Engine clunk / knock when throttle blipped

[hymnforthewretched]

Hey, tried searching and came up with nothing on this issue I have.

97 lX450 1FZ-FE
~ 190,000 miles

Runs good for the most part. No major issues. most maintenance up to date.

When I blip the throttle ( by hand or with my foot ) from idle or while driving it makes a quick clunk/ knock sound. from what I can tell it sounds upper end. I had my ear down on valve cover/ intake area. only does it from zero or near zero throttle and only when the throttle is blipped quick. Cant make it happen any other way. Audible from inside the cab and outside the truck.

Ill have a video up soon to share.
Thanks!

 

[hymnforthewretched]

 

[ppc]

Have you checked your timing?

 

[hymnforthewretched]

Have you checked your timing?

Not yet, not sure why it would go out of timing, but I'll add that to the list. thanks!

 

[ppc]

What fuel are you running? How long has this been occurring, more than one tank of fuel?

 

[hymnforthewretched]

What fuel are you running? How long has this been occurring, more than one tank of fuel?

I run Shell 89-91 depending on price. the last fill up was 89. Timeline is hard to say. I've noticed it more in the past month or so and was contributing it to a rattle in the exhaust somewhere. It very well could have been happening for longer. I'm pretty anal about noises though and I finally had a chance to look and hear where it was coming from. On my next fill ill put 91 in again and see if that has any effect.

Are you thinking it could have something to do with timing/ fuel?

 

[ppc]

Yes, It sounds like knock or piston slap from a wrist pin or connecting rod to me, not top end.

 

[hymnforthewretched]

Pretty sure its pinging. It seems to happen more when the truck is warmed up. I also noticed it under load a bit ( but not a severe as the throttle blip ). It was hot outside the days I noticed it and it was quite bad, the past day or so has been much cooler and the severity has decreased, but still unsettling. Ive never owned a vehicle that has pinged before, so the sound was new for me.

Im gonna check timing today, check for the 10th time for any vacuum leaks, pull the recently installed Denso plugs and check them out. Add some 91 and see what happens.

 

[mkmarz]

I'm with you on the pinging.

 

[hymnforthewretched]

I adjusted the timing, It was advanced at 11 degrees... 8 degrees off. This was likely due to chain wear over the years and me putting the dist. back in slightly off after changing the o-ring. Brought it back down to 3 which has seem to have made quite a bit of difference. I could still get it to knock with the throttle blipping, although not nearly as much and not as consistent. I had about a 1/4 tank left and filled up with some shell 91. Hoping this does the trick. I may try one heat range colder plugs, not sure if this is really gonna do anything though. Not really sure any if the seafoam type products are worth trying, Im not a believer in alot of the snake oil products. Having the injectors cleaned and flow tested doesn't like a bad idea at this point.

 

[ppc]

It may take some time for the ECU to re-learn the engine parameters. You might want to pull the EFI fuse under the hooh for a minute to reset the ECM and let it learn from scratch.

 

[hymnforthewretched]

So by now the ECU has had plenty of time and mileage to re learn. I've tried a reset a couple times. At first I thought the timing adjustment made a big difference, but it only made a slight difference. I still have pretty bad pinging, and now that I know what to listen for, I can hear different levels of pinging from my gentle 10 minute commute, to a 2 hour trip in the mountains on varying terrain conditions. Ive been using only quality 91 octane since I noticed the issue. Cant find any vacuum leaks and cant find any reason I would be running lean conditions.

I was thinking of having my injectors cleaned and tested and replacing the fuel filter, but short of those two things I really have no idea where to look next. The level and amount of pinging has me concerned. would love to get it sorted once and for all. I have little faith that cooler spark plug would make any difference, specially since I'm running the recommended denso plugs.