I noticed last night that there are some slight hesitations on WOT, 3rd gear from 2000->4000rpm. After 4000 it kind of "kicks in" and pulls strongly and regularly. I trashed it a bit on the way home and there were even 2 times when it did not pull at al until 4000, it was like shuddering all the way.
So, got home, checked for error codes, got none. Looked then at the group 032, readings were: +5.7% and -3.9%. Which means, if I'm reading it correctly, lean at idle and rich under load, indicating a split hose somewhere. Checked a bit under the bonnet and the only obvious thing was the DV (007p) wasn't fastened properly on the bottom, the clip was way too low and there was oily deposit on the TIP. So I took it off, gave it a clean/greasing while at it, and fastened it back properly. Then went for a run and nothing changed unfortunately. I also checked groups 015 and 016 and after waiting a minute or so saw 1 misfire on cyl 2 and 4 each. Waited 3-4 more minutes, no more misfires.
Finally today I managed to make some logs in 3rd, from 2000-ish to 6000ish, WOT. Would appreciate any input on them.
From what I can tell:
- boost builds up too slowly (feels rather like my previous k04 car, which had a pretty serious turbo lag; until this problem appeared I actually liked it a lot that pedal response was very good and lag almost non-existent)
- MAF reading is a little low
Finally, car specs: 25th anniversary golf, 1.8t auq. Mods: revo stage 1, 007p and forge shortshift.
About 1 month ago: looked around from under the car, no obvious oily spots indicating leaks.
About 2 months ago did: injectors check, new plugs (pfr6q).
About 5 months ago: new coilpacks.
Thanks a lot for any ideas
p.s.: I am thinking about buying a boost leak tester (have actually one but gave it to a friend when I sold the previous car and it's now 1500km away), but I don't have a compressor. Anyone know if it's possible to use it with a bike pump?
Lol @ expecting a 40 min response
* Your boost is coming on slow. Check for pre-o2 exhaust leaks. In particular, pre-turbo leaks.
* Your AFR actual is really lagging behind your AFR request. Could be a bad o2 sensor. Could be a pre-o2 leak. Could be something else. Check for pre-o2 exhaust leaks.
* You have a lot of timing pull. This could be because your IATs are high. But more than likely it's the engine pulling timing due to having to correct fuel and whatnot because of problems in the system. Go check for pre-o2 exhaust leaks and also intake leaks.
* Your MAF numbers look good in terms of peak numbers and they follow the trend of your boost nicely. I don't see anything that leads me to question the readings of the MAF
* Check to be sure the line from the n75 -> wastegate is holding pressure properly.
* Your log was very short. Did you take it in second gear?
* What's showing in block 032?
* Test to see what PSI cracks your wastegate
There are posts stickied at the top of the forum telling you how to test for intake and exhaust leaks.
Last edited by groggory; 05-28-2012 at 04:20 PM.
Thanks for the good analysis. I wasn't expecting a 40 min response, there are some days between the two posts
Here are some answers to your points:
- boost coming slow - right, this is exactly my feeling, as I wrote in the original post
- short log - was done in 3rd gear, from 2000ish to 6000ish. I'm not sure why it came out so short, could be because I'm using vag-com 3.11?
- leaks - as I wrote in my first post, this is my suspicion as well; I'm trying to get a compressor from somewhere so I can use the boost leak tester I have
- group 032 values are also in the first post, they read +5.7% and -3.9%.
I took a look under the bonnet yesterday and noticed the line to the green pcv valve was almost disconnected and there was moisture around it, I guess it wasn't fastened properly. I fastened it best I could, HOWEVER, I noticed that the line coming from under the manifold doesn't connect directly to the green valve...there's a short piece of connecting hose in between, with a piece of white piping inside it. Is this how it should be or a patchjob of someone? I anyway ordered the euroject pcv hose kit (y-hose and s-hose) and plan to replace them soon.
Thanks again for the nice analysis!
The stickies are about vac/boost leaks. Maybe it's my problem that I'm not a navtive english speaker, but by "exhaust leak" i understand a leak which is after the exhaust manifold, like downpipe or flex pipe or something. And those I've no idea how to find, except to look carefully under the car
And when that problem is fixed, I think many of the other problems will go away with it.
...soo.... Go do the exhaust leak test. It'll take less than 1/2 hour to do and will tell you for sure whether you do or don't have exhaust leaks.
Once you find them the next step is fixing them. The difficulty in fixing them will depend on where the leak is and whether any damage has happened due to the leak (such as blown gaskets).
Cheers guys, never heard of this seafoam thing...must not be big in europe?
I'll try to see what I can source here and try it out.
Also, boost leak tester and cigar lighter powered compressor are on the way (I'll get them next week), should help a lot in finding the leak.
When you say blown gaskets, which one do you mean? Can they be inspected with the naked eye?
The seafoam test will inspect your gaskets for you. If you don't see smoke, then they aren't leaking. Simple as that!
One little trick I've learned on the seafoam test is during the last stage of the test to have a friend hold a rag over the exhaust pipe or stuff it in lightly. This will increase backpressure in the pipe and make the smoke come out heavier from any leaks.
The gasket between the turbo and manifold gasket, manifold to cylinder head gasket and the turbo to down pipe gasket can all leak. To be honest there is not much visual inspecting you can do. I'm sure the Euro guys have some way of checking for leaks in the same manner as the seafoam method. If you have tools you could start checking to make sure that the manifold to turbo bolts are tight etc.
Wow, seems seafoam is hard to get in Europe. I was just looking.
I hear seafoam is sewing machine oil and Naptha.
Sorry, I'm not sure what you should use.
As boost leak tester and air compressor will only arrive next Wednesday, took a bit of time today to visually/manually inspect the engine exhaust to turbo manifold and the bolts seem nicely tight. So, no dice...yet!
I also saw a bit of wetness on the back of the combi-valve, towards the cabin...is this reason enough to worry or to think about replacing the combi-valve?
Ok, got the boost leak tester and found the problem: someone split (for whatever reason) the manifold-to-FPR hose and used a junction in between. The bottom part (coming from the mani) broke and was hanging out of the junction. It literally blew air in my face when I pressurized the system.
So, I put it back together and now the car runs perfectly again: no hesitation or stutter, at half-pedal or WOT, pulling strongly from 2000+ to the redline
Thanks again for all the help!
ps: after repairing the host and pressurizing the system, the pressure dropped VERY slowly and I could hear a slight hissing in the turbo area, behind the engine...coming from inside somehow. I guess this is normal?
Regarding the hiss, not normal.
Keep testing til you figure out where it is
So wait, are you saying that if I pressurize the system, it should hold that pressure in indefinitely?
Now after pressurizing it, it's dropping very slowly. The hiss could (I guess) even come from the air going past the throttle body and escaping out of the crankcase? It's for sure an "inner" hiss