Could be the wiper arm of the sender unit loosing contact with the windings . In a still situation the wiper arm comes off the windings but as you slosh the fuel around in driving the float walks with side to side motion the wiper arm back in contact . There should be a signal damper circuit in the display unit so you don't see bips in the fuel readings as the wiper looses contact . I could be totally wrong but I'm just thinking hypothetical .

 

Literally just had a new problem develop with the jag, with the hesitation and rough idle in park still present. Get paid in two days, was looking forward to fixing the leak in the AC system so I can get my aircon back but oh well.

Was driving back home about an hour ago, car was driving fine, then on the exit of a mini roundabout, when throttle was applied, the car hesitated and changed through various gears before settling on one. It did this all the way home, only 3 miles or so, with it getting worse as I went along, i.e, Id be accelerating out of a roundabout then it would lose power as if id put it into neutral, then it surges forward, then stops etc. Any common diagnosis, considering the current problems?

I will say that it has been throwing it down with rain in GB recently and the jag is not dry stored. I did check the ecu area a while back but the area seemed very dry, and I have an untouched security strap in place and didn't want to hack away at it. The last thing I did was clean the MAF sensor 2 weeks ago, so thats my bet, or TPS perhaps.

 

Transmission electrical connector will effect the engine regulation and can be easily cleaned without jacking the car on the left side . If it doesn't help it doesn't hurt keeping this item maintained . Have you cleaned the engine ground strap mating surfaces by the starter motor ?

 

Thanks for the quick reply as always Lady P, I haven't done any underside cleaning since I bought It. Il check that transmission connector today, and also check ECU again for signs of water intrusion.

 

Turned out to be rather simple in the end, It needed more fuel. since my fuel gauge isn't working I usually go off the fuel used function, in that If I put in 4 gallons, I'l reset the ODO and refill when it reaches 4. Must have made a mistake at some point with my numbers.

Crisis averted then. Although thats given me incentive to chase down this troublesome fuel gauge. In the meantime Il treat her to fuel more often, cant be adding a burned out fuel pump to the list of issues that need fixing!

 

I had a sticky fuel sending unit that was erratic. Two bottles of Chevron Techron in two full tank cycles fixed the problem. Fuel gauge is perfect now.

 

Yeah one of the few options left is that it might be junk in the tank making the contacts unconductive, will try some fuel cleaner when I swap out the fuel filter.

 

Just put another 6 gallons or so in, reckon probably at least 3 still in there so should have half a tank. Ohms at the fuel sender 290, fuel gauge reading 0. tested the resistance of the circuit by connecting to both wires that plug into the back of the sender and I get 1750 ohms resistance haha. So looks like a bad ground somewhere. Best places to look? I think starting at the cluster is probably a good bet.

 

Ref. Wiring Schematic figure 11.1 the ground ( BTG48R ) is not located around the instrument cluster . But is somewhere on the right side . Connector FC6 is on right side behind glove box on LWD . Pin FC9 -20 should see high resistance at empty and zero resistance at full ( ? )
You can pick up this reading before removing the cluster at the RS3 ( by the ECU ) 0 and the PI61 ( in the engine compartment by the washer fill neck ) and the ECU connector . My tank is below E so I will give you a reading from the ECU connector socket red PI105-20

Key off 683 ohms . Look at the condition of the connectors

 

Some bad luck this weekend, as when replacing the fuel filter the rotten fuel line decided to spring a leak, although we barely touched it so it would of gone sooner or later, better that it was in a controlled environment at least.

Will get it sorted next week, will see if I want to replace the whole line (£190), because the rot is only from the rear wheel to the filter, so putting in a new section of line might be a better idea.

Also got to sort some sill rot as some point.

 

Here in the states the raw tubing is hanging from the rack at the local parts store long with the tooling kit to make your bends and fittings to borrow . Might give you the option of saving shipping and splice repair as well as the cost of materials as you might get the other one next to it .

Any idea how to access the nuts on the filter bracket as I want to remove it and paint it up . I have the rear seat up and can't find the nuts

Thanks , Parker

 

Im pretty sure all the nuts are access from below. Although we only touched the one that tightens the filter into the bracket, there were two others I believe that are holding the bracket in place.

 

Thanks , when I replaced the filter it was the bolts attaching the bracket to the car that would spin . The bracket was ugly so I would like to clean the bracket up .

 

What do you think of the rust lady P? I dont think its bad for 22 years, but then I have nothing to compare it to. Expect it will be few hundred for some new metal and paint. Isnt visible so doesnt need to be pretty.

 

When I myself recast the bushings and powder coat the suspension members there it would be as I show off Lady P's delicates . I'm an engineer so it has to be zero timed ( airline term ) .

 

Just done some more testing since ive got andys bracket on my car now. Revving in park, engine warm, counting frames from start to 2000 rpm, divide by recording fps (25) to get times in milliseconds.
With MAF & no bracket 32 frames = 1280 ms (13 frames with drop in revs!)
With MAF & bracket 18 frames = 720 ms
Without MAF & with bracket 14 frames = 560 ms

Im not sure andys bracket made that much difference, I think that the hesitation varies day by day but it has definately made the response better, but still with the MAF unplugged the car gives the fastest response, although it was clearly running rich by the smell. I measured the voltage at the MAF on idle, got about 1.3v I think, hitting 2.85v with a big snap of throttle, so it seems to be working, maybe its just not responding quickly enough?

Also It looks like I need a new rear mount? Looks like the rubber is torn, should of tried to get a better picture really. Still got no idea about the rough idle either. pull a vacumm hose to lean it out, and it gets worse, unplug the MAF to richen the mix and it gets worse.. hmm...

 

Not sure I understand your frames per second /ms measurement but I do respect the way you came up with a way to measure something . If I understand correctly what you are measuring is the injector pulse timing and not the pulse duration . The timing is behaving correctly to the RPM so you can see that . The placement of that pulse ( CKPS ) is probably as important as the placement of the spark as a degree before top dead center in the 1 of 2 of the 360 degree rotation cycles . But the duration of the pulse changes and that you are probably not measuring . This duration is changed through the ECU mapping as is sees the MAF , TPS , ECT and RPM for the correct fuel mixture or trim .

Editing

Lagging or unresponsive injector cleaning with some MEK as a DIY ?

We'll look at a way to look at MAF , TPS , and ECT that you can do with a simple meter and a breakout board in the cabin as you drive around and duplicate the fault .

Do you have both a digital and a old school needle meter available ?

 

Shall we play ? Anyone welcome to the challenge of putting together a breakout board for a meter as he drives with your suggestions .

 

OK...more on the 'Rough Idle' issue:
I have a 1996 X300. Idles better in P than D. Stutters and splutters on acceleration. Has stalled a couple of times when coming to a stop.
So far:- replaced knock sensors; swapped out coil packs; changed plugs; changed crank angle sensor; checked temperature sensor voltage; cleaned TPS (did run better but problem is coming back). ECM removed and checked for leaky capacitors;
Next step may be the O2 sensors but I'm hesitant as to the cost if the threads strip on removal. 'Ticking' of the spark plugs can be heard through the radio when it happens.
Your thoughts?

 

'Ticking' of the spark plugs can be heard through the radio at the time of failure may be the coils grounding out to the walls of the spark plug wells ( very damaging to the Magnesium valve cover ) Pull the coils and look for physical evidence of this if is the case . And watch in the dark as arcing as they warm up . Solutions :

A . New Coils : $$$$$$
B . Regap the plugs for lower resistance back down to the original 0.035 : Free
C. Kapton tape on the coils to better insulate from the walls : 10 bucks Ebay

Fuel Starvation :

D. Fuel Filter
E. Injector Cleaning as they may be binding and not responding on short commanded pulse durations
F. Fuel Pressure Regulator

Better Spark :

G. Champion RC12YC plugs or 3 prong E3.48

Look for some corrosion on the O2 sensor connectors and clean the sensor wire shields grounds . Mine had alot . The shields only start at the connector and not at the sensor . Put some penetrating oil on the O2 sensor threads over night and try as it is cold up to a point you feel comfortable with . If they don't come out then heat up only the OD boss ( and wrap the base of the sensor with aluminum foil ) with a heat source before " running the engine " way of heating. Mine came with severely gulled aft sensor threads so I put them back in to address later with a 12mm x1.5 nut to be welded in from the hardware store . For now the unrepaired reinstallation is OK .

Cracked manifolds bias the O2 sensors to rich mixture STFT