rough running b4 v6

[peterklos]

Hi I have a b4 v6 which is running rough on idle feels like an engine with a real lumpy cam at idle plus when it revs to between 1500 to 2000 rpm it seems to hunt and is real rough running, after 2k it runs ok ??? have checked all the vacuum lines etc did remove dash recently

any ideas ???

regards peter

[jezza12v]

Hi, I have exactly the same problem just started with my 2.6E V6, did you ever find the problem with yours?

[peterklos]

Hi Jezza 12v i have been trying to find out what the problem is for some time but with no luck , some say the iac valve but that is ok , some say vac leaks , cant find any . i cant get the codes from the computer so stuck for ideas ?
i noticed it only runs rough after it heats up to normal temp ?
when you get yours fixed send me a email peterklos@optusnet.com.au
thanks

[jezza12v]

Yes, that's exactly it, it only happens when warmed up.....I'll be having a good look at it this weekend, I'll let you know if I find anything. Regards J.

[Aussie Wonder]

Have same problem. What was your solutions?

To be fair, I have replaced;
water pump, thermostat and timing belt
ICV (replaced)
new O2 sensors
all rubber vacuum pipes
All the filters - air, petrol and oil filter (new oil, all changes to service intervals)

Full service of injectors - which makes it a consistent high idle - no longer rough

Spark plugs work fine only 10000k - also has very strong acceleration.

items left, and getting more expensive
thermostat issues - checked and seems to give correct resistances
MFTS - but that doesn't feed the ECU???
Throttle potentiometer and idle switch - checked variable resistance (need ranges confirmed 800 - 2500) and switch is working on/off
ECU - not getting codes using LED in fuse box. not even 4444??


This engine does not have EGR system. No valves of things to worry about here.

Engine starts and idles 1100rpm while cold. Normal warm-up.
Once warm, it idles 1300rpm +/- 100rpm, and does not drive easily, surges at low rev speeds. Similarly, deceleration is non-existent.
Cleaning the injectors took out the lumps in the idle, and has made it silky smooth fast idle when warm.

Any pointers please.

[jezza12v]

Hi, well repacing the O2 sensors sorted mine, yours seems to be more of an idle speed problem, the only thing I can suggest which you don't seem to have done is replace the temperature sender that feeds the ecu. If the car thinks its cold the mixture will be rich and as I understand it the ecu will open the throttle to keep the O2 values correct...? J

[peterklos]

HI Aussie Wonder
first where in Aus are you located ?

I still have problems with my v6 I have replaced the same items as you and still no better , i thought the o2 sensors would have fixed it but still the same.

it is my wifes car and it drives her mad ok when accelerating but back off the pedal or when idle plus when you set off from start it has a big lag as if their is a vac leak and it is too lean !

any ideas appreciated , Audi service up here in Qld expensive

regards peter

[dsl55]

guys, not sure if you are all sorted now but i have just sold my v6 cab and had same problem, some days it would be fine, some days it would be really odd. some days it would idle at 2000rpm and others it would hunt really erratically. my mechanic plugged it into the diagnostics and found nothing wrong, checked for air leaks etc so all he did was reset the throttle settings through the diagnostic machine and it cleared the fault completely! cost me £10 so worth a try!

[jezza12v]

Have you looked at this? If the evap canister purge regulator valve is open when it shouldn't be for some reason this will upset the vacuum in the throttle body. Disconnecting mine when the engine is warm makes no change, disconnect it during warm up and the revs are up & down.

12v Pages - Maintenance

[greddy15]

try turning off the air conditioning, your compressor/ chiller may neeed replacement. or it maybe the alternator, turn on the engine and look at the belt drive to see if a metal part is vibrating. both were problems on my a4 maybe its the same?