help,it's not the fuel pump - RESOLVED
 

Hi all, although the symptoms pointed me to the pump, it's registering 55 PSI at the rail. When cold it will idle fine and give enough throttle to move into another spot. When warm it wont even idle, although fuel pressure remains good. I think this means I can rule out pump, filter and relay but I'm not sure where to go from here. Any pointers would be greatly appreciated......Roger.

What model (engine) and year is your Cat? And perhaps you can elaborate on what you mean by "When cold it will idle fine and give enough throttle to move into another spot"? Are you saying that it drives and shifts ok? Or is it only limping?

Agreeing with Jagfix, it is always nice to know what specs are having a hissy moment.

My guess is the CTS (coolant temp sensor), and/or the wiring at the plug is flaky.

Age is now almost certain to be creeping (maybe running) into the TPS (throttle position sensor), under the throttle body. It also suffers from oil ingress from running down the throttle shaft and directly into the TPS, thus reeking havoc.

The notorious "balck goo" in and around the throttle disc also upsets idle, mainly when at operating temp.

Bugga, did not realise it was a new thread, old age does that, your turn WILL come.

Might pay to edit your sig etc to have your car details pop up automatically each time you post, then there is less for you to think about, mmmmm.

Hi Grant and Jagfix, Sorry, I always think the car details are there. I'll fix that. It's a '93, 6 cyl, 4ltr, VDP. When cold it will hold about 1300 revs, sufficient to actually move. When hot it wont even idle. I'll check into Grant's suggestions......Roger.

Roger,

I keep forgetting that you guys got an EGR system (exhaust gas recirculation), and we did not.

I read here, and elsewhere, that this system reeks HAVOC with hot idle, so hopefully some one in your market will assist with info on cleaning the valve that is constantly mentioned???.

1993 xj40 vdp.
 

Now, it starts fine, from cold and, will continue to idle at 800/825 rpm for as long as you leave it alone. However as soon as you touch the accelerator it stumbles, detonates and cuts out and, then refuses to start, until it has completely cooled down. Once it showed code '48', 'idle speed control motor', but now just reads 'fail'. Plugs show a 'too rich' condition. I dont see how the ISCM would prevent it from running completely. Any comments would be greatly appreciated, as this has me stumped......Roger.

Roger,

Reading that a few times over morning coffee, and then backing up to the other bit of the thread, I reckon you got a TPS gone AWOL.

It finds a happy spot at idle, but as soon as you "crack" that position it gets to the damaged area, which is usually just off idle to about 1/3 throttle. The ECU gets "fuzzy" signals, so defaults to max fuel (usually), and throws a code/s.

That TPS may only be loaded with oily muck that has run down the throttle shaft. Many people have had success with cleaning it with a solvent (contact cleaner) in a p/pack can, some have not. Worth a try, it certainly cannot make it any worse.

Hi Grant, thank you, I'll certainly look at that but, seems to me that it's pointing more to an ignition problem. I'm surprised that no one else has seen a similar problem, or is this one reserved just for me, I wonder......Roger.

My XJ40 real time is limited.

We only had one, and that was a 1988 3.6 belonging to the teenage daughter, and she was NEVER home much, and the car was super reliable.

HOWEVER, when first aquired, the HT lead from the coil TO the cap was a tad sad looking, and when pulled to remove, the coil end stayed inside the coil, and NO amount of digging and prodding could get it out, it had literally "grown" into place, and a odd green coloured powder everywhere, so a new coil and HT lead set were installed. All good. Sooooo maybe??????, dunno.

I'm still thinking TPS, they give exactly the grief you mention on the V12's, and it is the same basic item. The V12's have issues with the heat, and XJ40 and X300 have issues with the oily muck running down the throttle shaft and entering the TPS and shorting the resistance medium, thanks to gravity.

1993 vdp xj 40
 

Hi Grant, thanks a lot. I did try another coil but, same result. I'll look into the TPS situation and get back.......Roger.

1993 4.0 vdp
 

Hi Grant, after trying everything else, I came down to the crankshaft position sensor, I could get no reading whatsoever from it and, therefore ordered and just received a replacement. I will be fitting it early next week and will post up any result. I still cant believe that no one else has had this problem, though.......Roger.

I don't think it's a common failure , I hope you get it fixed , keep us updated

1993 xj40 vdp
 

Yup ! it was the crankshaft position sensor, new one fitted, now runs well, again........Roger.

SWEET.

Someone with the "power" should put the CAS in the sticky area. Maybe old age is now causing failures??.

Good news, thanks for your update

Hi and thanks, Roger! I have a similar problem with an 89 XJ6. Do you mind telling where the crankshaft position sensor is?

Hi brokernv, the crankshaft position sensor is at the front of the engine, on the main pulley, at the 10 oclock position. It's held in place by an Allen screw. After undoing the Allen screw, it will pull out. The wiring goes to the front of the cylinder head, retained by some ties. I found, moving some hose clips made access easier.........Roger.

Thanks Roger!