knocking under load - fuel trims 81 lo, med, & hi

[King Salami]

Hey guys -
I already searched & read through about 6 posts concerning the same problem, but have not been able to pinpoint the cause of the rather heavy part throttle knock I've had most of the summer (only when the weather is hot).
It's definitely worse in the afternoon when the temps climb above 90 degrees and I can hear the pings, so it's not phantom knock. When I give it gas under a load, I get from 15 - 42 knock counts. It's especially prevalent in 2nd gear. It seems to hit when transitioning from vacuum to boost under load. When I logged the car, all my fuel trims were at 139, so I assumed a lean condition was causing the knock. I was running stock injectors & 1G MAS w/ the bottom honeycomb removed and a K&N. Intake temps were 100 degrees plus.

I checked my timing - it's at 7 degrees BDC; my CAS is maxed out in it's bracket & the plug is butted up against the TB elbow bracket. I wanted to get back to 5 degrees, but I don't know how to. Did the shop that replaced my timing belt screw up & index the CAS wrong or something? Anyone have a similar problem w/ your CAS?

I did an intake leak test & fixed a leaky BISS & turbo outlet elbow. I can still hear a hiss in the turbo (14B w/ 188K miles), but pressure bleeds down pretty slowly. 20 psi bleeds off completely in about 2 minutes

My plugs are gapped at .030 & all look medium gray

I checked my fuel press (not under load) - 37 psi w/ hose pulled off regulator, press dropped w/ vacuum & rose w/ 10 psi applied

I did an MCCC to clean out my cylinders and put the 550's in.

The knock seemed to go away. (We got much cooler weather during this time). My fuel trims changed to 125-135 lo, 85 mid, 81 high. The car ran strong & I only hit a bit of knock at higher rpms. I thought the problem was gone, so I put in the 2G MAS & EPROM ECU (w/ Stage 3 set up for the 550's and 2G MAS) I had in my garage.

Today it turned hot and the part throttle knock is back, worse than ever. My trims have settled down to 81 across the board since the ECU & 2G MAS install. (This chip may have been burned incorrectly if I'm still 20% too rich - maybe it was burned for a 1G MAS??)

One thing I noticed was that my o2 feedback trim was between 70-90 while cruising, but would jump to 110-135 when I bumped the gas. I'm guessing this is normal?

I'm guessing that it's a fuel-related problem since my trims are rich. What are the chances that a "weak" FPR is allowing fuel pressure to dive when I bump the gas? I'm pretty sure my fuel pump is keeping up because it pulled really well through the gears in the cooler weather.

Any ideas?

 

[90blacktsiawd]

Is it a possibility that the CAS is inverted? You can put it in either way but upside down will give you some problems. Part throttle knock being one that i had. If your not sure how to check i can get a link to an explaination for you. It doesn't take all that long. And like was said above maybe you aren't really grounding out the ecu when your checking timing. That would keep the problem around since you wouldn't really be changing anything.

 

[King Salami]

I grounded the timing plug on the firwall when I checked timing. I also had the shop who did my timing belt re-verify (because I assumed that they screwed it up) - it's at 7 degrees. One of the shop guys suspects a bad FPR or fuel pump. I'll hook my fuel pressure tester up & see what it does when I drive it.
My pump seems to be working just fine since it didn't stumble when I ran it hard during the cooler weather.
I also replaced my fuel filter. I may try replacing my plugs for giggles since they've got almost 20,000 on 'em.

 

[90blacktsiawd]

Timing doesn't necessarily have to be at 5*. It can be at whatever it's set to. Mines 5*. But I've seen anywhere from 0* - 10*. However much you can get away with running without any issues. And definitely change those plugs.