ChiquitinNegro

Hi all!

This is my second post in the forum....and I'm afraid none are good words...I'm havign some issues with my pony since I fixed others, and I'm asking for expert owners opinions. here's the story:

1. I bought the car, a 2005 GT, mechanical stock, only furniture adds on (no electrical consumption). Before selling it, the seller changes the TB (U know, typicall issue)
2. Drove the car for few months (like 4), tunning well, although the previous owner didn't take care of it in good manner
3. I take the car to a shop for basic maintenance: filters (all), oil and general check. After this, car still running well.
4. One day (like 3 weeks or so after check) , the CEL comes on, but the car runs the same, well. I take it to the shop, code PO340, have the CPS replaced and the DTC codes erased. A few miles later, hte CEL comes on again, same thing.
5. I finally discover the common alternator issue (thanks, Themustangsource), so I got the alt replaced. Somewhere between the points 3 and 4 I noticed a jerking/buking in 1st and 2nd gears between 1500-1800rpm when slight throttle.
6. Once I replaced the Alt, the jerking/bucking was still there, but no more codes. It may have loose a bit power. 1 (one) day after the alt replaced, coming home, an terrible sound suddenly appears in the engine bay and the car sounds like diesel!!!
I realized it was now the cam phasers (thanks again Themustangsource), so I ordered nwe cam phasers. Because my mechanic don't know a lot about Mustang (I'm in Spain), he opens all the distribution of the engine, so I decided to go on with a distribution replacement. I olso ordered nwe spark plugs (motorcraft) and new coils (thinking in jerking).
7. Once the job is done, I took the car off the shop and realize a pair issues: the jerking/bucking is still there, but now it is only in 2nd gear, and happens between 2000 and 3000rpm at slight throttle (i fyou push throttle gently, is hard to find that jerking), and the iddle is not stable. When I come to a traffic light and I stop th car, the rpm's drop to 500, like It was going to stall and then come back to normal 750-800.
In a couple of days the iddle becomes normal (relearning?), but the jerking/bucking still there.

Summary:

In the last 4-5 months: Tb replaced, alt replaced, new oil, filters (all), coils, spark plugs and distribution. My mechanic also cleaned and checked the injectors, all fine. Issue still concerning me: jerking/bucking in 2nd gear between 2000 and 3000 rpm, under slight throttle, If you push the throttle hard, won't notice it. In any other gear or rpm range, car works fine. Maybe It has lost a bit power....but I can't say it for sure.

So, now I'm thinking about admission trouble; my next steps are check and clean the MAF (It look like stock) and check for any vacuum leak. What do you think, guys?

I need some help from TheSource!

Thanks in advance to everyone



Edit: It's a 2005 GT, all stock with 58000 miles on it. Between points 4 and 5, with the slight jerking, I also noticed a 10-15% fuel consumption increase. Now the mileage is good, like when I bought it and emissions are perfect, so it looks like combustion is pretty good (injectors, sparks and coils cleaned/new)

Bert

it is really hard to sort out from here; but my first suspect is the throttle body -- I assume it is aftermarket (not Ford OEM) and it may not have been calibrated properly when it was installed; also I am not sure if the change of throttle body would require a tune but it might . . . I would probably look into the calibration procedure for the Throttle Position Sensor

ChiquitinNegro

Hi Bert, and thanks for your answer.

The TB was replaced like 9 months ago and the technician that performed that replacement did calibrate it. When the TB was replaced, the car run fine, so I dont think that maybe the problem, but I'll care of it.

This week I'm going to clean the MAF sensor, I'll tell you what happens then.

wanted33

Like Bert (and you know this also) it's hard to troubleshoot a problem like this when you've done a lot already. After the MAF you may want to consider a new fuel filter. It's not that hard to change, and cheap enough to cross that off of your list. And, even though the mechanic re-calibrated the TB I would do it again just to make sure. That's another easy process, just takes a little time, and if you're not familiar with the procedure just check out YouTube. That's how I learned how to calibrate the TB. Good luck, I hope you can find that problem.

ChiquitinNegro

Hi wanted, and thanks for your reply!
The fuel filter was changed like 4-5 months ago, it has now like 500 miles on it.
I alredy cleaned the MAF today and changed air filter and car seems to be smoother now.....but the jerking/bucking problem still persists.
Despite the TB was replaced, I don’t know if it is new, remanufactured or what, so I’ll keep it in mind. Anyway, no DTC codes un the dash. On the other hand, I’m not sure about what you say TB calibration, I mean, I read about the iddle relearn process (wich is automatic I guess) and the throttle calibration, something like this? But here in Spain we don’t have the machines for this car I’m afraid. We can diagnose almost everygthing but not sure about calibration...

Thanks for all your answers guys!

wanted33

Forgive me my friend, instead of TB I should have said idle relearn. Sorry, getting old don't you know.

I'm just thinking outside the box here, but here's what mine does for time to time. It will buck once or twice starting from a stop after a long drive on an interstate, or highway. I've learned to run up the rpm's a couple of time while stopped to help this situation. From my research this is caused by air building up in the fuel pump while on the long runs. We call that a "vapor lock" in my area of the U.S. It seems this little problem happens to many Mustangs of the same age as ours. I said that to say this, maybe just maybe it's your fuel pump. Again that's just a wild guess. Good luck, I hope you find the problem as I know it can be quite aggravating.

Jim

ChiquitinNegro

Thank you for your answer again Wanted! I'm going to try what I posted before, the TB calibration. As I said, car's battery has been disconected a couple of times and never did something like that for the TB. Hope that worlks.

Wishes

Bert

I hope someone who knows this better will chime in, but I think there are actually three things relating to the throttle body that might relate to your issue:

1) the throttle body calibration -- this involves using a volt meter to make sure the signals are correct and potentially adjusting the tune? to compensate if it is a bit off
2) the throttle position calibration -- this is a simple procedure that involves pressing the gas pedal slowly to the floor; I think it is in the owners manual\
3) idle re-learn -- I believe the computer does this automatically and it take some time to figure out how to manage the idle