Sluggish Acceleration and poor gas mileage

[mdashali]

So here is my story:
In preparation for my drive to Lake Tahoe (~500 mile to and fro) during the July 4th weekend I seafoamed the intake, changed oil and filter (@ 15K - i usually do 5k OCI), rotated the tires - all one day before my trip. During the trip I noticed that my GTI takes almost a second to launch from 1st gear (I have a DSG) and then my gas mileage for the whole trip was 24 mpg which is lower than my typical city average (26-27mpg). On top of this, I am getting vibration in the steering wheel when I go past 65-70mph. None of these problems existed before my prep for the long drive.

So here are my questions:
(1) Could Seafoam done any damage? I have used it previously on NA motors so I don't know Turbo DI motors are sensitive.
(2) Can I reset the ECM by disconnecting the battery without any side effects if that is going to help with acceleration problem? I know it sounds lame but I just want to make sure.
(3) Steering wheel rattle could be due to alignment issues. Is alignment covered under warranty and all dealers are generally equipped to do it?

Solution:
--------
Used VagCom to detect that cylinders 3 & 4 misfired. Bought a new set of OEM Laser Platinum spark plugs ($16 each) and replaced it over the weekend. The car drives now normally. The old spark plugs didn't seem to have been fouled that much. It looks like our GTI is very sensitive to the spark strength. I have saved the spark plugs for next time when I seafoam in another 15K.

I also used VagCom cable to do some tweaks - 5 blink turn signal, fog light cornering, remote up/down windows, gauge sweeping aka staging, coming home, auto head light switch off on key removal etc.

I still have to do alignment and wheel balancing to fix the rocking steering wheel.

 

[Uberryan]

Alignment is not covered unless you have a special tire package with the dealership. It's typically $80-$120 to have done. Better to get your alignment checked at a indie tire place.

Seafoam can do damage to some of the sensors on the DI motor, but I've never heard of it happening. I would unplug the battery for 30mins - 60mins and see if that does anything at all. I'm finding it odd that this would somehow affect the transmission. Possible that you mucked up the DV? That'll create hesitation and throw off your MPGs

 

[Conza1]

Hi Mdashali, real sad story btw.

Just for the novices, like myself, what exactly 'is' Seafoam?

That almost certainly sounds like it, oil/filters won't be, only other thing could be the tires are too low in pressure? That'd certainly explain a loss in MPG...'

Also, even that 26-27MPG is shocking, you should be getting almost 30 in dense city driving, and 32MPG+ if you include a few highways, ect, 26 I'd ask them what's going on, that's for sure!

(My sources for that 32MPG figure are these two sites.

A. http://www.volkswagen.co.uk/#/new/golf-gti-vi/which-model/engines/fuel-consumption/
B. http://www.markporthouse.net/rangie/fuelconsumptionconversion.htm#

Plug in figure from A, convert from UK to US MPG and there we have it, 31.8082 MPG).

 

[Uberryan]

Seafoam is a valve and injector cleaning solution geared to remove deposits off the intake valves. You can apply it to 3 different spots on the car. 1. The fuel tank to work as a regular fuel treatment, 2. directly to the oil to work as a cleansing solution 3. suck it into the IAT port via a hose, and air needle. Once allowing the solution to soak in, you're to let it setup for an hour or so, and then get in the car and drive it hard for a few mins, leaving a huge smoke trail of carbon build up behind you.

Once done, assuming you poured some into the oil filler, you need to change the oil within a few hundred miles. It's supposed to smooth out idles, and cleanse the valves to a degree. However, on a car with less than 50k miles, I don't see how effective it could possibly be.

Since the seafoam is a high concentrated octane, I don't see it actually doing damage, but if you mucked up a sensor, or killed the MAF, or something, then I could see the resulting factors occurring. Like I said, remove the battery for 30mins, and report back. The steering wheel shake might not even be related. You may have also fouled up a spark plug, or coil pack. May want to look into changing those out.

 

[ahhduma]

Also, even that 26-27MPG is shocking, you should be getting almost 30 in dense city driving, and 32MPG+ if you include a few highways, ect, 26 I'd ask them what's going on, that's for sure!

these are US ratings
http://www.fueleconomy.gov/Feg/bymodel/2010_Volkswagen_GTI.shtml

 

[Uberryan]

Ratings aren't the real focus here. It's how his car is not performing as it should on highway miles. We're talking at least 30mpg hwy, and 26mpg city.

With that said, getting 24mpg hwy is terrible. I suspect a fouled spark plug.

 

[Conza1]

these are US ratings
http://www.fueleconomy.gov/Feg/bymodel/2010_Volkswagen_GTI.shtml

Might have something to do with the reduced Octane of 93 compared to the rest of the world at 98... I have no idea why you guys haven't started importing the good stuff yet, my car takes 'minimum' 95 octane... We consider 91 to be cheap and crappy.

Anyway, the US Volkswagen site says to go to the site you looked up (such a cop out), so perhaps 5MPG is lost in 5 Octanes of fuel... then again you guys get it so so so so (5 minutes later) so so cheap, that you can't complain, I'm sorry, you just can't, wait till its 5 bucks a gallon, then come talk to us

 

[Uberryan]

...you people have gone way off the subject. It's not about standard ratings, and 91 octane. That shit is really only limited to California, with their strict emissions. Most states use 93 as a premium grade octane fuel, and 100 octane at certain gas stations.

 

[Killswitch24]

Tire imbalance can come to light after a rotation. Get your tires balanced before an alignment check, although, if you haven't had an alignment yet, @ 15k, you are over due.

 

[MBorVW]

Your tires need balanced or you need an alignment. Also there is a slight chance that one of your wheels did not get tightened all the way when you rotated tires...it happens! The one time I used a fuel injector cleaner in my Benz the gas mileage went down 4-5 mpg on that one tank of gas, then got better once that shit ran through the system. I really really don't think you need to use that stuff on a newer car...most gas you buy has an additive that does basically the same thing. I would only use FI cleaner on a high mileage engine from now on.

 

[SwiftGTI]

Not sure how you applied the seafoam, but if enough is added upstream to the MAF, it can apparently cause some damage:

"Sea Foam® Spray is a petroleum product that is safe for all surfaces however; when the Mass Airflow goes into "Burn off mode" any petroleum that has been applied directly to the sensor will super heat and possibly burn out the sensor wire.
To easily avoid this condition when using Sea Foam® Spray, take special care to ensure that the end of the cleaning tube that is installed in the throttle body is positioned downstream from the MAF sensor. The potential for sensor damage only exists when a petroleum product is applied directly to the sensor to the point of saturation."

MAF sensors tend to be pretty delicate, have to be careful with them.

 

[ElectricEye]

I don't see why you would Seafoam what is essentially a new car really...
Just use high quality gas (Shell, Chevron...) maybe an injector cleaner if you're obsessive.

 

[RacingManiac]

How fast are you driving on the highway? GTI is super sensitive to that when it comes to mileage I find. I get 28-29 MPG cruising at 70mph on relatively flat terrain here in Michigan and Southern Ontario on the highway. If I drop that to 65 I can get over 30 MPG. Increase to 75-80mph it'll get closer to 24-25MPG. Factoring in elevation and it can get worse.

@ Conza, its hard to compare MPG rating between countries until you've compared the actual rating standard. The drive cycle for the test can vary. Between US and Canada(which uses largely the same type of fuel), there is 2-3MPG difference in government rating for the car. As far actual observed mileage, 30MPG in city driving is pretty much impossible IMO for the car.

 

[NoPCZone]

I have only owned my Golf since April, have been monitoring MPG closely & have noticed a couple of things:
1- The A/C puts a definite drag on highway fuel economy. Having run the same route on similar days with and without shows a drop-off a couple of Hwy MPG.
2- Extremely hot weather also seems to cost some MPG @ highway speeds. Could be air density or rolling resistance or a combo.
4- My Golf has the 2.5 & AT and beats what you are reporting easily. The engine/tran combo is different, but the rest is the same and they share similar EPA ratings for fuel economy.

 

[NoPCZone]

3- The engine seems to be sensitive to fuel quality. 10% Ethanol Blends- very common here- shave a MPG or 2 from the highway cycle.

As to the rest, have you hit any potholes at speed recently? America's increasingly crappy roads will take a toll on tires, steering and suspensions.
Lastly, check all 4 tires for screws/nails. It is possible to pick up one that doesn't deflate a tire, yet imbalances it. I picked up a screw going through a construction zone detour less than a day after taking delivery of my car. The tire was fully inflated, but unbalanced.