Carby woes

So here's the deal, when I bought the C4, part of the deal was a valve adjustment and major service with carb and dizzy check(all done by a very reputable shop). Anyway, picked the car up and was underwhelmed with the power or rather lack of (felt like 200bhp vs 340bhp). On the way back home, could see lots of smoke in the rearview mirror (wtf!!). Once home, let it idle in the driveway for a while but had to switch it off cuz of all the smoke. Rang the workshop, told to take it for a long drive as it was sitting around for 6months. Asked about the lack of power and was told it felt right to them. Took it for a long drive and did jack****. Packed it up and went off to Greece for a month

So over the last few weekends managed to find some time to muck around with and this is what I've come up with so far
1. 2 distributor leads weren't pushed all the way in, instant increase in power and improved idle and slightly less smokey

2. today, cleaned out idle jets and adjusted idle screw "tuning by ear". Started on bank of carbs on drivers side, found that screws were at least 5 anticlockwise turns from closed(ie seemed way to rich to me). Adjusted each screw and idle improved significantly (and expectedly rose) and guess what, no fkn smoke out of that exhaust bank anymore

3. Move to other bank of carbs, adjusted 2 out of 3 carbs and again better idle, much less smoke. On to last carb and opening both idle screws from fully open to fully closed made no difference to idle. Pulling plug leads off each respective plug also made no difference to idle. So what do you guys think is happening here? Are both plugs fouled? (could not pull the plugs out as they were screwed in so tight, I got the ****s and gave up for the day). Is it a carb problem eg stuck float. By the way, good spark from those leads and airflow meter check shows all carbs are set similar. Compression/leakdown numbers are fine

I just think the smoke is just unburnt fuel and it feels like its running on 9 or 10cyls. Really disappointed it was handed over to me like that

 

Wow, that sux.

Id say the plugs are fouled too mate. Get em out and clean em up.

If they arent fouled................could be dead leads or something more terminal.

But would have to be fouled plugs.

 

There is a good spark from each lead, so leads seem fine

Either that carby is ****ed or the 2 plugs associated with that carby are fouled????

 

ya know what, 1.5-2 turns out is usually pretty much the right mixture at idle if the jets are the right size. something sounds very odd to me. I don't see how, after all the trouble they went to to get the car right, this was even possible!

definitely pull the plugs. during my 308 experimenting i managed to make it run rich enough that the plugs never worked again....but I'm not a pro, so I had an excuse...but it definitely can happen.

 

Mixture screw needles on that carby may be worn.
Its a tapered needle but vibration and age can wear a step into the taper then adjustment doesn't work.
But really theres so many things that could be wrong with that carb its just a guess untill its cleaned and overhauled.
So much for a "carb and dizzy check".

 

That's what I don't get either. They had a bit to do to the car and i feel they may have just rushed it out. Each of the screws is now set about 2.5 turns and it made a huge difference ie no smoke at all on one side and much less on the other. How "tight" should the plugs be screwed in? They are just not budging easily at the moment

 

Doesn't really explain why it makes no difference when I pull a plug lead off which is why Im thinking rooted plugs at the moment???

 

you don't screw them in tight at all!! they should move freelyish to the stop and then wind out a bit, but apart from the spring tension they should move freely.

you should pull out the jets and air correctors and see what they are and then put it on a dyno and make the necessary adjustments.

FIRST, pull out those two plugs. want me to pop over and do it for you?

 

I think you misunderstood, I asked about spark plug tightness

 

Spark plugs: Not very tight at all, 20 to 25 Nm, or 15 to 18 ft/lbs. Overtightening will likley strip the threads in the head, bad news.

Also, my experience has been that NGK plugs are the way to go.


M

 

Is this the Stag we're talking about?


The plugs shouldn't be that tight, but just get some leverage and make sure you're turning it the correct way.

I'd throw a set of plugs at it, that way they can be eliminated as a problem.

 

Errr... maybe the plugs havent been changed in a while because they have been hard to get out? Had a twin plug Nissan like that once, the dealer changed the easy to get at plugs but not the other set... although charging for the work!

 

But the spark plugs are on tight? Doesn't make sense if they recently did a compression/leakdown test.

M

 

Just pray they haven't cross-threaded the plugs after the test.

Pulling the lead off wont make an obvious difference if the mixture is way off. Those two pots wouldn't be doing much even with the leads on but as already suggested I'd start with pulling the plugs. Followed by picking up the Haynes Weber book.

 

I have no idea what a C4 is ............ and no idea what type of carby we are talking about .......... buuuuuuuuuuuuuuuuuut .... Is there a seperate butterfly for the choke ?? Could that be set wrong or loose so the butterfly is moving when not required ??

 

its the model after the daytona....same engine 365, carby's sit horizontal rather than vertical.....dizzies are nearly under the firewall

 

Weber DCOEs.

 

Thank god C4 didn't mean Citeroen .

 

oh..yes I did.

hey...definitely make sure the choke is properly turned off AT THE CARBY...not just the lever in the car. they often stick.

 

OHOS.
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Just go and pay someone who knows what they are doing to look at it. I'm sure IanB can point you in the right direction.

Stick to medicine where you make your money and are an expert.

 

I done learn'd sumthing



Nice OHOS all the same. There can't be many of those around.

Sounds like plugs out .. Check carby components .... Get a set of vacuum gauges and synchro them up and see what happens.
I assume air inlets are all clear and air filters are new.

 

Plugs should be firm mate, dont over tighten.

Obviously the person before you has.

NGK are the go alright. Have used them since 1999.

Did they REALLY do a compression test?

 

How many years you been waiting now...

 

Fixed