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So today I spent the day going through the negative earth points and everything checked out. Still does not run though,...
Hi Terry,
When you say "everything checked out," do you mean you visually checked them, or you physically removed the nut on every ground point and used a small wire brush to clean the nut, threaded stud, all eyelet/ring terminals on the wires, and all star washers, then flushed all the parts with zero-residue electronic parts cleaner, allowed them to dry, then reassembled?
The terminals were removed and decreased, before being cleaned with c02 contact cleaner, then reassembled. Once re-assembled this made no difference to the running of the car.
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Today I am hunting down a fuse 2 fault though.
Comes up but no fuses are blown.
Going to spend the weekend chasing that one.
Already found that the cruise control module has been removed. Which explains why it was not working when I brought the car home. Don't really use it, but might try fit an old one back in there.
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Picked up a newer ECU for $50 which is very reasonable. So will give that a go early next week.
Is the only thing that could be messing with the timing so badly. 30deg after top dead centre is hardly a small fault.
Will post the results once installed, fingers crossed it fixes it though.
The body processor ECU did arrive today, after it was fitted the fuse two and PAD error messages have stopped, hopefully permanently this time. Car never had pad sensors and the fuse was assumed to be the bad body computer. Very happy that this has been solved.
Hopefully, when the new ECU for the engine arrives it will sort out the other problem of the electronic timing and misfires.
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Having not run the car for a while it still starts and runs. This time at about 400rpm.
It gains revs well; however, when you back off the throttle to idle it almost dies completely. The car has a new throttle pot, so I am assuming the idle stepper valve has felt left out and wants to be replaced alongside everything else.
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Anyway - Slow progress at the moment. Hope to see the new engine management ECU soon.
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Hope that this is not a new problem that is developing aside the existing one though.
After a month waiting for parts to yet arrive again, everything electronic has been checked and completely replaced; and the result after installation is not good.
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The car still has the problem where the timing retreats instead of advances when the throttle is applied. This is even with the new ECU.
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At this point in time, it is an absolute mystery as to why it does it ?
There is both no reason for it, and no explanation possible as to why this issue has occurred and is persisting.
The car still has the problem where the timing retreats instead of advances when the throttle is applied. This is even with the new ECU.
At this point in time, it is an absolute mystery as to why it does it?
Hi Terry,
I'm sorry this is proving to be a tough problem to diagnose.
The two primary inputs referenced by the ECM for ignition timing are the MAF sensor (from which the ECM determines engine load) and the CPS (from which it determines engine speed).
Secondary inputs are the engine Intake Air Temperature sensor (IAT), throttle movement and position (Throttle Position Sensor or TPS), and transmission upshift signals (from the Transmission Control Module or TCM).
I can't recall if you've investigated the performance of your MAF or IAT, but those would be worth ruling out, if you're absolutely certain all is well with the CPS.
If you haven't done it already, I would strongly suggest you study the AJ6 Engine Management System/OBDI Diagnostic Guide that I linked to in post #43. It doesn't get into great detail, but it does explain the basic principles of EMS operation and the sensor inputs the ECM uses to determine fueling and timing. It may help you narrow down the suspects.
Certainly running out of ideas regarding this one. It is rather disappointing after all the work that has been compleated on it.
The sensors have been replaced with new parts, IAT and MAF are new and have been tested before fittment in a working XJ6 AJ6 to doubble check.
Everything replaced, which is everything, so far has had no effect.
I have read over the AJ6 manual so far and nothing sticks out remarkably.
No error codes for the transmission come up, no error light on the dash either?
Works fine too.
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The current problem is;
- Car starts and runns at idle well.
- Application of throttle, car runns badly, including backfires. 1000rpm limit.
- Any application of throttle alters the timing, up to 30deg after TDC.
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Will just have to keep trying, possibly getting some help from Jaguar Australia through the week.
Not a simple or beginner problem to resolve. It will need someone with a lot of experiance with this modle and similar to resolve.
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I will post the resolution to this thread when or if it is fixed.
I went back and re-read your initial posts on page one, i.e. the first things you tried.
From your notes, the original issue was that the car would crank over but had intermittent starting problems; however, when it did start, it ran fine.
Your diagnosis zeroed in on the CPS, but just to be clear, other than cold starting, the car was running fine prior to the replacement, i.e.
Before this started the car was intermittently hard to start. By that I mean, it was no trouble some days <snip> Previously the engine would run really well. No problems with rpm, and it would sit really well on 110kph on the freeway.
and
When the car starts and is warm it ran reliably for the rest of the day. This prompted fitting a new CPS.
So, to address the hard starting problem, you started swapping out CPS sensors (which apparently had no effect on your cranking/starting problems) - and - if I'm reading correctly, you then changed or opened up and did some reconnecting work inside the CPS plug, right?
Having the choice of 3 new CPS sensors as spares I swapped them with no luck. Ruling out the CPS sensor as the fault. It was suggested that the connection was the fault. In saying that the new sensor helps the car start reliably and having a new one in there helps.
The male connection to the CPS was changed and tested. The new connection has less resistance, but the fault remains.
It starts first go now, but will not increase in RPM without misfiring and running roughly.
Because you stated that the car ran well when warm, what comes to mind (admittedly from my desk thousands of miles away) is that the hard starting issue may not have been down to the CPS (could it be fuel/air supply volumes -or- more likely, failing coolant sensor/sensor connection not supplying enrichment information)
IMHO, the replacing of whatever in the harness connection has induced the secondary fault, the stumbling etc. Quite likely you have a bare wire or a small short in the connector and this is what's causing the weird running.
If I were you, I'd revisit this connector and heaven forbid, replace the CPS with the original that ran the car reliably. Occam's razor!
When the car starts and is warm it ran reliably for the rest of the day. This prompted fitting a new CPS.
Hello, I've read through your post, and don't see any mention of checking the crank pulley itself (if I missed it I apologize)
Have you confirmed the tone wheel on the crank pulley is not cracked and/or spinning free of the pulley itself? Or perhaps the woodruff key in the end of the crankshaft has sheared and your pulley is moving around a little?
Just a suggestion, as you seem to have gone through mostly everything else (that I can think of, anyway)
I will be out all day today attempting a few things.
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With reference to the CPS fault. With the old one in, the engine does not start or run at all. The old one is officially dead.
With the new sensor in the car, it starts and runs reliably. When the fault occurred I put another in and this did not make any difference.
Recently the mechanic on duty at the dealership soldered the joints together. This had the effect of nothing. To swap them over now it is a bit of a process. Never leave a dealership mechanic unsupervised, lesson learnt.
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In regards to the reluctor on the harmonic balancer [pully], an oscilloscope test shows a correct signal pattern.
This was tested at cranking, I am not able to test the car at speeds higher than 1000rpm due to the fault, or higher than cranking speed.
I was a bit concerned as well; however, without the correct signal, the car would not even start. Which is mildly reassuring.
Complicating the issue is the fact that the timing is way out when the throttle is applied. Which casts doubt.
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I am slogging it out all week on this one with a multimeter.
Will let everyone know if I find something, and it solves the problem.
So the only thing that required attention this week, was to redo the clip to the water temperature sensor as it broke on inspection. Once repaired there was not much difference to the running of the engine.
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In general, the backwards timing advance problem is still plaguing the car.
There is still no solution or explanation as to why it is doing it?
This week we are looking into getting another [new] cps to help see if this is the problem. It is the only thing that could possibly be holding the engine back from gaining revs.
Starting to feel like this is the last attempt to fix it.
Just trying to keep coming up with ideas since you've tried so many already.
I know you've installed a new, tested MAF sensor. Have you carefully checked the electrical connector at the MAF and its wiring harness? As I mentioned earlier, alongside the CPS, the MAF sensor is the other primary sensor input to the ECM for ignition timing. You can check for continuity and low resistance between the MAF connector and the ECM connectors, and you can backprobe the wires and see if the measurements conform to the ranges which I think are given in the EMS manual.
-Checking the gap between the reluctor wheel and the sensor.
-Checking the resistance on the ignition condenser.
-Inspect and test the MAF wiring.
-Test engine to ground, replace the earth strap with a new one while I am at it.
-Refit the distributor checking it mechanically and in accordance with TDC.
Seems to me I read somewhere the ignition timing will be retarded during a full throttle upshift event (foot to the floor and leave it there).
Have you checked the foot switch under the accelerator pedal on the floor?
Seems to me that if the switch were stuck down,it might cause some crazy timing.
Something easy to check,Cheers,Jim.
That's a good idea. Was the Transmission Fault Light on? If so, it could certainly be that problem. The wires on my switch were so twisted that it actually split the insulation. The wire was grounding on the stud for the pedal and giving me a Transmission Fault Light. The problem comes when people twist the switch for proper kickdown adjustment, but fail to unplug the connector first.
Ah! So is this a manual transmission car? That would explain the absence of a kickdown switch... It's easy to forget when all our US-spec cars are fully loaded.
08-16-2017, 12:11 PM
