HELP! 5 months on and still problem can't be pin pointed.

Can anyone pin point a fault that is causing mounting garage costs with no resolve. Since last autumn my 2005 hijet pickup starts up fine on idle, however, until it fully warms up the engine wants to stall and requires my foot to the floor while driving. It's feels an old fashioned car with a broken choke that won't up the revs till warm. The vehicle uses petrol and LPG but the fault occurs with both. I've been to a number of garages including a Piaggio main dealer who gave up. It's been at the last garage for over two months! The 3 pin coolant sensor, upstream lambda sensor and even ECU have been replaced at cost, yet still the problem persists!! Mechanic says that the ECU is flicking open the fuel injectors far too long causing flooding and black smoke. However, yesterday he told me he had discovered an additional secondary ECU attached to the vehicle that governs the LPG. When he unattached this LPG ECU the whole engine went dead, but re-coupling it then found the fuel flow had much improved to a lower level. Although improved the fuel is still rich and the overall problem remains. He had noticed the secondary LPG ECU had loosely taped wires. I'm desperate having been without wheels for so long and MOT now expired. Thanks. Chris.

If fiddling with the LPG ecu maks a difference I would take it to an LPG specialist because I am not convinced that ordinary garages are all that good with such systems.

Bit of a stab in the dark but I think that LPG has a different lamba to petrols 14.7 to 1 ratio so the ecu for the LPG should register the difference and adjust the flow and any taped wires get a soldring iron and some heat shrink to them, other than that talk to Highlyjetted as our resident electrics whizz.

I think you need to get back to basics, don't let anyone buy a part for it unless they can prove it does not work!

The parts replaced so far are the typical stab in the dark which most garages tend to do with these odd running electrical faults. And that ecu you were sold, oh my god, I've met so many lost souls who have fallen into that game - and it usually isn't a cheap game either.

If you go on the manuals section and get the porter 1.3 16v - electrical section you can see the whole efi system. Print it and make sure it goes with the van to who ever works on it. If they don't ask if you have a wiring diagram, or are not especially greatful then they are not the right sort of garage to solve this issue. Find an auto-electrician, not a spanner monkey.

Now for some leads....

There is a item called "IDOL-UP VSV" - I would find this, it'll be somewhere on the inlet manifold/throttle body assembly, it makes a new airway open up to allow the tick over to increase on cold start up etc. It is the 4th item on the top right of the "EFIECU" on the diagram - Sort of in the middle of the page at 7 o'clock.

It may be full of gunk which happens commonly on many cars, the gunk comes from the crank case oil breather, when its open no air could get through it anyway. It may also be knackard e.g. the solenoid is frazzled, to test you can activate it by connecting a 12v feed, by the looks of the diagram it would seem to be the white and red wire but by using a multimeter you could find out by seeing which wire is ground - the other is the activation feed.

If that doesn't solve your problem, and even if it does! - you should test the map sensor both electrically and also if its actually piped up and good. The map sensor is just a pressure sensor which measures the vacuum of the inlet manifold. I think from memory one pin is a 5v feed, one is ground and the other is the signal. With the pipe going to the atmosphere it should make 2.5v but I need to check that figure, and if you suck with all you've got it should drop by about 1 volt max.

Next one to test is the throttle position sensor, again it has 3 wires, a 5v feed, a ground and a signal wire. You should find it smoothly swings from about 1 volt to 4 volts, when you press the accelerator pedal from rest to the floor.

You may find you have one problem which is causing your crap start up idle, and another which is causing it to run rich.


I would expect the van to not run if I disconnected the LPG ecu - it has some wiring in place which can cut the fuel feed by cutting out the ground to the injectors (probably - there are other hacks), thus when you switch over to gas it just gets gas and not both!

That black smoke is usually causes because there is so much fuel in the exhaust gases it washes the carbon deposits out of the exhaust system - and if its running like that, the new lambda sensor will probably be fucked as they react badly with fuel and or oil.

If you get lost resolving this, and you live close enough to crewe, cheshire to bring it to me I'd fix it on a no fix no fee basis. Because I love fixing those ones which are a bit of a puzzle, but are not about lifting heavy metal stuff about.

Highlyjetted (Matt) rant over and out

p.s. Good luck

Thanks Highly Jetted (Matt) for your suggestions last spring. Your opening sentence "I think you need to get back to basics" rang very true when after 3 months in the garage they finally opened the throttle body and found a simple spring inside was broken!! It seems that mechanics concentrate too much on fault finding computer data when the problem is far more basic. Thanks again for your earlier kind offer of assistance. Chris

Great news Chris, hope the bill isn't too bad. This must have been going of for over 5 months now.