gary001

Hi All, would love some help with this.... I have had this 300CE for a few years now. I bought it with the loping bad idle and put up with it for years. It would only do it in neutral. About 6 months ago it started to break up at about 60 MPH so I had to look into it. I found the typical throttle body wire insulation was gone, so I replaced the wires. The car ran like a charm after repairing the wires , but still has the loping idle. I never checked for codes.

Now a new problem, the car cuts out while driving as if the fuel was cut off, then kicks back in when I pump the gas pedal. If I were to stop at a light, it would stall. Trying to start, it would start then cut out. Letting it sit for 15 minutes or so, it would start. No lights come on, on the dash board. Decided to make a code reader.

I have a 16 pole connector, the 300CE model is 124.052 with engine 104.992. mode. Right now I have 2 codes in pin 8 that would not let me erase them. They are 4 (hot film mass air flow sensor) and 11 (heater current to hi/low or short circuit). The mass air flow sensor and the exhaust oxygen sensor have been replaced. I have checked the engine wiring harness in many places and all were areas were found to be in great condition(must have been replaced). The cardr doesn't have a pin 3 or check engine light.

When I built the code reader beside the codes in pin 8, I also had 2,5,6,14 in pin 14 which I was able to erase. The only one that came back was a 5 code (stop lamp switch), which has been there since day 1. The switch checks out good. The dash board light only comes on when I have the headlights off.

Does anyone have a wiring diagram of this engine showing the oxygen and mass air flow sensor?? I would love to ohm out this wiring. Is there a curcuit for the heaters on these that is common??

I really like this car. Any help would be appreciated!!

chaser1

Gary,

Did you ever come up with a solution to your problem?? I have a 92 300CE that seems to have some of the same issues.

gary001

No yet. I have found the correct wiring diagrams for the pinouts of the ECM and have ohmed out most of the wires from end to end, to ground and to adjacent pins and found nothing. ( I have already checked the wiring harness in about 6 different places, It looks like it has been replaced in the past). I am thinking its the ECM. I just ordered a used one off of Ebay and waiting for it. If your having the same problems, check the throttle actuator cable to the connector, thats the first thing I fixed, the wire insulation was toast. It ran good for a couple of months (still has the bad idle when in neutral, but I lived with it). Then this cutting out problem came up which I couldn't live with. I'll get it, its just a matter of time.

gary001

Replaced the ecm. It ran good for a day. Got it back into the garage then it started cutting out again. I thought I had the problem fixed because I now have 12 volts at the oxygen sensor heater. I'm still getting maf and oxygen sensor errors, however the oxygen sensor errors are not "open or shorted heater coil" errors like before. After it cuts out, It wont idle and stalls, then it won't start. It cranks, reves up, then shuts off. I have scoped the crank shaft sensor and it looks good. Can the crank shaft sensor have an intermittant problem? or does this part just fail. I do not have any crank shaft sensor errors on pin 8. I would think if I had a problem with it, it would show an error. Any help would be great.

twhite2714

Hello Gary,

Was there ever a solution for the dash lights. I have a 1990ce and it drives great but the dash lights wont come on.

zibi1988

It seems to me like an electrical part is overheating in your car. Thats why after 15 minutes car starts. this might not be the sole issue. If you are positive your ecm isnt at fault try something easy like run some carb cleaner through the car while reving it. It helped my 300e alot.

ESTJ

Replaced the following:

Overload Protection Relay $18 AutohausAZ
2015403745U
Uro Parts - Overload Protection Relay; 9 Pin Connnection; With 10Amp Fuse Protection

Distributor Cap and Rotor $148.00 AutohausAZ

Smooth as silk now!! Good Luck!

russ.w

I have a 1988e and have a similar problem - after about 15 minutes it dies and after it cools it's off again. I will try the distributor cap and rotor first. Russ