Hesitation on light throttle

[Rewmer]

2002 4.4.

As the title says, I have an issue with a missfire / hesitation on light throttle openings. It manifests itself after a few miles from start up and only seems present on very light throttle openings, mostly after slowing down from a reasonable speed and then applying throttle again.
To date I have renewed the plugs and coils, cats and the PCV system. I have smoke tested the inlet to check for air leaks and done a compression test on all cylinders. Air flow readings have been checked against a known good MAF. I am now running out of ideas and welcome any input. Its also worth mentioning its a duel fuel car running a sequential LPG system, the problem is present on both fuels.

Iam starting to think perhaps the throttle body itself ????

[Big "J"]

Stop throwing money at it . I'd take it to a reputable Indy and have them hook it up to GT1 software and see what's causing your hesitation?

Good Luck and keep us posted, please!

[Rewmer]

Thanks , i did, who diagnosed a head gasket blown and wanted me to hand over £1500 to fix. After pressing him on how he got to this diagnosis he said it was his best guess.......

[bbultman]

Sounds like the notorious torque converter lock/unlock failure. Many of us here have had it, particularly with the 4.4 and 4.6. It manifests itself very much like a misfire about every 2 seconds under light acceleration. If it appears to go away in Sport mode or with the cruise control on, it's the torque converter. Both of these scenarios essentially lock up the TC so it doesn't keep unlocking. Search TC failure and symptoms on this site....there's a bunch of info. Brace for a TC replacement. I just drive in sport mode now and it's fine but a TC or full trans replacement is on the horizon. Best of luck.

[Rewmer]

Now that sounds interesting. But would the tc throw up a mil lamp with missfires ? This is what happens if I don't drive through it.

[bbultman]

I get no codes so if you're getting a code, maybe it's something different although I have heard of mil lamps for TC issues if it senses a heavily worn TC or a valvebody solenoid failure in the trans. The 'misfire' feeling from a worn TC happens consistently every 2 seconds under light acceleration from about 40mph to 60mph. When the TC goes from unlock to lockup it causes a slight load on the engine and makes it feel like a rythmic misfire. If your X5 is doing that, I can almost assure it's a TC which is a very common wear item on the X5s, especially if your at or over 100k miles. Try the cruise control and the sport mode and see if the throttle hesitations/oscillations go away under the same driving conditions. Please report back. It's always good to have more data points for other Xoutposters

[Rewmer]

Thanks for the tips guys. I have to admit that it does sound like a TC issue now Ive read up a bit, but mine seems to have some differences to what people have been describing. The "Miss fire" only last for a second or two if you keep gently accelerating. It becomes more prominent if there is a load on, ie my trailer. The gearbox changes are as smooth as silk up and down with no clonking. Going up a gentle incline with the trailer on and getting the speed just right I managed to get some faults registered which where all " missfire on cylinder x" and multiple missfires. so I am sure its an engine problem rather than trans. Ive ordered up some new O2 sensors as the existing ones look original and Ive got 130k miles on her now, so we will see if they have any effect.

[georgek67]

Sure you've thought of it, but fuel filter?

[georgek67]

Then again, just re-read you've got the same problem with the LPG system. Next.

[Rewmer]

Well guys, the more testing Ive done thanks to the pointers on here (thanks guys) It looks more and more like the TC. To this end Ive booked her in with an auto trans specialist for a diagnostic. I will keep you all posted.