Idle Screw O Ring

[shed_racing 0]

Afternoon all,

 

So, after the epic mission that started with a starter replacement and ended up with getting the injectors refurb'd, I thought I'd better attempt to sort out the idle. So, two questions, (or answers) please :

 

1. The car now idles at just over 1000rpm with no load; if I drop the idle to below this, when I add the lights and heater load, it drops to around 500 rpm and then obviously dies . . . Could someone please confirm the correct idle speed ? I think it's 950, but I can't achieve this (please see 2)

 

2. Pulled out the idle screw out of the throttle body for a clean, and there is no O-ring on the end; looked at the parts diagram, and there should be one, so I rang the local m-dealer who tells me it's now NLA; could someone please confirm the size/diameter ? I assume that the lack of this ring is allowing air past it, so I get the classic hunting occasionally and random idle that we all know and love.

 

Once I've got the o-ring back on, I'll reset the mixture/idle/throttle stop according to the Haynes book of Humour, but I don't want to start all of that without first making sure I've corrected all that I can . . . . or that I'm wasting my time !!

 

Appreciate your advice / thoughts.

 

Thanks guys.

 

Shed_racing

[welshpug 1,657]

you could try PTFE tape or threadlock on the screw, other than that try measuring the groove the o-ring sits in and the diameter of the hole and get an o-ring that'll fit.

[shed_racing 0]

Blimey ! Quick reply ! Thanks Welshpug - PTFE sounds like a good idea; may accomodate being wound in and out a couple of times more than threadlock (or, as I use, her clear nail varnish . . .)

 

Thanks for the speedy reply.

 

Oh - any idea as to a reasonable idle speed ? is 1000rpm too high (once warm, obviously)

[SurGie 54]

8 and a half rpm is fine once warm.

[shed_racing 0]

8 and a half rpm is fine once warm.

 

 

Ideal SurGie - thanks.

 

I had it set about that yesterday lunchtime, sounded perfect !

 

Trouble was, on the way home last night it was stalling at junctions (lights and heater on) so I had to wind it back up again to just over the 1K.

 

Did a quick search for alternator/charging/battery problems last night, but couldn't work out if around a 200rpm drop is usual when turning on both the main beam and the heater ? Never had it in any of my other cars, but then again, they're not French !!

[SurGie 54]

Sounds to me like a charge problem, my cars lights went dim when engine is cold but still turns over.

Have you checked the battery and alternator wires etc ?

[shed_racing 0]

When I was trying to confirm if the starter was shagged, I checked all of those leads, even to replacing the battery Earth clamp and cable ! I seem to recall running a multimeter across the battery and getting around 14.v volts at around 3K, so thought that the alternator was ok . . . maybe not ?

 

Seems like I each "new" car I get, it's par for the course to replace the battery, starter and alternator ! Still, if that's all I need to do, then I'll be happy . . . Will check the alternator again this evening when I get in.

 

Once warm and on idle, should I be getting over 12.5v across the battery terminals do you know ?

[lagonda 42]

My understanding is 950 rpm is the "correct" warm idle speed....also that lower is not a good idea as air then pulses past the AFM flap causing that to flutter & give the ecu all sorts of incorrect info....giving an even worse idle!

Yes, lack of O ring would certainly cause idle woes...trust you've checked the O ring isn't in the throttle body where the screw threads in? Wouldn't need to be too precise with the O ring....provided you find something that fits & seals, job done!

950 idle should certainly be achievable, but 1000 wouldn't be a problem. You will generally get some idle speed drop with headlights etc on, but not 200 rpm....if you still drop that much with 1000rpm idle, I'd check battery & alternator.

[SurGie 54]

Yes you will, iv had 14 before but as long as its 12 ish then its a good un.

 

Its could be negative or petrol problem, check the current to/at the alternator as well.

[welshpug 1,657]

you should get 14V minimum from a healthy alternator, 12.5-13 across the battery with the engine off.

[shed_racing 0]

Thanks Lagonda - kinda thought a 200 drop was excessive ! Will try and source a new o-ring.

[shed_racing 0]

Any idea what the current SHOULD be at the alternator ? I'll give that a go tonight, too.

 

Thanks again for the pointers - nuts and bolts I can do, but electrickery just confuses me.

[shed_racing 0]

Welshpug - is that 14v on idle, too ? I think I only got that at about 3k . . . . looks like it may be a new alternator, then !

[welshpug 1,657]

yes, should be at idle as well, does the alternator charge light work? if the wire for it is not connected to the alternator it will not work till revved over 3k.

[shed_racing 0]

Will have a look this evening - was poking around down there replacing the starter - I'm sure it's back on, but if it's anything like the starter exciter wire . . . . . Like I say, I'm not an auto-electrician by any stretch, but a green suede overcoat to the wire can't be a good thing.

 

Thanks again.

[mr_exe 1]

I've assumed its a 8v engine reading your signature, if so I have an AMC make of throttle body you can have if cover the postage.

[shed_racing 0]

WooHoo !!! Managed to get a multi meter across the battery ;14.4v at idle, 12.7v engine off.

 

Result ! no new alternator. (whew) - thanks, everyone for all of the advice so far.

 

Still, doesn't explain the ferocious drop in idle when there's load applied . . . . had another bit of a fiddle, and it's set at 1000rpm dead no load, which drops to around 800 - 850 with lights and heater on full; engine flutters a bit, but doesn't quite drop off the map.

 

Assume that this is the best I can hope for ! If it doesn't stall (or a bit of nifty footwork prevents it) then I'm happy.

 

Mr. Exe - thanks for the extremely kind offer; in replacing the starter (and refurb'ing the injectors, cleaning out 91k miles of gunk from the inlet manifold etc etc) I've messed with the rather bad initial setup (from when I bought the car), so I really need to start from scratch with the whole idle thing, so once I've got a replacement o-ring, I'll do just that

 

Injectors pre-refurb: 132; 132; 129; 129 - injectors post refurb: 150; 150; 150; 150

 

I guess the additional fuelling ( a whole 72cc/min, apparently) has screwed up the settings, and I was just trying to lessen the pinking when flooring it in the wrong gear.

 

If your offer still stands after I've flattened it and started again, I'd be very grateful.

 

Thanks again everyone for what has turned into yet another shed essay.

[shed_racing 0]

Sorry - yes, it's a 8v XU5 1.6

[lagonda 42]

Sounds like alternator OK, in which case high resistance somewhere could result in idle drop, as alternator has to work harder than it should at low revs. Recommend check earth connection, bolted to the gearbox....make sure it's clean & tight...also battery terminals.

Cleaned injectors will pass more fuel, so assuming someone has compensated previously, you would now need to weaken the mixture. As you say, best to start with everything clean & tight & start from there. Bought a big old Mercedes years ago...280CE...lovely car..asked vendor why he was selling it....said he couldn't afford to run it anymore. despite main dealer servicing, when I got it home, I found all 6 spark plugs were hardly screwed in, you could see bubbles of air coming up past the oil in their recesses. Threads were heavily carboned up. Fortunately had a spark plug die so cleaned up easily. Replaced perished vacuum hose, reset timing & mixture.... & it drove like a dream. Felt really sorry for previous owner.

[Anthony 1,003]

100-200rpm idle drop with full electrical load isn't unreasonable/unusual in my opinion, so I wouldn't worry too much - unlike more modern cars, there's no form of idle control nor can the ECU increase ignition advance to compensate, so the idle will drop.

 

If the engine won't behave and starts hunting and cutting out when there's load on the electrical system and the idle is slightly lower than usual, then in my experience it simply means that the injection system isn't setup/tuned properly and not anything to do with the alternator or battery. In particular, they seem to be quite sensitive to idle mixture, base ignition advance, and the relationship between the throttle stop and idle bypass screw - the lower the idle speed, the more sensitive it becomes to one or more of these being wrong.

[shed_racing 0]

Thanks again, all - went to the main stealer today who supplied an o ring to fit the shoulder at the sharp end of the idle screw (FOC, May I add !!) and brought it back; set the idle at 1000rpm, and it seems ok for the time being.

 

It's too pigging cold to reset everything today (plus I managed to slam my forefinger in the VW door when shutting it earlier 'cos I couldn't feel anything ) so I'll start again next weekend, when it's spring . . . . or at least when the ambient air temp is in the positive.

 

Lagonda - sounds like a deal on the old Merc - Usually happens that I'm in your vendor's position, rather than yours !! Good call.

[lagonda 42]

Yes it was a great car, joy to work on & acceleration was awesome with kickdown...also pulled our 1-ton caravan as if it wasn't there. Lent it to brother for his holiday.....and he carried on driving it when oil pressure light came on....cost HIM £5000 to get engine rebuilt...needless to say he was ripped off, doubt very much entire engine required rebuilding...but both instances typical of my brother. Wouldn't mind but he'd done exactly the same with his Golf a couple of years earlier....coincidentally sheared oil pump drive both times.

 

& guess what....surprise surprise, he was ripped off with the Golf as well. It was a 1.3, & he had an exchange reconditioned engine fitted. A few years later, we needed to change the head gasket...only the new gasket didn't fit. Took it back to motor factor.....and, yes, the gits had installed a 1.1 engine! Only plus point was, as I worked for his motor insurers, I was able to wangle several years refund of premium for him due to lower group rating!

 

Good luck with getting things set up better.