V8 idling

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charlienjo

charlienjo

Member
Posts
15
When I come to a standstill in my Disco 1 3.9V8 and dip the clutch, it idles at 1500 to 2000 rpm, then after about 5-10 seconds it drops down to normal 800 rpm, has anybody experienced this and maybe have a fix? Any info greatly appreciated!
 
mine does this from time to time, normally from cold, I assumed it was just the ECU sorting itself out but someone more knowledgable will come along soon. Where is the IACV situated?
 
Last edited:
At the rear l/h side of the plenum with the nice coloured wires.
 

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cheers buddy, bloody hell mate you keep a clean engine bay! I thought mine was nice till I seen yours (i'd eat my dinner off that lol)

is it just a case of unplug, spray the crap out of it, let it dry and put it back in, might go do that in a bit.
 
I unpluged it, unscrewed it (32mm socket), sprayed it with carb cleaner then refitted, don't have time to test it right now, but i'll let you know tomorrow how it runs
 
Removed mine once just to look see, it was nice and shiney so put it back, only to find the large fibre washer was breaking up and I did have one that size so had to make a new one.
I won't be touching it again unless I get a new washer first.
 
When I removed it it looked a bit sooty on the tip, not sure exactly how this sensor works? Drove to work this morning in a heavy downpour, cleaning it didn't make any difference, it seemed to be worse, a few times it went the opposite way and revs dropped right down to zero, then jumped back up again (without stalling), also seemed to be missing a little bit, I have noticed if you put your hand over the exhaust, there is a watery moisture mixed with soot blowing out, quite a substantial amount, any ideas on that?
 
charlienjo said:
When I removed it it looked a bit sooty on the tip, not sure exactly how this sensor works? Drove to work this morning in a heavy downpour, cleaning it didn't make any difference, it seemed to be worse, a few times it went the opposite way and revs dropped right down to zero, then jumped back up again (without stalling), also seemed to be missing a little bit, I have noticed if you put your hand over the exhaust, there is a watery moisture mixed with soot blowing out, quite a substantial amount, any ideas on that?
Click to expand...

Get yourself in to the V8 section and do a search - cleaning the stepper motor has been covered a couple of times and there is lots about idle problems. Watery moisture and soot is a bit vague, is this when hot or cold? V8's do make quite a bit of water and soot especially if you're only doing short hops and the engine doesn't get properly hot.
 
@ classic Kev, it blows the watery soot when warm, will check it when its cold, I drive approx 10 miles to work, half on motorway so it does get a decent run, I'll have a look in the V8 section at the stepper motor

@ mrnice, no I don't have LPG
 
charlienjo said:
@ classic Kev, it blows the watery soot when warm, will check it when its cold, I drive approx 10 miles to work, half on motorway so it does get a decent run, I'll have a look in the V8 section at the stepper motor
Click to expand...

10 Miles is not really a decent run!

there may be nothing wrong at all but if you want to check stuff out I would suggest:
1: A compression test. Also look at the condition of the plugs when you take them out to do the compression test.
2: Does the top hose go rock hard when warm.
3: Does it use any water?
4: Go to a garage and get the exhaust gas analysed to see if it is too rich.

I suspect others in here know where this may go! HGF, Air Flow Meter, O2 sensors etc.
 
Replaced the stepper motor, it still seems to idle high for a few seconds when I come to a complete stop, but then will hold a pretty constant 800 ish rpm. Now though intermittentley it will start to surge at standstill, the revs will surge between 0-800rpm, sometimes it will cut out but mostly it surges back up to 800rpm before it cuts out. I did find a suspect HT lead which felt a bit loose on the plug, so I crimped it up a little to get it tighter and it seemed to be good for a while with constant tickover (it was a little higher though at just under 1000 rpm), but then this weekend it did it again, surging at tickover then stalling. I'm going to replace all the HT leads as I suspect this is part of the problem, any other ideas?
 
If you're happy the stepper motor is working properly then I would suggest you need to remove and clean the plenum and ram housing, clean the throttle disc and make sure it is set correctly. Then check the ignition timing; if the timing chain is worn the timing can wander and that might possibly be the issue.How many miles has the engine done?

After doing the plenum/ram housing and ignition timing you should check and set the base idle speed.

It might pay you to change the plugs, leads rotor arm and dizzy cap just make sure the cap and arm are genuine parts NOT pattern.

Did you do a compression test?
 
Quick update - Decided to remove and strip and clean MAF for myself, put it all back together and problem seems to be solved for now! Thanks for all the advice
 
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