Poor Running

Right then, hopefully this won't go on as long as it could!  My 1800GTi Cabby doesn't run as well as I think it should - here are the 'symptoms'

1. When on part throttle, seems to sort of stutter, like in the old days when you had 'kangaroo petrol'
2. Really doesn't pull as well as I think it should, and seems to have a flat power curve
3. Idle runs faster when the engine has warmed up (about 1200rpm as opposed to the 800ish when cold)

Now, I'm thinking this might be down to ignition timing - however there is one curious thing that might or might not be connected.  Back in the summer (remember that?) if the car was left when warm for about 10-15 minutes, when I came to start it again, it would fire up, then die - especially quickly if I blipped the throttle.  This could be completely cured by disconnecting the electric feed to the fifth injector.  When the colder months came along, I thought I would try to look into this thinking it was the thermotime switch (TTS) - however, the readings I got from the Multimeter showed that the TTS only got 12v when cranking, not when running - if this is correct (which I believe it is) then I can't see how a faulty TTS would cause the problem in the summer, but also can't therefore see how disconnecting the fifth injector solved it!

So before I try to solve the poor running, should I continue to investigate this wierd problem - or are there any other thoughts?  As for the poor running, here is a list of things that have been changed to no improvement; Plugs, leads, dizzy cap (I think?), air filter, warm up regulator and metering head.  The fuel filter looks pretty new (car 10 months old to me).

Any thoughts?

Cheers

Lemond said

 
"it would fire up, then die - especially quickly if I blipped the throttle.  This could be completely cured by disconnecting the electric feed to the fifth injector…. I thought I would try to look into this thinking it was the thermotime switch (TTS) - however, the readings I got from the Multimeter showed that the TTS only got 12v when cranking…. - if this is correct (which I believe it is) then I can't see how a faulty TTS would cause the problem …. but also can't therefore see how disconnecting the fifth injector solved it!

So before I try to solve the poor running, should I continue to investigate this wierd problem

Short answer, mine anyway, is yes, find and fix the cold start injector before going any further. The flat running and the high idle can both be a result of the cold start injector remaining open. The flat running from being too rich and the high idle because the idle was raised to compensate for the extra fuel. The dying when you start it is also common from a CCV that is leaking.

You are correct in that the CCV should only recieve power during cranking, key word here is "should". If removing the connector causes the reaction that you state, then it must be spraying all the time for some reason. Could be wires are connected wrong or shorted some how, but removing the electrical connector while running should have zero effect on the engine. It can't be just a stuck open CCV as the electrical connector would make no difference, so I would take a close look at the wiring. Can you lower the idle, or will it start to stutter if you do?

Thanks for the info - I think I might be able to get a different fifth injector fairly easily, so I might try that anyway - at least I suppose I should check that it isn't constantly leaking.  I did check the electrical connection to it and it seemed to be working OK with the exception of the thermo part of the TTS working, but the time part didn't (i.e. it continued to read 12v whilst cranking even after about 15s).  I guess this could do with a bit further investigating!

Right - A bit of progess on this one thankfully.

It appears the TTS is shot - it gives 12v to the 5th injector when cranking even when the engine is hot.  The reason the hot start dying problem seemed to have solved itself was down to the 5th injector having a bad earth connection, hence hiding the faulty TTS when I reconnected it this winter!

Secondly, the high idle seems to be down to an inoperative Auxiliary air valve - when hot, squeezing the pipe causes the revs to drop.  However, before I scout the breakers to find another one, does anyone know if this is controlled purely by the electrical bimetallic strip, or should engine block heat cause it to open also?  I am wondering if this again could just be down to a poor electrical issue? (too dark to check with multimeter now!)

Still got the poor performance, but thinking sorting these issues before going any further ain't a bad thing.  BTW, I also checked the 5th injector for leaking, and it all seems fine

Look at the circuit properly for TTS and 5th injector - the 5th injector doesn't have an earth and the TTS earths through the engine block. And, the 5th injector is fed with a +12V signal off terminal 50, ie when starter is turning only - irrespective of temperature! Basically the whole lot is only energised if the starter is turning; the 12V is applied and the TTS switches the 5th injector on by completing the circuit to earth.

The aux air valve gradually CLOSES due to conduction heat from the engine (inlet manifold) and the bimetallic strip. If its electrical connection is broken, it would still eventually close (but take a long time to), if its stuck it would not close. You can take it off and observe the gap. Also you can check the resistance, to see if the heating circuit is damaged or okay. I have known them to be fixed by cleaning (soak in carb cleaner or similar).

That'll teach me to jump to conclusions then!  I mistakenly thought that the +ve to the fifth injector was switched, not the earth.  That'll explain a lot of things.  However, I am still pretty convinced that the TTS is shot, as when I disconnect the plug on the 5th injector, it starts fine when hot - which is does not with it connected.
I'll investigate again tomorrow…..