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Idle quality
speedyxjs - 15/12/10 at 02:32 PM

My engine has developed a problem with idle which seems to be a common fault with the 3.6 AJ6 engine. I can get it fixed but that means a £200 ECU mod. I have found a 3.2 AJ16 engine which come with the loom and ECU for £150 (recon i can get it a bit less). Thing is, even after delivery, this should still work out cheaper than the ECU mod as i can sell alot of the AJ6 parts back on ebay.

This would mean moving on to my 4th engine for this car and its not even IVA'd yet

This is all assuming that poor idle would be an IVA failure. The car wont even start without a bit of throttle and after some banging and shaking, stalls at idle. Is this likely to fail IVA?

[Edited on 15-12-10 by speedyxjs]

carpmart - 15/12/10 at 02:52 PM

I'm not sure if its an IVA fail but it will sure as hell make it a pain in the arse to drive!

MK9R - 15/12/10 at 02:52 PM

seems a little extreme swapping engines because of a relatively easily fixable lumpy idle!

britishtrident - 15/12/10 at 04:11 PM

First port of call on Jags with idle or starting problems is usually the coolant temperature sensor.

speedyxjs - 15/12/10 at 04:38 PM

quote:
Originally posted by MK9R
seems a little extreme swapping engines because of a relatively easily fixable lumpy idle!


If it is the ECU problem, its an easy but expensive fix. I hadn't thought of the coolant temp switch but now that you suggest it, i had read about it somewhere. Would it not improve as the engine warms up though?

RazMan - 15/12/10 at 05:07 PM

IVA will want to see it idling when they do an emissions check so I would imagine it needs to be sorted or it won't pass. Can the problem be sorted out in another way?

James - 15/12/10 at 06:10 PM

You know, when we get people posting on here about doing things 'a bit different' we really ought to mention to them the more you deviate from the norm, the harder the build is!

What is the ECU mod? Is it not something you (or one of the electronics gurus on here) could do?

How complex can an old Jag ECU be???


As for IVA... if the car runs crapily then it's just a reason for the tester to think the car needs closer examination for it to be safe! Impressions are everything with this sort of thing!


Cheers,
James

[Edited on 15/12/10 by James]

speedyxjs - 16/12/10 at 07:30 AM

Bugger

This is where i read about the problem. Apparently they add an idle adjustment screw to it but i wouldn't know where to start! I will however, borrow the coolant temp sensor off my tintop later and try that in the hope that that will fix it.

Thanks for all your help guys

speedyxjs - 16/12/10 at 07:45 AM

quote:
Originally posted by James
You know, when we get people posting on here about doing things 'a bit different' we really ought to mention to them the more you deviate from the norm, the harder the build is!


Yeah yeah What was originally going to taken me a year to build (ha ha!) has taken 4 years so far lol

RazMan - 16/12/10 at 10:34 AM

quote:
Originally posted by speedyxjs
I can get it fixed but that means a £200 ECU mod. I have found a 3.2 AJ16 engine which come with the loom and ECU for £150 (recon i can get it a bit less). Thing is, even after delivery, this should still work out cheaper than the ECU mod as i can sell alot of the AJ6 parts back on ebay.


Another thing to consider is how much your time is worth. If I had the choice of paying for a quick fix or swapping the engine (assuming you know your existing engine is good) I would get my cheque book out

scudderfish - 16/12/10 at 12:06 PM

quote:
Originally posted by speedyxjs
Bugger

This is where i read about the problem. Apparently they add an idle adjustment screw to it but i wouldn't know where to start! I will however, borrow the coolant temp sensor off my tintop later and try that in the hope that that will fix it.

Thanks for all your help guys


Reading that page they first suggest relocating the vacuum tube to elsewhere on the manifold. I'd give that a go first. The thing that they charge £200 for is a trimmer pot that costs pence. I guess they cut a track coming from the MAP sensor and put the pot in line so you can fudge it. This would be a fudge against the whole range though, not just idle.

speedyxjs - 16/12/10 at 01:49 PM

quote:
Originally posted by RazMan
quote:
Originally posted by speedyxjs
I can get it fixed but that means a £200 ECU mod. I have found a 3.2 AJ16 engine which come with the loom and ECU for £150 (recon i can get it a bit less). Thing is, even after delivery, this should still work out cheaper than the ECU mod as i can sell alot of the AJ6 parts back on ebay.


Another thing to consider is how much your time is worth. If I had the choice of paying for a quick fix or swapping the engine (assuming you know your existing engine is good) I would get my cheque book out


Engine was an ebay bargain and the seller didn't know whether it ran. I took the coolant temp sender out today and noticed it was only touching the tip of the coolant so topped that up a bit but that didn't really help. What will the IVA man class as a good idle speed? If i set the idle at about 1k, its not too bad and certainly much better than at 800. Im going to speak to an MOT tester friend sometime and see if he can put it on his emissions kit so fingers crossed i may not have to spend much money getting it to an IVAable state.

Cheers

NS Dev - 16/12/10 at 02:17 PM

we've worked on and owned LOADS of these old jags and I've NEVER had an issue with an ECU. Coolant temp sensor faults plague them, and the only way to be sure is a new sensor, but they are only £10 so I would just put a new one in for a start! The AJ16 suffers exactly the same temp sensor fault as well! We bought a complete manual 3.2 sport the other day for £250 as it would not run/idle. New coolant temp sensor and now its perfect!

The other thing to check/replace would be the airflow meter.

Dont' believe the utter crap that is spouted on the good ol tinternet. Everybody on "the forums" says the fault with idle and light throttle running on AJ16 engines is the lambda sensors...........again, we've never had an issue, its always the coolant temp, and occasionally the airflow meter as well.

NS Dev - 16/12/10 at 02:18 PM

ooh ps ok there is a common ecu fault on the AJ16, its called it getting full of water, but that's kinda obvious! Wasn't wise to mount it below the bulkhead grommet I guess!