W210 Limp Home

[abh3]

My '01 W210 4matic wagon w/155k sometimes goes into what I think is a 'limp home' mode when flooring the accelerator to pass, the throttle becomes very lazy and unresponsive though it will drive at highway speeds. Turning off and restarting restores it to normal function. There are no check engine lights or other indications of problems like erratic gauges, unsual shifting or misfiring. Maybe I'm nuts but I think it's more of a problem when the weather is colder, now that it's getting hot as hades around here again it seems to occur less often. This has been going on for some time now but as I seldom do much serious passing at full-cry (wagon w/ kids, etc) it hasn't been a big issue. Any thoughts?

Sorry if this has been talked to death, I searched and didn't find much...

[Alastair]

When was the car last serviced?

Particularly, the Fuel-Filters...?

First port of call with any power related fault, Change all fuel filters!

[RichardM98]

Your issue doesn't sound like your car is in Limp Home Mode. LHM is an electronic strategy to protect your transmission but allow you to get home or to a service facility. In one form you are locked in the gear you were in when LHM was activated and the engine's rpms are restricted. In the other you have only 2nd gear and reverse and your engine's rpms are also restricted.

If your engine is unable to develop full power, there are several possibilities. From restricted fuel delivery (as mentioned) to restricted exhaust gas flow. Beside the fuel filter (you can have the fuel pressure at the rail measured), you could have a collapsed catalytic convertor blocking exhaust gas from full flow. Bad O2 sensors and MAF sensors usually trigger codes but not always a MIL (CEL). You might want to scan with an OBD II scanner to see if there are any pending codes. Also, your coils, plug wires and plugs could be an issue. Or maybe a combination of a little bit of all of the above. Finally, bad gas? If you use one station regularly, try a different one for a few tankfuls and see it there's any change.

I'm afraid you'll have to do some detective work (analysis) to sort it out.

Good luck.

[abh3]

But a fuel filter wouldn't 'clear' itself in the moment it takes to turn off and restart the car, it's an instantaneous fix. Further, not every full-throttle pass results in this problem, it's very intermittant and the car pulls quite well regardless; it's AFTER the full throttle application the symptom might appear.

Sorry I wasn't clear about that in the first post, it will pass just fine but subsequent to the pass it may exhibit this laziness. The laziness is most obvious when starting from a complete stop, press the accelerator and it's very slow to respond, press further and it finally RPM build. It's not a slipping transmission, it's the engine not revving. It has recent plugs, O2 sensor, MAF and filter, there is no misfire or 'stumbling' like my old 440 with too much Holley carb on it way back when.

I haven't checked the codes though I have a scanner, I'll do that when kids get home from school (they used to ride in it, now they drive it!)...

[abh3]

Checked codes, nothing at all... Could the TPS be going out but not setting a code or CEL?

[arkie]

Originally Posted by abh3

Checked codes, nothing at all... Could the TPS be going out but not setting a code or CEL?

On one occasion we had a 98 E320 that had no throttle at all, no codes, turned out to be the pedal position switch (which is a potentiometer up near the brake booster that the throttle cable attaches to). This simply sends a pedal position to the ME that it processes to generate a throttle opening at your electronic throttle actuator (ETA). ETA problems generally generate a CEL, an ASR light, and a lopy idle and no way to get engine RPMs over about 1100 rpm.

I wouldn't guess around at this, take it to a good shop with SDS so they can dig deeper as you are dealing with expensive parts to start parts swapping without the ability to look at live data.