88' Mondial 3.2 k-jetronic adjustment

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What is the purpose of the screw adjustment and what should it be set at? How do you know when it is set correctly?

 

That Phillips head pan head screw is just being used as a "plug" to seal the access hole to the mixture screw (which is a 3mm female Allen head setscrew about 1" down the hole). The mixture screw is used to set the air-fuel ratio to something like 1.5% CO before the catalytic converter (or 0.6V~0.7V DC on the unplugged O2 sensor wire). Use this link to get a copy of the 281/83 Mondial8/QV WSM and read Chapter D:

https://www.dropbox.com/scl/fi/twng41f9fpi3ipww7q95v/Mondial8qv_workshop_281-83.pdf?rlkey=5sgpj4yz33jepzrec4x8lcwel&st=nj3cf0lf&dl=0

It is for the K-Jet without Lambda system, but it will give you a lot of background information for your K-Jet with Lambda system (if US version) or even a KE3-Jet with Lambda system (if a Swiss version).

 

First you ask all over Facebook about this screw, we told you to leave it alone unless you are very experienced with this adjustment. Now that you are here, I'll tell you the same thing and ask why you are so obsessed with this adjustment? If you adjust it incorrectly, even by 1/8 of a turn, you can really mess up your fuel injection system!
Alden

 

Thank you Steve! This is the type of response that is expected from a group of knowledgeable Ferrari owners. Although, I am not comfortable with adjusting this without the proper gear, I love to learn about the car that I will forever have.

 

Alden, this is an unnecessary response. You can provide value in many ways on threads like this which you clearly don't understand how to do. Providing actual facts about the car and fuel system that you seem to be an expert on would have been helpful similar to what Steve has provided. If you need assistance on learning how to respond to human beings I can surely help you out. Thanks have a great weekend bud!

 

The adjustment of the k-jet is quite straight forward. The only quircks are
1) the tuning screw is sensitive.
2) the mixture should not be adjusted if the car is not idling (and no tool should be left inside the kjet if the engine is not idling).
3) adjustibg screw works "in reverse" (clockwise = richer)

From then on if the OP has previouly adjusted some carbs, the k-jet is easy to figure out.

This being said, if the mixture is wrong, chances are that the issue is somwhere else (ex: crude in the WUR inlet).

 

+1 -- on the K-Jet with Lambda models, the mixture shouldn't even be touched without first confirming that the WUR cold and warm control pressures are OK and the Protection Relay system is working (i.e., the Frequency Valve is vibrating/buzzing).

 

To be honest I am adjusting mines when I go to the Alps in summer. I do not know how efficient is the altitude compensation of my WUR, (it still has its stock gaskets in the lower chamber) but at more than 2000m, the setting has to be adjusted by 1/16~1/8th of a turn.

The petrol station do also blend a varying amount of ethanol depending on the external temperature (max amount in summer), which makes it even harder to keep a consistent "perfect tune".

So adjusting can be a good idea but my recommendation would be to refrain from 1) knocking the WUR cold pressure pin 2) mess with the adjustment screw. Many forums do explain how to adjust these, but these should be the last items to tune. (That's how my k-jet tune was totally messed up by the previous owner... All my system had were clogged mesh screen, this could have been a no brainer to fix, except I had to fully disasemble the WUR in order to revert what he did!)

 

Will not be adjusting the mixture valve. I am experiencing some other systems which may be the culprit. air hose that goes from the intake to the air valve #30 in diagram is collapsing under normal idle. Also hearing popping periodically from the intake area during acceleration (generally on warmup). During down shifting the rpm’s dip very low (possible vacuum or intake pressure issue). Any ideas how to diagnose the parts of this system? Could the culprit be something in the air intake diagram?
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The hose #30 that goes to the AAV (Auxiliary Air Valve) is very thick and tough, if it is collapsing under vacuum, it is beyond failed. They tend to get hard as a rock with age and crack, I can't imagine it actually collapsing as you describe unless it is badly perished inside. Yours are probably original, and should be replaced. Newco Products has the 3/4inch (19mm) hose with the fabric wrap that looks close to the OEM hose (albeit branded Continental), Italian Car Parts has the hose as well. Any correct size thick walled oil resistant hose would work if appearance was of no concern (and would be much cheaper).

The popping sound might be coming from failed air injection check valves (#3 in second pic), they don't last forever, there is a rubber check valve flap inside. The OEM replacements are quite expensive, but it cross references to some Dodge and GM applications which are sort of available. In a pinch the Standard Products AV7 is widely available, the hose nipple is a bit smaller than OEM but the hose can still be clamped sufficiently for it to work. The t fittings (#36 and #8 in first and second pic respectively) also rots away from inside.

You might also take a close look at the air sampling tubes that go into the headers, they can corrode and fail at the nuts that hold them in the header, giving an exhaust leak that could cause some noise that would be more notable on acceleration.

 

Or could have been replaced by a hose that is not designed to withstand vacuum.

 

Thank you for the replies. I found some corrosion on the dreaded WUR (plug connections) much I cleaned and put some dielectric grease on. My symptoms have gone away. As I was scoping around under the car I noticed a wire connector removed and can’t seem to find any spot it can connect to. Front drivers side engine bay.

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Is your rev meter working ?

 

Yes, tachometer is working.

 

The only thing I can think of , this connector is from 1 of the 3 electromagnetic sensors on a QV wiring harness. Not used on a 3.2 mondial that uses 2 sensors.

 

How many wires and what are the insulation colors of those wires? Does the other end of the cable go back towards the Microplex ignition ECU connector or somwhere else? Is your Microplex ignition ECU labeled MED120B or MED120B/D?

 

Not really in the right place, but is it the connector for the 3.2 secondary cabin heater pump? It is in the location where one could identify it as one of the crank sensors.

 

Is anyone familiar with the testing the ignition power module Bosch 0 227 100 137 is working correctly? The car feels and sounds like it is running on one bank. I just installed 2 new ignition coils.

 

You can always swap them, and see if the no-spark condition moves to the other bank (but you'll need some heat sink paste to do it properly, and if you do need to replace them -- but new ones often come with a little heat sink paste).