Great Lakes 4x4. The largest offroad forum in the Midwest banner
1 - 7 of 7 Posts

·
Shake n Bake
Joined
·
256 Posts
Discussion Starter · #1 ·
i have a 96 f150 351w efi and whenever i tow something it starts to spark knock, i tried octane booster and it didn't make a dfference.
 

·
Brian R.
Joined
·
2,093 Posts
Look for cracked or missing vaccum lines. If there is a small line off or a vac leak the ECM can still correct the air/fuel ratio under normal conditions but when you add a load it will be too lean to make the power it needs to pull and will rattle. Last three trucks I have had had this happen at some point.
 

·
Brian R.
Joined
·
2,093 Posts
Then you need to find your vaccum leak. If I am wrong I will buy you a pop.
 
G

·
I have a 351w performer with a holly 650 should cure it.
Better do somthin quick my last efi leans out the rear pistons
and then you will have a 7 cyl.
 
1 - 7 of 7 Posts
Top