Poor fuel economy please help

[tdi52479]

Hi Im new to the forum looking for a little helpfull advice for my 05 jetta tdi 5 speed. I bought the car new in December of 2004 and was getting appox 38-40 miles per gal city and 47-51 highway. Sometime in May I noticed that my fuel economy changed to 26-29 city and 36-40 highway and no modifications were done to the car. The dealers will not help me since ive eleminated my muffler and cat sometime late last month (witch did give me about 2-3 more miles per gal). I think it might me a bad mass air flow but I thought Id get some more opinions before I go ahead and order <font color="black"> </font> a new one. Thanks for your advice.

Mike
05 Jetta GLS TDI 5 speed
Johnstown PA

 

[vikingrob]

Change in driving pattern, commute, speed, shift points?

 

[TomB]

The emissions controls are an integral part of the TDI. The ECM monitors the pressures, air flow and oxygen presence. The modifications you made probably broke some balance.

Getting rid of the muffler is one thing. Dropping the catalytic converter is just plain silly. It really does make the air better for everyone at very little sacrifice to the engine performance.

The EGR does more impact on MPG than the catalytic converter.

Again, why did you make your car illegal and want to dump all that extra pollution into other peoples lungs, especially the diesel by products? So you can gain some perceived MPG?

Sorry, I am pretty open-minded on most modifications but having seen what the air looked like before 1973-4 when the catalytic converter was introduced, I cannot stand by and not say how dumb this modification is. Really...

Why does someone take a perfectly new car and do this... It is just not reasonable or understandable.

 

[ofhs93]

How many miles are on it? Maybe need a fuel filter...or air filter...is the snow screen blocked.(did they still have them on 05's?) There are a lot of possible things to look at...we need to know more about the car and driving patterns though.

 

[tdi52479]

My Jetta is a 2005 but has the body styly of a 04 if it helps. I have tried almost every different driving condition windows up and down with and without ac and so on. The thing I dont understand is that the car had no mods to it befor this problem started. My exhaust was done about 3 months after the fuel econo went down. The only reason I pulled the cat it for the sound and it does sound great. Sorry to you guys out their that dont like it but we are all different and we all like different things so If your not going to help me with some advice please dont badger me.

 

[ofhs93]

We still need your current total miles and the type of driving that you do. Could be a blocked snow screen...a new fuel filter needed...MAF....lots of things...give us as much info as possible.

 

[tdi52479]

most of my driving consists of city driving with little stop and go traffic. I also make highway trips about every other weekend for a total of 100 miles round trip. The car now has 15000 miles and had about 8000 when i noticed the problem. The only problem I have noticed other than fuel economy is that once my egr stuck while going up hill and i had to pull over and shut the car off due to a loss of power. thanks again

 

[Aggie05]

Sounds like you drive the car pretty hard. Durring the summer, most cars get worse mileage. Perhaps you are seeing the results of this.

Were I you, I would fix my car back to stock (put the cat and muffler back on) and take it to the dealer.

 

[ofhs93]

Do you purchase your fuel from a hi volume station? Like a truck stop or somthing similar. If your EGR has stuck then it sure sounds like you might have some blockage in that intake area. Constant city driving at low speeds really is a killer for these cars with the crappy fuel that we have here in NA. Have you taken a peak at your EGR with the hose off and a flashlight? It's highly unusual for buildup to suddenly kill your mileage...are you sure this is not something that has progressivly gotten worse over a number of months?

 

[TomB]

Sorry you think it is badgering. Like I said open to most mods.

Hmmmmm. Let's see some things.

We have to listener to your "better sounding car", i.e louder without a muffler. Why? Some derived pleasure from exhaust noise?

We have to breath more pollution again for your "better sounding car" without a catalytic converter.

Hmmm and I am the one badgering. How about your actions? I guess they are totally impactless to everyone else who shares this earth with you, huh? They don't harass anyone when you drive down a public road past all those homes, huh?

Trust me. I have done it all too. Then I started thinking and found what a waste of time, effort and money it was. There really are better things in life besides "cool sounding exhaust system." Really.

 

[tdi52479]

All of my fuel is purchaced though BP and always has been. As far as driving conditions I do run it hard from time to time but I have tried running tank fulls with no more than 1/4 throttle durring the whole take and notice about 2 mi per gal difference. I have puller the intercoller hose off and it looks pretty gunked up inside near the EGR. This was deffinitly an abrubt change in fuel econo when it happened b/c i have always tracked miles per gal from day one.

 

[Wypij]

... I bought the car new in December of 2004 and was getting appox 38-40 miles per gal city and 47-51 highway. Sometime in May I noticed that my fuel economy changed to 26-29 city and 36-40 highway and no modifications were done to the car...

'sometime in May' - this means late Spring. This is a far shot, but check the brakes, esp. rear ones. Maybe Winter wasn't that kind on them and they are blocking?

HTH

 

[Audi5000TDI]

It probably started when you started running biodiesel. It's good for 8 to 10% less miles per gallon.

 

[Mike_M]

It probably started when you started running biodiesel. It's good for 8 to 10% less miles per gallon.

More like 5%.

But check your math. He's getting 25% less fuel economy!!!!

That's not caused by biodiesel.

Mike