VW Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hey fellas. new hear and looking for some advice. I have a 2003 jetta 1.8t that keeps getting a P0172 CEL . It comes on in about 100 miles after resetting it and its due for emissions. Some times it has a little bit of a rough idle. Sometimes when i start it up cold it misfires then clears up. sometimes its perfect.

The car has had a lot of stupid issues lately so a lot of the "common" causes of this code have already been replaced. and this is the only code that has stuck thru all of the repairs.

Brand new VW maf sensor
replaced the cat with a known good one from another 03 1.8t jetta
replaced the fuel pressure regulator
fixed a air leak from PCV to VC to DV.
New set of NGK plugs gapped at .030
all 4 coil packs (one at at time bc they suck)
timing belt was done like 10k miles ago.
checked for vac leaks with no success other than that PCV hose.

Im really lost on what to do. I hate just throwing parts at it but it seems like there are no answers anywhere except for stuff to "try"

thanks for your help
-Kristin
 

·
Premium Member
Joined
·
9,716 Posts
def sounds like a vac leak.

could also be a hole in the turbo inlet pipe / intercooler piping

also check under the intake manifold.. if its stock and not gutted out like mine is.. theres a black bracket from factory attached to the intake manifold.. its by the oil dipstick..
under that bracket theres a rats nest of vaccum lines / pumps / plastic connectors.. notorious problem starter for vac leaks and this code.. its a PITA to get in there to check each tiny hose.. some are extremely short. theres also two small nipples on the bottom of the intake manifold for vac lines to connect as well.. and another on top of the t body everyone looks past.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #5
hmmm..thanks guys. I did some vac leak testing with some brake cleaner but didn't come up with anything. I'll do a thorough check down under the intake manifold. Did replace the dipstick rather recently, maybe broke something off at that time.
 

·
Premium Member
Joined
·
9,716 Posts
thats a possibility for sure.

those plastic connections get extremely brittle over time.. hot / cold constantly and then you so much as look at them and they break.. i swear.

also.. you said you just did the pcv system also..
did you replace the upper hose / pipe for the pcv.. or the bottom as well?

ive seen numerous people replace the top hose.. because it was split etc.. and never bother with the bottom tube.. which usually almost always splits while trying to replace / repair the top half.
just food for thought.


also did you replace the pcv valve itself? its pretty cheap.. like 10 bucks i think.. something like that.. might be worth a shot also.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
did a real thorough check today for vac leaks. I came up with nothing. sprayed around everywhere and had absolutely no change. Not sure what else i can try
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
Had the car smoke checked. couldn't find a vacuum leak anywhere. Im stumped and really need to get this fixed asap
 

·
MK4 & MK5 Owner
Joined
·
8,444 Posts
The code is for a rich running condition. Is the fuel filter new? Air filter new? Any exhaust leaks before the o2 sensors? Downpipe gasket/manifold gasket. Fuel injectors clean?
 

·
Registered
Joined
·
517 Posts
Do you have a scanner with live data capabilities?

If so, look at the fuel trims. Both long term and short term fuel trim levels.

P0172 is a rich condition. This is not caused from a vacuum leak.
A vacuum leak would show a lean condition and high positive numbers on the short term fuel trim.

You have a rich condition, possibly from a leaking fuel injector. Your fuel trims are probably high negative numbers because the ecu is trying to correct the rich condition by reducing injector "on" time.

Pull the plugs, look for the one with the most soot. That could point you in the right direction as to which injector is leaking.
 
1 - 10 of 10 Posts
Top