Moderate runaway?

mattbondy · Post by **mattbondy** » Wed Apr 08, 2009 3:38 pm

Lately, if I bring my Jetta over 80 km/h (which is rare since I have a slushbox) it will maintain speed without any accelerator input. My first thoughts were a stuck accelerator pedal/cable or a hanging injector. However, just the other day the low oil pressure light flickered at idle and sure enough the oil level was a bit low. I have been watching the oil level and it is dropping fairly significantly when this event occurs.

On the bright side, at least I know the oil pressure warning system is functional. Any thoughts on how this will progress? Is it going to get worse quickly?

Another interesting tidbit I came across today (in Scientific American), some researchers have achieved something like a 25% increase in fuel economy using a magnetic field at the injectors on a diesel to modify the viscosity of the fuel. Apparently the spray pattern improves. According to the article I read, power consumption was very miniscule.

I just googled this one, I would assume it is the same researchers.
http://pubs.acs.org/doi/abs/10.1021/ef8004898

surfcam · Post by **surfcam** » Wed Apr 08, 2009 5:57 pm

To me it doesn't seem like a run away but more of something sticking. I think you could vent the crank case somewhere else and see if it still does it. You might have started something with that with that magnetic idea. I can see some of are members being stopped for having cables and isolators hanging out of their hood.

mattbondy · Post by **mattbondy** » Wed Apr 08, 2009 8:00 pm

I will definitely test the condition that way (take off crankcase hose). It is too bad I dont have a tach, the engine does not sound that different at 80 in 3rd compared to 50 in 2nd. I have only come across this problem at higher speeds.

I have already done a little investigating with respect to the accelerator, the pump return does not seem to stick at all and neither does the pedal. Even if I use my foot to pull back on the pedal it has no effect. The injectors however are suspect. They are probably quite old and, I am hesitant to admit this, were in this old head I bought that was sitting around in a local VW shop for who knows how long. This problem does not date back nearly as far as the head replacement.

82vdub · Post by **82vdub** » Wed Apr 08, 2009 9:29 pm

I'd suspect the throttle arm on the IP is sticking. I've had that happen before. You can pull up on the gas pedal, but that does not make the throttle lever return. I would try to lubricate the throttle arm on the IP (where the large spring is) and see if this makes the situation go away. Could be moderate runaway, but I think runaway is something that once it starts, it keeps building RPM until it can't go any faster. I think it's something throttle/cable related. Try duplicating the problem by actuating the throttle arm directly while under the hood. Or, next time this happens, quickly blip the throttle and see if the RPM comes down.

Post by **Fatmobile** » Wed Apr 08, 2009 10:51 pm

Having the max fuel screw set too high can cause that.
Also a bad injector.

Residual fuel left over after the burn,
pools up and is still available on the next cycle.

rabbit_man · Post by **rabbit_man** » Thu Apr 09, 2009 10:22 pm

I'd suspect the throttle arm on the IP is sticking. I've had that happen before. You can pull up on the gas pedal, but that does not make the throttle lever return. I would try to lubricate the throttle arm on the IP (where the large spring is) and see if this makes the situation go away.

I had that same issue a couple years ago, I just sprayed a puddle of wd-40 into the little dish in the throttle arm above the springs and it fixed it.