Jolting and Stalling during Acceleration

[SaintGeorge]

Hey all,

Having issues with the rig and would appreciate some as I am stumped.

CAR: D40 STX (2008) Thai Built

Engine: YD25DDTi, Diesel.

Checked, works good:

• ECU, general fuse box, ABS fuse box
• Engine oil
• Transmission fluid, clean and good level
• Coolant
• MAF
• Vacuum tubes

Explanation:

• RPM stable at idle always.
• Able to accelerate full throttle to 3rd gear 90% of the time.
• 60-80km rpm jumps around, sometimes stalls, struggles to maintain speed or accelerate further.
• Sometimes gears slip when trying to jump to 4th gear ONLY.
• Looks as if it’s trying to find the right rpm in relation to how much I’ve put the pedal down, jumps between different rpms for a few seconds.
• If I let go of the pedal at 60km+ the car will kick back and RPM will fluctuate, sometimes drop down <1000rpm and either stall or wake up.
• On rare occasions the car will barely have any issues but other times it will be dangerous to drive in.
• Burns rich when struggling.

I've checked with my OBD2 reader and i'm getting no fault codes.

Common rail pressure: ~32000kpa at idle, rpm at ~750.

Calculated load value: 18.4%

Intake manifold absolute pressure: 103.0 KPA

I'd appreciate help of any sort, and am happy to answer any questions.

Thanks,

George

 

[Old.Tony]

Hi there, sorry I've been away in Tasmania and haven't been on the forum at all (since the middle of November!).

It sounds like the TCM either has poor communication (debris in the plug?) or there's a sensor problem inside the gearbox. It might be as simple as the neutral position switch (it's one of the switches on the side of the gearbox). Unplug everything, plug it back in, see if that improves things.

A mechanical workshop's OBD scan tool has more extensive information available, including things like turbine speed in automatic gearboxes, TC slippage rates etc. If you have a mate who has access to one, that might tell you more about the gearbox.