Rusty isn’t happy

[stujags]

Not sure what’s happened but after a short while of running cold, Rusty has decided to not like starting unless fuel pump fuse is pulled out, otherwise it’s like she is flooding. Lots of oil around throttle body and appears to be blowing more out the breather. Has she finally had enough?

[ptjs1]

stujags,

Could you just clarify a few things:

- You say that the car has been "running cold". How do you mean? Is the car just low on the temp gauge or is the engine definitely running cold? What temp does the coolant show via an OBDII interface? Is the thermostat stuck open? Does the top coolant hose gradually warm up from cold, or does the stat open and then the top hose suddenly heats up? Is the engine running rich?

- When you say that the car needs the fuel pump fuse pulled to start, how does that happen? If you pull the fuse before turning on the ignition, are you saying that the car will start with no fuel pump running? How long does it run for before you put the fuse back. My AJ16 won't start if the fuel pump doesn't activate and it really surprises me that yours will.

Have you cleaned out the breather hose all the way through, MAF & Throttle body etc? Is there a lot of pressure coming off the rocker cover if the hose is removed?

Cheers

Paul

[stujags]

Thank you for interest, I’m guessing stat is stuck open as temp gauge fluctuates from nearly normal to almost in the blue.
To start the engine, I initially crank with fuel pump working. This results in a very short start and immediate stall. Then I must remove the fuel pump fuse and the engine will start and run rough. If I put fuse back in at this point the engine floods. Once warmer I can insert fuse, engine is still rough at this point. I would say too much fuel or not enough air.
I’m thinking low idle air supply might be blocked as throttle butterfly was dripping in emulsified oil.
There seems to be a steady vent of vapour coming out breather hose so hopefully not rings ?

[ptjs1]

stujags,

I think you're close to identifying the issues.

I know it's difficult if the engine doesn't want to start or run well. But I would try and pin down if the stat is stuck open. A simple check via a cheap OBDII plugin will identify the ecu-signalled coolant temp (although admittedly a faulty temp sensor can confuse things). Alternatively, there will be a distinctive change in the feel of the top hose rad-side of the stat when it opens.

But if you're pretty certain, you might as well change the stat anyway.

A cold-running car will run rich anyway based on the coolant signal input to the ecu.

I would then clean all of the breather circuit and the throttle body, and also very carefully clean the MAF. Also remove the air intake elbow and flexi and thoroughly clean them as a lot of oil can build up in there. Also check the spark plug wells as a lot of oil can build up in there and drown the plugs and cause really rough idle running.

After all of that, I'd see if the car wants to start and run better, before I started looking elsewhere.

Good luck

Paul

[stujags]

Thank you for help, sounds like this weekends project. I will update on progress

[stujags]

Did a super quick throttle body removal, back side of that was clean, inlet manifold looked clean enough and low idle inlet is clear. Breather system clear and breathing. Scanner flagged up a load of MAF errors, I cleared and didn’t come back but engine fault still the same. I’m thinking replace the MAF ?

[ptjs1]

stujags,

I'm really against changing any parts unless I can visibly see a problem or measure it electrically. I always feel you can end up chasing your tail, spending lots of money and losing sight of the real problem.

You seem to have a problem of rich running / overfuelling when cold, that goes when hot. So that could be something physically improving as it gets hot (plug, coil, injector spray, air gap) or something getting a poor cold signal (MAF, coolant temp sensor). An open stat won't cause the problem you've got. And IMO, the immediate start problem means it isn't a lambda sensor problem.

Start with the cheap / free diagnoses. If you've now verified that you haven't got excess oil contamination in the inlet paths, go to the next areas. Check the plugs are firing properly when cold by pulling them out one at a time and watch them sparking. Pull the injectors one at a time and watch their spray pattern when cold.

Check the resistance setting on the coolant temp sensor when ambient / cold temp. (I'll dig out the values if you haven't got them). A really quick and dirty test is to pull the temp sensor wiring plug off and bridge it then start the car. It'll then not use the temp sensor resistance and will put the fuelling setting into open loop. It just might identify the issue if the car now starts better.

Don't buy a MAF....yet!

Good luck

Paul

[stujags]

Is this just a massive coincidence or more to it ? The very same day this problem started I had the break light bulb failure warning when breaking. I haven’t checked if it’s just the bulb but I was thinking last night that I have never had a bulb failure or warning light until the very same day my engine started to play up ?

[stujags]

Possibly some progress, I have no back lights (indicators, break lights ok) Is the fuse or some sort of connection to the back lights that could be causing my problem?

[ptjs1]

stujags,

I don't see how they could be linked.

I'd start with the obvious such as fuses. Seems extremely unlikely that four bulbs would blow at the same time.

Are rear sidelights working? Are front sidelights and indicators working?

Paul

[stujags]

Everything works other than rear tail lights. Indicators & break lights are ok. Very strange, Going to check a few things over weekend.

[ptjs1]

If you've got brake lights working and front sidelights, then your light switch is working, plus ignition switch etc. Start by just checking the rear sidelight fuse.

Cheers

Paul

[stujags]

Really appreciate your help, got the lights working that was just blown fuses, strange they all blew at once but anyway all good now. Back to the rough running engine, have been over everything suggested and nothing makes a difference. Only thing my plug in says MAF air flow 0, have attached some live data but doesn’t mean much to me.

[ptjs1]

stujags,

A few thoughts:

First of all, you have to be really careful of the OBDII readings on an early AJ16 engine. Jaguar implemented an early version but it's not really fully compliant until 1997. So you have to take everything with a pinch of salt as some of the readings will not make sense, some are downright wrong and MAF and Fuel trim readings can't be trusted.

Having said that, there is evidence that oil-based filters, such as K&N, can play havoc with Jaguar MAFs. You mentioned that you had a lot of oil in the filter / inlet tract which could have caused / still be causing the problem. Oil mist can fry MAFs. But first try and VERY carefully clean the MAF wire just with electrical cleaner spray. And make sure there is no oil still trapped in the plastic corrugated elbow. The folds can literally fill up over time.

Your MAF reading is very low, even at idle, but I remember that early Jaguar OBDII MAF readings on some diagnostics were reported as being out by 2 decimal places. So a reading of .06 g/sec should actually be interpreted as 6 g/sec. Did that MAF reading increase to anything at 2000rpm?

Does your lambda readings change with rpm or are they flatlining? A failed sensor can flatline read and cause overfuelling, although, as mentioned, I wouldn't necessarily expect it to immediately affect the start fuelling.

How did the car start when you forced it into open loop mode for starting by shorting the coolant temp sensor plug? It's important to try and see if this is the root cause before you look further on a MAF failure.

I'll try and think further!

Paul

[stujags]

Thank you for info, Maf reading is zero at all
Revs, disconnecting it makes no difference to reading’s or engine running.
The temp sensor seems to be working, temp increases Gradually to 90, if I unplug it shows -40. This makes the engine stall, I guess it richens the mixture more as car thinks it’s -40. Bridging makes no difference to starting.