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Hi, my name is Robbie, I live in Sydney and I need HELP!!!

sorry for the length!

Well, the problem with my 93 model 30X started about 2 months ago while I was driving home from work. The car started jerking through the rev range and would die at idle. I parked it on the side of the road and returned later in the evening to pick it up only to find that it would not even start. I instantly thought Dizzy! I changed the dizzy 2 days later for a reconditioned unit, yet the car still would'nt start. Finally, Changing 2 fouled spark plugs, numbers 2 and 6, the car finally started, but sounded as though the engine was blown. I checked compression on cylinderS 2,4 and 6 and it was about 145 psi. My mechanic told me the Dizzy was stuffed and we got another one on warranty and put new plugs in. Car started fine but intermittently a very rough idle and then all of a sudden would go back to a normal idle. He cleaned the injectors lightly and the car seemed to be ok. I drove the car like that for about one month, but it still did not feel right. there was still a slight miss at idle, and the car was jerking and stumbling on acceleration. VERY uncomfortable. one day the car just died while sitting at the lights. would only cold start for the next day or two. brought the car to Mazda to finally fix this problem. Initially they said that the ignitor in the Dizzy was stuffed. Put a new Dizzy on and the car started fine again. I drove out of mazda and the car was actually driving very smoothly. I put petrol in the car, and to my great surprise, the idle went rough all of a sudden. brought it back, and they said the injectors needed cleaning.still a rough idle. Then they said i needed to overhaul the injectors, and put new seals in. still i have this intermittent, excessively rough idle. (I might add that the revs were hunting up and down at idle. I reset the computer and now idles perfectly at 670RPM). I cannot understand what could be wrong, they have checked everything, they have tried to pull codes, yet nothing in the engine bay seems abnormal.They even did a compression test to find 175 psi. I have noticed that the number 2 cylinder never fires properly when the rough idle comes, and that particular spark plug seems to always foul.
I NEED HELP BAD!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Vacuum leak possibly. Take a can of starting fluid and spray it around different areas around the intake manifold and such. All different areas around there. If the idle jumps when you hit a certain area, you have a vacuum leak.

Your problem could be caused by a number of things, pull your engine codes for starters and go from there.

Mazda checked for vacuum leaks by doing the exact thing you said, right in front of me, and their seemed to be no alteration in idle.
They have also tried pulling codes and tell me that no codes come up!
Strangely though, everytime it goes into rough idle mode, it's always the number 2 cylinder which does not fire properly, even with new spark plugs.

if you have not already done so I would replace the spark plug wires.

Andy P. 93 GS

So did you ever figure out what it was? I am having same trouble. It's getting worse quick, and I'm thinking it won't be running at all soon enough.

SLOW30X wrote:Strangely though, everytime it goes into rough idle mode, it's always the number 2 cylinder which does not fire properly, even with new spark plugs.

Spark plug wires? pull them and check for any and i mean ANY crack!

sometime spark goes pipe to cylinder wall instead, no explosion then and wire resistence within limit