Jetta Engine Problems


#1

Hello,

Been having trouble with my 2005 vw jetta gli 1.8T. On the highway from about 60-75 mph, the engine will randomly cut out (feels like my foot isn’t on the gas at all even though it is). All the power in the car stays on and it will only cut out for maybe 3-4 seconds. Occasionally it will completely shut off as if the car stalled (it’s a manual), which is dangerous on the highway. It will start back up and continue but will usually do it again. Funny background, I didn’t have this problem all winter when it was colder, but today was a warmer day (in the 80’s) and I was in stop and go traffic right before it happened too. I was thinking maybe something in the fuel delivery system, but the car idles and starts just fine. Could it be a MAF sensor? I thought a car would still run without a MAF just not very well? Any ideas would be very appreciated!!!


#2

At higher speeds the ability to get air and fuel into the engine and the exhaust out becomes the limiting factors for performance. So suspect things like a plugged fuel filter, faulty fuel pump, plugged air filter, or plugged cat.

The ignition system can become taxed at higher speeds too. Does the CEL come on? Have you had the trouble codes read out of the computer memory?


#3

No CEL’s have been thrown yet or I would have suspected a coil pack since they tend to go bad quickly on that car. So fuel delivery should be my first attack?


#4

Pretty sure it’s not my air filter (just replaced) or cat (high flow). I just figured it wouldn’t start or idle if the fuel filter or pump were going bad? Only thing I’ve noticed is that it seems to start up really rich.


#5

By starting rich, do you mean you notice the smell of gasoline on cold starts? That’s probably normal, the computer richens the mixture for cold starts. Fuel pumps can fail in numerous ways. One way is that it simply can’t pump the volume flow (liters per minute in other words) that it could when new. That problem would only manifest at higher speeds when fuel flow rate was at the max. Same thing w/the fuel filter.


#6

By rich I mean it coughs to life as if it is flooding, exhaust is black/dark. Not something I would expect from a 4 cylinder.


#7

Maybe it’s just cold weather, but it’s more than I would expect even from a cold start


#8

Sorry, I don’t mean to doubt you on the fuel pump, it just seems to work perfectly fine under all other conditions. It will start without hesitation, functions perfectly under heavy load on a highly tuned car. I can put it on the floor in any gear and it won’t cut out, although fuel delivery sometimes hesitates or lags a bit.


#9

@bsa07eagle‌

“seems to start up really rich.”

You definitely need to hook up a fuel pressure gauge

You might have a leaking injector or regulator

In any case, it sounds like a fuel problem is a good possibility

Some vehicles start and idle just fine with low fuel pressure . . . don’t assume anything


#10

Hmm, kinda forgot about my injectors, how do you test them?


#11

Do you have a scan tool and a fuel pressure test kit?

Does your fuel rail have a test port?


#12

No I don’t, never done much fuel diagnosis before.


#13

Thanks for the update

While some may not agree with me . . . I think the best choice is to get the car professionally diagnosed and repaired


#14

I think I might do the fuel pump myself and if that doesn’t solve it I’ll get a expert on it


#15

@bsa07eagle‌

A fuel pump would be an expensive “hunch” . . . in my opinion

If your problem is resolved, your hunch was correct

If not, your hunch cost you quite a bit of money

I’d seriously consider taking the car to a pro


#16

If it dumps black smoke on start up then maybe something is fouled up? Pull your spark plugs and make sure theyre not toasted.

Sounds like the computer is telling the engine to run rich for some reason and the air/spark ratios are off. Sounds like a sensor of some sort to me.

If youre comfortable enough with this, disconnect a fuel line and turn the car over. It should shoot fuel pretty decently, which would eliminate the fuel pump theory.

Im not a pro by any means, just some guesses.


#17

Thanks for the advice everyone, I think I’ll just replace my fuel filter since that needs it anyway and go from there. For my education, why would this happen only in hotter weather? My engine isn’t overheating and fuel shouldn’t be affected by outside temperature should it?


#18

Only happening in hotter weather would further indicate my guess of a crank position sensor or cam position sensor. Those, from what i have read, can be temperature sensitive, and fail when they get too hot, then they cool off and the car miraculously works fine. Again, a total guess but, i do think it sounds like a sensor of some sort, not something mechanical like a fuel pump


#19

Wouldn’t I get a CEL with a sensor though?


#20

If a sensor is skewed, the pcm might accept the sensor’s output as valid