1990 Mazda 626 - Off With His Head

For sure, I think I called them rare but no-one cares, which is definitely true. I've driven a slightly newer 323, and the first car my dad let me drive (off road) was a much older 323, but all those models are now so rare to find in the UK. I had a quick look on HowManyLeft, and counting up all the 1987-91 "GD" platform 626, there's less than 40 still on the road by my maths.

Edit: That first offroad jaunt was an A or B plate Mazda 323 hatch, pale green with beige interior. I've got a physical pic somewhere, will try and find it. Was considered old/rare/curse word even back in the latter 90s when I drove it. Gloriously outdated interior was my main impression at the time! Still remember dad telling me to ease of the throttle when turning so I didn't break something. Attached below a pic stolen from the internet that I think was similar.

My BIL had the earlier 323, from ROR in piccie.


*webgrab

.... He dropped by my house and I cobbled up the 'over axle' back box from scrapyard pieces. I haven't a welder so lots of clamps + gungum paste. Saw off a few more MOT 🔨✔️


OVIMOR

Not a whole lot to report this week so far:

- flushed the cooling system
- fitted new radiator + coolant
- fixed nut on rear sway bar
- painted wiper arms
- topped up screenwash

Nothing rock and roll! I'm still waiting for that rotor arm. Now that I've done the cooling system, I've noticed that when it's hot it's idling quite high. The misfire is still there, albeit improved since I put the new plugs, dizzy cap and coil in. I'm suspecting I have two issues now, something ignition related causing the misfire still, but also an air leak or gummed up carb that's throwing out the mixture.

Other than give it a wash, not a lot more I'm willing to do until the rotor arm turns up...

The list remaining:

- wash exterior/detail
- wash engine bay
- welding to pockets
- welding to sill fronts/wing area
- fix misfire/high idle
- sunroof is sluggish, lubricate
- MOT
- tracking
- wheels
- lows
- timing and aux belts

Really hating this car at the moment, nothing I'm doing seems to be getting this running issue sorted.

Spent the day yesterday stripping down the carb, cleaning and inspecting. Carb was reasonably clean inside, bit of scale at the bottom of the float bowl and in a few passages, but nothing obviously blocked. I did notice that the switch on the side that detects idle position was sticky and not always engaging (due to a weak spring), so I replaced the spring and that's fixed. Put everything back together, ran the car up to temperature and it's still running crappy. The combination of nothing I do improving it, cold weather making the unit a miserable place to be, and general winter depression is getting to me.

I'll write down the car's symptoms to see if it sparks any ideas for me, or you:

Starts from cold OK, smoky though with a slight misfire. Once warm, tends to idle high at about 2200 RPM, and blipping the throttle causes it to hang before gradually returning to that figure. Plugs are blackened, same on all four cylinders. Reluctant to start when warm, unless some throttle is applied. Putting the auto transmission into gear results in the revs dropping too low, hard stuttering and often a stall. Putting the transmission back into park will sometimes cause it to remain at this low stuttering idle, blipping the throttle will generally bring it back up high again. Once moving, car runs ok and accelerates fine, no obvious lack of power.

I've checked all the vacuum lines, and sprayed carb cleaner liberally everywhere to try and find any air leaks, none found. I've verified the operation of the choke, can see it opening and closing at appropriate cold/warm engine states. I've replaced just about all of the ignition system (dizzy cap, rotor arm, spark plugs, coil). Fuel level in carb is spot on.

Things I still could check:

• cam/crank timing, make sure it's not skipped a tooth on timing belt
• Voltages at the engine control unit (I have manuals for this), to check that all sensor inputs are sensible
• Check operation of coolant sensor on the block (rad one has been checked and is OK)
• Check all the solenoids that control vacuum, in particular the "main air bleed control solenoid valve", "air bypass solenoid valve", "ignition timing control solenoid valve", "idle up solenoid valve" and "OD release solenoid valve".
• mess around with the idle and mixture screws. Loathed to do this, as I don't have a good baseline, and the manuals do not specify anything useful like "two turns out" so this would be guesswork and may just be masking a problem elsewhere.

"Plugs are blackened, same on all four cylinders. Reluctant to start when warm, unless some throttle is applied."

Sounds like it's running very 'rich' , mixture control?

Yes does sound rich alright, I'm reluctant to play with the mixtures until I've rules out everything else, as there is no evidence they were messed with, and the manual doesn't give you any baseline to work from. 

BITD... (Well, perhaps some on here still do)... Gunsons ColourTune was the go to for carb twiddling.
Alternative is more time consuming = bray up the road, cut IGN, stop, plugs out THEN 'tweak' Repeat... 😕

Old skool tuner shop will have a good idea around carb twiddling 👍

Don't lose heart, m8


OVIMOR

Is this of any use?

Carb Instruction Sheet

Idle Mixture Adjustment

What colour are the plugs now ?