So just like the subject line says...I have never had a problem before with any engine just using an air nozzle sucking up some Purple Power de greaser, letting it sit, then hosing it off. This weekend, things changed. I tried to be careful with directing the de-greaser and water away from any sensitive areas, connectors etc.
After it was all done and blown dry, I tried starting it and had trouble catching, surging and stalling. Kept trying and it kept wanting to, but no deal. I further tried to disconnect any engine managmenet connectors to make sure they were all dry. I let it sit for a while and it started and idled fine, however, it would not accelerate. It would continually cough and stumble when throttle was opened even slowly. More like a put-put and would die if opened further...like it was starving for fuel. Let it sit overnight while I charged the battery and next day, same thing. Started and idled smooth, but when throttle opened, would not accelerate. Thinking I might have introduced water in the fuel tank at the filler cap when washing the car, I let the engine run at part throttle where it was running but not smooth hoping to run all the water through the injection system if that's what it was. I still wasn't sure what it was at this point and during this slight revving few minutes, I noticed some smoking on the side of the exhaust area. That's when I saw the down-pipe just before the cats, red hot glowing! I immediately shut the engine down hoping not to cause a fire.
So...was it running lean causing a very hot mixture enough to make the exhaust pipe glow? Lean because no fuel pump helping? Can the 4.0 run without a fuel pump, gravity only such that when asking for fuel during an acceleration, it stumbles? Was it running too rich? Can't see how that could be from any sensor out of whack or not working due to any connector being wet. I did not think to check the fuel pump fuse or relay because it starts and idles ok. Is the relay in the engine compartment?

Thoughts?

 

Dizzy cap... it may have condensed. Wipe it dry...

 

Hi C&P

The Fuel Pump Relay is in the Boot/Trunk behind a piece of Carpet Trim and tucked right under the inside of the Fender/Wing behind the Bracket of the Boot/Trunk (Strut) so not exactly easy to see or get to (Drivers Side on a UK Car)

Probably not that though, as it was too far away from your Power Washer, where as you may have just found out Power Washing the Engine of an XJS is like the 7 Deadly Sins all rolled into one

Have you got an AJ6 with a Coil or an AJ16 with Coil over Plugs?

Maybe wouldn't do any harm to go over the Engine with a Hair Dryer or something like that including around the Crank Position Sensor and the plugs of the Injectors which are under a cover but could still have got splashed

Before I got to know better, I did the same thing myself with my V12 which made such a racket that I thought I'd dropped a Valve! so if its any consolation you are not alone

 

Didn't think there was a dizzy on the 4.0 AJ16. Coil over plugs and CPS. It just feel like a fuel delivery issue.

 

OB, I'm sure I didn't get water on the FP relay, but was thinking more of something else being shorted in the engine compartment which may have caused the fuse or relay to short indirectly, if that's even possible, when first turning on the ignition or starting to crank.

 

OOPS.

I would remove the coil cover plate, and remove the coils. Maybe ingress of water past the SUPERB coil gaskets.

Thats what I read by what you are describing.

 

Sorry. AJ16 is coils, AJ6 is what Im familiar with, this happened to me once, and the dizzy was wet. You probably got water past your coil seals. Check those first

 

You could have introduced water into the ECU.....because of where the ECU is located in the AJ16, many of us have had water drip down into the ECU from simply detailing the car, never popping the bonnet open. Or perhaps from water drops making their way down thru a vacuum line. Either way, it’s a common failure more in the AJ16 cars unless you have taken measures preemptively .

 

Hi C&P

In that case with an AJ16 water may have trickled down into the Fuse Box and Blown one of the Fuses for either the ECU or the Engine Management System

Have a look at the Fuses in the Fuse Box just underneath the Knee Bolster it could be Fuse Number 20 or one of the others so check them all

 

It won't run (or start) without the fuel pumped at pressure, so I wouldn't start there.

As Grant says, water in the coil pack and plug recesses. Also check the TPS.

Good luck

Paul

 

Did the problem get resolved?

If note the same thing happened with my 96. Got water into the large ECU (?) connector located on the passenger side in the engine compartment. You can see looking down into engine compartment just to the left of the steering fluid filler container.

My engine spitted, sputtered drove crazy for a while (1 day) till I pulled the connector apart and dried with hair dryer.

Once dry all was good again.

Softball60/Paul

 

you where fortunate. I and others destroyed our ECU’s , and not even power washing the engine.....

I recommend all AJ16 XJS owners remove their ECU’s and pack their connectors with Motorcraft XG12 (which is really nyogel 760g repackaged) thinly coat the inside and the pins and pack the stuff on top of the connectors where the wires go in.

 

Sorry for the delay in replying and thanks for all the replies. I have been away from the car for over a week now and have not had a chance to try and start it to see if it is still acting the same.
I went with the fuel direction just thinking all it needed was more fuel when I advanced the throttle, even slowly. It crackled a popped with any advancement but would settle down to an ok idle when left alone. The crackling running as I mentioned, is when I noticed the down pipes getting red hot so naturally thought it was running lean and looking for fuel that wasn't there.
Where is the ECU? I don't member shooting water in any direction where there might have been any electronic boxes.

 

carsnplanes,

I still think you're getting a hot pipe because youre throwing unburnt fuel down the pipe rather than a lack of fuel. I'd still be looking at the coils and plug recesses for water fouling first.

Good luck

Paul

 

Hi C&P

The ECU is at the base of the Passenger Footwell (UK) Car, tight up against the inner Fender/Wing (inside the Car) and although its quite a big piece of kit, it takes a bit of finding as its buried out of sight behind some plastic trim

Have a look at these Photos, which will show you exactly where it is

Also it is well known that Water can trickle down inside the Car and maybe get into the Plug and cause Corrosion but before you get into that I would check all the Fuses

As well as pulling and then re-seating those 2 Blue Hella Relays which are just above those Fuses, as some of these Relays have thin Blades which have been known to lose Contact

Where should you find that's the problem, then it may pay to replace them with a different make that has Thicker Blades

Also Note that these Relays are ones with Diodes and are Not Interchangeable with the ones without Diodes

Very much agree with ptjs, it also sounds like un-burned Fuel to me, so I would definitely Check that out beforehand, as pulling out the ECU is not exactly an easy 'Walk in the Park'

Location of the ECU in an XJS 4.0L Car

 

It is not a box but a very large multi pin connector. It is located below the abs pump located in the engine compartment passenger side of vehicle.

Every though I had mine bagged in plastic while I cleaned the engine compartment, it still managed to get wet!!! Used a hair dryer to get rid of the moisture along with some electronic pin cleaning fluid.

Softball60/Paul

 

Ok guys, confused now. OB says the ECU is in the footwell inside the car, and you say a plug in the engine compartment. We are talking about the engine management ECU, correct?

Also, I hadn't thought about it running rich. I was always thinking lean as I felt the symptoms felt like a lean condition due to sputtering when I advanced the throttle thinking it was lacking fuel. Perhaps it was running rich, but once i got it to start, it idled fine, unless the idle "program" is different. I checked that the gasket was in place under the plug/coil cover never expecting water to enter there. But hey, I'll take a look and see of the wells got filled with water.

 

The ECU is definitely inside the car in the footwell as per OB's description.

 

“Sorry for the confusion but if you look at my original post I stated ECU (?) connector located in the engine compartment”

The question mark was because I was not sure if the connector was related to to ECU inside vehicle.

(My next post identifies a specific location) underneath the ABS Pump)

It was the connector that got wet not the ECU........

All I know is that when I pulled the connector apart and dried it out “All was Good again”

Softball60/Paul

 

Ah ok.....So the plug you must be talking about leads from the engine comp to the interior. I see this plug but also see that it has a sealed boot which is ty wrapped.
So when I finally got the chance to try to start it again, it started and ran as it should. I did remove the coils to check for water and there was none...now, but may have had some before. While coils were out, I cleaned and re-gapped the plugs. The rear three plug cavities had some oil down in there so will change the rubber cam cover gasket next time.
But now my alternator is not putting out!~ ughhh. 11.5 volts while running. Is there a replaceable regulator on the stock alternator? It would usually contain the brushes on the regulator I would assume. I guess I might have doused the alternator too much as well.