So, just had my whole exhaust rebuilt, front to back including 4 new o2 sensors.
Good thing I got the truck for a sweet price, though it ain't so sweet anymore (it's on the cusp of losing any kind of sweetness at all now.)

So, still looking to improve overall performance and there's a couple issues.

1) A constant low slap/tick

2) A slap / tick that is accompanied by small idle surges when the engine is cold (as it's warming up). Once it's warm, this one goes away.

I've got a multi meter and I'm trying to test things like the EVR solenoid, DPFE sensor, etc. that can affect these symptoms, and I'm, thinking it's possible that my DPFE is #$%@$#%, but i'm not sure.

I've got 5 V signal and 5 V ref from the battery, the solenoid seems to be fine, but ....

HOW do I backprobe the DPFE to test its effectiveness? It doesn't make sense. There is no outlet voltage, and the harness has incoming power on both SIG and REF.

The DPFE is suppose dto be 0.2 to 0.7 V cold and 4v to 6 V warm. I know it works warm, bust as mentioned above, the problem is while the engine is still cold.

AAGH!

Without buying a new sensor, how does one go about figuring out if the existing sensor is working properly?!

 

I tried to test the DPFE also and could not get the voltage to change as the engine warmed up so I replaced it and nothing changed. now I have a spare.

 

My suggestion is to buy a good scan tool ,this will give you the readings your pcm is seeing in real time cold or warm.

You can look at what dpfe sensor is doing

do you have any chk eng light? if not and you have scanned the pcm for faults an you have none
Don't think you have problem.

With the scan tool you can see and do more than the old volt meter

Sorry this didn't answer your question

Rich

 

Thanks, you both helped. I'll go with a combination of your thoughts and 1) not buy myself a spare DPFE! and 2) Keep trying to find a Ford scan tool (i've only asked at one auto parts store and they say there's nothing cheap enough for a do it yourselfer to buy yet. My Haynes book says there is though.

I had it in for the new exhaust system and the shop cleared the codes, but I have a feeling that the EGR flow efficiency code is only temporarily gone.

It's not so serious it can't wait a while though, so thanks.

 

small idle surges at idle sound like the IAC. if not already done you might want to pull it for cleaning/inspectiion.

 

daniel76: I would replace the dpfe sensor relay it will cause eratic
surging in opperation, & this can happen cold or hot, to back-
probe the sensor do the test cold & preform the test KOEOFF &
just unplug the sensor & probe the connector the voltage @ this
point it is a slave to the dpfe relay, this is what is the realtime
voltage dictator. You may have to have the ecm reflashed if you
keep getting codes, this is due to the new flow capacity of the new exhaust & the ecm knows the differance of the before & after. Also the hoses that connet the dpfe relay can be a vaccume
leak source & cause the surging static or moving.
keep us informed turbo ted

 

The 5V going to the DPFE sensor is developed from the PCM. I've found an easy way to measure voltages is to use a straight pin, to contact the conductor of a wire through the insulation. The small hole does not hurt the insulation, and the conductor will not be broken...You can use an aligator clip on the straight pin.

 

You can get a voltage change as the EGR valve is opened as the truck runs. Put a hand vacume pump on the EGR valve, with the truck warm, and ideling apply vacume to the EGR VALVE the voltage should increase as the valve opens. Note the engine should start to stumble or stall as well. If you dont get a voltage change at the DPFE sensor, it might be bad, or the passages in the throttle body may be stopped up. Seen this a lot. Good luck. Let us know how things go.

 

You wrote:
"2) A slap / tick that is accompanied by small idle surges when the engine is cold (as it's warming up). Once it's warm, this one goes away."

The tick, tick, tick is the classic Ford piston slap problem on the modular engines. Ford says that it DOES NOT cause any long term problems but I am very hesitant on that one. We will see.

I have a 97 F-150, 4x4, with 4.6L V8. I bought it in March of 96. One of the first ones made....

I have had the piston slap problem on my truck for the last 5 or so years. How I combat it is using a very good grade of oil (Amzoil, or Mobil 1). After switching to Amiziol, I would only hear the tick, tick, tick sound of the pistons slapping the cylinder walls for about 15 to 30 seconds. Then it was gone. Before I switched, it would do it for a full 2 minutes or more.

This is just what I have seen and heard about....