89 replies to this topic

[Ozymandias]

One step forward, three steps back...

 

Over the weekend I:

 

1) checked the vac hoses - discovered that the fuel trap was leaking like a sieve and not holding a vacuum at all, so replaced it. This can't have been helping!

 

2) checked the MAP sensor port and manifold nozzle for crud with cotton wool - both seemed very clean.

 

3) as far as possible checked the sensor wiring - it all looks OK, but then who knows...

 

4) checked and adjusted the throttle cable - it was a bit loose so I tightened it up (to do this I turned on the ignition, pushed the linkage to full open then adjusted until the lost motion bit was in the middle of the two prongs).

 

I didn't have the chance to change the oxygen sensor, but the garage said they'd tested this and it was working OK.

 

It's STILL running really rough - like it's missing when I rev the engine. It's not bucking and misfiring through the air intake like it was before, but it's stuttering and hesitating, all through the range - like the timing's out and it's not firing right.

 

The idle still wavers, but not as badly. But in terms of running it's almost worse than it was and it's doing it all the time now.

 

Any ideas...?!

[IainStallard]

For the same of a few quid, try changing the rotor arm. I found mine to be very corroded causing similar running issues

[FlyingScot]

Mmm sounds more ignition related as Iain has written above. Also check the coil and the wiring to and from it.
I had an SPi that the coil was on its way out, tested okay when cold but when warmed up created a misfire.

FS

[Ozymandias]

New rotor arm and coil ordered!

 

I wanted to get some new HT leads as well, but the ones for my car (part no GHT279) are now obsolete - can I just use normal SPi ones (mine are for SPi with aircon)?

[FlyingScot]

Yes leads are pretty much the same.
Got these for mine http://www.minispare.../C-27H7779.aspx

FS

[spiguy]

Think the above advice is good. If you want to eliminate the O2 sensor and the inlet air temp sensor then you can safely disconnect both of those and the car should still run smoothly using the ECU substituted values. I know recently ryomini on here had a similar issue and traced it to the O2 sensor or it's wiring, by disconnecting the O2 sensor- cleared it right up.

[Ozymandias]

Thanks - I'll try disconnecting one at a time and then together and see what happens!

 

The problem gets curiouser and curiouser - driving home last night (15 mile journey) it stuttered and missed to start with and then about half way home suddenly got loads better, accelerating with barely a stutter.

 

At home I removed and cleaned up the rotor arm and contacts (they looked pretty clean anyway), replaced one of the vac hoses which I thought might have a kink in and checked over the coil wiring and HT leads, which seemed fine.

 

Took her for a run and she was running OK, still the odd stutter and a lot of burbling from the exhaust on deceleration.

 

This morning... stuttering again until she'd warmed up, then much better (but not brilliant!) - idle bobbing up and down between 700-100 rpm, burbly exhaust, the odd stutter.

[IainStallard]

Where are you based? I'd love to be able to help out with this issue as I have all the diagnostic equipment available

[Ozymandias]

Where are you based? I'd love to be able to help out with this issue as I have all the diagnostic equipment available

Not too far from you, Iain! I work in Reigate and live in East Grinstead - I'd be so grateful if you could help me!

[IainStallard]

 

Where are you based? I'd love to be able to help out with this issue as I have all the diagnostic equipment available

Not too far from you, Iain! I work in Reigate and live in East Grinstead - I'd be so grateful if you could help me!

 

PM me and i'm sure we can organise something!

[Ozymandias]

By George... I THINK I'VE GOT IT!!!

 

The engine was stuttering like crazy on start-up this morning so I decided to have a quick squiz under the bonnet.

 

I could hear a TICK, TICK-TICK, TICK sound coming from somewhere that sounded like a spark - sure enough, there was a massive blue spark arcing from the central "nozzle" of the coil to its spade connection with the condenser every couple of seconds or so!

 

Now, presuming that this spark should be going to a plug and not across the engine bay, this would explain my misfire issues...

 

I've got a new coil, HT leads and rotor arm on order - should I get a new condenser as well? Is it just that the coil is fried?

[spiguy]

You won't have a condensor, condensors are fitted where there are mechanical contacts (points). Do you see some kind of capacitor connected somewhere ? (eg on the coil bracket) - could be a suppressor to cut down electrical noise for radio / TV interference.

 

I don't have one on my 92 SPi.

Edited by spiguy, 15 July 2015 - 10:14 AM.

[Ozymandias]

That's what it must be then, a capacitor - it's a little aluminium cylindrical job mounted on the coil bracket, with a wire that runs to one of the spade connections on the coil.

 

I really hope this arcing is what's causing the problem - it can't be healthy, in any event!!

 

I've ordered a new dizzy cap too, just to be on the safe side.

[spiguy]

Have you tried simply disconnecting said capacitor and see if your problem goes away? Also, which terminal of the coil is it connected to, -ve or +ve ?

[Ozymandias]

I haven't tried that - I will!

 

I don't know whether it's going to the +ve or -ve on the coil - will I be able to tell by the wire colour code?