Hey All,

So, I'm still fighting my '95 F250's 7.5L with the emissions system.
Here is my previous thread about it:
https://www.ford-trucks.com/forums/1...60-7-5l-3.html

I ended up replacing the EVP Sensor (x2), the EGR Valve, and the EGR Solenoid. Everything was fine and the ODB1 diagnostics were giving 111 for KOEO and KOER when warmed up. I drove it for several months and it ran like a champ, but I hadn't hauled anything with it.

Fast forward to last week and I took a trip from Texas to Michigan hauling the 5900lb dry weight RV with it. It was running fine for the first two days, but that was only hauling for 1-2 hours at a stretch. Then, on the third day we did 6 hours. After about 2 hours of driving it started making the sound in this video:
https://photos.app.goo.gl/6biMar5EVKuEiwC77

I think this is pinging? Is that right? It's kind of a "tat-tat-tat-tat" sound that only happens when under "heavy draws" of the engine where it's pulling up hill. As soon as I am on a straight and flat road or let up on the throttle, it goes away and sounds normal again. It also was sporadic and seemed to be related to temperature. As I got further north into cooler weather and earlier in the day, it never did this until it got hotter outside (Over 90F) and the engine was heat soaked.

Finally, when I came off the highway for my first fill up after a few hundred miles, it started doing it's surging and stalling thing that was my original issue whenever I come to a stop. When I got it into the gas station, I yanked the EVP sensor plug, Check Engine Light came on, and I had no more issues other than the "tat-tat" sound in the video above under heavy draw. It was, however, quieter than it was when the EVP sensor was plugged in.

I haven't pulled codes yet, but I'd hazard a guess I'm getting the same 334 code about EVP Sensor Voltage too low.

Any ideas where I should start looking or next steps? I made it 1300 miles to Michigan just fine and just was easy on the throttle, but I'd really like to not put the engine through any damage if it's pinging. Also, it hasn't done anything weird with the EVP sensor unplugged and isn't acting strangely or making weird sounds driving it around not hauling.

 

What is the base timing set to? If you're still getting detonation with the EGR disabled then it's not the problem, the timing could be a little too advanced or the pistons have carbon deposits that lead to preignition in the heat soaked engine under heavy load.

 

on an empty tank, fill it with 93 to see if the pinging goes away. If so, you probably just have to back the timing off a hair

 

Thanks gents. I'll give 93 octane a try.

So is that ticking/tat-tat sound ping from the video?