S1 Mi16 Surging Long Post

[Haze 0]

Hey Everybody

 

 

Ive got a problem with my 89 s1 mi16 (motronic 1.3 ecu),

Its got a bit of a surging (ie revs go down and up) problem which starts very faintly at around 3000rpm then gets gradually more noticeable to about 3700 where it gets VERY noticable until about 4600, where it goes very smoothly.

 

It doesnt miss at under load, only at these rpms. this leads me to think it SHOULD be more a fuel problem....it is also slightly worse when cold but not majorly different.

 

Now what led up to this -

It all started when i pinched a spark plug lead while trying to put the stupid original spark plug cover back over the spark plugs...

 

It started to miss under load, replaced leads, rotor button and cap

(bought from Eurocare, in burswood WA, who have given excellent service and prices)

 

Tried taking coil off at night half darkness, ratchet slipped and broke the air bleed cap and sprayed HOT (turned car off only 5 min b4) coolant on my face, minor burns -> etc... maybe the coolant has sprayed on a component...

 

couple weeks later

-replaced faulty coil (open circuit in secondary windings) with 2nd hand EB falcon type (tested good with multimeter, only difference was the secondary winding circuit which was 7.6k ohms compared to the pugs standard 6.6k ohms )

 

This is when it mainly started to surge.

 

-replaced battery (sat around for 2 weeks with a crap battery...)

 

-replaced spark plugs - no difference to surge.

 

(ALSO: ignition module was replaced about 3 months before i bought it)

 

-replaced injector o-rings/filters and 2-pin plugs

-a couple of bits of old fuel hose, the rest was good.

 

Got a lot better, didnt start to surge until about 4000

 

-poured in NULON total fuel system cleaner (excellent stuff)

 

got slightly better after a few k's

 

Other things i have done:

 

-wd40'd every connector and relay under bonnet

 

-reset throttle switch

 

-checked carbon canistor connections/hose - all fine, replaced a couple of hose clips with screw clamps.

 

-checked fuel pump/filter hoses and connectons -all ok.

 

-checked air flow meter with ohm meter, seems fine

 

My diagnostic light didnt work so i had to hook up a LED to the diagnostic plug and earth.

- no fault codes.

- unpluged airflow meter and ran for a few seconds.

- redid diag. and the air flow code came up, so i knew that it was logging faults ok.

 

The only thoughts i have left is

-the ignition module has packed it in again from excessive current draw due to faulty leads/rotor button/cap and coil.

 

-coil not suitable (unlikey i think)

 

-Engine speed sensor faulty

 

-ecu faulty

 

-injectors faulty

 

-o2 sensor

 

Does anyone have any other suggestions to what it may be? before i take it to a specialist, prob Eurospares

 

its probably something really basic as most frustrating things usually turn out to be...

 

Thanks for reading this uber long post!

Hayden

 

drove it the day after i stop working on it and it felt as though it got worse as it started to surge earlier and for longer. instead of the 4000rpm start, it is back to 3000rpm...

 

cheers

Haze