I am a Lincoln Mercury Tech working on my buddy's Discovery II for a hesitation when cold or a restart after it has sat for a while.
It usually only does it for a very short period of time and clears up within a quarter mile or less. After that,it runs fine.
My buddy says it started about a month ago and had been running fine since I worked on it earlier this summer. I did some routine maintenance
such as replace the spark plugs,oil change,air filter,BG Fuel system service (injector clean and 44k in fuel tank) andreplaced plug wires
When I start it cold,it fires up fine,idles up ok,but when i put into gear and hit the gas,it hesitates almost to the point of stalling and it backfires
through the intake. I know it is running lean,but can't seem to fine a reason for it.
I pulled DTCs from the vehicle,P0171,P0174 (lean banks 1&2) and several misfire and catalyst damage warning codes.
Fuel pressure is 50 psi and holds steady after shut down. checked Coolant and Air Temp PID values and they were normal.also checkedfor vacuum leaks and leaks in between throttle body and MAF sensor
I visually inspected MAF hotwire and cleaned oil residue off with a q-tip and rubbing alcohol,problem is still there.
The Vehicle has 128,000 miles on it.
I have read several posts of people saying that the MAF sensors are troublesome,but have no way of testing one to condem it as faulty.
Any help would be great! Thanks



[IMG]local://upfiles/8340/0F577B843C044DBF8328B37C1EA8F03E.jpg[/IMG]

 

First thing, the Bosch MAF's won't take to being cleaned, they'll just up and die on you.
Did you have any code related to either 3rd. or 4th. gear out of ratio. If you did along with both banks running lean, then you will need a MAF, make sure to order it on line, $130, as apposed to doing to the dealer, near $200.
What brand of plugs, what gap and what brand of plug wires did you install?

 

As a matter of fact,I did have an incorrect ratio for 4th gear code
(P0734)
I installed Bosch Platinum +4 plugs ,no gap adjustment required
Plug wires Im not sure,except they were blue
Thanks, Karl Kuenzel

 

So you need a MAF, best price around is thru Tony at Cerrone's, 650-365-4145 at around $130 and postage. They are pretty much plug and play and that truck will run fine again. Tell Tony, Mike said Hi.

 

Awesome,Thanks for all your help Mike. Actually,my son works at the Toyota-Jaguar dealership which is also Engle Imports
Parts. From what he tells me, they are a major parts distributer of British car parts here in Kalamazoo. I'll have him check on price and availability on a MAF sensor.
BTW. Does the Discovery have learned adaptive strategy for fuel trim,if so,will disconnecting the PCM clear it?
Thanks again Karl Kuenzel

 

Two thought, you will need to clear the codes with your scanner and yes you can re educate your ECU, just drop the negative battery cable for a couple hours and you are set.

 

Hi Mike! Got the MAF sensor yesterday and installed it.What a difference! runs great cold now with no hesitation or backfire and now it will shift up
to 4th gear. Thanks a Million! Karl

 

Glad it worked out for you.