over-revving... - page 1 - Troubleshooting - VWDiesel.net The IDI, TDI, and mTDI source.

• over-revving... by rod1e on 15 May, 2007 03:27
• 1.6NA Transporter TD pump with LDA blocked off....
  This is not runaway caused by breather hoses and I don't use any oil....
  (I know, it's weird... used to a litre a 1000km)
  
  Drowned the IP in WD40 about 5000km ago and it seemed to dissappear after a while, but it has started again over the last 1000km...
  Mostly happens through 1st and 2nd at mid revs, but if I go over 60km/h in 3rd and change, the revs drop normally when I hit the clutch... (running round town in 2nd have to brake to bring the revs down....)
  A while back I was hanging about talking to someone and it was standing idling for about 20minutes... suddenly it started revving... ran over and turned it off... started it up again and AOK. Ran a bottle of redX through it, still over-revving after 2 weeks, but only while driving...
  It's not the cable as it still sticks in hi revs with the cable disconnected...
  
  Any ideas of a fix that don't involve the guts of the pump...
  Been told about a sticky IP syndrome but no real specifics...
  Thanks...
• #1 by jtanguay on 15 May, 2007 11:25
• cheap fix might be diesel purge... but it sounds like you have some sort of idle speed boost if it's just doing this randomly... usually the idle will stick higher when you have the residual fuel screw out too much, but will drop back down with a load on the engine, and will stay down until you hit the go pedal again.
  
  very weird!!!
• #2 by rallydiesel on 15 May, 2007 12:22
• Turn down your max fuel screw and readjust your idle. A quarter of a turn on the max fuel screw or less should fix it (hopefully).
• #3 by saurkraut on 15 May, 2007 12:35
• I'd like to see one of these fabled idle speed boosts.
  
  try moving the IP throttle arm a little, the let it go.  If it doesn't snap brisquely back to the idle stop, you have the sticky-pump-corrosion-gack-on-the-throttle-shaft-thing.
  
  The sticky injection pump thing is basically corrosion and gack get into the throttle shaft where it goes into the pump housing.  cycling it back and forth while spraying with WD40 sometimes frees them up.  Use the extension tube thing to get the WD40 into the throttle shaft area.  WD40 might be bad for the timing belt, so avoid spraying it all over the pump.
  
  running postions, lotions' or snake oil through the fuel system will do nothing for the sticky-pump-corrosion-gack-on-the-throttle-shaft-thing.
  
  I could speculate the a sticky throttle shaft thing, along with some harmonic vibration thing, caused your idle runaway.  But i won't.
• #4 by jtanguay on 15 May, 2007 12:48
• yea but he said he was talking to a buddy, being nowhere near the pedal with his foot and it started revving... unless his vehicle is haunted, i highly doubt its a sticky throttle shaft...
  
  i would almost suspect faulty cruise control... or something like that... unless he has the automatic timing advance/idle speed boost.
• #5 by burn_your_money on 15 May, 2007 12:51
• tempermental injector perhaps? It stops working properly so engine speed needs to increase via the governer to avoid the engine from stalling?
• #6 by rod1e on 15 May, 2007 13:39
• Thanks...
  No cruise control and I don't think any automatic timing advance/idle speed boost... this is a pump off an '87 JX engine...
  
  The idle-runaway seems, I hope, to have been a one off event... I had, a few weeks before, put in a set of exchange (rebuilt) injectors... don't know if that could really cause that to happen... (it was sticking before I put them in anyway)
   
  It's not random.. seems to like to stick at mid revs... If I floor it while driving it seems to come back down normally... If I do it standing, it sticks about halfway...
  
  The gacky-throttle-thang approach suits me for now... I'll have a go at it tomorrow and let you know how it goes... I don't want to start messing with the screws straight off...
  
  I guess there is a lot of dust and dirt roads 'round here...  :oops: I haven't had the van anywhere near a washer for 2 years... so it's a bit manky under the engine cover...
• #7 by saurkraut on 15 May, 2007 14:16
• "I could speculate the a sticky throttle shaft thing, along with some harmonic vibration thing, caused your idle runaway. But i won't."
  
  well, i said i wouldn't, but i will.  I have a lawn mower that has a tired engine, and an automatic choke.  If I kill it when its warm, I have to take the air cleaner off, hold the auto-choke open, and pull the rope.  I then place the air cleaner on, and the long screw in the center threads it self in due to the vibration of the motor.  I've farted around with the rpm, and if the screw isn't tight, i can make it screw in or out by varying the throttle.
  
  Its a streach, but these engine might just vibrate a little more than my lawn mower.  And with the throttle cable flapping away at idle, and a sticky throttle shaft that is reluctant to return to idle, who knows..
  
  I'd still like to see this idle boost contraption.
• #8 by jtanguay on 15 May, 2007 16:33
• apparently some N/A pumps have auto timing advance/idle speed boost...
• #9 by saurkraut on 15 May, 2007 17:21
• i've seen two types of auto advance.  the audi 5000TD pump has a wax canister on top of the pump, that I think went to the mechanical lever.  The late US 1.6 pumps had a canister on the front of the pump with a steel tube going into the pump.  I wonder if that worked with wax as well.  Any body cut one open?
  
  I've seen cruise controll vacuum pots, but I haven't seen an idle boost yet, so thats why I ask
• #10 by rod1e on 17 May, 2007 00:58
• OK, I've had the levers off, loads of WD40 but no change, still sticks at hi revs unless I floor it...
  
  Noticed this....
  
  ... seen this kind of thing on carburettors where the spring wears the housing away but don't see how this could of happend with the plastic spring "guard"... could have been replaced I suppose...
  
  Now what?? Pump to bits??
• #11 by saurkraut on 18 May, 2007 06:20
• Did  you verify that the shaft was binding?  Judging from the wear, that coud be the problem.
  
  At a bear minimum, your pump needs a new top cover. I'd look for a different pump, send it to a repuable rebuild place for new seals and the works.  Then you have the use of the vehicle while your waiting for the next pump.
• #12 by Vincent Waldon on 18 May, 2007 09:23
• Someone else can/should chime in, but I'm pretty sure there are pump configurations where the bushing extends above the pump housing.
  
  In otherwords, yours looks fine to me !!  I don't see any machining marks like you'd expect if it was abnormal.
  
  
  Vince
• #13 by saurkraut on 18 May, 2007 09:47
• I guess the real issue here is it the throttle shaft thats sticking, or not.
  
  
  If the throttle shaft is sticking, and we have visable significant wear in the aluminum boss in the vacinity of the throttle shaft, than its probably time to consider a rebuild.
  
  If its time for a rebuild, why rebuild a pump that has some significant visible wear.  Might as well look for another pump to rebuild so you don't suffer the loss of the vehicle while the pump is being rebuilt
• #14 by Vincent Waldon on 18 May, 2007 10:15
• Yup, totally agree with the "find another pump" strategy if a rebuild is in order... eBay and the For Sale forums are a great place to start.
  
  I'm just not sure the pump housing is all that worn.... and even if the casing has some spring wear it's the brass bushing that the throttle shaft rides in... a fairly cheap part if that's the problem.   Or perhaps the throttle shaft o-ring is swollen and binding the shaft... another cheap part.  Or there's something up with the governor assembly.
  
  Either way there's downtime I guess...
  
  
  Vince