Been having performance problems lately on my 5000S...

The car will lose power at highway speeds regardless of pedal input...

Also will act up at start up. Car will idle at correct RPM's but feels rough. If I give it gas it just sputters with no increase in RPM's. It does not stall out or drop below normal idle speed...

Most of the time, it will clear itself up if i let it set...

Does not seem to matter if the engine is cold or hot...

I have no fault codes stored...

Fuel pump is it's general noisey self...

Rotor, cap, plugs all fairly new. Wires are of unknown age but look decent:)New fuel injectors 1 year ago...

Any ideas? It's snowing/sleeting here and I really don't feel like playing car mechanic:(

Steve Ankney
88 5000
Michigan

Is it a "KZ" or "NF" engine ? -If it is a "NF", is the yellow engine warning lamp
lightning?

I've had the same problem. Sometimes what I do is, I turn the key and wait till the OK light goes off before I turn it all the way. That usually eliminates the problem. It's almost like a diesel which needs to have its glow plugs warmed up first. I can't remember if the 5000 has a manifold heater of any sort. Mine runs into that problem in warm weather too.

First of all, lack of power at hwy speeds is a classic indicator of a clogged fuel filter.

Secondly, crank up the car, then put your hand over the exhaust tip (NOT on it, but about a half inch away from it). See if there is a goodly amount of volume (purely subjective) coming out the tailpipe, if there isn't, then you have a clogged catalytic converter. If you suspect the cat is clogged, pull the blue cap off the test port on the exhaust manifold - its the little tube thingie that sticks up next to the intake manifold - then crank the car up and go for a ride. If it runs better, it is probably the cat.

Third thing to check is the wires, put a multimeter across them and see if the resistance is too high.

Good luck, my friend!

-Steve Jensen
87 5kcstq

I had very simmilar problems with my 5000S then i removed the metal screen from the fuel pump wich was clogged and presto, back to normal.

I'm going to try and get the car home tommorow so I can look it over some more...

The fuel filter has been changed about 6-8 months ago...maybe it's clogged?

A couple of people have suggested the mesh fuel screen being clogged. I'll have to check that out...

I'll also check into the clogged cat possibility as suggested by Steve J...

I have some spare wires laying around that I nabbed off a parts car. I'll see if they make a difference...?

I'm kinda thinking I may have a bad differential pressure regulator as this episode is mimicking the exact same symptoms as when the DPR went bad last time. I replaced with a used, known good one...

LMK if anybody has any more suggestions! And thanks to those who have responded already. I owe ya guys a beer:)

Steve
88 5000 with a rather nasty habit of sucking money away from it's owner...
Michigan

while writing this I thought about your fuel pressure too, see you got that.

Good luck !

If you have spare parts from another car, you can try to change:
- the lambda probe,
- the pressure regulator at the CIS (grey or black plastic part with "BOSCH"
inscription with to screws mounted at the CIS),
- the engine temperature sender located at the water flange between 1st. and
second cylinder plug (the upper one),
- the electronic control module, and if it is an "NF", the ignition control module,
- the complete CIS-E unit (KE-3-Jetronik in Germany called) mass air flow sensor with fuel metering valve

I´m sure it´s not a problem with fuel pump, fuel filter or ignition (plugs, wires
distributor cap etc.)

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I don't want to contest any expert opinions here but have you checked the relay for the fuel pump? My 5000QT was acting the same way until I replaced the relay for other reasons and now a lot of little things have perked up including starting, cold and hot power and idle. Might be worth a try. bimmerparts has the relay for $19.95 if you need one.