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Discussion Starter · #1 ·
not sure if the garage is a better place for this (mods feel free to move it)

I am trying to troubleshoot a P1136 intermittent, and read a whole lot here about this. consensus seems to be vac leak, dirty/bad MAF, possibly fuel inj and supply issues, ...

so, i tested with boost leak tester, no hissing at all. only very faint gurgling in the oil cap. maybe I still have a minor leak. I can retry with spraying soapy water over connections, or run it and spray some starter fluid. re-tightened clamps for a few vac hoses and IC tube.

I also did a full log to WOT for the MAF. I did this stationary. Do I need to log these on a road test? not clear on that, other posts keep referring to 3rd gear pulls.

So, MAF values at idle (all at 90-92 Celcius) are around: 2.x with a couple of dips to 1.97 and 1.92

elsawin tells me spec at idle should be 1.80 to 5.60 g/sec
vagcom measuring blocks say range is: 2-4.5 g/sec. As was the case in the past, I am inclined to not take the vagcom ranges as very reliable.

For 6160 rpm it shows its highest reading at 29.53 g/sec (some serious sucking going on!) and on the way there the MAF values change with the RPMs.

car is a 2000 1.8T. no other codes.

idle trim is 2.x%, part throttle at -0.8%

just passed CA smog check with flying colors a month ago, phew! (I did it early thinking, I have no CEL might as well do it now).

I cleaned the throttle and serviced the PCV system at about 4000 miles. There was barely any trace of oil vapor in the TIP to IC path. New stock plugs and AF about 2K ago.

I also did a TBA via vcds, just now, thinking I haven't done it quite some time. I cleared the codes, but haven't driven it too much so not sure if the P1136 will come back after all readiness monitors complete. would it register again immediately, before the ECU relearns fuel trims?

Also, elsawin says nothing about possible MAF issues for a P1136 but it seems most posts refer to that a possible source of this problem. My MAF was replaced on recall a few years back.

TIA for any help or recommendations.
 

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Check the lines coming from the N75 valve. Previous owner of my car had issues and codes, and a loss of power that resulted from the N75 feed line off the turbo tearing somehow. They replaced the MAF initially, only to find later that it was that little hose. Also, don't rule out the check valves and vac lines. They don't always show with a boost leak test, especially newer motors which have solenoids or little pumps that control them. You usually find those vac lines, pumps, solenoids beneath the intake manifold.

Also, wouldn't be a bad idea to hook a fuel pressure gauge up to rule out pump, and regulator.
This is where I got that advice: http://www.passatworld.com/forums/4...ussion/151551-help-cel-p1136-what-causes.html
 

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not sure if the garage is a better place for this (mods feel free to move it)
so, i tested with boost leak tester, no hissing at all. only very faint gurgling in the oil cap. maybe I still have a minor leak. I can retry with spraying soapy water over connections, or run it and spray some starter fluid. re-tightened clamps for a few vac hoses and IC tube.

I also did a full log to WOT for the MAF. I did this stationary. Do I need to log these on a road test? not clear on that, other posts keep referring to 3rd gear pulls.
To me, an error code of P1136 (lean) with fuel trims that are well within specification (10% LTFT/multiplicative, 6% for STFT/additive) seems a little hard to understand. But the code is the code and the numbers are the numbers.

I think the consensus on the boards here is that most common cause of lean codes in these cars is vacuum leaks, but an aging MAF can certainly give you one since the more frequent mode of failure is underreporting of air flow.

If you test the MAF, it has to be a WOT run (second gear is fine) with the engine under load. With no load, the turbo does not spool: the air flow numbers you get without the turbo are clearly going to be quite different.

If you haven't encountered it yet, do a search on "MAF sanity check Ross-tech" to get to the most cogent explanation of fuel trim numbers I've seen. This includes a suggested formula for estimating if your MAF is functioning reasonably: expect about 0.8*(hp) in grams/second for a properly functioning MAF.

For a chipped 1.8T, that comes to about 165-170 g/sec (=0.8*210) but will be a bit lower for a stock AWM (=0.8*170 or so).

------------

Addendum: sorry, you don't have an AWM but the formula still applies to whatever the rated hp.
 

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If your fuel trim numbers are good and lean code is intermittent, I would suggest replacing the PCV. Check the freeze frame for the code and see if it's been set while idling. And check the fuel trim number when it's been set.
 

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Discussion Starter · #5 ·
Ok, I will log a WOT run in 2nd gear but after doing some calculations with gear and final drive ratios to see what my top speed will be it looks a bit jiffy. At 6160 rpm, in 2nd gear I will be at 56mph and where I live its hard to reach that speed on most roads including clogged freways. Do I need to wake up at 3 am on a Sunday ... the things I do for this car.

Is it okay if I go wot in first gear (30-smthg mph)? Are all gears rated for wot rpms? I have a 5MT still with the stock gear oil and it meshes like butter so I don't want to mess that up.

I guess all we are after is forcing about 120 g of airmass per second through the MAF to see if it will report it, and we are basically using the turbo as a very powerful vacuum. (By my calculations that is equivalent to about 200 cfm!)

Gigi I have a 2000 ATW (150 HP) I don't think they had freeze frame data yet.

I'll recheck the PCV system and valves but I went through it a little while back and replaced the PCV valve, dogleg, SJP. I don't have any VC leaks.

Can I use a propane torch fed via a tube around various connections as the engine idles? I'll do it in a well ventilated area, but I also wonder if the ECU will be smart enough to compensate for the richer mixture. Can I unplug the throttle (it is a DBW) ?

Thanks for all the help again.
 

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I have never tried 1st gear for MAF testing nor read about others doing it. It might be fine or it might be the load is a little bit less than you need.

Because load is basically a percentage of momentary over maximum possible airflow, if the turbo isn't completely spun up, the number will be artificially low. I'd just try it and see. If it's lower than expected, go for a second gear run whenever you can to be sure.

I don't think the ECU is fast enough to compensate for very sudden mixture changes, so you should see a little stumble with the propane. I'd let someone who's done it comment on that, though.
 

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Discussion Starter · #7 ·
Now, two codes. Yes!!!

bvariant thanks for all the guidance.

I was able to do a few 2nd gear pulls to WOT but windows laptop crashed badly so no log file. Hard to not see this as some kind of sign. So now I am only left with the option to try to set up vcds on my wife's macbook air and that reads like a recipe for any good masochist.

A couple of questions I have:

1) during the pulls i kept it gunned and at some point I looked and the needle showed over 7300 rpm. Where is the Rev limiter at? I need to keep my eyes on the road when I do these pulls so I would like to rely on a Rev limiter being there. I really don't want to throw a rod.

2) I now have two codes (p1136 p0441) . Yes, baby give it to me, give me all you've got, not just two. Two is cake for a B5er right? Anyway I replaced the n80 a few months back. I don't have any hard start problems after a fillup, I don't overfill, I don't smell gas in the cabin. Would these two codes now point to something more definitive?

3) I pulled the vac hose coming off the intake behind the alternator (for DV actuator?) and the engine stumbled. When I remove the oil cap I get suction and blow alternating fast. I would like to think both of these are normal. Vac at idle is 22 inches. I also removed and cleaned the MAF and airbox.

I plan on taking various hoses apart and check for leaks and broken check valves I may have missed.

If and when I get the Mac set up for another wot log, what blocks should I be logging? I used groups 3, 32 and 115 (rpm, air mass, ..., ltft, stft, boost requested, actual ...) on the first run.

I am beginning to envy the guy whose gf cut his timing belt. I am still trying to break up with my German psycho-bi..., err ... i mean, princess.
 

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Discussion Starter · #8 ·
I was able to log the MAF and it went up to 126 g / sec on most runs, and on one run it went up to 132.

So does this mean that the MAF is okay? My engine specs say it peaks at 150 HP.

I also tested the N80 and it seemed to work, but not really. After a few actuations it gets stuck. This is only a few months old. Ill replace it again this time i am thinking of getting the much cheaper Audi B7 N80 since I have an adapter plug lying around. Anyone have any thoughts on going with the Audi valve?

In the meantime I am wondering if a stuck N80 could be the cause of the P1136 and how.
 

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From what I have experienced, If the purge valve (n80) was stuck it may cause a lean code but it will usually throw a evap purge incorrect flow , or evap leak detected. But you never know replace it and retest.
 

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The N80 is a bit like a 5th injector so when the ECU decides to pulse it it assumes it will see a richer mixture so it pares back what it sprays via the injectors. If the N80 is stuck closed the ECU has no way of knowing that directly, but it will hear about it from the O2 sensor reporting a lean condition.

The N80 is pulsed at part throttle and its probably responsible for more fuel delivery than just a couple of whiffs of gasoline vapor.

I have only had the 441 by itself only and it was the N80. I don't know about the Audi valve, they may have different duty cycles, but the VW valve is bloody expensive for what it is.
 

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Discussion Starter · #11 ·
Update time.

It's been a while now that the code is gone, and changing the N80 canister purge valve did it. I went with the Audi one as stated above, much cheaper and so far it works perfectly.

Thank you, everyone for the help. I learn a lot every time I come in here. Very knowledgeable and helpful folks.
 
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