I have a '92 Mk1 MX5 with 41,000 miles on the clock. Prior owners were two lady drivers. As it had never had its cam belt changed, I had it done at approximately 40600 miles. Afterwards it did seem smoother and quieter than before. However, a problem has arisen in that recently the engine cuts out when it is de-clutched and twice it would not immediately restart. It seemed as if the battery was flat and would not turn the engine over. If left for 30-40 minutes it restarts ok. I took the car back to the garage that did the cam belt, they did not think it was related to the engine cutting out and suggested replacing the spark plugs and HT leads which was done. They also said that the failure to restart may be something to do with the starter motor ie two different problems. For a few miles the car was fine but now the engine cutting out when de-clutched has started again and I have had one experience of the reluctance to start. As far as I am aware the battery is fine.
Do you think the cam belt change had anything to do with the current problems? Do you think I have two different problems or are they related? Any ideas as to what might be causing the engine to die on me and then become difficult to restart? Someone suggested that the 'idle speed air valve' on the carburettor might want cleaning.
I know it is an old car but I love its shape and handling and any suggestions would be most welcome.
Edited by Dynamic Dave on 10/07/2008 at 14:02
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sabre,
I don't think that your car has a carburettor, I think all MX5s are injection. I'm at work at the moment and the MX5 bible is at home. I'll have to check later. Two thoughts,
1 The garage have to remove the cam position sensor to change the cambelt. Maybe it isn't fully located and secured.
2 The battery is in the boot on this car. It is worth checking the security of the leads, especially the earth. It doesn't need much of a voltage drop caused by a bad connection to give problems with a starter motor.
Hopefully screwloose or one of the other experts will be along with chapter and verse shortly ---
hth
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Not a lot to go on here; so it stalls coming to rest and then may not even crank over - until it suddenly will?
Any fault codes recorded? It does have an idle control valve, but that wouldn't cause it to fail to crank.
As mjm says; this could be a power feed or earth issue; maybe a connector getting overheated and the whole engine is losing power once the alternator drops out at idle.
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I'm not an expert, but it's possible that the camshaft(s) or crankshaft have been rotated slightly when the cam belt has been fitted, so they are now slightly out of sync with each other.
The MX-5 has a non-interference engine (ie the paths of the pistons and valves don't overlap, meaning that if the cam belt were to snap the pistons and valves wouldn't meet and wreck the engine).
I would think that if the belt were wrongly fitted the engine is likely to still run, albeit slightly down on power, but it would be more prone to stopping when allowed to drop to idle as yours does, and would sometimes be difficult to crank as you describe because the pistons are either pushing or pulling erroneously when the valves are closed, creating either an excessive pressure build-up or vacuum which prevents the engine from turning over normally. This would explain why even a fully-charged battery cannot turn it over.
A garage once fitted a cam belt to my old Octavia in this manner, with similar results. Fortunately I was able to get them to refit the belt correctly, and no harm was done.
Edited by Webmaster on 21/09/2008 at 13:39
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Thanks for your thoughts. Re the cam belt being incorrectly fitted, I can follow tour thought, but, after it was done I thought it was running smoother and quieter , would it have done that if it was incorrectly fitted.?
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Hi
It not only stalls when coming to rest but stalls when one releases the accellerator.
I do not know how I would find fault codes - is there somewhere they are recorded? There is a diagnostics box under the bonnet but i do not know how to use it.
Re your reference to something getting over heated, it does seem to be related to heating ie it works ok when the engine is cold but starts playing up when it is hot. I will check all connections.
Edited by Dynamic Dave on 13/08/2008 at 19:34
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Hi
I have been away and could not reply earlier.
Thanks for your thoughts. I have checked the battery and the connections are ok, but the problem remains.
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strangly enough, my mother in law to be has this problem too...
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>>strangly enough, my mother in law to be has this problem too...<<
What, she dies when de-clutched? :)
From memory of changing cam belt on son's MX5, 1998 1,6 the only sensor which has to be removed is the cam position sensor. Again, from memory, it works on the inlet cam. Maybe there is a common error apearing.
I have the manual at home, post back if want any info.
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