200 RPM related to fuel?

AZ TDI'er

Member
Joined
Nov 10, 2006
Location
Tucson, AZ
TDI
2005 Golf
[FONT='Verdana','sans-serif']I've recently been experiencing engine surging when accelerating above 3200 RPM's. Outdoor tempertures have been well above 40 degrees here in Arizona. Interestingly enough, when the fuel tank hit below 1/4 tank full, the problem went away. As soon as I filled the tank back up to full again the problem returned???

Wonder if it's a fuel tank pump, bad couple tanks of BD (probably not likely), or something else?

I've been running B99 biodiesel for about 48K of the total 55k miles on my 05 Golf TDI. The fuel filter was changed less than 5k miles ago and has always been changed at recommended increments. The BD I've used is always Soypower biodiesel provided by a quality and reliable source who regularly tests for quality. Has anyone had a similar problem or have a solid opinion what this problem might be related to or whether it sounds like a BD issue? I'm a believer (so far) in BD as a good alternative fuel, so I'm not willing to speculate yet that my problem is related to BD.[/FONT]
 

AZ TDI'er

Member
Joined
Nov 10, 2006
Location
Tucson, AZ
TDI
2005 Golf
Thanks. For all I know it still could be a clogged filter.

I'm going to run the tank to empty then fill w/ B5 BD and see if the problem goes away. Going to try to rule out (or in) a bad batch of B99 BD.
 

DBLVSN

Active member
Joined
Aug 12, 2005
Location
Tempe, AZ
TDI
1998 Black TDI NB
Funny that you mention this problem. I've noticed the SAME PROBLEM with the last batch of BioD that I purchased from the same suplier here in Phoenix. When I buy BioD, I usually drive over on empty, fill my tank, and purchase 30 gallons in containers that I use over the next few months so I don't have to take trips into 'the city' proper as often.

I purchased my last quantity of fuel on Nov. 27th.

What I've noticed with this particular problem is when I shift from 2-3 and ocassionally 3-4 (RPMs in the neighborhood of 2500-3500) the car seems to react like the clutch is slipping. I get a 'power bog', the engine 'RPM sound' (I admit that I haven't watched the RPMs when this occurs) increases, then the gear seems to 'catch' and all is well again. I'm 99.9% sure that this isn't the clutch as the vehicle has no problems at all moving from a stop to 1st gear. In my experience, when a clutch is going out, the most noticable 'shift point' is from stop to 1st (massive slipping, stalling, etc.).

Anyway, please feel free to private message me directly or, since we are local to Phoenix (I'm in Tempe) we may be able to meet, compare notes, and if needed, approach the supplier directly.

Please let me know if you have additional info or find anything else out.
 

40X40

Experienced
Joined
Feb 12, 2006
Location
Kansas City area, MO
TDI
2013 Passat SEL Premium
AZ TDI'er said:
[FONT='Verdana','sans-serif']I've recently been experiencing engine surging when accelerating above 3200 RPM's. Outdoor tempertures have been well above 40 degrees here in Arizona. Interestingly enough, when the fuel tank hit below 1/4 tank full, the problem went away. As soon as I filled the tank back up to full again the problem returned???

Wonder if it's a fuel tank pump, bad couple tanks of BD (probably not likely), or something else?

I've been running B99 biodiesel for about 48K of the total 55k miles on my 05 Golf TDI. The fuel filter was changed less than 5k miles ago and has always been changed at recommended increments. The BD I've used is always Soypower biodiesel provided by a quality and reliable source who regularly tests for quality. Has anyone had a similar problem or have a solid opinion what this problem might be related to or whether it sounds like a BD issue? I'm a believer (so far) in BD as a good alternative fuel, so I'm not willing to speculate yet that my problem is related to BD.[/FONT]

I believe you have a plugged fuel filter. Change it and get back to us. You do understand that a filter can plug in just seconds if there is enough crap in the fuel?
The filter is the cheapest thing to replace when experiencing symptoms like yours, so do it soon and let us know how it went.

Good luck!

Bill
 

AZ TDI'er

Member
Joined
Nov 10, 2006
Location
Tucson, AZ
TDI
2005 Golf
Thanks DBLVSN and 40x40,
Wow, can't believe someone else ran into the same problem. Now I do wonder if the manufacture or dealer's have or had a bad batch out there???
I started noticing the problem after the batch I bought in the end of Nov to first of Dec. The problem started out really subtle, but is now very noticeable in lower RPM's, but always gets worse with the more gas peddle I apply. Just like you said feels kinda like clutch slip, but I know it's not. Clogged fillter is looking like a possibility w/ engine being appartently starved for fuel under acceleration. I'll pick a new filter up tomorrow and let you know if that fixes it. I'll also empty the tank before that and fill with a small amount of good quality diesel 2 from another supplier. I buy from Arizona petroleum in Tucson and it's the Soypower brand. I've never had a problem with their fuel, but I suppose anything can happen. I will call the dealer here in Tucson and tell them I "might" have had a problem related to their fuel.
 

DBLVSN

Active member
Joined
Aug 12, 2005
Location
Tempe, AZ
TDI
1998 Black TDI NB
Well, it is good to hear that we may have found the potential source of our problem...if fuel supply quality IS the problem...

Respectfully, I don't think's it the fuel filter, at least not on my car anyway (but I have been known to be wrong in the past :)). For the record, I usually run nothing less than B50, about a year ago I changed to NOTHING BUT B100.

I last changed my fuel filter 8 months/6199 miles ago. The recommended VW service interval is 20K (with a check/inspect at 15K [although I don't know how to really 'check' the fuel filter other than look at is and say "no leaks, must be ok"]).

Since BioD is a much better solvent than PD, rumor has it that when you first switch over to BioD you will eat a filter, even if relatively new, VERY QUICKLY as the BioD is getting rid of all that 'gunk' in your fuel system.

I'm not sure what happens after the initial changeover to BioD , but I religiously change mine every 18K.

If there are furthr insights I'm sure that AZ TDI'er and I will be 'all ears'.
 

BioDiesel

Veteran Member
Joined
Oct 29, 2001
Location
CT
TDI
'98 Jetta
Don't rule out a problem with the in tank fuel pump.
PD's pumps have been a high failure rate item.
Although I think they just fail, not weaken as your symptoms indicate.
 

AZ TDI'er

Member
Joined
Nov 10, 2006
Location
Tucson, AZ
TDI
2005 Golf
DBLVSN said:
Well, it is good to hear that we may have found the potential source of our problem...if fuel supply quality IS the problem...

Respectfully, I don't think's it the fuel filter, at least not on my car anyway (but I have been known to be wrong in the past :)). For the record, I usually run nothing less than B50, about a year ago I changed to NOTHING BUT B100.

I last changed my fuel filter 8 months/6199 miles ago. The recommended VW service interval is 20K (with a check/inspect at 15K [although I don't know how to really 'check' the fuel filter other than look at is and say "no leaks, must be ok"]).

Since BioD is a much better solvent than PD, rumor has it that when you first switch over to BioD you will eat a filter, even if relatively new, VERY QUICKLY as the BioD is getting rid of all that 'gunk' in your fuel system.

I'm not sure what happens after the initial changeover to BioD , but I religiously change mine every 18K.

If there are furthr insights I'm sure that AZ TDI'er and I will be 'all ears'.
DBLVSN:
I ran B50 the winter before last without problems. I can't remember having problems last year w/ the B99, but I'm wondering if the few cold days in Decemeber 2007 combined w/ the B99 to do something.

I will give the filter change a try, but I wonder if the weather (dipping into the lower 40's at night and cool in the day) has been a factor to combine w/ a poorer batch of fuel. If the new filter doesn't work, I plan to switch to B5 and see if it helps. If not, I'll end up taking it to the dealer probably. I'll let you know if the filter change and/or the change to B5 does the trick.
 

DBLVSN

Active member
Joined
Aug 12, 2005
Location
Tempe, AZ
TDI
1998 Black TDI NB
AZ TDI'er,

From what I know about BioD, the colder weather shouldn't effect a 'commercial grade' biofuel. Yes, BioD can gel at low temps, but the commercial grade stuff should have enough anti-gel additives to prevent cold weather problems. In addition, yes it as been cold, but "Arizona winter" is not as cold as winter elsewhere by any means.

Please let me know what happens with your VW and I'll keep you posted with mine. I'm not going to change my fuel filter as of yet. I have 3/4 tank of B100 left and I'm contemplating either mixing it with PD now, or waiting until I get to a 1/2 tank and mixing it in then. Hopefully there will be an improvement.

Did you get any feedback from your fuel supplier?
 
Last edited:

AZ TDI'er

Member
Joined
Nov 10, 2006
Location
Tucson, AZ
TDI
2005 Golf
DBLVSN said:
AZ TDI'er,

From what I know about BioD, the colder weather shouldn't effect a 'commercial grade' biofuel. Yes, BioD can gel at low temps, but the commercial grade stuff should have enough anti-gel additives to prevent cold weather problems. In addition, yes it as been cold, but "Arizona winter" is not as cold as winter elsewhere by any means.

Please let me know what happens with your VW and I'll keep you posted with mine. I'm not going to change my fuel filter as of yet. I have 3/4 tank of B100 left and I'm contemplating either mixing it with PD now, or waiting until I get to a 1/2 tank and mixing it in then. Hopefully there will be an improvement.

Did you get any feedback from your fuel supplier?
Well, I have 2 pretty certain theories now. Sterile, weak or otherwise bad B99, or just plain too cool weather for B99 (in my car, not necessarily yours). I'm favoring the cooler temp idea.

DBLVSN:
Here's what I know:
Today, I drove the car until the tank got down to around 1/4 full of B99. It did the same thing as last time, it stopped surging and ran perfectly well. But I had also drove for about an hour both times. It could be my car does not like B99 when it's 40 degrees at night and barely warms up to 50 or 60 for a couple hours a day. My guess it has something to do with the cooler air temps and combustion air being slightly too cold and the B99 not being at optimal temp.

I'll outline what I think is happening. Again, this is just my car, your situation may be totally different. When I filled up the tank to full w B99, I started getting the engine surging at higher RPM's. This only happened after the temps started dipping this winter. When the tank got down to 1/4 full and had been driven for an hour it went away. When I filled back up again w/ B99, same problem. Today I let it go down to 1/4 tank and the problem went away. It ran great. Full power no surging all the way up to 4500 RPM's! After that I added 3 gallons of ULS diesel; roughly a B50 mix. The car continues to run great. I did not change the fuel filter, since this clearly (at least to me) indicates the filter is not the issue. If it were the filter, it would clear up both times when the tank was at 1/4 and then magically re-appear when filling the tank.

My theory (aside from a sterile or weak/bad batch of fuel) as a tank empties out, more air occupies the tank. Air is much easier to heat and will warm up more quickly than a solid, like fuel. Fuel in a full tank takes time to warm up. As the tank emptied the return line from the injection pump was able to more quickly heat the fuel in the tank, allowing it to overcome whatever problem occured with creating combustion in the clyinder (surging).

Now, I still need to rule out any potential problems with the fuel tank or fuel tank pump. Because this problem started as soon as the tank was filled to full. As soon I as run the car for another day, I plan to fill all the way up w/ B50 (Not B99) and see what happens. If the trouble is gone, it's pretty clear to me that my car didn't like the b99 at these temps, or maybe there's a chance that we got a bad batch of fuel.. I dont know. I guess it could be that the fuel quality was such that it wouldn't allow complete performance and combustion at temps around 50-60 degrees outside. I may still contact the distributor of the fuel. I guess I got lazy, but I wanted to be sure I could at least have better information before getting them concerned. I think it's reasonable to think either the fuel or the temps were the cause. Everyhing I mentioned above could as likely been related to a sterile or weak batch of fuel too for all I know.

One thing for certain, I don't think I'll risk running B99 in the winter again. It may be fine for most people, but I think my car gets grumpy w/ it when it's cooler. I tried to get away w/ it last winter and noticed some problems w/ engine performance. The winter before that, I ran B50 and didn't have an issue.

Let me know what happens if you go to B50 or less. My guess is, the problem will go away......
 
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