Please help diagnose

[killr3v]

Two weeks ago the car stalled out of nowhere. Tried starting it several times and it wouldn't start. I checked that the engine was getting fuel, the spark plugs and COPs. They all seemed fine. I then decided to reload the tune. The car started right up. I thought the problem was over. I then drove it for several days with no issues except for surging at idle. I decided to purchase the latest ford alternator discussed in the alternator thread to see if this would cure the issue. I had gone through two alternators from autozone.

Before I installed the alternator I decided to retighten my exhaust since I had a few leaks. I then installed the alternator. I started the car and noticed that it now misfires. Thursday it decided to stall again. It didn't want to start so I tried reloading the tune. This time that didn't help. I tried one more time and it did start but it was misfiring even worse. I rechecked the coils and plugs and they seem fine. Drove the car and it is hesitating horribly. Checked for a clogged fuel filter but filter is perfectly fine. I datalogged and it seems to get enough fuel. I am at a loss here.

 

[Rypper1]

Mine did something similar to that and it turned out to be a bad Throttle Position Sensor. Put a new one on and haven't had any further trouble. Might not be your problem but worth looking into.

 

[ArtQ]

When you datalogged what were your short term fuel trim numbers?

 

[mac10chap]

I would start with the cheap stuff. Clean the MAF and TB. Are you throwing any codes? Have you thought about buying a new set of plugs anyways just in case? If these are good, then you just have a new set on layaway for when you need to replace. You say it is misfiring...is it a random cylinder misfire or is it related to specific cylinders?

I know that O2's would not cause a misfire but they could be responsible for the surging and running like shit

 

[AbdullaGT500]

Do you have a check engine light?

 

[killr3v]

I don't think i did the short fuel trim Art. I'll need to check that out again. I had a spare TPS sensor so I installed that and it didn't help. The only codes it's thrown were TPS related but like I said, the spare TPS didn't help. I'm thinking of doing the plugs like you said Chap. I will check the o2 sensors as well. I did notice though that if I unplugged the MAF the idle stopped surging. I've checked for vacuum leaks about 3 times already.

 

[kevinatfms]

what were the TPS codes? sometimes the TPS codes are related to the pedal assembly not the TPS on the TB.

 

[mac10chap]

stupid question maybe, but is you're oil cap on? I know that I left the oil cap off on my Expedition about a month ago and it did the same thing. It was surging and bogging, and threw codes.

Long shot, but still worth asking...

 

[05xgt]

what were the TPS codes? sometimes the TPS codes are related to the pedal assembly not the TPS on the TB.

What he said. If it's an 05 early build it could be in the pedal assy. This happened on mine as well, sudden shut down, when it would run it would surge and go into limp mode. Twenty dollar replacement and it was done. Hope this helps.

 

[G.T]

My money is on the MAF.. Disconnect your MAF and see if it starts..

 

[killr3v]

so it could be the pedal assembly? I'll check that out. I will also see if the car will start without the maf. I bought some new plugs just to rule them out. Oil cap is on haha

 

[AbdullaGT500]

What are the codes? You can look up the number and find out exactly where the problem is instead of guessing.

 

[killr3v]

2112 and 2104. I swapped the plugs to some new HT1s and the car is running great now. I'm gonna datalog in the morning for the short term fuel trim to make sure fuel is good. I really appreciate you guys' help with this.

 

[mac10chap]

2112 and 2104. I swapped the plugs to some new HT1s and the car is running great now. I'm gonna datalog in the morning for the short term fuel trim to make sure fuel is good. I really appreciate you guys' help with this.

good deal bud...usually something easy like that

 

[killr3v]

Yeah I am definitely relieved it wasn't something huge. I datalogged and short term fuel trim was:
1- .68
2- .66

I don't know what that means so...Art if you would tell me if that's good?

 

[kevinatfms]

thats about right for the STFT. what were the long term's?

 

[ArtQ]

I'm not sure what you're loking at there. You should be able to see fuel trim for each cylinder. Very healthy would be between -1.5% and + 1.5% average is most likely going to be +/- 3%

 

[killr3v]

I'm not sure what you're loking at there. You should be able to see fuel trim for each cylinder. Very healthy would be between -1.5% and + 1.5% average is most likely going to be +/- 3%

Well the options on my tuner were short term fuel trim 1 and short term fuel trim 2. This was with the handheld. I didn't use the laptop.