Dead 1992 Eunos 1.6

[nedski]

excellent well done. patience of a saint

[dafeller]

AFM would make sense. I think, not sure but think, that if there is no signal from the AFM then the ECU won't fire fuel or spark i.e. if the ECU doesn't see airflow then it doesn't now the engine is running.

I looked at some of the discussion on the web about AFM faults so I opened it up for a look. This site had good pictures:

http://www.miata.net/garage/afm_fix.html

It was all dry and pristine, but it didn't look very neat. The three pins that are soldered to the circuit board had extra metal foil from the two right-most connections (4 and 5 in the diagram), as if the tab on the end of the wire had a double connection. These 'leaves' were sort of messily folded over or above the soldered connection and when I first looked in I thought that they might be damaged. The leaves not only seemed to be touching each other but when the rotary switch was rotated by hand, the brass 'finger' extending from it (and which trips the switch at 1 in the diagram) looked like it might touch them. I trimmed the excess off and cleaned the contacts with a pencil eraser if only to make them look a bit neater.

If I had been more methodical about it all I might have a better idea of what resolved to make her run!

[nedski]

If you get too good were gonna come to you for answers

[dafeller]

I feel more lucky than good, I have to tell you. It took me three weeks to get this solved, with well more than half of that not really paying any attention to the car. I'll tell you, though, I now know more about my MX-5 than when I started!

[dafeller]

WELL, the latest in the repair story that will not die:

After I got it started last week, I drove it in to Cambridge for the day and it was ace. On the way home, it started to misfire, and actually expired in the drive to my building. Super. The next day it restarted, but it would only start for 10-15 seconds then chuff to a halt. When I did get it to catch, if I held it over 2500 rpm it would stay lit, but the tacho would bounce around and it would not idle or run below 2000 rpm.

So, I reviewed all I had done and even though I had opened up the AFM, from all that I could read on the internet and this forum it sounded like an AFM problem. Today, I went and got a working replacement AFM and she started right up, but would only run consistently with the jumper across F/P and ground in the diagnostic port. I then figured that the fuel relay was part of the problem and put a working replacement in for that.

Heaven.

So I took it out and down the A1 to get some petrol and feel the breeze in my hair. Ten minutes later and up to operating temp, she died on the A1. Now, I have replaced all available components and really had nothing left to offer. Oddly, each of the times it had died on the road in the last week, it was up to operating temperature before it died AND it had just started to rain when the misfire came on. I suppose if the Beatles had been on the radio at the same time I would have blamed that as well, but it goes to show you how desperate I have become to think that the weather was affecting things.

After I let it cool down some, i tried it again and no go. I swallowed my pride and had my girlfriend come out to me and call the RAC. The guy was most solicitous, towed me off the carriageway and listened to all that we had done to date, etc. After putting more petrol in the car and opening up the fuel pump area to make sure it was working (it was), he checked for spark in no. 4 cylinder and got nothing. He then checked 3 (spark) and 1 (no spark). AHA! pulled the coil pack off the head and noticed that the two little wires coming off each coil on the bracket were loose, and the nos. 1 and 4 especially so. He tightened those up and Joy was ours once again!

I will admit that having tested, removed, replaced and retested this coil pack (my original) before reinstalling it the last time, I had never looked at the bottom of the coils, or even notice that they have little covers over them. In my case, there is only one cover. I think tomorrow I will loctite the nuts and cover them with electrical tape.

There is no way to say that the loose nuts were THE problem all along, or just another of several intermittent problems that were contriving to make solutions so elusive. I think now that I have the new fuel circuit relay in there, I may reinstall my old and ostensibly pristine AFM and see if it all runs like that. Today with the old fuel relay and the new AFM, it would not; I had to jumper the fuel pump to get it going. But I haven't tried the old AFM with the new relay and properly adjusted coils, so that will be one last event.

I am hoping this is the last installment in the saga, boys. Thank you all for your kindness and support.

[Mazda Mender]

Lets hope that you can start to enjoy her properly and worry free at last.
M-m