Sudden Loss of Power

[timm9]

I have used the search feature, but did not see any posts matching my issue. The other day I drove the 380SL approximately 12 miles to an appointment and shut the car off. After the appointment, the car started and idled fine. Upon merging onto the highway, I experienced a sudden and severe loss of power. The engine never faltered or died, but would not accelerate or maintain a speed above approximately 20 MPH.

I was able to limp home intermittently having to coast in neutral, then feather the accelerator and going back into gear attempting to gain momentum. While I did make it home, most of the way I never made it out of first (1st) gear. After parking the car I pulled the air cleaner and discovered the plastic holding edge of the filter had split allowing the folded elements of the filter to unfold and appeared to be blocking a substantial portion of the air flow to the intake. I replaced the filter but apparently, that is not the problem. Prior to this, the car was running very smoothly.

The fuel filter, accumulator, and fuel pump are new with less than 3,000 miles on them. I have also very recently replaced all vacuum lines and connectors, pods, plugs, wires, and rotor. I’m starting to get the very sickening feeling that after the previously rectified issues with the cracks in the Air Guide Housing http://www.peachparts.com/shopforum/showthread.php?t=221171 and running very rich, possibly the Cat is plugged. Could the extremely rich fuel mixture have killed the Cat? Unfortunately, I live in a very rural area and would have to tow the car to get to an emissions shop. Is there a way to test the Cat without specialized equipment?

Any suggestions would be greatly appreciated.

Thanks!

Tim

[MAGV5]

Tim, Yes a too rich mixture for a long period of time will kill the cat. It won't happen overnight, but will eventually stop enough of the exhaust flow to product the symtoms you are describing. I have a 87 500SL that had the cat blocked . Best way to check is disconnect exhaust before the cat and test drive car.
Good luck
Magv5

[timm9]

MAGV5,

Thank you for the response. I ended up trailering the car to a muffler shop in the next county, and after testing everything, it turns out it is not the Cat(s) or pre-cat(s). Car starts instantly, idles without a miss, but will not handle any load, nor allow a normal increase in RPMs while in park. I will be concentrating on the fuel system starting tonight after work.

Thanks again!

[ctaylor738]

It sounds to me like the air sensor plate is not able to move the control piston in the fuel distributor. So when you hit the gas, the throttle plate opens, but the FD doesn't supply additional fuel. Jumper the fuel pump and see if the air sensor plate moves up and down easily. This could be caused by high control pressure. Can you check it?

Another possibility is that rust or debris came loose and is clogging the strainer in the fuel tank.

Maybe (I hope not), something in the air guide housing has gone south again.

[timm9]

Hi Chuck!

It's always a pleasure to hear from you! I changed out the fuel filter and no luck, additionally the fuel pump is running and is not making any unusual noise like it is failing. I doubt there is anything going on with the air guide housing as the idle and RPMs at idle are perfect after replacing the OEM strap with a regular hose clamp, and again tightening the hose clamp after running for a few days. I have not yet jumpered the pins and done the 'fuel/stop watch' test for the pump, which is on my list. Quite some time ago (3,000 miles) we suspected the WUR was bad but that turned out not to be the case, thank you again. This morning I had just a few minutes before work and did inspect/play with the air sensor plate, and it did feel like it had more 'resistance' than when you had me inspect it previously.

Thank you for the suggestions/help! Hope all is well with you and yours!

[ctaylor738]

Same here.

Remember that the throttle is a mechanical connection. You push on the gas pedal, it opens the throttle plate and supplies the air. The air sensor plate and the FD piston then need to move in tandem to supply the fuel. If you have more than 3.8 bars of control pressure, or a hang-up in the piston, then you won't get the fuel to go with the air.

[timm9]

Thanks again Chuck! I have been working 7 days a week for the last few months and having trouble finding time to work on the car. After work Sunday I tried to pull up the manual (CD) and the link to the 'compenent location' link will no longer work. Is the FPR on an 82 380SL behind the glove box, or above the fuse panel in the kick pad?

Thanks!

[ctaylor738]

Above the kick panel. Large, black, with a large red/white/black wire running to its socket.

[timm9]

Thank you again for all of the assistance. After my last post I found myself in the position of having to concentrate on getting 4 pieces of equipment ready for the snow removal season, so the SL took a long ‘back seat’ in my life’s priorities.

I did resolve the problem but will need to make a confession first. With my crazy schedule, I often find myself trying to do these things at night after work by myself, and sometimes having an extra set of hands and eyes can make all the difference. Originally, I made the mistake of ‘assuming’ the issue was major before exhausting all of those little ‘possibilities’ first.

A few days ago as we were finishing ‘hard facing’ cutting edges and chains, I asked one of my drivers to lend me his ‘eyes’ with the SL. Long story short, the problem was with the bushing at the front (engine side) end of the throttle rod. The (plastic?) bushing had completely disintegrated, allowing the throttle rod to move past the ‘stop’ on the bracket and could not be seen without climbing up on the engine with a good flashlight. While I’m pleased to find and resolve the problem with a $2.00 part, I’m disappointed in myself for making assumptions that cost me what little good ‘driving weather’ I had left.