Having problems with your 1999 Mazda 626 ?

Ex-wife had used this 99 626 Mazda 4 cyl for 4 yrs and said it vibrated so bad at idle she had to put it in neutral[automatic trans] at stop lights with the a/c on. When I used it she was right. I found low compression on 2 adjacent cylinders, 30-60 psi. Pulled head,had valve job done,honed cylinders, installed new set of std rings[piston ring grooves still tight],new timing belt,all engine & trans mounts changed,idle air control valve replaced,new platinum tipped spark plugs, water pump, idler

Posted / edited by AnonymousUser on : 16-07-2018

Answers :

Check to see if the big hose going from the air filter to the throttle body has a split in the hose convolutes. Thus air is bypassing the MAF sensor. IS CEL light on? Clean MAF sensor wires with carb cleaner too. rpeort results.
Have you checked the harmonic balancer? Most four cylinders are rough at idle no matter what. This is a big problem on the four cylinder Escorts (based on the Mazda BG chassis) and there is no solution. Have you driven other four cylinder 626's to see if they have this issue.

The harmonic balancer could be busted or it could have just had a bad internal balance from the factory. You would have to get the crank balanced and that sounds like more trouble than just putting up with some vibration. I would also still replace the coil since it is out of range. It could only get worse and may just leave her stranded somewhere if you leave it.

If it has a vacuum leak or if the O2 sensor reading is off, you will get carbon build up. You can also get carbon build up from a bad PCV system, be it the valve or improperly routed hoses. It could even be the PCV intake filter is clogged and not allowing fresh air to circulate. I would also check for excessive engine movement as you may have a weak engine or transmission mount.
Repair Help & Product Troubleshooting for 1999 Mazda 626

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