93 Mk1 Starts then dies, fault 10

[alexcruncha]

Hello members,

The other day I was driving my 93 Mk1 Eunos for around an hour and just as coming home the engine died. When I tried to restart it, it fired up for around 1 - 2 seconds then died. I have tried several times over the last few days but it just starts for 1-2 seconds and dies. So now it is permanently broken down.

I have read it could be CAS, AFM, ignitor amplifier, coil pack, bad connectors/wiring to many places, vacuum leak and a few other things.

To diagnose it here is what I have learned so far:

1. Tachometer is working.
2. Putting a jumper on F/P and GND in diagnostics box doesn't help the car run (although I hear the relay and fuel pump working when I do this)
3. Using an LED there is a fault code stored, I disconnected the battery and retested before starting and fault code was gone. I attempted to restart and the same fault code returned. I appear to have fault code 10. I see one long flash being repeated every 4 seconds (followed after the initial 5 second flash). At first I wasnt sure if it was fault code 1 or 10 but I did see youtube videos of how long the flashes last for to indicate the tens or 1-9 part of the code. I see the tens part of the code is indicated by a flash lasting around 3/4 of a second while the 1-9 part of the code is indicated by a flash lasting around 1/4 of a second. My flash definitely appears to be more closer to a second so I believe it is a fault code 10 being stored (Intake air thermistor in airflow meter).
4. The AFM being connected or disconnected makes no difference to symptoms. Problem still exists in exactly same manner.
5. Pushing the throttle when trying to start will increase the engine speed for the first 1 - 2 seconds the car starts but will not help it run any longer than 1 - 2 seconds.
6. Tried taking the fuel cap off.
7. Disconnected and reconnected electrical connections to AFM, CAS, Igniter but no luck.
8. Car had new lead/plugs as well as silicone water and vacuum hoses a couple of months back (so I believe these are all fine)

I am a bit stumped with this one as I have read CAS is usually fault codes 2 or 3 and ignition related problems are usually fault code 1 while AFM problems are usually 8 or 10. The thing that gets me stumped is that I read that jumping F/P and GND will usually get the car to run if it is an AFM issue and this doesnt work for me. Also, the fuel pump appears to be working as I can hear it going when jumpered. Since it will always consistently die within a couple of seconds (no matter how much throttle or if the fuel pump is going) I am more inclined to believe it is an ignition problem but the fault code shows otherwise.

As of yet I have not tested to see if its sparking past the initial 1-2 seconds. So thats my next test.

Does anyone with more experience than me have any ideas? Either way I will update this post as I make progress.

[alexcruncha]

An update:
I found that the car continuously sparks if I keep cranking the engine but the plugs are dry. Therefore, this suggests to me it is a fuel issue rather than an ignition one. I think that rules out a few things.

Also, I can keep it running if I give it plenty of throttle and switch the ignition on/off rapidly.

[Mazda Mender]

1.6 or 1.8 ?
M-m

[alexcruncha]

1.6 or 1.8 ?
M-m

Its a 1.6

Also, I pulled back the carpets to inspect the ECU and connectors to make sure there was no connector damage, water ingress or rust. I also opened the ECU and inspected the board to make sure there were no burned components. Visually it all looked to be in perfect condition and no signs of any issues (however I do appreciate ECU issues might not be visible). But at least I ruled out a few things there.

[alexcruncha]

The following post describes the exact same symptoms I have with the exact same fault code. In that case it turned out to be the ECU:
https://www.mx5oc.co.uk/forum/yaf_posts ... way.aspx?=

I deduct from all my research and testing my issue is likely to the the CAS or the ECU. I have ordered both parts second hand from the bay along with a new CAS o-ring (so even if it is not the CAS I will at least change the o-ring which looks to be leaky on mine). I will post the results I have with them when they arrive.

[Mazda Mender]

It is more than likely going to be the CAS buddy.
M-m

[alexcruncha]

So the ECU and CAS arrived. I first switched the ECU and it didnt fix the issue. I then switched the CAS and it didnt fix the issue. I also used a multimeter on the AFM and can confirm this part is functioning as it should and all connectors on the sensor are ok.

So, I am stumped. Not sure what to look at next. Considering visiting the mechanic but I dont want to give up just yet.

[Mazda Mender]

Is she getting fuel now?
M-m

[alexcruncha]

Is she getting fuel now?
M-m

When I checked last she wasnt. I didnt check since replacing the CAS but it seems this wasnt the issue.

Further to this case I do have an AFM fault code (10) which mentions air intake thermistor (basically air intake temperature sensor). At first I thought my car didnt have one but on closer research I found the AFM (on early mk1's) does the following 3 things:
1. Measures air flow (via variable resistor that is controlled by how open/closed the flap is
2. Engages fuel pump (if air stops going through fuel pump disengages as a safety feature)
3. Measures air intake temperature (via thermistor, which has a small probe sticking out at the top of the intake right in front of the flap)

So, with my multimeter I was able to rule out that points 1 and 2 above are ok but I have not been able to check point 3 the thermistor works correct. Therefore, I am hopeful it is the thermistor sub-component of the AFM that is broken (which is what the fault code suggest). I have a second hand AFM en route from ebay. When it arrives I will post the results. If it is this I will feel a little silly as I should have trusted the fault code and replaced the AFM from the beginning.

I got the above info here: http://www.rivercityroad.com/garage/afm_stuff.htm

[blackyb]

Thats the mx5 spirit, never say die and it will never beat you. Drive you mad perhaps but once solved its the theme for a good and useful post.

[alexcruncha]

Thanks, well I have an update which unfortunately is a bit of bad news sprinkled with good news.

I received my AFM today. I hooked it up, cranked the engine and it started then died like before. I nearly lost it

Since I changed the CAS for a used one at the weekend I decided I would recheck for fault codes (to make sure I havent created an issue by changing the CAS). Heres where it gets interesting. The whole time I had been getting a fault code 10 (AFM thermistor). Today I got two codes, which were 1 and 10 (short flash and long flash separated by 4 second pauses). I realised I may have disturbed something and triggered another code (as to replace the CAS I had to also remove the Coilpack as it was in the way and disconnect/reconnect a few connectors). So, I removed the battery to reset the fault codes. I checked for fault codes right after reconnecting the battery I confirmed it was reset with no fault codes. I cranked the engine a couple of times (and it died just the same as before). I rechecked for codes and low and behold no more fault code 10 showed up now the replacement AFM is in but now we have a consistent fault code 1 (ignition issue).

Aside from believing I am cursed I also believe that the AFM might just have been the fix (now the fault code 10 doesnt show up) but my removal and refitting of the CAS and Coilpack might just have buggered something else up (probably a coil pack connector). I am sure I have plugged everything back in. I did remove all 4 HT leads from the coilpack as well as disconnecting 2 connectors on the top left of the coil pack (by the CAS). But those were refitted. When I did this I did not however disconnect all electrical connectors from the coilpack and just moved the coilpack out of the way enough so the CAS could pass through.

So, bottom line is I believe I may have fixed one thing and broken another.. or maybe the car is playing tricks on me. Either way it still doesnt work and I am starting to get fed up. Damn it

Anyway I will keep trying to get to the bottom of this and update the thread when I have progres. Think the next step is to have a check over of the coil pack installation. Does anyone know if there anything I may have missed when reinstalling the coilpack? And has anyone ever seen a bad CAS create a fault code 1?

[alexcruncha]

..or could a CAS fitted completely out of alignment cause this issue? (producing a fault code 1)

[alexcruncha]

Update:
Well this is embarrassing... by the powers of deduction I have found out that from the start my fault code was 1 and I mistakenly thought it was 10.

I found this out as the other day when I replaced the AFM I got codes 1 & 10 and after clearing the codes got only a 1. Today I decided to put the old AFM to see if I could replicate the code 10 to confirm it was the AFM thermistor. When I did it I could only get a fault code 1. I realised I may have triggered 1 + 10 together due to messing around with disconnecting the thermistor when i put the replacement AFM on. But the long and short of it is that its highly likely I misread the fault code 1 for a 10 from the beginning.

So, logically now is time to buy a replacement coil pack to try out. I am not going for the ingniter (yet) as I have a tacho reading. Back to the bay. Will update you guys on my progress when it arrives.

[blackyb]

Dogged determination and never say die attitude is what makes a Mender a Mender!!

[alexcruncha]

Update:

Used 1.6 coil pack arrived today from someone breaking a mk1 MX5. Bottom line is it didnt fix the problem and still throwing a fault code 1 after clearing the codes. what to do?

Seriously I'm losing patience with this issue. My MOT is due in 10 days and really wanted to sort it out before then but dont know what it could be.

Does anyone have any ideas what could throw a fault code 1 if not the coil pack? Could the igniter be screwed eventhough the tacho still works? Ideas anyone, please.