BobbyT

Did you change the belts?

SS21

Not yet, it’s on the list. I will change them as a matter of
course and to rule out one more possible cause. I also want to do some more afr readings under high load as I noticed a very audible ping at around 5k in 4th which I have never heard before.

Hopefully get round to it this weekend.

paulbuxel

Hi, I have almost exactly the same symptoms "pinging under load around 4000rpm. Did you ever find a fix? Thanks, Paul

SS21

Been meaning to update this...

I changed the belts (genuine) and it made no difference.

Only thing left I think is to check valve timing to make sure cam pulleys have not slipped slightly, unless there are other suggestions?

badabing

Did you have the injectors cleaned and tested ?

jb911911

Hi i have the same pinking issue car is on 145k miles

All parts on the car is genuine

I had the following done to try to get to the bottom of the pinking

distributor tested with new, still pinking old one put back
knock sensors changed
car is running on e5 99 shell petrol
used 5 tanks of petrol with wynns injector cleaner still pinking ( but runs allot better )

Can any one help ?

kevin2012

I had a "pinging" issue since I brought my 1995 993 and it had been pinging for all these years when the engine is hot in hot days.
Finally after changing number of parts, I had solved my car Pinging problem. The problem was the leaky intake manifold slacks. After changed all 6 slacks and o-rings, no more pinging.
Hope this help.

tosha

I have a ‘96 993 with 117k miles and I’ve been observing pings and decrease in power after engine warms up. The worst part is that on sudden throttle at around 3k rpm I’d get really disappointing slight hesitation. Car felt great when cold and slower when hot.

The biggest improvement came from changing the MAF (cleaning didn’t seem to help), though the pinging continued but less frequently. It looks like the fuel pressure regulator was the change that solved it for good (pressure at idle was 2 bar less than spec with old one). I’ve just done about 45 minutes of driving after this change and it looks like the pinging and hesitation have been fixed. I’ve been trying to solve this since I got the car in 2017, so almost in disbelief that this may be behind me.

wellcraft290

Guys check the dual distributor belt. I’m sure it is snapped. I had this on my 964. Started to ping. Was the belt.

tosha

After driving some more with the new fuel pressure regulator, I can say the pinging is gone. The car is still noticeably perkier when cold, so something is still reducing power when the engine is hot. I also noticed that the exhaust sound is much nicer when car is perky, and more dull when it's a bit underpowered. The slight hesitations I noticed before when I'd get pings is also gone.

It seems like I'm getting closer and closer to ideal fuel/air mixture window by refreshing parts that appear to be in spec, but some root cause is still moving me out of that window as engine temperature rises.

Next steps for me: check idle valve, replace O2 sensors, and maybe replace the intake manifold vacuum units 993.110.462.02, and 993.110.461.03 (cribbed that from @pp000830 PDF). I might also twiddle with the cylinder head temp sensor and add a resistor to lie to the ECU about temperature as an experiment.

kevin2012

My engine pinging issue has come back. It was solved 2 years before after changing all those leaky intake slacks. I had checked and there is no any obvious air leak this time.
@tosha May I ask if the new fuel pressure regulator really solved your engine ping issue?

Also, like my pervious situation (https://rennlist.com/forums/993-foru...ot-broken.html), there is no ping at all if I just use either of the distributor to run the car. Cheers!

tosha

@kevin2012 yes, the pressure regulator seems to have fixed my issue. the previous regulator was off by about 2 bar.

kevin2012

Thanks Tosha. Appreciated! I will change that too.