93 F150 Pinging and idle surging

[michael lamont]

I have a 93 F150 with 302, it's been a great truck. I do all work myself but this recent problem has me baffled. The truck has been pinging like crazy (everytime I drive it, 4th + 5th gear mostly) and randomly has an idle surge condition, mainly when pushing in the clutch to upshift. The surge backs down to normal idle if I hold the clutch in and wait 5 or 6 seconds. I receive NO ckeck engine light! Always get code 11 on a scan. I have made the following repairs over the past 6-8 months. Fresh tune up (except wires) New IAC, new fuel injectors, cleaned EGR, cleaned throttle body, set timing with spout connector removed, new O2 sensor, new fuel pressure regulator, new fuel filter, tried difference gas octanes and brands, cleaned air filter (have K&N). I also get that whistle when it is cold out. I have check may times for vacuum leaks and have found none. The truck runs fine (with exception of the above), OK gas mileage, runs cool and has a good curb idle. I have a new TPS to try this weekend but don't think it is the answer.

ANY ideas or thoughts would be greatly appreciated! I really thought the new IAC would be the answer but...no. I'm truely puzzeled.

Thanks in advance,

Mike

[mustangmike351c]

you might try putting the stock filter back in.

[michael lamont]

I've had the K&N filter for five years or more with no problems but for the cost of a new stock filter it's worth a try. Thanks.

[w8crz]

how about the knock sensor?

[publius21st]

Mike,

This is a long shot, but I've heard of it causing these random idle surge problems: something flaky with the ECT (engine coolant temperature) sensor. For some reason, fault in the sensor or a intermittant wiring fault, the resistance goes up, making the ECM think the engine is cold and it goes into fast idle mode.

If it's the wiring, then it can be a PITA to track down. The best thing to have is a scan tool like the Auto X-ray EZ-Scan 5000/6000, or one of the PDA or laptop scanners with a trigger capture mode that saves several samples of data before and after you hit the trigger button.

When it surges on you, hit the trigger, then look at all the data and see if anything looks funny.

-Richard

[jeverett]

The 89 f150 i had did this. I'm not sure what it was called, but there was a little thing that bolted to the side of the intake that was hrroble nasty inside. I took it off, cleaned it, and it ran like new. I think It was the IAC..or the thing that controlls the idle air mixture.

[michael lamont]

Thanks for all the response. I believe I've determined the cause of the pinging condition. I noticed spark plug wires (which haven't been replaced with new) 7 and 8 were in close contact with each other. I've read that this could cause a pre-ignition condition in the #8 cylinder. I separated the wires and that seemed to cure the pinging problem. Will be replacing all the wires for sure. I still have the surge condition and the ECT (engine coolant temperature) sensor makes sense. I'll check the wiring and maybe just replace the ECT sener itself.

Anyone have any thoughs on the air intake temp. sener causing any problems like a surge condition?? (location of sensor: drives side front lower intake manifold next to the first injector)

Thanks again,

Mike

[jcougar88]

Originally Posted by michael lamont

Thanks for all the response. I believe I've determined the cause of the pinging condition. I noticed spark plug wires (which haven't been replaced with new) 7 and 8 were in close contact with each other. I've read that this could cause a pre-ignition condition in the #8 cylinder. I separated the wires and that seemed to cure the pinging problem. Will be replacing all the wires for sure. I still have the surge condition and the ECT (engine coolant temperature) sensor makes sense. I'll check the wiring and maybe just replace the ECT sener itself.

Anyone have any thoughs on the air intake temp. sener causing any problems like a surge condition?? (location of sensor: drives side front lower intake manifold next to the first injector)

Thanks again,

Mike

Change your tps sensor. That sure cure your surging problem.

[who fan]

I have a 93 5.0. The temp fixed mine after replacing the o2 twice. computer thought engine was cold causing it to run rich in turn idle was rough at warm up.