CO and HC out of spec

The right hand bank of cylinders seems to run rich however having had it on an analyser it is not the case.
I have recently installed new plugs.

The RHS is running slightly weak with CO at 0.4% but HC's are over 1000ppm.
Plugs are consistent in the RHS bank, black and slightly wet seeming to indicate its rich, confusing! I am sure it is running rich as I can smell it.

The LHS bank is within spec and all plugs look normal.

I recently tested the cold start injector, when the engine is warm there is no fuel output as expected.

I have a complete set of fuel injection system including the fuel distributer but I don't what to change anything like that until I have at least found where the fault is.

I'm unsure where to start looking anyone got any good ideas?

Thanks

P

 

High HC indicates faults in ignition. Check again spark plug extenders (measure ohms), spark plug wires and check connections inside distributor cap. You can cut off couple off millimeters of each spark plug wires and rejoin them in distributor cap.

 

Ignition cables are new and there is a good spark to each plug indicated on a timing light.
When the engine was out 9 months ago I checked each and every extender, all within spec and the plugs are new.

I have just had each plug out and all the sparks are good IMO.




P

 

do you have a scope phil? then you just see if the igniton wires are ok or not

with a CO only 0,4 % it is normal to have high HC
how many rpm then? what happens when you raise the rpm? when the HC is going down then to max. 250 ppm before the cat ( if you have?? ) then the wires are ok

adjust the CO to 2% or 3% and you will see how the HC is coming down

when I adjust the settings I always look to the HC and I adjust as long as the HC turns again. so when the HC is as low as possible you have right adjusted. same I do with carb cars, not only F

but even if the ignition wires seems to be ok: I once had on a 308QV the same problem. the plug extenders had right resistance, but the sparks have been going through those extenders directly to ground.

 

Ok. When these symptons started? After you installed new plugs?

Second place to check is intake leaks. Maybe you have some rubber connection loose?

 

The symptoms (the rich smell) have been evident for a while. It is only once per a year when during its MOT test that I get the figures, from there I make an adjustment.
The manual says CO of 0.7% +/- 0.2% with HC less than 300ppm
When the engine is revved to about 2000 the HC comes down but still not inside specification.

Romano, I am presently counting the plugs, extenders and leads out of the equation, mainly because plugs are new and leads are okay and I can't believe that I have 6 extenders all bad and all one one side of the car. Also I have run the car with plugs out and there is a good spark at the plug. I don't have a "scope" but I do have an ignition timing light and it show all "leads" fire. I do not have any cats and the gas probe was inserted into the end of the exhaust.


P

 

Anyone have a feel for how much to turn the mixture screw to say make a 0.1% CO adjustment. I am hoping to get another shot at the gas analyser next week and it would be good to have a feel for what I am doing before I start. The screw is in such a bloody awkward location

P

 

May I offer a suggestion. Consider the purchase of a hand held exhaust gas analyzer. Several excellent units available and can be used for accurate road testing. Not expensive and can save you a lot of time and grief.

 

That screw is very sensitive. I would say that 1/16 turn would be 0.1% in CO. After adjusting, plug that screw hole and wait 10...15 seconds before read CO.

I borrowed wideband lambda from my other car to get mixtures adjusted. Of course you cannot get HC-readings with it...

 

This is extremely lean -- I'd say the consensus here is that 1.0~1.5% CO is no sin at all (especially on a non-cat version). Check the 512TR WSM page C62 for another reference. They even added such weasel words (paraphrasing) "if you can't get the 0.7% +/- 0.2% spec, 1.0~1.5% is OK too" (and that model, being EFI, has a better chance of meeting that lower spec, and they acknowledge it still might not ).

 

phil,
you may check the ignition wire from the coil to the distributor cap, also this cap
with the timing light you don`t see if the spark is ok or not, you only see that you have a spark

about half turn of the adjusting screw is 1 % CO
try to adjust so much that the HC just will turn from going down to going up again. how much CO you have then? normaly if all is fine between 1,7% and 3.5% and the HC is below 250 ppm

I wonder a little:
you write -The symptoms (the rich smell)-..... and also -The RHS is running slightly weak with CO at 0.4% but HC's are over 1000ppm-

but with 0,4 % it is never rich, it is lean. but may be unburned fuel comes out? this then seems to be because of the high HC and has nothing to do with CO.

good luck to find the mistake and let us know when you found please
I think it is an ignition problem. you may change the left coil to the right side and otherwise. also the distributor cap - just to test

 

Turbopanzer - unfortunately the only one on the market in the UK that I can find that is remotely affordable, is rubbish, and only analyses CO so not much help Is anyone happy to buy and ship me an affordable one from the US. At my expense of course
Otus - thanks for the tip, I will use that as a good starting point.
Steve - thanks once again, I think I have always tried to get to the WSM figures and I guess that it at the root of my problem. I'll reset to 1 to 1.5% and see what that does to the HC's.

Off to the garage again

P

 

My conclusions are the same Romano, the CO is so low that there is unburnt fuel and that makes it "seem" like it is rich but as you say it is weak with CO of 0.4.

P

 

you write a HC more than 1000 ppm
how far you can test HC? more than 1000? if not then you may go to a place where they can test more ( I can test here up to 3000 ppm ). because then you just see if the HC will go down when you adjust CO.
but as I mentioned before, I think a problem of the ignition or somewhere getting wrong air

you are sure it is the right side? so left exhaust outlet?
I once had wrong air from the vacuum hose for the break booster, but this has been on the left side

I´m just on my competition programming my controlsystem and have problems and trouble with hexadecimal system, with dasylab, with sending strings to the relaiscard for the warning bulbs in the instruments over RS232, that is why I´m online the whole time

so we all have our problems, some with original things, some with selfmade things

 

If your serious Phil...pm me. I would be more than happy to get you a unit to fit your needs.

 

Phil,

Allow an old threat to once again rise....

Did you resolve the issue(s)?
Any key bits of wisdom to share?

rgds,
Vincenzo

 

Not resolved yet as the car is off the road for winter. However I did find out she appears to be running rich because she was so lean. There is unburnt fuel in the exhaust. First job out of the garage in Spring is to get in to a proper gas analyser and set up correctly.
Hope this helps.

Phil

 

Thanks Phil - keep us posted!
rgds,
Vincenzo

 

Phil, why not just get an AFR meter for $200 or so and use that to adjust. I have a PLX unit in my 930, and it works great. The unit has an 02 sensor, that replaces your current sensor. It then does the reading, and mirrors the o2 sensors results back to the computer. No welding required, no new bungs to put in, etc... Also easy to move side to side...

My testarossa seems to have been running slightly rich too. I am getting a film on my rear white bumper after a while. Easily comes off with a rag and wax...

Since doing my major now, I did check my spark plug wires and they were all pretty much shot! The proximal 1cm of the distributor was hardened... the first inch of the coil was black/burned...

I was shocked! The recipts for the major mentioned replacing the wires 5000 miles ago when the PO did it from what I recall... No way this much wear happened in 5000 miles...

Hopefully that clears any issue, as I am sure it must have been firing below optimum. It was starting to occassionally miss at idle too...

Silly things happen with these cars. On a honda the wires last 100,000 miles... On a testarossa... not so much...

Good luck

 

Mixture needs to be measured and adjusted with the O2's disconnected. They should be 1-1.5 %. When the O2's are reconnected it should drop to about .6 or .7% and that needs to be checked because malfunctioning of that is very common.

During all of this it should have a HC of 200 PPM or less or you have a running/tuning issue.

Both numbers need to be considered.

 

AFR read by itself is just a false sense of security. If the HC is not known and preferably the O2 and CO2 also it is pretty meaningless. In fact if I could only read one gas it would be CO2 and not CO.

 

The porsche and ferrari worlds are so different...

The porsche 930 guys live and die by the AFR. Thats what they use to tune runs and pass emmissions...

I know little about emmissions... because we don't test in Wisconsin if car is over 1o years old...

But if the AFR is stoichiometrically correct at 14.7... why wouldn't the other numbers be spot on?

The 930 guys tune to an idle AFR or 13-13.5, with the o2 sensor off. When you plug it in, it goes to 14.7... (pre-cat)

Of course... ahem... the cats that (were) are there help pass emmissions too... ahem...

Brian, what usually fails causing problems? Injectors? o2 sensors? I assume its the latter, as the default mode in open loop runs rich...


The gas analyzer companies even provide a chart to convert AFR to co%

http://www.mgexp.com/article/co-afr.html

 

A lot of people think that. People who understand combustion know better.

CO% is burned gas. Just how does that accurately tell you what or how much went in the top? You have no idea of how much or how well what you put in actually burned.

Of all 4, CO2 is by far the best indicator of combustion efficiency.
In California we lived and died by four gas analyzers for a very long time. Out of necessity we learned what they did and how to extrapolate their information a long time ago. When I opened it was the #1 piece of equipment on my shopping list. I would not even consider opening the doors without one. When I get a car that does not run or does not run well it is the very first tool I use and it is the last thing I use during any tuning.

 

Cam timing, valve clearance, any ignition abnormality, ignition timing, compression, throttle imbalance, burning oil, bad injectors.

I can adjust the mixture to 14.7 with all of those problems. If I had HC or 02 or CO2 I would know something was wrong. If I had all 4 I could narrow it down. If all I have is CO I can have a car that does not run as well as it should and have no idea. CO tells the least as far as combustion efficiency goes and who really cares, I can turn that screw every which way. The other 3 gasses tell me something of use.

 

Fascinating...

Living in california I am sure you spent a lot of time tuning cars to pass inspection .