I thought I'd give the old girl a treat tonight but it seems to have backfired on me. I removed the air intake tube and cleaned the throttle body using an aerosol throttle body / air intake cleaner. There was a lot of black gunk that I managed to get out from under the throttle butterfly which I opened by hand.

Whilst I was there I disconnected and cleaned the electrical connectors to the TB. All seemed well and I put everything back together having first checked I hadn't dropped anything into the TB.

Then came the moment of truth and I started her up. All was perfect for about one second then it just stopped, as if I'd turned the key off. There was no hunting or stumbling......just dead. She cranks fine but she's not firing at all.

Any thoughts would be appreciated please. One thought I had was if I have managed to flood it with the cleaning fluid and the plugs have gone wet and if so is it likely it will just evaporate if I leave it a few hours and all will be well again?

She's not throwing any codes and was running fine yesterday.

Thanks,
Andy

 

I assume you didn't spray directly into the throttle body?

Check the electrical connections to the TB. They are notorious for cracking or breaking the holding tabs. I had to keep mine on with a tie wrap at one point. Also make sure you didn't bend any pins.

Just for fun, try doing a hard reset and see if that helps. Also take a look at the MAF sensor and its connection if you cleaned it as well.

Otherwise, there are plenty of no-start threads here on the forum.

Good luck and here's hoping it is a simple fix.

 

Unplug the connectors and make sure they are thoroughly dry of any moist cleaner residue before trying again. The throttle body has some very small signals that can be messed up by even slight conduction through the cleaning fluid.

It is best to use cleaner make for electrical contacts on the connectors, because they are actually coated with a minuscule amount of lubricant, and the throttle body cleaner will wash that away. Over time this will cause the contact plating to wear out prematurely.

 

Follow the thread -

Is it broke ---------> yes
Did you bugger about with it ---------> yes
Retrace your steps

I would have thought it unlikely that a squirt from the aerosol would kill all 8 plugs. Is the intake back on correctly? (They crack underneath very easily).
Is the butterfly returning to the closed position? (It's actually driven by a servo motor).

It is possible that because the butterfly was moved the servo was resetting itself and the engine just stopped. Normally an engine will simply restart - but not a Jag. It could be flooded. Hold the pedal to the floor and spin it for 10 secs, then lift back to 1/2 way on the pedal to let it fire. (With the pedal to the floor the injectors are all closed off).

 

Hi Steve, it is possible the contacts were still damp on the PPS, TPS and the throttle motor connector so I'll take your advice and let them dry off. Incidentally, I did use a contact cleaner spray to clean the connectors but thanks for the warning anyway.

Thanks for your input Jim. I checked the throttle movement using my scan tool and it is closed (6.7%) to WOT (100%). Whilst it was off, I had a good look at the air intake tube and it looks in good condition and there was no sign of any splits etc. I didn't realise the injectors would close off whilst cranking at full throttle so I'll try your suggestion and see what happens.

Thanks both.

Andrew

 

Yes check all your connections and also the ones you did not unplug.

Did you remove any plugs with the battery cables connected? If you did do a hard reset. It is always a good practice to disconnect your battery cable before you remove ANY plug.

How much TB cleaner did you use to clean the TB? When attempting to start the car have you noticed if the engine is spinning a little faster like it has no compression? If this is the situation you may have cylinder washing.

Check your connections first and look for anything you might have come in contact with that might have been dislodged.

 

Thanks Gus and others. I waited a couple of hours last night and tried starting it again and straight away I knew things were better, as she was firing unevenly for a few seconds and then caught and ran a little rough for a short while longer and then just settled down nicely. An uneventful two hundred mile trip today followed and I think she was running smoother than before.......or was that just my imagination!
My guess is that I ended up with too much cleaner down the TB and had I left it longer before trying it I wouldn't have experienced the problem.
Thanks,

Andy