Phantom problem
 

This problem has happened to me with a variety of different cars and I have yet to figure it out. I should first mention that this current problem is not affecting my 944 but my 1989 Volvo 240 DL. I know its not a Porsche but you guys have been so much help with some of my other problems and the Volvo guys are not being any help so I figured I would give it a shot here SmileWavy.

The Problem: While driving along on the highway at about 60 Mph all of a sudden the RPMs start to drop....so I put my foot down more and nothing happens...the RMPs just keep dropping. The car just seems to loose power. While this is going on it may sputter a bit and start to accelerate, but only briefly. So I pull over and turn off the car. After waiting a bit I start it back up and it runs just fine. I have now driven it another 50 miles since it happened and I have not had another incident. Just to see if I could cause it to happen again, I got in and drove rather aggressively but could not get it to happen again. I should mention that I recently had an 1990 Alfa Romeo 164L which did the EXACT same thing. It happened first going up a hill on the PA Turnpike and it happened again several times over 3 months. We never found the problem. The only thing I did notice with the Afla was that while driving on the highway before the problem initially happened I noticed that car would occasionally shuddered briefly with no lose of power.

So....am I looking at ignition or fuel? People have told me that it could be a bad fuel filter, sediment in the bottom of the tank, fuel pump etc. I should note that on both the Alfa and the Volvo the coil, wires, cap, and rotor are new. I would really appreciate any help that would lay this problem to rest once and for all.

-Graham

Had a similar problem with my parents' old '86 245 DL (240 DL wagon). Fuel pump relay. Cheap and easy to swap out, so it's worth trying.

Aaron

I had a similar problem with an MB 300D. It was a bad fuel filter.

Well I just changed the fuel filter...so hopefully that will fix it, but I will also change the fuel pump relay. So I guess the verdict is that its not ignition?

In my experience, an engine running "rough" is usually ignition. An engine running "weak" is usually a fuel problem.

I don't know if this applies to your situation or not, but my old MB had TWO fuel filters. Just something to look in to.

i had the exact problem about 1-2 months ago, cept eventually when you pull over to start your car up again... it wont start, id say its a bad fuel pump relay, was in my case

two pumps, one in the tank.SmileWavy

Well then its been established...its a fuel issue and hopefully its just the relay :-) As always you guys are a big help!

i didnt read the whole post again, my bad, i thought you were saying the problem WAS in your porsche, but i dont know about relays in volvo's, so ... sorry about the post

Interesting, sounds like a problem I had with a 1988 F-150, dual tanks. Did not occur until I fueled up the front tank at a particular grocery store's gas station; now it will not run well at all on the fuel in front tank & I have to use the back tank always. Still, could be fuel filter @ tank if your system is similar. Depressurize first.

I had a friend with an 85 240 DL and is doing the same thing. Sometimes no start and sometimes it starts. It stalled in the highway and had to be towed home.
I had the chance to troubleshoot the problem. Checked the outside fuel pump, it was running and we were getting fuel. Checked the fuel pressure regulator return and there was no fuel returning to the tank. So we replaced it, still no start.
Bought a Haynes manual and went through the ignition checks. Distributor has an ignition pick up coil. It has three wires. When you jump two wire terminals with ignition ON according to the manual, you should get a spark. We were getting spark but the spark was erratic and sometimes a continuous spark. Really strange. So we figured the pick up coil was bad. Bought the distributor ignition pick up coil and it was a pain to replace.
Did the ignition check once again and we got consistent spark.
Started it up and it fired up.Cars this old will have multiple issues. Troubleshoot systematically and patiently and you will get rewarded.
Good luck.

moisture in the fuel can also cause that effect, dry gas and injector cleaner is a cheap attempt at repair.