6 replies to this topic

[bozy6666]

Hi all, can anyone help with this one please, i have a classic mini with what i have been told is a 1989 1.3 metro MG engine, it went for MOT and failed on hydro carbons i have changed the oil and filters, re set valve clearances, checked ignition timing and Co level, changed plugs + leads + dizzy cap and rotor arm but still cant get the HC much below 1200 also the car doesn't idle very well but cant find any air leaks

any ideas will be much appreciated

[ACDodd]

The only thing you have not checked is the valve seal. Cylinder leakage test shows this up perfectly. The MOT also has a fast idle test. Maybe you should discuss this option with the MOT man. The A-series has to be in dia condition not to be able to pass the fast idle test.

AC

[bozy6666]

I have just carried out a cylinder leak check and a compression test all cylinders were 200+ psi and all were less than a 5% drop on the leak test

[ACDodd]

If the engine is mechanically sound you need to set the timing at 5 degrees before TDC at 1500 rpm Vac disconnected. Ensure the plugs are set at 0.035" with the OE leccy ignition. Fuel mixture should be 2.5 to 3.0%CO at idle, Idle at 950rpm. Also set the tappets at 0.014 intake and 0.016" exhaust.


AC

Edited by ACDodd, 06 August 2012 - 06:47 PM.

[bozy6666]

If the engine is mechanically sound you need to set the timing at 5 degrees before TDC at 1500 rpm Vac disconnected. Ensure the plugs are set at 0.035" with the OE leccy ignition. Fuel mixture should be 2.5 to 3.0%CO at idle, Idle at 950rpm. Also set the tappets at 0.014 intake and 0.016" exhaust.


AC

are your figures correct for valve clearences the reason i ask is according to autodata they are both 0.35 cold and the timing was quoted at 11degrees at 1500 without vac, im wondering if i have the wrong model

[ACDodd]

They are not factory figures they are what works. The clearances are to reduce valve overlap lift. The factory timing figure for Later MG metro engines, was 5 degree BTDC at 1500rpm vac disconnected. Retarding the static ignition timing reduces HC's.

Basically the recommendations here are a package of measures to lower your HC's.

AC

Edited by ACDodd, 06 August 2012 - 09:09 PM.

[Jordie]

hydrocarbons is usually unburnt fuel. check your firing on all cylinders correctly.....get it running warmed up and at idle, pull each plug lead and listen to engine tone. it should drop / run rough as you remove each one. remove one at a time and replace. if the engine note doesnt change when you remove the lead, thats the issue.

recently had this on a car, passed all bar HC on emissions. car had been serviced with new plugs etc. turned out to be a faulty plug, even though it was brand new just about. replaced with another plug, back for test and passed no problem.

Good luck with fixing it and the retest.