VR6 throttle oddity

[Cnut 0]

i would check tps and wiring to it.replaced mine and it has cured throttle respose on a mk3 sc vr.

 

I forgot to mention that jerkyness only occurs when the engine is hot, when cold it is smooth.

 

I have now replaced the fuel pump but that hasn't made any difference. Surely if the tps was faulty it would exhibit the jerkyness hot and cold?

[dr_mat 0]

When cold it's running uber-rich, overfuelling always makes it run smooth.

When it warms up it's trickling the bare minimum of fuel in to prevent it from stalling, everything has to be in absolutely perfect condition to make it run right in those conditions.

[Jim Bowen 1]

mine has similar probs but only when cold and for the first couple of miles, goes away quite quickly and drives fine

 

i know my coilpack or leads are a bit dodgy as when they get wet they spark where they shouldn't

[adevr6 0]

my symptoms were high reving when the engine was cold/revs hunting when hot.new switch and wiring to throttle switch cured it-instant power!!!

[mr_fusion 0]

Right, looks like this thread is being brought up yet again...

 

I have been experiencing really similar problems recently, been through most of the checklist to no avail.

 

I fitted a magnex cat-back, decat pipe and raceland 6 -branch header and new lambda probe recently, all working lovely.

 

Then, recently when pulling away when the car is warm the kangarooing starts when changing up from 1st to 2nd gear (from traffic lights etc). This only happens when pulling away in low gears. If I am a but more sedate on throtttle, the problem I can usually avoid the problem. MPG has also been rubbish (13-17mpg around central london)

 

Other symptom is that the idle rpms will hunt slightly between 650 and 1000 rpm every 10 seconds or so when sitting stationary.

 

VAGCOM was throwing the classic 00533 code - "adaptation limit not reached" (idle), which is why I started with the ISV

 

I know the carbon canister solenoid isn't working as the cable was shorting out and frying the ECU relay 109, so i disconnected it. Would this exhibit problems like I am having. Its been unplugged for several months now (since when the rotrex was fitted on my old engine before I blew it up) and never had these problems till now.

 

Ok, things I have checked / changed:

 

New 2nd hand MAF

New 2nd hand ISV

New blue temp sensor

Cheked ignition switch (which is only 6months old anyway)

New wiring to lambda probe (old wiring was down to a few strands)

Cleaned out throttle body and associated parts (including new ISV and MAF)

TPS is fine. I cracked it open and cleaned it with contact cleaner. VAGCOM shows smooth throttle angle values.

I have some blue igniters on the way (should be here tomorrow) and a set of iridium plugs BKR5EIX.

 

I have removed the ISV damper completely now and replumbed the ISV in without it.

 

I pulled the existing plugs and the front three where wet and black, indictating poor spark to these from the leads perhaps?

I cleaned up the plugs and leads and refitted, car revs and drives much cleaner and more smoothly now but I still get the loss of power as mentioned above.

 

Dashpot is sticking a little i think as it doesn't seem to be damping the throttle at all now (needs a bit of WD40 i think)

 

I am hoping the new plugs and leads tomorrow will sort the issue, nothing else so far has and its proving to be an expensive month!...

[mr_fusion 0]

p.s engine is less than 6 months since fitted and has 70k on it (old one had 140k) - OBD1 with distributor

Clutch is 1 year old

Has new big end bearings etc, arp rod bolts (so on and forth)

 

and fuel filter is about 6months old also...

 

new lambda probe is a cheapo universal one however, might consider putting the old one back in as a last resort...

[mr_fusion 0]

right then.

 

put the new plugs and leads on this evening. engine seems to run smoother and quieter now but i am still having the same problem.

 

I am beginning to think its a fueling issue now, either FPR, Injectors or Fuel Pump.

 

I will pull the intake manifold of tomorrow and check the injector wiring as they have only recently been put back in after the new engine was put in and one of the connections may be dodgy. I will pull all of the injectors while I'm there to check if they are gunked up (unlikely though)

 

The fuel pump is the original as far as I know, can't say I ever hear it working away in the boot so its probably fine...

 

Any thoughts anybody i.e anything else to check I may have missed?

[mr_fusion 0]

Ok, pulled the injectors last night and ultrasonically cleaned them in meths 4 x each.

 

However, i think I may have worked out what the problem is....

 

I mentioned earlier that I had disconnected the plug to the evap purge valve... now realised that if its disconnected the valve stays open (previously assumed the valve opened under voltage and was normally closed).

 

So theoretically there is a permanent vacuum leak from the throttle body when the wiring is disconnected. (cleaning the injectors can only be a good thing though, so might help my MPG)

 

I will put it all back together tonight and sort the wiring out to the valve. Alternatively, are there any dangers in joining hoses together to seal the leak?

[mr_fusion 0]

well, buying the ultrasonic cleaner was the best £24 i've spent in a while.

 

http://www.maplin.co.uk/Module.aspx?Tab ... 4&doy=30m6

 

Engine fires instantly on the turn of the key now, took about 3-4 seconds before. If you have the time and skills to pull the injectors (not very hard with the right tools and a bit of time) then its definately worth it if your injectors are original and have never been touched.

 

Idle is also rock solid now (although this is probably down to reconnecting the evap purge solenoid wiring again). Doesn't hunt whatsoever, just sits at 700rpm. VAG COM also reports this to be so.

 

Still getting the 00533 code however (idle adaptation not reached) but is intermittant. Car doesn't buck off the line as far as I can tell, but will have to drive it around a bt more to be sure.

[Jim 1]

well, buying the ultrasonic cleaner was the best £24 i've spent in a while.

 

I'm just amazed you can pick up that sort of kit for £24 in Maplin! Superb! If it does a good job of cleaning injectors, well, its considerably cheaper than buying new ones!

[mr_fusion 0]

well, after a couple of days of running.. everything is perfect!

 

getting conistently better mpg in stop/start traffic around london (23mpg this evening) so very happy :-)

 

will have to take it on the motorway soon, but i reckon it will be in the 30s (previously the highest I have seen is 27mpg)