Hey guys,

No, this time it isn't my Jag... This is an XK8 but heck, it is the same enginewise as the X308... So treat this as an X308 post!

Right, my friends car (1996 AJ26 4.0l NA US Model) will not inject on cylinders 2a, 3a, 1b and 4b (or 2, 3, 5 and 8). The car starts - when cold - and runs at first totally perfect. He can drive around 60 miles and then switch the engine off. Start it again and it will run for 2 seconds on all 4 cylinders and then only run on 4. Mechanically the engine is absolutely sound. New tensioners were fitted last year and all works properly. I started the car, ran it, worked like a charm. Switched it off, reqd out the codes, deleted them, started it again and it was a bag of poop...

After reading the codes we get hints towards the secondary ignition circuit and the mentioned cylinders:

P0352, P0353, P0355 & P3058

Also P1336 & P1368

All 8 cylinders have ignition sparks... We have checked everything possible and can't find anything. The injectors have a ground if you do a continuity check between the ground pins of the injector loom. The injectors also are at first given signals but they are then removed as soon as the engine is sent into failsafe mode.

The ignition modules and coils were checked and replaced, they are fine. As said, the sparks are nice and strong and are on all cylinders.

So, what do you think is worth checking? As said, when totally cold, it runs like a gem. Turn it off and turn it on: it runs like a bag of poop... We can't get any firther right now.

Cheers

Damien

 

The early ECU was is subject to capacitor leaks. Open it up and check for discoloration on the circuit board.

 

We did that. Looks like new inside. No discolourations... ThougH I think it is a dead ECU but I want to avoid telling my friend to get a new ECU if it isn't it...

 

There are companies in the US that can test and rebuild the ECU and I expect the same is true in Europe and England.

 

Yeah, there are enough, but as said, I want to be totally sure BEFORE the ECU is sent for repair (about the same price as a used ECU) and find out, it isn't at fault.

As said: electrics seem fine... The wiring is all there. The engine starts up perfectly every time but when warm will instantly cut the injection to 4 cylinders. It still runs amazingly smooth for a 4 cylinder V8

Just seems quite "weird". The fault codes hint towards ignition issues but they can't be...

 

So it runs okay on closed loop but not open loop. Try disconnecting the MAFS and check the temp sensor resistance. ASI rebuilt my ECU and they tested it first for $55, which was then applied to the repair.

But taking the car to a shop with full diagnostics may be the best choice.

 

Temperature sensor is brand new and original. MAF is also brand new and original.

Question is when is open loop activated? Within 3 seconds of the start? As said, the first 3 seconds it runs PERFECTLY (when warm). But then straight into failsafe mode.

 

I think about 175 F is when it goes into open loop, so if it's above that temp on startup it's very likely 3 sec or less. The fact that it can be driven 60 mi from a cold start is confusing.

 

Yes, very. As said, it will ALWAYS start and run. And when cold you can drive it as if it was new. But once turned off and restarted, it will cut off 4 cylinders.

And when it runs like new, there are NO issues what so ever. It doesn't make any nasty noises in the engine bay (no rattles or so) nor are there any mechanical noises from inside the engine. It is absolutely quite and runs as smooth as a brand new V8. Not a beat missed.