924Board.org

[Scislowicz]

Good afternoon all,

I'm trying to troubleshoot a very poor idle. I have corrected several vaccum leaks, and I have recently replaced the DIC flywheel sensor. In the course of trobleshooting an ignition problem, I did remove and put back the distributer cap, wires, and coil. Everything checked out to spec. Anything else I should look into? I read what was one FAQ on this issue...The control unit is hanging free from when I checked out the sensors, but the contacts seem to be ok. The motor refuses to run faster than 2000 rpm, and the idle is at about 300 rpm, with backfires.

Thanks!

Jan

[TroyDest]

Jan,

My '82 931 was doing the exact same thing several months ago. It happened a couple times intermittently. The last time I got stranded at work on the way home and had to fix it. After spending all night checking wire connections in the engine compartment, the only problem turned out to be the connection at the DIS under the center console. After I unplugged the wires and plugged them back in, the car has run great ever since. Good luck, Troy.

[Scislowicz]

Thanks Troy!

Hmmm. Replacing the DIC sensor with a new one is what I had to do to get the car to fire at all. Next time I get up north to where the car is stranded, I'll try cleaning and reseating those contacts again. The contol unit was hanging free near the pedals as I was swapping wires. Is there some kind of direct ground between the unit and the chassis of the car? Now that I mention it, I guess its possible that leaving that unit to hang was enough to weaken the contacts. Cheers! Jan

[TroyDest]

Jan,

I'm pretty sure the DITC unit is grounded through one of the wires in the harness. But, check the mount anyway and run a separate ground as a check if necessary. I think the 'hanging free' unit could have definitely caused your problem. Like I said, all I had to do was unplug and plug back in to fix my problem. It must need a perfect connection down there. Nowadays, any time I need a perfect connection somewhere I use dielectric silicon grease on the connection. It prevents corrosion and stuck connections and promotes conductivity. It is available from Permatex (dielectric tune-up grease P/N LCO372) at local parts stores and is usually sold for lubricating spark plug boots. It also works for lubricating spark plug boots!

Best of luck! -Troy

[TroyDest]

One other thing. You already checked your overboost switch right? If that is not making a good ground, all the motor will do is idle - poorly! The wire connection on mine broke and did something very similar. To check, just ground the wire going to the overboost switch (the one spade sensor screwed into the upper pressure duct).

[Scislowicz]

No, I forgot all about that switch. I had checked it during my initial troubleshooting, but I don't remember verifing it after replacing the DIC sensor. Thanks!!
Jan

[924RACR]

Yeah, that connection on the control unit can be extremely flaky! Mine is to the extent that I can't drive down rough roads, or it'll shake loose and the car will lose power... then I'll reach down, while still driving, wiggle it, and it'll connect again, and off I go! A little disconcerting to those who borrow the car...

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[928924931]

Hi there guys. Just (nov 2001) bought a 931 after 14 years with a 924 lux. Been reading lots of posts about power outputs. Of course you guys mostly suffer from the debillitating effect of all the detox stuff, which we Brits don't. I have heard over hear that a good cam grind plus a little head work can get at least 150 ponies out of the 924, with no loss of reliablty. I know a bloke who has demostrated the relative speeds of his 924 against his 944s between two fixed points, and the 924 runs out at 103 mph against the 44 s 107. I have driven the modded 924 and it feels quick. Not hugely fast by 911 0r 928 stds, but faster that Rabbit v5s or 2.5 litre Opel SRI,which aint bad with near 30 yr old technology. Being new to the 931 I now find I need some ideas about a misfire that has occured quite suddenly after a period of lying idle whilst the clutch slave cylider was replaced. No 2 cyl was worst, but with the lead off that plug the engine still "misses" on other cylinders. Sometimes they all chime in and you're off like a rocket, others it's a p.i.t.a. I have changed the plugs, 'strib cap rotor arm, cheked for broken tappets and valve springs by removing the cam, but that clicking noise I now suspect to be the wastegate after reading some of the informed comments on this site. I have earthed out the overboost switch lead with a short wire. Disconnected the engine cuts, but connected there is no noticable difference compared to connecting to swich. The connector inside looks to be making good contact too. Being a turbo virgin I suspected the flywheel sensor as there didn't seem to be much else to check. Fuel is passing through the engine, as frequently the accumulated unburnt fuel backfires. I hope you guys can clue me in, as if the flywheel sensor is unsevicable I am going to have real trouble sourcing a replacment. Porsche uk don't list it anymore and after-market independents are finding the part elusive as well. Any help would be appreciated

[ This Message was edited by: 928924931 on 2002-04-04 02:24 ]

[ This Message was edited by: 928924931 on 2002-04-04 02:35 ]