Still losing power for a second on the freeway - PeachParts Mercedes-Benz Forum

VW1300 · #1 02-02-2010, 11:31 PM

OK - starting about a month or two ago, I noticed that I would occasionally lose engine power when driving on the highway. It would go away for a second, then come right back up. Sort of like a hiccup. I wouldn't even lose much speed, but I can feel it because the gas pedal gets a dead feeling all of a sudden, and the engine quiets down. It happens almost every day now at least once, sometimes twice.

I thought it might be a fuel filter getting clogged, so I changed those. That led to my primer pump cratering (I think), and the engine not starting. I replaced it with a new pump and now I'm up and running again. But I still got some hiccups on the highway while driving to work today.

Am I getting air in the fuel injection system somewhere? Where/how do I look next to diagnose what's going on?

thanks,

Charlie

79Mercy · #2 02-02-2010, 11:47 PM

Pull out the tank strainer and clean it. That requires you to drain all the fuel from the tank.

layback40 · #3 02-03-2010, 08:12 AM

Try a run with the cap off the gas tank. You may have vac in it.
air bleeding in over night may be happening as well.

kerry · #4 02-03-2010, 10:00 AM

Quote:

Originally Posted by layback40

Try a run with the cap off the gas tank. You may have vac in it.
.

X2. A test for a clogged tank screen which avoids emptying the tank is to switch the input and return fuel lines to see if the problem goes away. If it does, clean the screen. If it doesn't, look elsewhere.

dadette123 · #5 02-03-2010, 10:19 AM

While you are at it, you might as well check to see if you tank vent valve is clogged. In our area of the world, mud daubers like to build there. Though, if you haven't noticed any excess pressure build up when you remove your fuel cap this is probably not part of your problem.

biopete · #6 02-03-2010, 11:38 PM

Quote:

Originally Posted by dadette123

While you are at it, you might as well check to see if you tank vent valve is clogged. In our area of the world, mud daubers like to build there. Though, if you haven't noticed any excess pressure build up when you remove your fuel cap this is probably not part of your problem.

When they clogged the vent, a long road trip with 2 hours at a time rolling at 70 mph, I "ran out of gas". That gas cap was so hard to get off. Filled up the tank with my wvo i had in trunk for the trip, it only took 12 gallons. Odd. Got home and got under the car, and noticed the tank had been crushed in. Little buggers.

Just know if you ever feel a little suction when taking off the gas cap or your gas tank takes a deep breath when you take it off, your vent is getting clogged. Clean it before running long highway trips or leave gas cap off until you can.

chasinthesun · #7 02-04-2010, 09:28 PM

I had this issue the other day ,fuel related ,the return lines were all seeping fuel , one real bad ,when I got on the pedal and it almost died mid rev then nearly stalled in the middle of a main road I was on.Since I wastnt daily driving the car it was not real visible that they were bad.Replace the lines and see if it goes away.Bap geon in Houston has the lines ,order 4 ft ,runs $1.65 a ft , cut your replacement after you pulled the line off with needle nose plyers,and get all fuel filters and see if this cures your issues..

VW1300 · #8 02-05-2010, 10:45 AM

Quote:

Originally Posted by kerry

X2. A test for a clogged tank screen which avoids emptying the tank is to switch the input and return fuel lines to see if the problem goes away. If it does, clean the screen. If it doesn't, look elsewhere.

OK, thanks for all of the ideas. I don't think I have a clogged vent - never noticed any suction when removing the gas cap, but will check since that is not too hard. Could be it's only partly clogged right now. I've noticed that the hiccup happens almost the same point in time every day on the way to work.

Kerry: that is an interesting idea. Where do I switch the lines? Up on the engine? How long can I drive safely this way without clogging anything up front?

thanks,

chasinthesun · #9 02-05-2010, 10:51 AM

You may be going through the end of the road for compression on one of the cylinders ,check your compression and see if you got good numbers across the 5.

toomany MBZ · #10 02-05-2010, 11:03 AM

Quote:

Originally Posted by VW1300

OK, thanks for all of the ideas. I don't think I have a clogged vent - never noticed any suction when removing the gas cap, but will check since that is not too hard. Could be it's only partly clogged right now. I've noticed that the hiccup happens almost the same point in time every day on the way to work.

Kerry: that is an interesting idea. Where do I switch the lines? Up on the engine? How long can I drive safely this way without clogging anything up front?

thanks,

Yeah, swap the two rubber lines under hood, one of which is the cigar hose, that is a return line. Have plenty of fuel in the tank.

VW1300 · #11 03-18-2010, 11:45 PM

FOLLOW UP: The power hiccups on the highway weren't due to a clogged strainer. I had one on hand and meant to change it, but hadn't gotten around to it yet. The problem continued but I noticed the accelerator pedal was getting really mushy too. A look under the hood showed the accelerator pivot mount on the firewall was deteriorating rapidly. I installed a new one and the hiccups have gone away. The pedal feel is much more solid too.

I think what was happening was the rubber in the pivot was deteriorating, and the rod linkage that comes out from the pivot bracket was shifting in its little hole every so often, resulting in a change in the throttle - the cheesy plastic bushing-like mount where the rod fits in was gone. The nylon ball in the pivot socket was also on its way out, it just crumbled when I removed it from the socket during repair.

Thanks for all of the ideas though.

toomany MBZ · #12 03-19-2010, 10:59 AM

Glad to hear you resolved your issue.

vstech · #13 03-19-2010, 11:23 AM

ok, all, this is a good wake up call for all of us to inspect our throttle linkage!