" Engine problems "

[Eduardo Castrejón Elbjorn]

Friends:
1984 automatic 944

1.-I need your help, my engine idle is sometimes lower sometimes good (900)and sometimes higher.
2.-The smoke in the exhaust is black ( I believe is richer ).
3.- Today clean the injectors (good condition ), change sparks. But the engine feels as the same.
4.- How I can check if the O2 sensor is good, the fuel pressure regulators and the air flow meter ?
5.- Any other suggestion ?

[Lawrence Coppari]

Have you checked all your hoses to see if you have a vacuum leak? I would remove every hose one at a time and test it for leaks. Vacuum leaks cause problems in these cars. Does it run ok at full throttle and higher rpm? A vacuum leak might be insignificant when large amounts of air are being used by the engine. But at idle, it is a different story.

What about fuel pressure regulators? I don't know how to check them but someone else on this list probably does.

[T86951]

check to see if you are getting vacumn to the 2 fuel pressure regulaters (one on each
end on top of the fuel rail, they are round about 2 inches long and 2 inches in diameter
and each has a vacumn line going into them). If you don't have vacumn there with the
motor running the car will idle slow (real slow when cold) and stumble and run bad until
you really get the rpm's up under acceleration, plugs black and overrich conditin, bad gas milage. The vacumn lines should run to a tee and go somewhere behind the trottle plate for constant vacumn. I had that problem same as you and that was it, no vacumn to the regulaters. I have told several members about it and a couple times that was their problem. I doesn't cost anything to check, with the motor running pull one of the vacumn lines off one of the regulators and touch the tip of the line with your finger to see if it has vacumn, it will be only slight cause its a tiny line but you can feel it if vacumn is there.

[Eduardo Castrejón Elbjorn]

Ok, I already check the vacuum line from the body throttle to fuel pressure regulators and don´t have vacuum leaks,
When I disconnect this vacum line the idle is higher and the engine don´t shakes.

1.- Other lines ?
2.- Other suggestions ?

[drew1]

Just my thoughts,

I think the vaccum lowers the fuel pressure so it seems without any vaccum that the pressure hhould be higher and the motor should run richer.

To see what happens, clamp the fuel return line to the gas tank and see what happens with the vaccum line on and off.

[Eduardo Castrejón Elbjorn]

when the engine is cold the problem is worst.
I really don´t have idea of what is the problem.

[drew1]

Eduardo,

Had any luck yet? If not , I got to thinking it might be the little air valve that bypasses the MAF sensor. It has 2 wires on it and about 1/2" or 12 mm hoses connected. Another thing that might cause this over rich problem would be the temperature sensor in the MAF sensor. It could make the DME think the air coming in is always real cold, about like a choke hanging up on a carburator.

drew1

[drew1]

from reading another post, i believe that little air valve is called the idle stabilizer.

drew1

[ch944]

Cold start valve, auxiliary air vale,idle stabalizer, after this week I think they are one in the same. Anyhow resistance should be between 20-55 ohms on the 2 wire. Also check your engine temp sensor. O2 sensor only comes into play after the car is warmed up. While cold the dme is getting it's info from the engine temp sensor. Haynes, chapter 4!

CH

[ch944]

Also, check your speed sensors if all else fails. Good luck, the 6mm cap screws are a *****.

CH

[Eduardo Castrejón Elbjorn]

Thanks to all for your answers:
I need to spend a lot of time in the hoses, I already bought and I waiting for the haynes manual repair and the bosch f.i.maual.
Thanks
Eduardo Castrejón Elbjorn.