artysan

Yes, primarily first gear. But the same thing happens if I am rolling in second at 1000 and gently accelerate. Problem disappears above that rev level. It is not rhythmic, more of a screech that immediately stops as revs rise above idle. I can make it do it parked by blipping the throttle abruptly from idle, or by holding the brake and slightly briefly engaging the clutch enough to load the engine in the idle range. So, off clutch or on clutch makes no difference.

Loren, I'll check but nothing changed when I removed the old plugs (about 15,000 miles use) and installed a new set. I use copper antiseize and check gap - a real stickler - so it's unlikely. However, I did not know this bit of wisdom and I will check for it. Thanks. Peter

My 1993 968 Coupe, bought used at 51,000 miles and now at about 90,000 miles, has an issue where any acceleration causes a loud chirping, or perhaps pinging (for lack of a better word) sound below about 1300 rpm, even in first gear off the line. Above these start-off revs, there is no detectable problem and performance seems normal. Belts and rollers were replaced at 60,000 mi, well before the problem began. I have recently replaced all filters, plugs, cap and rotor - and checked my timing and balance belts (perfect condition and tension) - no change whatsoever. I use only 93 Octane fuel - from a variety of sources - and have run my last two tanks with Techroline at the prescribed doses. Mobil 1 0W-40, with regular changes. The only conditions which improve this somewhat are cold engine / very cold weather starts and the exact opposite, a hard-run up-to-temp engine. Is this ringing a bell for any of you experienced 968 wrenches out there? On my very short list are: Variocam, MAF.

I have had this happen on my 1993 968 Coupe. It is a transistor inside the headlight controller module, which actually looks just like a relay but has many more pins. This module contains 4 relays and the transistor/diode logic that work with the mechanical sensors and motors in the headlight assemblies. I can't imagine very many people have the electronics background to actually replace the single surface mount transistor that fails, but it is for some reason always the 'lowering' transistor that fails. I did the fix and everything was fine for quite a while, but the problem has returned. I also have noticed that a trim ring in my passenger side headlight has broken off its mooring and suspect it may be physically constraining the lowering and causing the transistor to overload and blow, so I plan to fix the headlight first, then replace the transistor again. I have included two diagrams for you. One is a physical layout of the controller circuit board and pinout of the module for troubleshooting. The other is an actual schematic of the controller. The transistor which fails is a PNP type. I used a 2N3906, a very common part, and carefully retrofitted this non-surface-mount component to the surface mount circuit board. It also commonly burns out a couple of resistors in the chain as it takes a bit of current to blow this part. If these instructions are more technical than you are comfortable with, they should be detailed enough for any electronic bench tech to do the repair for you. Check for mechanical issues first though. 968 headlight CU.pdf 968 headlight CU 2.pdf