Throttle issues, surging, hunting, power loss.

[Greenm3]

Im having issues with the car running at the moment, the idle is good, but hunting ever so slightly, you can hardly see it on the tacho but can feel it. It does this at cold and warm when driving along at constant speed.
Also during gear changes the engine feels like it is going to die when you come back on the throttle, but i've tried keeping the clutch in to see what will happen and it drops down quickly but stops at idle.
My first thoughs are:

1 Air leak unmetered air entering through the PCV system so I'm going to check that, its probably that little ******* of a vlave come out of the pipe at the back of the head.

2 Lamda, no harm in changing this as I've just got a new turbo and my old one was pissing out oil.

3. My DV is bust, or ive got it around the wrong way from the turbo change. I hope not that would just be embarresing.

4. ISV, though i cant see how this would affect the enigne when I'm driving along at about 2-3000 rpm holding a constant throttle position.

5. The TPS, how do i check that it is working correctly?

finally 6. The fuel pump / filter /pressure regulator, how can i diagnose these?

I can't go around ordering losts of parts as I'm short of funds after the fitting of a re-built engine, and then a new turbo!

Any ideas or btdt's? Anything to narrow it down as it's very annoying just makes driving around town not very smooth. Makes me seem like a learner driver, I could ride the clutch to make it smoother but thats new as well and I dont fancy getting another one soon. Sorry for the long post!



Michael

[S2central.net]

Have a look at the technical chapter on Motronic at S2central.net - theres info on how to test the throttle pot amongst other things...

Could indeed be an air leak though...

Always worth remembering the life expectancy of lambda probe is ~60k miles

[UrS4boy]

Check your diverter valve:

Check this link to how the diverter valve is supposed to be oriented

You might also want to read some throttle position sensor info:

Click Here

But really, at the end of the day, my money is on the MAF. Several similar strange engine running symptoms have been cured recently when the owners cleaned and/or changed their MAF (don't break the hot wire !!!). Check the MAF connections too.

Click here for MAF info

[Greenm3]

Thanks for the info, I know its not the MAf as its only a month or so old and was working fine when i first installed it, suppose if i'm unlucky it could be but I think I will rule out the other things first.
Michael

[Greenm3]

Update: its not an earthissue, been outside with the multimeter, checked all the earths and the sensor earths that was as far as i could go as it got dark. I suppose it's a good thing, I didnt realy fancy ahving to do any wiring, though it doesnt rule out any issues with power getting to sensors etc. Though have notice my volt meter is reading a bit low (I think). What sort of charge should i be seeing whilst driving and stopped, could all these prblems be due to a rubbish battery?
The battery was completly dead a few weeks ago and would lose its charge overnight because it hasng been used for a couple of weeks, but after a long run it has been fine the past week. I'm seeing just over 12V most of the time.
How do i check to TPS with my multimeter? what ranger of values should i be seeing and when?

So many questios as usual, I want to rule out the lamda next, will see if I can get one for the weekend. Also would help if I could get it on Vag Com, is there anyone near Eastbourne with it who fancies coming to give a hand?

Michael

[Acidburn]

sounds like what mines doing atm, its been parked up for two weeks and the battery was dead so I jumped it and was getting symptoms like what your saying. My volt gauge is reading just over the 13 but i've been told it should be closer to 14 than what it is, i've just slapped the battery on charge to sort this out.

12v afaik is low and should be 13+

[4WheelDrifter]

Check the usual suspects first. The cheap tests like checking for fault codes, do a proper pressure test, and check the DV diaphram isn't split.
While you've got the multimeter out check things like the G62.

You should be seeing >13.5V whilst driving, 12V stopped.

[Greenm3]

Update, pulled the fault codes, first time i got 4431, ISV code. Secode time after clearing them the were no faults detected. Though this s the least of my problems because whilst doing this it pissed all its water out of a split i assume on the **** of a hose to reach at the back of the block. So got to repair that now!
SO could just be a new ISV, but doesnt the code mean "Open or short circuit, check circuit breaker or fuse for +12V supply" does this mean my ISV is broken or the wiring is dodgy somewhere.
Michael

[4WheelDrifter]

You can visually check the ISV to make sure it runs freely, and do the output test to check that it is working.

The leak at the back of the block is probably the plastic housing broken. Unless you have the metal 3B one?

[Greenm3]

The leak from what i could see was froma rubber hose going on to the block, though not all my hoses are the standard ones because of the rebuild. Are there any water hoses which go stright on to the back of the block? it seems to be under the temp sensor.
Michael

[4WheelDrifter]

The hose doesn't go straight onto the block, but onto a small housing that bolts to it. Sounds like you have a the usual split plastic ABY item.

[Greenm3]

Fixed it, it was the heater hose had split, checked the fault codes again, this time though didnt get the isv code got 2341, which is the o2 sensor. Which hopefully confirms my diagnosis of ruined lamda sensor.
Will change it and see if that helps, though odd that the ISV code has gone, must be intermitent. I dont fancy getting a new ISV anytime soon, the are pretty damn expensive!
Michael

[Knight Rider S4]

If you unplugged the ISv when the car was started or ignition on this fault code will come up

[Greenm3]

ah that will be it then i was checking it with the multimeter, so that will explain that code thanks!