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Stalling fixed, next...

big-yin

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Oct 13, 2018
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scotland
Over a week ago I helped fit a new fuel filter, no stalling issues thus far on my 99 100 4.2TDi.

However over the weekend the AHC got stuck on low. When I press the up button it flashes N a few times then does nothing. When I drive away it stays on Lo.

I’m hoping to get it on the ramp tomorrow to see if anything obvious is going on but anything specific I should check? Also is it still safe to drive about like this?

Thanks.
 
As generic info, check you’ve not dislodged or disturbed anything around the fuel filter, wiring connections and such. Also check the fluid is not low. If it is, check for leaks.
 
It appears from what you have written that the AHC was fine immediately after you changed the fuel filter and started playing up a week later.

To get a full picture of what AHC is up to you really need Techstream so that you can check the pressures. It could be that the fuel filter change is completely innocent and your pressures are too high.
 
It appears from what you have written that the AHC was fine immediately after you changed the fuel filter and started playing up a week later.

To get a full picture of what AHC is up to you really need Techstream so that you can check the pressures. It could be that the fuel filter change is completely innocent and your pressures are too high.

Yes this is correct. Hmm ok looking quickly it just looks like OBD2 based comms. Does that use generic OBD2 parameters or Toyota specific to check the pressures? If generic then I have software/cables already I can use, although I need to go on a hunt for the OBD2 port, must admit I thought it was pre-OBD2 being 1999 but will have a look over lunch. Thanks.
 
It is not OBD2. The port is just above the brake pedal. There are a few readers that work with it but it is generally accepted that Techstream is the one to go for. Available on eBay with a cable.
 
It is not OBD2. The port is just above the brake pedal. There are a few readers that work with it but it is generally accepted that Techstream is the one to go for. Available on eBay with a cable.

Nice one, thanks, will have a look, worth having anyway.
 
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Forgot to say, you will need a windows laptop or tablet to run Techstream. I bought a cheap Chinese Windows tablet that I use with it.
 
Forgot to say, you will need a windows laptop or tablet to run Techstream. I bought a cheap Chinese Windows tablet that I use with it.

Yeah thanks, I'll use a laptop from my day job so all good :)
 
Once you get it installed it might give you some clues with error codes. If there are no codes the spec for the pressure is

Front 6.4 - 7.4 MPa
Rear 5.6 - 6.7 MPa

I know yours will not lift but at normal height it should be 500mm from front hub centre to wheel arch lip and 520mm at the rear.

If the front pressure is too high you can crank the torsion bars so they take more of the weight. At the rear you need to either add spring spacers or replace the springs.

Has the AHC fluid been changed?
 
Once you get it installed it might give you some clues with error codes. If there are no codes the spec for the pressure is

Front 6.4 - 7.4 MPa
Rear 5.6 - 6.7 MPa

I know yours will not lift but at normal height it should be 500mm from front hub centre to wheel arch lip and 520mm at the rear.

If the front pressure is too high you can crank the torsion bars so they take more of the weight. At the rear you need to either add spring spacers or replace the springs.

Has the AHC fluid been changed?

I've not changed the AHC fluid during my 2 months with the car. It has gone up and down fine before and you can see it on max when its on low then drops when it goes up. Thanks for information, very helpful.
 
The main issues with AHC are normally maintenance, or rather lack of maintenance, and the sensors. The sensors can corrode, sometimes salvageable with a strip down and clean, or the actual arms on the sensors can snap.

If you can get yours lifting again it would be worth considering flushing it with new fluid. This is the maintenance item that a lot of people fail to do.
 
Maintenance also includes keeping an eye on the pressures. If they are routinely too high you are putting too much strain on the system which will lead to premature failure.
 
Hello Big if you find that your pump is u/s i have one that has done less than 100 thou from an 2001 when i swapped it for ironman kit can be yours for your time and diesel am i somerset for various nasty crimes commited in a previous life
 
Hello Big if you find that your pump is u/s i have one that has done less than 100 thou from an 2001 when i swapped it for ironman kit can be yours for your time and diesel am i somerset for various nasty crimes commited in a previous life

Thanks, i'll keep you posted. I tried to find the OBD port but couldn't see one. There is a plastic connector under the bonnet on the left labelled diagnostics but looks to be very old school but above the brake pedal wasn't any obd connectors.
 
FIXED! I thought I'd start from scratch and check fuses, then found the AHC fuse was blown. £3.48 later and its working again, yay. Thanks for advice & comments.
 
That's great. Still a good idea to check the pressures. Fuses don't normally blow for no reason. Maybe the pump was overworking?
 
That's great. Still a good idea to check the pressures. Fuses don't normally blow for no reason. Maybe the pump was overworking?

Yeah I would like to but can't find the OBD port above the pedals, maybe mine is an early one which doesn't have it. Will investigate it a bit more over the weekend.
 
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