Rough warm start & idle 2008 xlt 4.6l
 

I have a 2008 f150 xlt 4.6l. It currently has 178,000 miles on it.

There is no CEL or pending codes

shortly after purchasing it used about 6 months ago, it started having a rough idle when reaching operating temp. It then started having an extended warm start after sitting between 15mins- 2hrs. I replaced all fuel injectors 3 months ago after getting them tested and having a couple leaking. It cured the rough warm start, but did nothing for the idle. The rough warm start has since returned. Seems like a rich start when warm as it tries to start but continues to crank for an extra 4 or 5 seconds. This is only on a warm start. Cold start and idle are great.

things that I have done to it:
~ new plugs
~ new air filter
~ new fuel filter
~ new PCV valve & hose
~ new camshaft position sensor
~ all new fuel injectors
~ cleaned throttle body
~ tested & cleaned MAF sensor

all OEM parts

I just got a new EGR valve that I am going to install tonight.
I also inspected the ECT and noticed one of the wires had a gouge out of it. I soldered it back together, but would an exposed wire ruin/short out the ECT sensor? I have not tested it yet. Will do that in the next couple days. Is there a reliable chart that I can get to gauge the resistance at different temps? Any help/input is appreciated!

pic of the damaged ECT wire
https://cimg6.ibsrv.net/gimg/www.f15...d53fb3eb0.jpeg

I would suspect the FPDM. Check the backside and connector for corrosion.

I will inspect it tomorrow and see what it looks like.

The new EGR did not fix the warm idle or start. The old EGR was coated in carbon and not in the greatest shape.

This might help:

https://www.ford-trucks.com/forums/5...rd%20%2B-15%25

Bit of a difference between a 93 Aerostar and a 08 F150......

I ordered a new ECT sensor. It should be here tonight. Will update whether it fixes anything.

Have you checked the FPDM yet?

Did it fix it?

the FPDM looks to be intact and in good shape, but will need to test it to be sure

my particular engine did not have a CTS. The CHT sensor supplies data to the ECU. I replaced it bc it was not accurate in resistance due to temp changes. It did not fix the idle or hard warm start.

I am starting to think that I need to check the new injectors that were put in. Maybe there is a hung up injector that may have sprung a leak. I replaced the injectors before I replaced the PCV system which may be letting some blow by into the system. Any advice is appreciated! Thanks for the responses to this point.

You could try disconnecting the injector wire connectors one at a time to evaluate change. Could also do this for plug coils.

Could be vacuum leak. You’ve probably visually inspected the hoses, but you could try disconnecting them one at a time.

Does your OBD device read cylinder misfires, fuel rail pressure, fuel trims, MAF, IAT? Are there still no codes?

That's all I can think of right now. If you let us know the result of these suggestions/questions maybe we can help further.

Status?

the rough warm start was due to a leaking injector. Once I cleaned all the injectors out it fires up cold or warm.

it still has a rough idle when it reaches operating temp.

mu obd scanner does not read the above values. I would need to take it to a shop to get that info. I am going to dig deeper and see if it’s possibly a vacuum leak somewhere that I haven’t noticed.