extremely high afr reading on idle

[Nad-5GTT]

Hello everyone,

This is my first post here sure not to be my last:laugh:

Problem 1,

Ive just bought and fitted a aem uego afr gauge kit, got the car started with abit of choke and it was reading in the 12's then turned choke off and it steadily went up 13,14 etc untill it went past 18 then off the scale, if i rev it it goes into the green but straight back into red zone.

I will add that cars been off road for numerous amount of years, and that i was am experiencing hunting at idle.

Problem 2,
Whilst im here i did have a GRP A carb that idled lovely, but i went and bought a standard carb rebuilt it, then put it on only to find that it idled horribly, so i put the grp a back on and this then idled rough ie hunting.

Ive since sold the grp a and am running with the standard carb,

Questions, are the two linked? how do i sort the above problem?

regards neil

[Nayls]

Sounds like you have an air leak

[Junglist]

sounds a bit like mine though mines steady on idle, soon as i drive its all over the place mainly off the scale.......?

what air leak could caues this . exhaust ?

[Nad-5GTT]

Sounds like you have an air leak

ok, wheres the best place to check ive just taken my dump valves off and put an offcut of broom handle in place for time being:laugh:, should i use some silicone around inlet to carb gaskets? obviously i wont put any on the carb base side. any other ideas all the vac lines are new with no splits.

[Scoff]

Whenever a carb is disturbed (taken on/off/rebuilt/etc) it's quite likely that the idle jet gets blocked. The big brass screw on the drivers side of the carb - undo it, remove the jet, clean it out and re-fit. Try it then. You might find it takes a couple of attempts to clean it out properly.

Failing that, look for air leaks and a crappy idle mixture screw or seal.

[Nad-5GTT]

Whenever a carb is disturbed (taken on/off/rebuilt/etc) it's quite likely that the idle jet gets blocked. The big brass screw on the drivers side of the carb - undo it, remove the jet, clean it out and re-fit. Try it then. You might find it takes a couple of attempts to clean it out properly.

Failing that, look for air leaks and a crappy idle mixture screw or seal.

ive cleaned that big brass screw a few times now, and have replaced the mixture screw:confused: if i adjust the mixture screw it makes no difference what so ever.

If i get any time today ill whip carb off and give it a dam good clean, is it worth me putting silicon sealant around the manifold gaskets or are the gaskets fine on there own?

Am i going to be putting stress on the engine if im running the car whilst trying to sort the idling issue/ high afr or will this be ok as its only ticking over.

Cheers for the quick delivery on my aem afr gauge by the way:D

[Adam 005]

When refitting carb you should always use new base gaskets.Has the breather system been changed in anway if not is the restricter in the breather system.Are any of the breather hoses split.Did you use a rebuid kit on the carb?

[Nad-5GTT]

When refitting carb you should always use new base gaskets.Has the breather system been changed in anway if not is the restricter in the breather system.Are any of the breather hoses split.Did you use a rebuid kit on the carb?

Hello adam, yes i did use a rebuild kit when i overhauled carb i belive the rebuild kit comes with the base gaskets so i assume i used these, ive known about the idling issue for a while but have been concentrating on other bits of the car, but now ive seen what the afr's are doing :eek: im going to make this my priority.

The annoying thing is i had a grp a carb that idled fine, then i bought a standard carb rebuilt it then found it idled crap, so i put the grp a back on to find that this now idled crap.

[Adam 005]

Hello adam, yes i did use a rebuild kit when i overhauled carb i belive the rebuild kit comes with the base gaskets so i assume i used these, ive known about the idling issue for a while but have been concentrating on other bits of the car, but now ive seen what the afr's are doing :eek: im going to make this my priority.

The annoying thing is i had a grp a carb that idled fine, then i bought a standard carb rebuilt it then found it idled crap, so i put the grp a back on to find that this now idled crap.
sounds like an air leak very common in 5s.as per my other post what state is the breather system in(pics would be good).are the one way valves on inlet manifold o.k?Check the plastic spacer between carb and manifold is not cracked not very common but it does happen.

[bigdur]

I had the same last week, turns out the end of the mixture screw had snapped off and was jammed in the carb body causing it to run massively lean.

[Logg]

have you checked for leaks in the the pipe that goes to the AEI/dump valve/boost gauge.

[Matt Cole]

They are old now and rarely work as they should :(. I found that the only way to clean one properly was in an ultra sonic tank. made quite a difference in a few of my carbs. Other than that the base that the mix screw screws into becomes damage as normally they are overtightend and the seat becomes damaged. have alook and see how far the mix screw protrudes and if the seat taper looks to be reasonable for adjustment.

[Nad-5GTT]

Alright fellas thankyou for the advice, ive found the culprit turns out it was my dump valves (ive had them in a box for many years brand new never been used on road barely 2hours of ticking over in say 6 years but im guessing that they've just perrished) :crap: Ive now got 2 broom handle stumps sticking out from intercooler pipes :laugh:

With adjustment to mixture screw im able to get a variety of afr readings at the moment ive left it at 14.1 what is the best reading for idle?

Now if i hold revs at about 2000rpm the afr goes up to around 16 - 17 but if i rev it they drop into the green safety part on gauge sorry couldnt see what reading it was it goes round so quick:o

Im unable to see what it does on road as it has no mot hopefully next month.

How do i get the afr reading to come down whilst being held at a steady rev, is this going to damage my engine, i was going to try and sort my fuelling out with help from you lot after its got an mot but im worried ill ruin engine whilst the emissions are being checked during the mot.

regards a happier neil:laugh: fing cars

[Nayls]

14.1 is ok for i idle.

i would'nt worry about the reading from a rev at standstill,see what they are like when driving (after your Mot)

put your carb spec up and what reading you get from light throttle through to WOT and people will suggest where and what needs adjusting.

also your boost level will be needed.

Best of luck with your mot! :):agree:

[Nad-5GTT]

lovely thats great, just got brakes and a cv gaitor plus a few little things to do then i can mot her, ill put a post up regarding fuel setup when she passes