Yeuper1

What if the scanner detects a code .the code said it has a bad ecm can it steel be the cps?my car starts but turns off after a few minutes an who not turn on till it cools down.

art_arev

What is the code? Hopefully you are using a pro level scanner.
Post it

S430LUCKDRAGON

Question I mean I see this thread is pretty old but its worth a shot I was looking at an ML 430 yesterday 1999 I diagnosed it as CPS there was no check engine light but is it true they don't throw a code ? I know it didn't in my 2001 ml 430 I had a few years ago , but my problem was replacing the stupid thing it would not come out not with a small pick vise grips channel locks it was in there pretty good I never did get it out has any one else came across this problem ? I was thinking of jacking up the car and removing wheel and wheel fender to hit it with a flat head and a hammer ?

art_arev

Use the correct torque socket E8 or normal socket 6mm with long extension & it will come out. If you cant access it from the top , remove the wheel & the liner & access it from there.

S430LUCKDRAGON

The bolt was already out , I don't understand why it would not come out once the bolt was removed any ideas ?

art_arev

rotate it back & forth & it will give in, then pull it out.

barijan

Just my 2 cents for the files.
If the problem is that it's difficult - or very difficult - to start when hot, but it DOES START and idles rough for a while and then runs fine after about 10-20 seconds, so it's not the CPS.
Faulty CPS has not mid-term. It makes the engine stall even when running, and it DOES NOT START anymore until the CPS cools down. After that, about 10-20 minutes later, car starts again perfectly, no rough idle, just to stall again when it gets hot.

On gasoline MLs, if you can start the engine, and it runs rough for a while and gets normal after a few seconds or after revving the engine, the most probable thing is a vapor lock, caused by low pressure on the fuel rail.
But it's not simple to diagnose as it may look at first.
Such problem may be caused for several reasons, as listed below:
- Faulty pressure regulator. It's incorporated to the fuel filter. Most likely.
- Old or clogged fuel filter.
- Faulty check valve at the fuel pump. Incorporated to the fuel pump.
- Worn fuel pump.
- Bad fuel pump relay, fuse and their contacts. Less probable, but it happens.
- The combination of bad fuel with hot weather - too much alcohol on the mixture can make it prone to vaporise.

yorbcbud

1999 ML430. 408000 kilometres. Car starts and runs perfect when cold, after a few miles starts to run rough, no power on hills, and chugs bad at lights, turn off car, restart, and car runs perfect again for a while, then problem returns, turn off, then restart, runs perfect again. No wait time between restart required. CPS?

barijan

Hi yorbcbud.
It's very unlikely to be the CPS.
The CPS, when gets bad, has no mid-term. It works when cold and quits working completely when warms up, and them, engine stalls and doesn't start again until it cools down. There's no chugging or something like that.

The symptoms you describe leads to cylinder misfire - one or more cylinders. When that happens, the ECU shuts down the misfiring cylinder to avoid further damage, so the car chugs, looses power and, if you turn it off and restart, everything gets back to normal. At least until the next misfire.

I bet if you pull the codes you'll get some - or lots of - misfire codes.
If the code points to specific cylinders, you'll know where to start looking. Probably cylinder's spark plugs, wires, coil or injector.
If it's multiple or random misfires, it could be related to fuel delivery, vaccum leaks, clogged cat or a faulty MAF sensor.

First step is to get the codes, and let us know.
Also, check out how many miles you already have on yours spark plugs. Try to pull one out and check its conditions.
Good luck.

yorbcbud

Thanks very much. I will do that asap. I appreciate your quick response. I'll check the codes and see if you're right I just bought the car yesterday. Seemed like a good deal for 500 Canadian dollars. Hope its that simple. High kilometers, but runs fantastic till that issue arises. Ken

yorbcbud

I also wanted to ask, where is the security code printed on the Bose stereo head unit? Previous owner didn't own it long and never turned on the stereo.