Stonejag 10 Posted June 22, 2013 Tried to get down south to visit my folks this weekend but the car won't let me! Drove fine for an hour or so and then conked out completely. Symptoms are sudden onset of very unstable engine RPM - the gauge is all over the place, swinging wildly up and down by 1500-2000 revs. This is accompanied by violent bucking and loud backfires. Seems to go away briefly with pressure on the gas, but immediately kicks in again on overrun - it's impossible to drive as every time you let off the gas it starts bucking again. Then it stalled, which shouldn't be possible in an auto! Pulled over and checked the obvious, nothing evidently wrong so I restarted it and got it to the nearest services. Gave the throttle pot and MAF connectors a squirt of WD40 and checked the PCV hose for oil sludge - nothing. Started fine so I continued on, only to find it went again when it warmed up and I had to get recovered :( Suggestions from the recovery guy after warming it up and having the symptoms reappear - crankshaft sensor, EGR valve (don't think OBD1 cars had those though?) and fuel pump - any ideas? I've been having hot-start trouble for a while and I've had the revs oscillate a little before when coming off the throttle - nearly undetectable though, nowhere near as dramatic! I'd been having quite a good run without anything major dying, too :( All suggestions welcome! Stone Quote Share this post Link to post Share on other sites
VR6 Gar 10 Posted June 22, 2013 Big Vac leak? I had similar symptoms yesterday after forgetting to plug a vac line back in. Not that likely as it seems heat related but you never know, the heat could be opening up the split/leak. Quote Share this post Link to post Share on other sites
dumptyboy 0 Posted June 22, 2013 Engine temp sensor possibly, when was it last changed? Quote Share this post Link to post Share on other sites
Ruggy 10 Posted June 22, 2013 I'd say definitely crank sensor, I had exactly the same problem, only ever happened when warm/hot. New crank sensor sorted it, hasn't come back since changing it. Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted June 22, 2013 +1. Crank sensor. Take it out and check for swarf first as they are well over £100 for a new one! Quote Share this post Link to post Share on other sites
James. 7 Posted June 23, 2013 Same again on the crank sensor. Quote Share this post Link to post Share on other sites
Stonejag 10 Posted June 23, 2013 (edited) +1. Crank sensor. Take it out and check for swarf first as they are well over £100 for a new one! Fortunately the AA will be paying! Might get the fuel pump done at the same time since the recovery guy said it was tired :norty: Where would swarf be / be coming from - somewhere in the sump? If so it might explain my recent high oil temperatures if it's been catching in the oil pump screen... Stone Edited June 23, 2013 by Stonejag Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted June 24, 2013 Just bits of random metal particles that float around the engine! It builds up over time and can weaken the signal but it doesn't happen in all engines. If AA are paying, yeah replace it! Make sure they don't get a cheap arse Chinese one that will last 2 minutes! Quote Share this post Link to post Share on other sites
Stonejag 10 Posted June 24, 2013 The two guys running the place are dealership-trained and used to race Golf VR6s, I trust them :) Thanks for the tips, I'll see what they reckon when I talk to them in the morning. Stone Quote Share this post Link to post Share on other sites
