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Bad Idle, gas fumes, limp mode? after some work

5.6K views 28 replies 11 participants last post by  vwb5t  
#1 ·
So I'm not going to say what I did, but recently I took off my intake manifold, valve cover, throttle body, coolant tank, fuel rail, and fpr. Replaced all the gaskets, flushed coolant, changed oil, deleted my pcv system am now just venting it into the atmosphere straight off the crankcase.

I did a lot of work and everything went smoothly, pretty positive I have all the hoses/clamps/sensors all tight and attached. But I'm having a couple problems.

Car in question is an AEB 1.8T.

First one is I have a bad idle when the revs come down. When I start the car it'll turn over fine then almost stall out, bounce up and down between 400 rpm and 1000 rpm. Then it'll idle fine after about 4 bounces. Also if I'm just accelerating and get off the throttle and am in neutral, when the revs come down it'll do the same thing.

Next thing I noticed is my car has some smells of gas fumes when I get in it. Not really sure how this happened but really need some input to what this could be.

Lastly, my car feels like it's in limp mode all the time and won't get out of it. It is chipped but for some reason, it'll boost to 4psi and just sit there at WOT. Any clues to what this could be.

I also detached the battery cables to do some things so my ECU was reset which I thought may be the problem since the ECU hasn't adjusted yet to the new timing (idle problem?)

So...what I think it is, is my FPR. I don't know how this could be but it kinda makes sense for these problems. Not sure about the gas fumes but if the fpr isn't regulating the right amount of fuel when the revs change, that's why it'd idling bad. And when boosting it's not putting in enough fuel when it needs to be. But other than these problems, the car runs totally fine once moving and accelerating/cruising. Just when the revs come down and accelerating fast it's weird.

I'm gonna test out my buddies 4bar tomorrow and see if that changes it but I'm really clueless to what the problem is. Any help here would be greatly appreciated or any experiences with the same problems.

Thanks. :thumbup:
 
#3 ·
Hmm interesting. No I never have. And that's wierd that you say that it went bad instantly. Because a week ago before I tore everything apart it worked fine. I'll swap one out and see if that helps. thanks for the quick reply :thumbup:
 
#6 ·
First, you need to adapt the TB. That's why your RPMs are all wonky.

I could almost bet that the FRP and MAF are fine. you didn't touh them, their not going to fail just sitting there.


The smell is your attempt at deleting the PCV. It's coming right out of your crankcase, hanging out in the engine bay, then getting sucked in thru the vents. You need to route a tube from the crankcase to outside the engine bay. I think vwb5t did something like that.
 
#7 ·
Good to hear that the TB is the idle problem. Gonna check it our real soon.

Yeah I didn't touch the maf, I did however take the fpr out and then put it back in, but doing that shouldn't have done something that big.

And I did use some radiator hose to vent the crankcase. Just used some radiator hose off the plastic "chicken wing pipe" and had it vent down behind the tranny and subframe, right next to my downpipe. Maybe it's not long enough? I made it pretty long so it vents straight to the ground but i dunno...
 
#9 ·
I'm getting pics tomorrow dum dum...but I'll text ya anyway to make you happy haha. And I did run a line down from the crankcase to dump it down. But i'm pretty sure it comes out near the center console, and that's what is causing the fumes to be smelt in the cabin.
 
#14 ·
i deleted all that on my car, but i kept the puck valve i ran from the breather adapter on the block to the puck valve then ran another hose to dump in just behind the drivers axle on the ground, never got a gas or vapor fumes in my car.

question when you removed and reassembled the injectors and FPR di you use new gaskets? you might have a slight leak causing the fumes. also did you unplug anything as you took it apart? check all the plugs to sensors and make sure they are secure.

oh and i deleted my PCV cause i had it al written out for my BT program and then i stripped it all to save weight on the car, you'd be surprised at how much all that crap actually weighs
 
#16 ·
how about we stop the off topic posts and work on this dudes issue, start a new thread if you guys wanna argue over it. :poke:
 
#19 ·
they shouldnt be, hell i got rid of the purge valve as well and had no fumes

by chance what did you do and what else did you get rid of, PM me if you dont wanna spill the beans on here
 
#22 ·
I've deleted both the evap and pcv system. I kept the purge valve connected to the harness and the bottom hose, but took off everything else. It's just tucked behind my fender now...

For the pcv, I deleted everything, plugged the hole in the turbo inlet where the puck valve was. Then just used the plastic tube that was already on the crankcase and connected a hose to it, which vents down by the tranny. I can get pics if you'd like but it's pretty self explanatory.

I also just got done with the vagcom. Did the throttle body adjustment and it is still idling bad. I got the usual code for my evap being deleted, and my 2 misfiring coilpacks which I'm aware of. However I did find two new codes that I have not seen before.

One was this:

18010 - Power Supply Terminal 30: Voltage too Low
P1602 - 35-10 - - - Intermittent

And the other:

17954 - Boost Pressure Regulation Valve (N75): Short to Plus
P1546 - 35-10 - - - Intermittent

I've been reading up on both, the N75 one seems to be like a loose connection somewhere with the wiring. I DID fool around with it, which was only tucking the wire somewhere but nothing else. Don't see how the wiring could get harmed from that. I checked it a bit ago and everything looked fine on the harness. But this may be the problem with my idling and boosting? I dunno. I'm gonna try and swap a different n75 in and see how that works.

But the voltage code is interesting. I read some stuff on it and it's saying that it comes up on chipped cars when you pull off the wires on the battery. People have said that this can lead to less boost (which I experienced) and that i'd make the car idle like crap. So it seems like somehow, my ECU is being reset every time I turn on my car, making it run bad every time I drive it.

Any input on these would be great.
 
#21 ·
limp is a boosted passat issue where the car actually cuts the boost and fuel on the DBW cars, its not a DBC thing like he is discussing.
 
#23 ·
theres your boost issue, same thing with a buddies 99 ended up being a short in the water proof boot on the plug end he too was boosting 4psi until we fixed it.

as for the rest did you plug and cap the evap holes?

the power code is just a code that comes up when you pull he battery off, its there to tell it was pulled that was it, its not tied to boost control
 
#24 ·
Yeah hopefully it's just the valve and I can replace it w/ no worrying about wiring. Do you think this is the idle issue too?

Yeah I plugged the smaller hole on the tip for the evap which was the only one I needed to do. Only other plugs I have in the bay was the bigger one from the pcv on the tip and the one behind the TB on the intake mani. Checked them today and all are in place and tight.

And I cleared all the codes so that power one shouldn't come on again.
 
#27 ·
Why would you get a fuel smell from venting the PCV? You could vent it to your nose and you wouldn't smell fuel. Unless for some reason you have fuel in your oil.

My guess is you didn't seat the injectors correctly, or you bent the fuel line going to the fuel rail too much while maneuvering it around and there is a crack at a joint where the hard lines run along the firewall. Have a friend start the car for you after its been cold for a while and the fuel system has depressurized and while you're looking around the motor. You should see fuel dripping or squirting out from somewhere.

Give the injectors a good push into their seats too. Did you use new Injector gaskets?
 
#28 ·
So I figured out the sensor for the n75 valve wasn't connected securely, somehow...so I fixed that and now I have boost! Very nice to have that back ha. But the idle issue is still existent. I'm gonna see if it goes away tomorrow since I'll be doing a lot of driving but I'm hoping it's not something else.

And silverstoner, I'll check on the fuel injectors. I had a feeling that could have been it but it looked like they were seated right. NO I didn't use new injector gaskets, didn't even know there were gaskets for the injectors. Unless you're thinking of the intake manifold gasket right beneath that...which I did replace.