DA VINCI

Do the cuts happen without load?

If it's only on load, you may have an overrich condition at midrange, causing an interruption in the combustión process. This is easier to find in longest gears (more time available to fill the barrels). A faulty WUR, bad regulated Co, etc... may be the culprits. Check the gap of the spark plugs as well. Too big and there wont be enough voltage to make a spark when on boost (high density in the cylinder).


I used to have some ramdom cuts when on load and it happened to be the coil. I changed the coil and problem solved with the addition of more power (probably due to a stronger spark).

Metal Guru

When my car was too rich, it stumbled badly and there was the characteristic black smoke from the exhaust. I would rule out over rich if it's cutting out like the owner says it is.

Augusto

No, according to the mechanical gauge full boost is obtained (the car has stock 0.7 bar spring).

Augusto

The cut happens with load. Very noticeable in third gear. Past 4.000 rpm. It is a sudden cut, and the engine drops to 3.000 rpm.

The CO values are 1.7 %. The WUR is new.

I will check the spark plugs; the car was running very badly due to a faulty WUR, maybe they are fouled. Will check the coil also.

Augusto

I only notice a rich mixture with black some at idle when cold, I think it is normal.

cobalt

Trust me there are numerous threads on this topic the unit is only calibrated to read a max boost of 0.7 no matter what the actual boost reading is above 0.7. Do not trust your gauge to tell you much, it will read 0.7 even if you are at 1.0. Cut out is set between 1.1 and 1.2 bar IIRC. The actual set points for WG to open are per the TSB info I posted. If you have a 3.6 you should be closer to 0.8 than 0.7.

Repair Information: 1994 3.6 Liter Turbo Max boost 0.79 to 0.85 bar 1992 3.3 Liter Turbo Max boost 0.75 to 0.81 bar

If you need me to I can post a scan of the TSB which will tell you the same info I posted verbatim.

Augusto

Hello Cobalt,

Maybe I am not explaining very well. I know the digital boost gauge on the car is only calibrated to read a max. boost of 0.7 bars, so I run a line from the intercooler to inside of the car with a mechanical gauge to compare the readings from the original one. This mechanical gauge will tell me the maximum boost disregarding the one on the car. I obtained a maximum boost of 0.7 (this gauge has 2 bars maximum reading), so now I am sure that I have no overboost issues and the overboost cut out switch should not activate.

cobalt

I understand the cut out is not a result of over boost. Your approach is sound but I think you are missing my point. I am trying to point out that if you are only seeing 0.70 on the mechanical gauge which should read 0.7x than something is amiss with the WG. I still don't know if you have a 3.3 or a 3.6 but factory WG should open higher than 0.70 in either case. If the mechanical gauge is not seeing at least 0.75 for 3.3 or 0.79 for 3.6 than you may consider addressing this issue first and see what happens. At least you will have resolved one of what might be several smaller issues which more times than not are what impact the CIS injected engine.

You may find out your spring is weak or you have a leak. IMO in either case it should be addressed first and move forward from there.

Augusto

Thanks Cobalt. Sorry, my car is a 1991 3.3.
I know undertand that you are explaining. I tried with a new overboost switch with same results.
I tried the WG route...and did notice air coming from the WG exhaust at idle.
Is this normal? The WG was rebuild with new asbestos gasket and diaphragm.

Do this slight leak can cause an overboosting problem?