5KTQ hesitates, makes popping sound, error 2141

[cjcasati at hotmail.com]

Hi all,

My 1986 5KTQ 178K miles has developed the following over the last 2 weeks,
getting worse every day:

- hesitates, then engine catches on
- under full throttle hesitation gets worse, popping sound from underneath
the hood, check engine light comes on briefly
- pulled error code 2141 (knock sensor max, timing fully retarded)
- in the early stages the hesitation occured only when cold but the car
didn't pull that strong anymore during warm acceleration.

I have checked/replaced a lot before installing the Charlie spring (sensors
and almost all of Scott Mockrie's check list) and the car has been great
since then but I have not done spark plugs or fuel filter. When I installed
the waste gate spring I noticed that the waste gate diaphragm was intact but
old, could be torn now, and I also disabled the fuel pump cut out during
stock overboost per instructions (I will see about the QLCC to avoid that).

Phil Payne listed in the archives overboost, compression (don't have a
leak-down- or compression test) or lean fuel as culprits, based on what I
wrote can you please help me troubleshooting this? I didn't find much else
in the archives.

Thank you so much as always, any pointers are very much appreciated

Christoph
Richmond, VA
86 5000 TQ 178K
88 90s 158K