M113 - No Response to Accellerator - Thoughts? (MB Doc?)
 

So I'm driving my 2000 (preMBUSA) G500 (M113 engine) and starting to pull out from a side street into a 5 lane main drag with somewhat limited visibility to the left. I intend to pull out and turn left into the middle turn lane and move over to the main traffic lanes. As I start crossing the first lane from the left, there's an approachng car, but he's far enough away not to worry.

All of a sudden there's a speeding car passing him in the second lane, and there's only one way to clear them both: Full floor boarded accelleration with a hard left turn under accelleration into that center turn lane. Both left front and left rear tires smoked a bunch and left long black tracks with this manuever (no ESP or ETS on this one); but I made it with just inches to spare, as the speeder never slowed in the least.

I drove for another mile or so with normal driving characteristics and accellerator response. I made a turn onto a side street and at that point there was no, as in zero, response from the accellerator. I pressed it to the floor, and the engine continued to hold completely unresponsive at idle speed. It would not accellerate at all.

I let it drift to a stop and pressed on the pedal with no response. It was in gear and the engine was turning at idle speed, but it would not go. I put it in neutral and pressed on the pedal. After a few seconds, I finally got a very weak response. I put it back in gear. If I accellerated very easily, it would go. If I pressed down harder, it would not respond.

I stopped to fill up with gas and turned off the engine while I did so. After fillup and a restart, it drove normally. I put another 50 miles of normal driving - stops, go's, easy starts, fast starts, slow city drivng, interstate driving, etc - on it with no problems.

Any thoughts as to what might have happened in this no accelleration event? This engine is "fly by the wire" for the accellerator. Is this a harbinger of looming failure? Btw, no error codes were shown on the OBDII plug, but most of MB's proprietary codes aren't readable there anyway.

Thoughts? Ideas? Suggestions? MB Doc? Anyone?

TIA!!

Follow the throttle cable and see if it ends up at a throttle position sensor, sort of a can-shaped sensor that the throttle cable is actually pulling on. Wondering if something may have came loose on that, like a simple lever problem that may have come and gone. If nothing else maybe you can try repeating the fast throttle action you had to give it and see if the problem is repeatable. The lever loosening up is about the only thing I can think of that would possibly cause this and not set a code. Unless the cable actually broke, but that of course won't clear up later on. I don't see how the cable could "stick" at closed throttle. If it stuck at open throttle you'd have a different problem. Pretty weird. I bet the duck-azz charging at you would have had his bell rung if he hit your G, or was it another big vehicle?
Gilly

Gilly, Thanks for your quick and accurate response.

Actually he was a young "ricer" driving a small "ricer" - probably a small Honda. He'd have been hurting badly, if he'd have hit.

Thanks also for your response on the probable problem. I think you're right on. I had posted on another forum without any response. Then, all of a sudden I got three responses - two from owners of the same vintage G500 who have had the same problem with the TPS unit. Then, another mechanic who specializes in vintage G's piped up with the following, which probably explains it better than anything:

Attached is a photo of the "problem child" unit. I do have an additional couple of questions:

1.) Does replacing this unit require any calibration or fine adjustment?

2.) Should that screw cap in the lower left corner of the photo (on the throttle cable?) be screwed in place? It's been unscrewed and free floating on the cable for the three years I've owned the truck.

Thanks again for your great assistance! Happy Trails!

I wish I could be 100% certain, but I do believe that the TPS or whatever you want to call it is a plug-n-play, should be just fine. The small cap, eh you probably know better than I. I'd just push it back onto those threads, give the cable a drop of 3in1 oil and call it good. Yeah, I don't believe it should just float on the cable either.
Glad someone else was able to chime in with the same ideas. Being out of the loop for quite awhile, I wasn't aware it has been a problem, really confusing why it would affect the 113's only, should be same basic part if not THE same part as a 112 and there are lots more of those out there I think. Why would this part have to be different on the V8....hmmmm.
On a personal note, it's too bad people have to drive like that, people are just in WAY too big of a hurry these days, you ever notice? I notice it alot driving my Sprite, man it might be that the car is so small, but people really seem like they want to drive right over me with that thing. Did this happen this weekend. I REALLY notice that when I'm driving the bus to Chicago, weekends are just the worst. As we put it, "the amateurs are really out on the weekends". Don't know what they do during the week, but they wouldn't live long if they were driving every day like that, so it's a good thing they are in their offices, stores, or what have you.
Gilly

I checked my data base on this....code P0120 should show if this happened.
PO120- Throttle Sensor A circuit

The problem should be the accelerator pedal pot..


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Gilly.....question is....why did you buy a LBC anyway?
I would have maybe spent that much restoration effort on perhaps a TR3 or a
Healey.
With those at least they have a little better power but a lot more value too.

Reason is...I drove many of those in the UK back in 1960's. Used to deliver them brand new to dearships all over the UK from Birmingham and Abingdon Works..

I had to deliver a MK11 Mini Cooper once...'66 or 67 ish....was going to get a hi-po engine, so I could thrash the living daylights out of it delivering it.....was approching first big roundabout after coming through the Dartford Tunnel at a little over 90, hit the brakes hard and finished up in the weeds on the central reservation/median.:eek: ...later at the shop, found the brake caliper on one side had only been drilled on one half of the caliper !

Best one was a bright yellow MBGTV8......wot brakes !....burnt them out in the first two turns !:rolleyes:

The fastest, but most deadly was the Sunbeam Tiger V8..200hp...the front brakes where the same as the regular Alpine...... solid rotor, single pot Girlings with Ferodo pads.:eek: :eek:

Now, there's a car I would restore.

Those where the dayz:)

PS.....wot about a Cosmo tri rotor in the Sprite ? :silly:



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Heh heh. Probably better material for off-list. But anyways (ahem) the Sprite kind of dropped in my lap, a guy had to be leaving town asap and I had the chance so I took it. Body was good, but car was a basketcase. In retrospect I probably would have waited for something German to come along, maybe a 914 or a pagoda roof SL fixer-upper. BUT after researching it, I did find the Mk2 948's are pretty rare, mainly because they are under-appreciated, or have been for quite awhile. I may hang on to mine on spec that they may go up in value eventually. The Mk2 has none of the cuteness of the Bugeye, yet have none of the enhancements that came later, such as window winders, door handles, and fold-back tops. Many were simply scrapped when a buyer couldn't be found, or converted to hobby racers or in the very least had bigger engines and disc brakes installed. Very hard to find a numbers-matching original that's never been modified. I like it. Not an interstate-driver for sure, but for short stretches at highway speeds it's OK, a nice little fun runabout that gets many happy glances and makes me smile when I drive it. Makes me smile when I can wash it with a spray bottle and an old towel!
Gilly