320is Motronic Problem

[James MacKinnon]

I have finally got the 320is back on the road and using it daily.

However, I have hit a bit of a problem:
Whenever the car hit 5000rpm the engine would stall out (as if hitting a rev limiter) and even cut out at times. The car would then start again with no problems.

Been all round the car looking for possible reasons. Not rotor arm, disi cap or leads (all brand new and even tried on a friends Evo Sport so we know they are fine). Not fuel sender unit, not the ignition coil.

I then try a complete ECU out of an M3 Evo Sport and the car drives perfectly well, problem gone. So the problem is definitely the 320is ECU. Upon opening it up, I discover the 320is chip has been modified (remapped when still in Italy - they kindly left a sticker on the chip indicating the mod: “320is M Modificata”). However, last time I used the car (almost 2 years ago) the car had no hint of this problem at all. I tried a variety of M3 chips (old and new) in the 320is ECU but car doesn't even start. I try the 320is chip in a variety of ECUs (old and new), car still doesn't work. So cannot decipher whether it is a chip problem or an ECU problem.

I'm still using the car but with the Evo Sport Motronic and it drives very well and performance is definitely as good as ever.

Has anyone hit upon this or a similar problem before? Suggestions?

[Jeroen]

James,

Well IMHO the ECU and chip problems are connected. My guess would be that there's a problem in the ECU and it probably damaged the chip.

There are quite a few known ECU problems like the power circuit switching the injectors and idle control valve. A few transistors and power resistors are known to fail but they're not that expensive to replace. As a precaution I had several of these known weakpoints fixed and that cost me EUR 50... not bad at all compared to a new ECU at abt EUR 660 (try finding a used example )

I'd advise you to have the ECU fixed and the chip replaced by the stock one. I know some addresses here in Holland that would be good at that but there are probably a few experts over there as well.

Good luck, keep us posted!

[James MacKinnon]

Thanks Mate,

I'll take a fresh look at the problem with the suggestions you have given me. I know someone over here who will be able to have a look at it and see what's what.

It's been a long haul but I'll soon have the car up to scratch once again.

I'll post a reply when the problem has been identified and resolved (just hope it doesn't require an ECU!!!).

Thanks,
James

[Jeroen]

James,

Well since the car is running fine with the current M3 ECU... differences are really small. As far as I know any 2.3 M3 ECU will do (with a 320iS EPROM) so that shouldn't have to be too difficult...

[hardtailer]

put the 320is M modificata chip in the Sport Evo Motronic. If it works (and it should work if the chip is ok: I run a 320is chip in my 2.3l M3), then you know it is the Motronic.

Easiest is to look for bad soldering joints using a bright light and a magnifying glass. concentrate on the parts that are attached to heat sinks as those drive the injectors and the ignition coil. I reckon you'll find the culprit there.

If not do an extensive search on s14.net, as ergarding the ECU the S14B20 is no different from any other S14.

[rui freitas]

hi!!! had the same problem 2 years ago its very simple the problem is that the spark cables are worn out because they are in touch with each other . its a comun problem in the s14 engine. already left an idea about that ... my advice instal new cables and take them of its original black enclosing ramp. instal them each and every one in separate ramps and theywont worn out so easy and even encrease bhp and torque at low revs... hope it helps .my best regards. Rui Freitas ( seen this in a dtm article about the s14 it was used for racing and it works!!!)