1994 F150 5.0 2WD, 190k miles.

Symptom: Engine pings badly when in closed loop (any acceleration or rev). Revving is accompanied by white smoke from exhaust. When in open loop engine runs great except under load, then pings.

Relative info:

• No CEL, KOEO and KOER show no codes, only 111 (system pass)
• Timing set at 10 deg BTDC with SPOUT unplugged (could be 11 deg, depending on where the mark is read in relation to the pointer)
• Replaced O2 sensor
• Replaced fuel pump (unrelated issue)
• Replaced IAC valve (unrelated issue)
• Cleaned and verified function of EGR
• Cleaned MAF, IAT and throttle body
• Previous owner replaced plugs (Autolite copper) and wires, cap and rotor
• Previous owner replaced fuel filter

Back story: Purchased truck approx. 2 months ago. Since purchase truck has exhibited spark knock (ping) under load (accelerating up hills, etc.) but otherwise ran great. Pulled codes and found codes 213 (SPOUT or SAW circuit open or shorted) and code 225 (knock sensor not tested). Found SPOUT connector missing (now assuming previous owner removed it in an attempt to mask the pinging issue). Fashioned a jumper for the SPOUT and checked codes again - 111 (system pass) for both tests. With the jumper in place it now pings under any acceleration and even while just revving. It does not, however, seem to ping under load like it does with the SPOUT removed.

Next steps: Since there are no codes and the timing is set correctly, I'm thinking the ECU may be to blame. I've found online some instances of bad capacitors inside the ECU...I just so happen to have a variety of caps laying around so I'm going to pull the ECU and replace any that show signs of wear or malfunction.

Can anyone offer any insight into what maybe causing the aforementioned behavior? Wrong, misgapped or fouled plugs crossed my mind but I would think that would manifest itself the same in open or closed loop (SPOUT connected or disconnected).

Thanks
Evan

 

Does it even have a knock sensor? If so I bet it's bad or unplugged.

 

Wouldn't that be reflected as a trouble code?

 

Maybe, maybe not. You DID have a code saying that it wasn't tested.

 

That code was because the SPOUT connector was missing, keeping it in open loop (running on a preset fuel map, essentially ignoring certain sensors). Once I reconnected the SPOUT the knock sensor no longer caused a code.

On another note, I found a cracked vacuum line (pink line - TAB solenoid?). Picked up some 5/32" rubber vacuum line and am going to replace all the brittle hard lines this weekend.

 

Cracked vacuum lines will cause it to run lean, which can make it ping - if it doesn't have a knock sensor. If it does, it should pull enough timing to quiet it down but it won't run particularly well.

 

I replaced all but one (HVAC) vacuum line with 5/32" rubber hose. Doing so made a noticeable difference in the driveability - no longer pings while revving and pings much less while accelerating. Hopefully replacing the HVAC vacuum line will help even more.

I used a Mityvac to check the VRESSER, TAD, TAB and EVR solenoid. All held 20Hg of vacuum but the EVR. Went to the parts store and checked a brand new EVR and got the same result...apparently it vents to atmosphere unless it's energized. I'll test it tomorrow with power on.

 

If it still pings after doing all that, try a couple tanks of premium gas and see if it goes away. Wouldn't hurt to put some GOOD cleaner in the gas such as Techron. You may have a bunch of combustion chamber deposits, which will cause ping.

 

Put a bottle of Techron Concentrate Plus in the tank then filled with 93 octane gasoline. After a couple miles I could hear no ping whatsoever. I also ran a can of Seafoam through the brake booster vacuum line (second time I've done this). Will test drive in a minute.

Hopefully the Techron and Seafoam combo will clean out enough carbon deposits that I can run 87 octane gasoline without issue.

 

Be careful with the Seafoam - that stuff can cook the cats and if you suck too much in too fast you can hydrolock.

 

The cat is pretty new, it should be able to hold up to a Seafoam treatment. When adding Seafoam through the brake booster vacuum I cover most of the hose opening with my thumb and just barely let it suck in the fluid. I'll do it in 5-10 second increments, let the engine settle then repeat.

It didn't smoke nearly as much this time after using the Seafoam. The engine ran a bit rough and pinged under acceleration for the first few miles (I attribute it to all the carbon deposits burning off) but then smoothed out and now it purrs like a kitten.

Will keep this thread updated as I go through the tank of 93 octane gasoline with Techron Concentrate Plus.