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Uneven Mixture on cylinders?

My car seem to have uneven mixture to some cylinders. I sometimes have trouble when engine is cold and the engine only will start up and run on 4-5 cylinders. Only solution is to remove the fault plugs and clean them.
problem is only when engine is cold and often when the car has previously was started up shortly (like to move the car once or twice etc..)
I can clearly see two plugs are black while the rest is normal. Number 3 is most black and always is the first to fail. When I clean the plug and get it to fire, it run all normal. But still black colour on plug.

I have changed plugs, different types, colder ones. new plug wires (electromotive ignition, no distributor). Moved injectors around (no difference). checked all fuel pressures CIS etc. (ok). Have run with out cold injector connected. (no difference).. Afr on all cylinders at same time is ok. I don't think i will try afr on each cylinder......

Anyone had to adjust cylinder mixture and can give me some tips? other suggestions??
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Old 04-22-2012, 03:22 AM
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This will get you started -

CIS injector flow testing
Old 04-22-2012, 04:33 AM
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Here are some other search result for "CIS Flow Test" -

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Old 04-22-2012, 05:16 AM
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I would also suggest a leakdown test, at least on the two suspect cylinders. What you're assuming to be fuel fouling may actually be oil fouling.
If the leakdown is good, then go where Ronnie pointed you to check and/or adjust fuel flow. Of course, there's always the possibility that the fuel distributor itself may require rebuilding.
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Old 04-22-2012, 06:29 AM
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I think it may be a valve guide issue, do the leakdown.
Old 04-22-2012, 09:37 AM
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Use to be all trouble shooting began with a compression check. Do leak down if you choose but you can not fire a cylinder that can not build compression.
Turbo motors often break rings and hole pistons long before progressive failures like guide wear.
Start with the basics. I hope your compression is good and all you need to do is work on fueling or spark.
Old 04-22-2012, 11:02 AM
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Thanks for good tips! I'll do some more troubleshooting.
I was also thinking oil, but I have no blue smoke and I since the problem only appear at cold start I figured this is when it would most sensitive for to much fuel as it allready has fuel enrichment and not enough temp to hold spark plugs clean.

I started doing a leakdown but could't figure out my leakdown tester. I couldn't set inlet pressure more than 2 bar before the leakdown gauge was maxed out ( set point) and when I set it correct it was very sensitive. I could get big variations every time did same cylinder over. I gues this is due to the low pressure??? Also when I let the hose open to air I got 50% leak. Should't it be 100% when hose is not connected??
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Old 04-22-2012, 11:22 AM
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Have bin a while now, but I did a cylinder leak test on number 3 & 4 ( the two that has troubled me). They was fine. (10% and cold engine that has bin standing through the winter) I could maybe get better numbers if I tried some more.

I have now gotten rid of the problem by adding some lubrication in the fuel (prolong).
I noticed right away that the car idles better when cold. I have now bin using lubrication in the fuel the last year and not had problem since.... I started the car today after it had bin standing for several month trough winter. It fired at once and idles very good. Before cold air and standing for a long period always gave me problems and it did not idle good before after a while.

I guess today fuel (unleaded) may have less lubrication than before? Also when car is standing still time to time some extra lubrication will do good when fuel is evaporating and leaving a protective lubrication to all mechanical parts in the CIS and keeping them from corrosion etc...
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Old 02-16-2014, 06:25 AM
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Can't help but wonder how long the same gas has been in the tank and everywhere else by now.
When you said the spark plugs are different colors does it look like carbon buildup from rich fuel mixture or burning oil.

There have already been a lot of replies. If fuel pressures and injector flow test comes out good then mechanical engine wear as in exhaust valve guides and rings is probably it.
Old 02-16-2014, 06:55 AM
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The plugs look like carbon buildup from fuel. I don't think it's related to burned oil. A good cylinder leak could still mean leaking valve guide etc, but all oil related should be when the engine is running. I only had problems after the car had standing still for longer periods and when the first seconds start up. When I got the engine running I had no problems as long as long as it was in daily use.
Like I said the engine is running perfect now and has for over a year after use of "injector clean" (lubrication). I think this is keeping my fuel system to work better.

Not long ago I heard about 911 sc that didn't run on one cylinder. Turnes out this cylinder didn't get fuel at all. Injectores tested and was ok. After somee "injector Cleaner" it suddenly fired and all cylinders fires again....

It might not be the fuel it self, but maybe a combination of age and that the car is standing still i periods that needs some extra lubrication and protection....?

I am very sure this made the different for me.
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Old 02-16-2014, 09:20 AM
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A quick easy way to judge individual cylinder fuel mixture and exhaust temp is get down on your hands and knees while the motor is running in nuetral and measure the temperature of the individual exhaust header primary tubes just below the flanges where they are coming out of the heads with one of these... Non-Contact Infrared Thermometer with Laser Targeting

The middle cylinders #2 and #5 usually run hottest.

A google or ebay search will find lots of them and this harbor freight works great and goes on sale local to me for around $25 sometimes.
Old 02-16-2014, 09:34 AM
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Good tip! Thanks!
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- 79 930 "ruf" 380whp, K27, andial IC, Headers, electromotive hpv.
- 88 "gt2" (project)
Old 02-16-2014, 02:35 PM
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