S-Series ECU Differences

[SimonR]

Hi again all,

Got an ECU question this time!

I picked up a new unleaded cylinder head this weekend and it came with a new unleaded ECU (NNN 10001).

I also already had an unleaded ECU (NNN 10009) and the original leaded unit with which the car came.

When I got home from collecting the head, I plugged in NNN 10001 and the car would barely start until I floored the throttle and even then misfired, coughed and spluttered and wouldn't idle. I tried the later unleaded ECU (NNN 10009) and the original one and both worked fine first time.

Now I'm assuming that the other one is faulty but wondered if anything could be done with it - unleaded S-Series ECUs aren't that common and I know someone who would benefit from owning one.

Thanks!

[E_T_V]

It might be wise to actually check that it is faulty before assuming it is. It is possible that the earlier ECU required the carb to be set up differently from the later one, i.e. richer or leaner. I'd check the operation of the stepper motor with the engine off by simulating a hot and cold engine to check that the stepper motor is being activated correctly. If it isn't then it may be repairable. There are several places on the good old internet that refurbish ECU's.

[G Force]

Hi, Both the unleaded ignition ECUs that you have are for a 1.6 Maestro and the NNN 10001 is definitly faulty. I have seen lots of 10001 go that way and personally I would just bin it.

I would also try use your old ECU to begin with, because the head is new I think it will be some time before it starts pinking and meanwhile you will benifit from better performance and economy compared with your unleaded ECU. you can just swap them over if it starts pinking on light throttle.

I also thought when you change the head check to see if the restrictor is fitted to the oil gallery feed to the head in the block itself, this was a modification around 1986 to stop the head gasket oil leak in that area and reduce leakage from the cam covers & seals. Its worth fitting one if you can get hold of one.

Cheers Gary :)

[SimonR]

I also thought when you change the head check to see if the restrictor is fitted to the oil gallery feed to the head in the block itself,

Thanks for the info Gary. I'm interested that the old leaded ECU gives better performance and economy - why should this be?

Also I had heard that an ECU from a Rover 200 with an S-Series engine will also fit the Maestro, is this ture?

Thanks! :)

[G Force]

Hi, Because unleaded fuel is slightly more volatile they retarded the ignition Characteristics to stop the engine pinking, this gives a slight reduction in performance mid range. You will probably find that with the old ECU and the new head you can run with unleaded petrol for a while before it starts pinking.

The old 200 ECU will work OK with your engine but again the advance characteristics are very slightly different.

[e692wtt]

I use Unleaded + FBHVC-approved additive in my Monty, which is 1988 model year and so not approved for Unleaded and still has the original 'leaded' ignition ECU. The knock sensor sorts out the timing and any pinking is minimised when I use premium unleaded. If I use Super Plus/Optimax/Ultimate then the ECU is able to take advantage of the higher Octane rating of the fuel, and Monty runs a lot better and much more happily - he feels like a different car! :)

When I fit the 1300 miles Gold Seal S-series Simon has let me aquire, to Monty, I will still use the same ECU.

I've also used the igniton ECU from a 2.0i VDP Auto Montego in Monty, and while the engine pinks quite a bit it pulls up steeper hills in higher gears than with the original ECU (but this was before I changed the o-rings in the carb, so I need to try it again to quantify this). I appreciate that so much pinking isn't good in the long term, so it's for special occasions only and I don't trust it at high speeds.