Limp Mode after revving..?

[Benzer]

Since my car does not have ASR, could I get some help here in describing what Limp Mode feels like in these engines.. On others I have driven, all it does is prevent the over drive to come on.. So this is my scenario. As previously posted the only codes I am picking up are related to the Knock Sensors on Pins 17 & 19.

When the engine hesitates under load, sometimes above 4500 rpm others above 5500 rpm, the engine will feel a little rough then level out. Since the car was on the move I had never paid attention to an eminent loss of power.

Today the engine hesitated around 4800 rpm and I was forced to a complete stop, (no comments as to why), As I took off, no matter how deep the pedal went all you could hear is air come in through the throttle body, but the car would hardly pick up. I turned the engine off and then restarted, problem solved, it all went back to normal..

So, would this be Limp Mode kicking in due to the faulty Knock Sensors..? There was no CEL after this incident or all others before..

Thxz guys..

 

[Jimbo]

It'll feel like you are running on only 6 cylinders; that's how I describe it...usually turning the car off and restarting resets it until whatever is causing the LH mode to come on does its thing again....like yours did. Yes, sounds like your car is going into LH mode.

CEL might not come on either....but code(s) are usually tripped and stored in the CAN as you already found. Many times, ASR has nothing to do with LH mode....but the ASR lite oftens comes on on cars equipped with it.

First of many things to look at is the upper wiring harness for cracks in the insulation....and of course, the knock sensors on yours. It can be a beotch to track down what is causing the LH mode, even a weak alt throwing an occasionally spike will cause it. Often times its as simple as a neutral lock-out switch or the brake lamp switch. Or it could be as expensive as the TB.

 

[Christian_K]

There are simply different types of emergency running modes incorporated into the engine management systems.
The most famous one and usually described as "limp-home mode" is only happening at ASR equipped M119 LH cars, in which the ASR light will come on (if the bulb wasn't removed by the previous owner ;-) ) and the accelerator Pedal will only work mechanically, means you can only accelerate very clumsy after 2/3 of the pedal-way. In Detail the Throttle-Flap can mechanically only be opened by approx 1/3, so acceleration will be slow.

There are other emergency running modes like the "safety fuel shutoff", which allows not to rev higher than like 1200rpm and very slow, almost NONE acceleration at all,
or the EZL can shutdown ignition on a whole bank if certain error have been detected.
Or if your overload protection switch at your transmission is defective, the EZL will retard Ignition above 4000rpm forever by some degree, which results in a very noticable power-loss until you replace that switch.
There are still other emergency running modes though, but i currently can't recall them all.

 

[Benzer]

Christian,

Will the darn transmission overload protection switch cause a lack of low end response? (I am out on the field and am stacking up on a list of parts I need) I did get the code for the trans overload switch after servicing the tranny.

What did happen just a day or to ago was a terrible, terrible misfire, felt very much like having the plug wires hooked to one or two cylinders incorrectly. This happened after starting the car up when coming back from the store.... Turned it off, back on,...still misfiring.. Restated again and problem solved.. I take it this has nothing to do with the tranny overload protection switch..?

I ask, only because it seem's that on these engines, even the wiper blade rubber inserts, play a critical role on how the engine runs...