Pinging under partial throttle (EL Gli Manual Wagon)

[Luke222]

Hi there, have pinging under very slight throttle (obvious on gear changes) roughly between 2k-3k rpm. Happens worse once the car has warmed up after a minute or two, and doesn't happen under hard acceleration, very low in the rev range or very high in the rev range. Only happens when feathering the throttle. Very strange. Tried the following:

- New fuel filter (new pump only a month ago also)
- Checked timing, and when we conservatively retarded the timing on purpose (to the point with no power), it got slightly better but it was still there
- 98 fuel, no difference...
- Checked vacuum leaks
- Inlet manifold replaced already
- Had a look under the valve cover and everything looked great. Even ran the engine briefly and no noticeable tappet type noises. Checked the tappet clearance and everything was normal.
- Used wide band oxygen sensor to check air fuel ratio, and its normal when the pinging is done on purpose.
- Compression check, fine.

Running out of ideas, weird symptoms and had no luck finding the cause.... Any help would be greatly appreciated.

[FTe217]

Welcome Luke, hopefully someone can respond to your post.

[13726548]

How have you determined it is pinging ?

By sound only, or have you fitted a knock box to identify the noise ??