Pinging/knocking - Premium octane gas
 

I was just wondering if other's here with 5.0's are having to run premium octane gas in there trucks? My 96 F150 4x4 pings/knocks like made when I put regular gas in it.The timing is stock, I have 9mm Ford Racng wires and new autolite plugs. I also have a K/N cone filter on it....I have noticed that it's gotten worse since I put the 31x10.5" tires on it. I have 3.55 gears and when I'm climibing a slight grade it will knock like mad under a "light and lugging" throttle unless I run premium gas. I've checked my spark plug wire routing (mine has the sticker on the rad support) and etc but I don't see anything wrong.

Is there something I might be missing here? Any common problems? It sounds like most of it is coming from 3,4,7 and 8.

Have you checked the ignition timing? Also, check to see if your knock sensor is working properly, and also check your fuel pressure. You might be slightly too lean under certain driving conditions, causing detonation. Also, do you have a check engine light on? It might be low EGR flow, since the computer uses EGR as a combustion chamber "coolant" to lower combustion temperature and pressure for reduced NOX and increased fuel economy (allows increased ignition advance). If there is no EGR flow (or not enough) the computer will allow too much advance and ping. Also since the ECM cus back on fuel flow with EGR, if there is not enough EGR, it will be too lean, and therefore it will ping.

Good info because I've been having the code for "Insufficient EGR flow" come on and off for the last little while. I bought a EGR gasket so I can remove/clean the valve so I guess I better get out my book and start doing some checks/tests as well. I'd really like to fix this problem as it drives me nuts listening to it.

I'll have to go out to the garage and get my Haynes book but what could be reducing the EGR flow? Is there a sensor for that? I didn't think my 96 had a knock sensor? That code has been registered 4 or 5 times in the last few months. My buddy has a Snap-On solus ro read the codes so that's how I know what the code was.

The 96 uses a differential pressure feedback (DPFE) sensor to sense EGR flow directly. I'm sure the Haynes manual lists some test procedures for that sensor. I'd also try cleaning the mass air flow meter sensing elements. Just gently wipe off the hot wires with rubbing alcohol and a q-tip. Be careful not to break either of the wires.

Dis it come with 31 inch tires or 235/15?Might have to reset the psom.I might be out in left field on this one.Mine came with smaller tires and I put 31's on.Reset the psom for the 31's and I think it shifted better with the original setting.Seems to lug more but mine doesn't ping.

Be sure to check the EGR tube for rust or a crack as well.

No cracks in the tube, I'll see what it looks like as soon as I get it off. I never reset my psom when I put the new tires on - 235/75/15 was the stock size. The truck drives fine and the pinging is almost totally gone with premium gas but I still want to cure it if possible. I'll clean the mass air as well - good tip....I'm a diesel truck tech so I don't work on EFI gas stuff very often. All my summer toy's are carb'd too. Mine lugs a little bit but nothing too severe. I have one long grade to climb on the way home each day in traffic and that is where I alway's hear the rattling. I'm off all this week so I'll have a look at it.

Remember that the 31" tire swap is like going to a 3.3 rear end vice 3.55 original. Does it down shift on the grade? The 4R70W is a wide ratio transmission to allow a higher rear end (Lower number) to run on the highway but has lower gear to allow pulling from first gear.
In addition to EGR check canister purge operation and any vacuum leaks.
Good luck.

you may need to remove the upper intake to throttle housing "neck" (hope i said that right). It seems they carbon up in those egr passages and will give you that code and problem; all you'll need to replace is one gasket $4-5. i've seen folks replace the DPFE and egr and still have to do this.
to see if you need to do this, remove the egr and the intake hose from mass air sensor to throttle body. Hold the throttle open while blowing compressed air into the intake side of the egr passage. You should really hear it flowing into the throttle bore; if you don't then you know it's clogged.

Good tips, I'm hoping to look at this in the next couple of days....I'll keep you posted.

I vacuum checked my EGR valve today - works good, I did find the EGR passage in my plenum was plugged up - I cleaned it out and I didn't hear any rattling on the hills when I came home from work so maybe that's all that was wrong. I'll try cleaning the mass air sensor tommorow. Where is the knock sensor? My Haynes book talks about it but it doesn't tell you where it's located? I'll also check the EGR canister purge operation and differential pressure feedback (DPFE) sensor tommorow. I didn't hear or see any signs of a crack in the EGR tube - but I'll look closer tommorow.

The 96 may or may not have a knock sensor, but if it does, it is here, looking at the back side of the engine:

https://www.ford-trucks.com/user_gal...oid=52797&.jpg

Cool, thanks for the tip. I'll have a look at it tommorow.