Pls help diagnose C36 loss of power, diag printout included
 

Gentlemen, My 95 C36 lost power and started misfiring recently. It went into 'limp-home' twice mode by shutting off cylinders 1 & 6.

I sent it to the dealer for diagnosis and they replaced the MAS ($$$ :eek: ) and the coil for Cyl 1 & 6. They said its fixed but when I drove it hard on the way home it went into limp-home mode again. Also I can feel that the power is significantly down.

I scanned and attached the dealer's diag printout hoping some of our savvy techs can help me diagnose. The dealer obviously wants to throw parts at it but that is way too expensive.

So far we had changed the plugs, 3 coil ends, air and fuel filters plus the aforementioned MAS and coil pack. The wiring harness had been replaced about a year ago.

Need help guys!


Hmm... sorry I can't seem to attach the print-out file. I'll type it in instead

=======================
HFM

MB number 202 545 96 32
Diagnosis Ident 46/00

012 Idle speed contact
air mass
Implusibly large

040 Injection Valve Cyl.6
Y62y6 -//-,

094 Transmission overload
prot. switch S65

104 Fuel Safety Shutoff
recognized

035 Lambda control
rich stop/mixture too lean

084 Short-term self-adjustment
idle speed part load exceeded

117 Attempt at starting performed
with IFZ locked

110 voltage supply to HFM control
unit N3/4 implausible

==========================
TPM

182 Safety fuel shut-off switch
signal for HFM N3/4

==========================
ASR

011 Solenoid valve relay A7k1

==========================
ASD

Control unit does not answer

==========================
EGS

Control unit does not answer

That's it guys. Will appreciate any feedback

Your throttle actuator may need to be replaced due to the "Fuel Safety Shutoff" codes. Before going any further with the plug and play diagnostics I might suggest having a fuel volume test perfomed. Cylinders one and six will be the first to suffer when the fuel volume drops causing the 2 cylinders to run lean. When do you need fuel volume the most, under a hard throttle condition. IMHO-A fuel pressure test is always followed by a fuel volume test, 1-ltr in approx 25 seconds on most MBs.

Pop the fuel rail out and swap injector 6 with injector 3, if there is an issue with injector 6 the problem will move to number 3

Have the fuel pump volume checked...........if it is determined that it can not be the "cause" of your complaint other diagnostics will be needed :cool: We'll do what we can to help you avoid opening your wallet too wide to address this matter ;)

Thank you for the reply, I shall tell the dealeer to do that when I bring the car in next week. I've been babying it lately and the misfire does not occur but power is significantly down.

Also, there is this weird 'stepping' increase in RPM when I press on the accelerator fully, i.e., instead of one continous rush or pull from idle, it sort of races to a plateau, pauses there for a quarter of a second or so, goes to another plateau, pauses for a while etc until it hits redline. about 4-5 times before shifting to 2nd. Weird...

I bought a new MAS as per the dealer, no change whatsoever... :mad:

Probably would not hurt to install a new Over Voltage Protection relay. It may be a contributing factor, even if it isn't the casue they do have a high failure rate. It provides switched power to the HFM control unit and the air mass meter. If the contact points are sooted from arching over time you may not have sufficient current to drive all of the devices. It may have a voltage drop throught the relay

Solved
 

I finally solved the loss of power/misfire problem. It turned out that the wiring going to Injector Valve #6 had been caught under the valve cover and had been partially severed. There are 2 wires, both white/green and one of them is damaged.

I soldered the wire and taped the thing- power back to normal, no more misfires. That blasted dealer made me buy a unneeded $$$ MAS and coil!

Don't stress over the MAS. If it was in the car for a while, it probably needed to be retired anyway. Feel good about a DIY repair well done.:D

i want the price ifz control unit so that i can buy
thank you