SWMBO has recently purchased a 1990 Toyota Corolla GL Estate (1.3 litre). The car is fine apart from the fact that it idles much too fast (1400 rpm) and is a bit heavy on fuel. I assumed that this would be a simple matter of adjusting the fast running screw on the carburettor, but when I came to do the job, it was obvious that (a) the idle adjusting screw was not playing any part in the idle setting as it wasn't contacting the throttle linkage and (b) the carburettor was a much more complex beast than I was expecting, with a dashpot, cam breaker, choke breaker etc.
Clearly the whole carb appears to be out of adjustment and it's a job beyond me and my Haynes manual. So, I'm wondering if this is work that I need to go to a Toyota main dealer for, or can I entrust it to my local friendly independent (who is a Citroen specialist - I've used him for years and have been unable to track down a local Toyota independent)? Clearly I can ask him if he thinks he's got the necessary kit and info, but I thought I'd ask here first. maybe the Tune-Up guys can offer an opinion - Is this the type of job that a general motor engineer can handle or is it too specialized? Obviously, with a motor of this age I'm reluctant to pay main dealer rates unless I really have to!
Grateful for any thoughts on this
RM
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As a first step to solve this problem I'd suggest making sure the cooling system is O.K.By this I mean renewing the thermostat and checking the coolant flow to the automatic choke.If this does not fix it then you will be into carburetter work or an exchange carburetter.These carbs. are adjustable but so often the adjusters are completely siezed up which is a problem as an exchange unit is extremely expensive. Your local branch of Tune-Up may well be able to help you with this.
David Davies (Tune-Up Raglan)
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Hi RM,
Certainly sounds like a carb / choke (possible coolant flow) problem, BUT, also worth checking the distributor vacuum advance diaphragm. If you distributor has two vacuum hoses going to the vacuum capsule on the side of the dizzy, pull each off in turn (with engine running) and check that there is no vacuum pull on the open capsule port (with the other pipe still connected). Alternatively, remove both pipes and apply vacuum (suck !!) to each port in turn - you should not be able to draw air through either port with the other open to atmosphere. If there is a passage of air through the unit the internal diaphragm has failed, and this does produce a high idle speed (vac leak back into manifold), and poor mpg as vacuum advance is not working correctly.
Bad news is that a new vacuum unit is only available from Toyota (although not too difficult to fit), but last time I bought one it was around £140 + VAT !! If buying second-hand you will probably have to buy a complete dizzy, but check vacumm unit as described before comitting.
Good Luck, Adam
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Hmmm,
Thanks David and Adam for your replies. Interesting that you should both mention choke/coolant possibilities. When the car starts from cold she idles fine, it's only as it warms up that the revs increase. I bought the vehicle cheaply from my brother and it had suffered from an overheating problem which he cured by changing the radiator cap. Since I bought it I've changed oil and coolant (which appeared mighty rusty although the vehicle has a full service history) - no sign of further overheating. Brother says (and I believe him) that he had no idle speed problems, but the car was standing unused for a couple of months before we took ownership. The symptoms would indicate a problem with the choke mechanism.
BTW - Is there a Tune-Up franchise that covers the Bournemouth/Poole area? Couldn't see one on your website.
Will have a look at the diaphragm over the weekend.
Regards
RM
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Brian Littler is your man I think. Now runs a garage in Bournemouth rather than a mobile unit. Can't help with a 'phone number, Sorry.
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Brian Littler's number is 01202 859321
Regards, Adam
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Thanks guys for the information. I assume that Brian used to have a Tune-Up franchise but has reverted to a garage operation? If you think he can handle this job then I'll give him a call, although I'll probably have a quick look at the distributor diaphragm myself first.
Regards
RM
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Brian is still very much part of the Tune-Up operation (which is NOT a franchise by the way, it is a licensed used arrangement as far as the name is concerned,with most of the operators being former franchisees of another company). It is just that he has decided to comit to a static operation instead of mobile.
Regards, Adam
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Before looking at the automatic choke I don't suppose the throttle cable might be too tight, thus preventing the throttle linkage from sitting on the idle screw as it should.
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