fuel feed problem, help!

[jmcmath]

For a couple months now I've been experiencing an intermittent fuel feed problem.

When absent the car runs beautifully.

However when present the effect can be anything from a slight hesitation (when accelerating or at constant throttle) to violent bucking (especially when accelerating from a stop).

Sometimes the engine even cuts out when at a stop if I am not constantly on the throttle to goose it when it starts to stumble.

A by-product of this problem is occasional backfires and a very acrid, over-rich mixture smell from the exhaust when starting up again after it cuts out.

Everything I can think of has been covered:

-fuel tank resurfaced 10 months ago
-fuel lines and trigger points replaced at the same time
-throttle switch is new
-recently fine-tuned by 914 specialist
-recently replaced fuel filter
-rotating gasolines from one fill-up to the next

Unfortunately when I had it serviced recently the problem was dormant and so my mechanic was unable to address the issue
specifically.

Where could the problem possibly lie?

Any and all suggestions hugely appreciated-this problem is driving me batty.

Many thanks.

[Steve M]

I had one instance where I left the pressure sensor vacum line disconnected after I had done some work on the engine.
I had drove the car for about a block and my heart fell to the floor pan. The car had died half way but I was able to start it up again. The car felt sluggish and it was nowhere near the performance I was acustomed to and the exhaust was black when I looked in my rear view mirror.
I went back to the engine and found the sensor disconnected, reconnected it and afterward all was fine.
Quick and easy check on this situation may be to disconnect the pressure sensor and start the car and see if anything is different. Or start the car and disconnect the vacum part and see if that changes anything. Or drive around and disconnect the vacum part and see if anything is different.
I say disconnect the vacum part because I dont know how the electronic part will react when you disconnect it when there is juice running through it.

[bowlsby]

There are other things to check:

Fuel presuure a constant 28-30 psi?

CHT sensor checked out..lead not broken?

Check all grounding points for solid connection and no corrosion?

Functioning and calibrated throttle valve switch?

Sounds like a loose connection problem of some kind given that its intermittent...

[Pritchard]

I'm not exactly sure if this could cause your problem, but have you checked the fuse for the fuel pump? It is the first fuse on the relay panel in the engine compartment. Mine occasionally will work itself loose because the copper clip is bent.

Just a thought.
Pritchard

[Dave Bell]

For instant check of how the fuel pressure is , plumb in a cheap guage at the fuel rail test point in the engine compartment. A little rubber hose, a fitting or two, a couple clamps and an inexpensive gauge.... lash or mount gauge to location of your choice where you can view it in the engine compartment. I put one in a couple of weeks ago just for the purpose of instant trouble shooting.

See: http://www.gaugestore.com/060psiwikgau.html

for an inexpensive 0 - 60 psi gauge that works fine.

- Dave

[JP Noonan]

I would have a look at the injector connections and the common injector/ECU ground at the block. Replace the ground spade terminals at the ground point. The injector connectors can be squeezed carefully with pliers to make them bite in the injector tabs better.

My 75 2.0L would backfire and seemed to only be running on two cylinders, well, because it was only running on two or three cylinders. Every once in a awhile all four would kick in, but then it would go dead again. It turned out to be the injector connectors. Of coarse it me forever to figure it out.

[jmcmath]

Many thanks to all. Will have at look
at the various items pointed out this
weekend. It certainly would seem to be
a loose connection somewhere.

[jmcmath]

Just to confirm a happy ending to this story and provide others experiencing the same problem with guidance: after noticing the
excessively rich smell coming from the exhaust it dawned on me to check the cold start valve. Sure enough it was sticking open and causing the engine to run rich at operating temperature thus causing it to bog down and stumble.