what am I doing wrong. 1.8t vacuum leak

i was having miss fires and a too lean code on my passat. cold engine would not rev past 3000 with out hickups

code reader (torque app and bt odbii) said reandom missfires and too lean

i changed the plugs and coil packs it was a bit better but I had some oil in the plug well. I figured my pcv system was shot.

replaced the prv (puck) valve and the misfires codes (mostly) went away getting to the lower pcv is a bitch ( so i haven't done that yet) but i found more vacuum leaks

so I replaced the suction jet pump and associated stuff. and found that the "bulkead join" for the brake booster was leaking, replaced that. changed some suspect clamps etc.

still too lean. long term fuel trim goes up to 25% after about 30 - 40 min of driving and throws the code. (this is better used to be 15 min)

so I thought spray some starter fluid and see when the engine sped up. nearly cold engine.

nothing. not even spraying on an open vacuum port on the intake manifold. is there a better fluid to spray brand etc. i thought i would only need to be close to the leak to cause it to speed up.

also is the blue circle where my MBC will go when I fix all this E36 M3.

not my car but you get the idea.

25% seems like a huge amount. Either a giant vacuum leak, or a serious lack of fuel. Pump okay? Replaced the fuel filter in recent history?

The lack of response to the starting fluid's kinda funny, too. I don't have a great theory about how that's not having an effect. Try spritzing some right down the intake snorkel just to see if you get what you expect?

In reply to Ransom:

i thought 25 was hige too. but it looks like thats where it throws the code.

the starter fluid was the thing throwing me off. a lot. i can try it else where in the system. like the snorkle

is there a brand of fluid that people think will work better. I just bought what was on sale at autozone

didn't even think it might be pump or filter related.
I no longer hear a leak but i suppose it could be so big that it doesn't whistle.

fearing a bad 02 sensor, reading lean when it isnt so the car keeps tryign to rich it up.

Is it idle fuel trim or load fuel trim? Idle fuel trim would be more of an air leak issue and load would be something more like the MAF.

The PCV under the manifold has the highest failure rate on the 1.8T. You'll need to replace all the hoses to it also.

But really at this point it seems to make more sense to smoke test the intake and crankcase system. Whether you do it yourself or pay somebody to, it should be cheaper than throwing more parts at it.

In reply to NEALSMO:

HMM. remember this is using torque. the long term fuel trim just keeps moving up untill i get MIL. seems to idle the hickup is definitely under load. if i go slow it works fine.

so far I have been throwing cheap parts and vacuum hose ant clamps. i could have lots of failures here. the car is 15 years old my mother in law gave it t me and my wife drove it and i ignored it mostly. now i drive it and i am annoyed.

i suppose i should just bite the bullet and do the damn pcv then I can rule it out. should help with the weepies.

so if at idle the short term trim is mostly stabile then its not a leak? or i suppose i could clear the codes and idle it for an hour and see if the long term trim moves up.

A couple things you could check free or almost free....Verify that your fuel pressure is at spec. Low fuel pressure will definitely create the symptoms you describe. You can usually rent pressure gauges at the local parts guy.

I have little experience with VW, but on some cars you unplug a suspected MAF sensor and the ECM runs the engine off a programmed default. IF this car can do that simply unplug the MAF and if the car runs much better then you know the MAF is sending an incorrect signal. If the car won't run without the MAF plugged in then this won't help you eliminate the MAF.

One other thing I just thought of.... A tank of E85 or very watered down fuel will usually run the fuel trims to 30% really quick. Possible fuel issue? You can check for water/alcohol with an old water bottle and some water. I can describe that test if you need it.

Try a can of CRC emissions cleaner or a can of Cataclean. that might help if its O2 sensor related

In reply to appliance_racer:

i will try the MAF. it will run without it per teh webz and i didn't think of that one. google shows the same sysmtoms I am describing.

Check under the intake manifold some where near the the dipstick. happened to my roommates 1.8t golf and was a crusty vacuum hose that we found there.

Here's a good video that explains the long term, short term, and idle fuel trims and how to use them to diagnose.

Ross-Tech

If you aren't familiar with Ross-Tech, you should be as long you own a VW/Audi. Lots of great info on their site and youtube channel.Ross-Tech

Misfires can be caused by coils themselves and also trigger a lean code due to the misfire. If you are getting individual cyl misfires, move the coils around to see if they follow the coil or not. If this is an AEB code engine there is a separate ignition module that can also be an issue.

In reply to Paul_VR6:

I replaced the coils and plugs. I was getting misfires on all cylinders. the are gone now.

In reply to revhard:

that one was waiting for a warmer day, along with the pcv. its moved up on the list.

Something else I thought of that would be free to try would be to see if the Cat Converter is damaged. The ignition misfire basically allows un-burned fuel to enter the catalytic converter and that raises the temp of the core above it's melting point. When the core starts to deform and mess with the exhaust flow goofy things can happen with what the O2 is seeing. I don't think that is likely the case but it crossed my mind later this afternoon.

more information. i cleared codes (and long term fuel trim) and idled for 20 minutes. short term trim and long term trim are zero

then i drove 3 miles lterm fuel trim is at 8%. short term fuel trim drops back to 0 ( i was parked when I took the second picture.)

you can also see at idle my "boost" was -11 ish. whn driving foot of the gas it goes to -12.7. before i started fixing leaks it would not go lower than (higher than) -10 psi. so the leaks were real.

the fact that my 20 min idel was 0 ltfuel trim menas i got most of the leaks yes?

my problem is the fuel trim under load.

thats all i could do this morning

I didn't catch the part about the coils, good. If your ltft is low at low load and goes up as load goes up it's usually a fuel delivery problem. It's relatively easy to flow the fuel system (by time) out of the return line with the fuel pump relay jumpered. Flow specs should be in the service manual.

The improvements on vacuum and fuel trim mean you definitely fixed A problem. By your last statement of "under load" leads me to believe you really should look at fuel system.

Just an FYI, The short term trim is based on the long term trim. For example if the long term trim shows 10% and short term shows 5% thats actually 15% off of programmed fuel trim for a given air volume. Again I'm not a VW guy but that how the Korean appliances work.

That looks like you have a MAF or fuel delivery problem.

Do you have access to MAF (grams per second) live data?

At idle you should be at 2.3-2.5 g/s

At 2500 RPM in neutral should be at 10-11 g/s

At WOT (3rd gear for manuals) till you reach 4K RPM it should be at 130 g/s

(These are all based on a warm engine BTW)

If it doesn't meet those specs you have a bad MAF, which is a very high failure rate on VW/Audi.

In reply to NEALSMO:

At 2500 it's 70 cfm. Which is a bit more than 35 g/s At idle 700 its 26 cfm. Or 13 ish g/s. According to torque.

Unplugged maf it seems much punchier with. But stft at idle is very high. Plugged in its 0.

Stripped screw on air cleaner heat shield keeps me from parking lot maf spray clean

What is the code #? If it's the P0171 then you need to trace all hoses, vacuum and pressure side of the intake system. I had this code and found cracked vacuum hoses on the vacuum side and leaks at the connection at the intercooler in. Check everything.

smokindav wrote: What is the code #? If it's the P0171 then you need to trace all hoses, vacuum and pressure side of the intake system. I had this code and found cracked vacuum hoses on the vacuum side and leaks at the connection at the intercooler in. Check everything.

It's a too lean code, but i fixed a lot of leaks and can't find any more unless it's the PCv way under the intake. Too much snow to do that so I am checking there things. After fixing the leaks the electronic and driving off throttle gonna re vacuumy.

Did you check the "pressure" side of the air intake system?

In reply to smokindav: no.... crap

In reply to scooterfrog:

drove 150 miles in 3 trips withhte maf unplugged. curerd the major hicup i was seeing. no misfires. if the longterm fuel trim is correct it is adding way less fuel 2-3% instead of 20+ so either its nto working because it needs mroe than the 02 sensor.

here are my thoughts.

maf needs cleaning replacement. it was lying, saying it was passing way more air than it was, so it was ecu dump fuel to run richer but still to lean.

maf was working and i had a lot of unmetered air in the system so (vacume leak) and it needed the fuel. but it was smelling gas, but without the maf it smelled better. and perf was better.

thinking its the first i think the only way to know is clean and hope (still not known good but if its any better that would be confirmation) or replace with new (more likely good)