Crank, Start, bucks underload.

[83 944]

hey there everyone, ive been searching and diagnosing this problem for a few days. im a porsche guy but my girl has a 85 325e. and i dont know a great deal about these cars but they are similar to the 944s.

since im new ill tell you about the car.

85 325e 2 door 5 speed. i installed es front valance, m tec wheel, basket weaves, is rear spoiler, bilstein hd all around with h r lowering springs. came with sport seats 125K all power options work great a/c ice cold again. been a reliable car and we love it.

okay so what i have done and what is going on. (sorry for long post)

NEW
water pump
timing belt
tensioner
plugs
wires
coil
afm
dme
these i did when we bought the car and to now maintenance.

Now the car idles up and down between 700 and 1100 and wants to try and dry if you give it partial throttle car surges faster. Give it full throttle it revs up fine. fuel pressure at the rail is 25 to 30psi when it idles up to 1100 and 30 to 35 when the idle drops down. that seems low to me. i couldnt find actual specs. when you try and drive it the car jerks like crazy through all rpms and every gear. the primary pump is running and tested pressure coming straight from the pump and gives me same pressure as the rail. would a bad transfer pump cause this? the car is low on fuel ( reserve light on) and i just got done corning the car to the left hard when this happened so all the fuel left would have gone to the intake pump side.

I tested the FPR and its doing its job. no rust or gunk in the take, and no vacuum leaks. i bought a smoke machine from my old shop when they bought a new one. idle valve ohmed out good and is doing its job. DME tested good, AFM tested good, Speed and reference sensors tested good. i couldnt find values on the front crank sensor and i dont know what the world that thing does anyway. it goes to the Diagnostic plug.

So i tested a lot and what i need to know is

What is the fuel pressure supposed to be at the pump and rail.
will a bad transfer pump give me these symptoms?
crank sensor on front crank pulley values and purpose?

much help is appreciated this is her daily and she is driving my 944 to work!

thank you for your time

[jlevie]

At idle rail pressure should be ~30psi, rising to ~36.7psi when the throttle is open or if you disconnect the vacuum hose.

[83 944]

so my pressure is a little low but it should make the car react the way it does. im curious about this transfer pump. does anyone know?

[83 944]

anyone?

[THQ]

I wish I could help, I'm having the same issue.

[bddog]

First put some gas in the car. Make sure the pumps are working.
If the idle is running up and down like you said you more than likely need to buy a new idle control valve.
Here is a temporary fix. Take a penny, drill a 1/4 inch hole in the center. Pull the air meter side of the hose at the idle control valve.Insert penny and re attach the hose. This should even out your idle at 600rpm . Good until you can get a new ICV.
Just bite the bullet and buy a new one. Cleaning them with solvent can ruin them.

[E30_fiend]

Idle hunt is also indicative of a vacuum leak.

Start with your intake boot and see if there are any serious cracks in it. Then move on to the smaller hoses. The last place to check would be your crank case vent tube but that's hard to get to.

Good luck.


Taylor

[M-technik-3]

When was the last Fuel Filter replaced. Most of the time under idle conditions car idle great, add some load and well the pump can not pump added demand through the clogged filter.

It's a cheap item that is often neglected since it's not seen.