andy_1100
01-12-2017, 01:29 PM
Up to the next problem that Im facing.
Background:
1995 C280 160k km
My regular fuel consumption is about 10.3 L/100 km, at some point about 2 month ago I noticed my car running rough and fuel consumption gone up to abot 12L/100 km, no CEL so I plugged an OBD2 scanner and it gave me a misfire on one of the cylinder. Changed one coil - that fixed it, in about a week after that another coil went bad. So I pulled 3 coils from my 1997 S320 and replaced all of them. I thought that should bring my fuel consumption back to normal, but it still stays high (also outside the temperature dropped below freezing I guess it doesn't help either)
Now I noticed I have hard time starting the car if I leave it for 1/2 hr -1 hr, It cranks but no start. I have no CEL, I have no problem starting cold or hot only if I leave it for a period of time. I watched my temp gauge and I can see this problem occures when coolant temp is below 70-75 deg C. If I floor accel pedal it starts but the RPM goes up and down for a sec untill settles.
When it starts cold my RPM goes up and down for a sec until settles at high RPM as it should at cold start, I do get a blip once in a while, but the RPM goes down as it warms up. When hot RPM goes up and down for a sec until settles at~600 -650 rpm.
I've check throttle body linkage and seems to work OK, it doesn't bind.
Another thing that I've notice and not sure what to make out of it: using ELM327 OBD2 adapter I get a reading on the LTFT (long term fuel trim) and it always stays at minus 3.9. There's no reading for a STFT (short turm fuel trim). I feel that LTFT should change a bit as I open or close the throttle, not sure if it reads the correct port. This car is 1995, pre OBD2 so limited info is available.
Im not really sure what systems are involved during the car start, anyone would give me a suggestion where to start the troubleshooting.
This is a plan I formulated so far :
1. Check/test Crankshaft position sensor
2. Check/test Camshaft position sensor (got a new one coming)
3. Clean MAF sensor (I can see it working OK on OBD2)
4. Clean Intake temp sensor (I can see it working OK on OBD2)
5. Replace OVP relay (I had some problems with it so I have a new one coming)
6. Check all available systems for faults at 38 pin diagnostic plug. The ELM327 adapter for OBD2 port doesn't give much info.
7. Run a diagnostic on the A/C control module for potential faults.
7. Replace coolant temp sensor (4 pins one, I think it sends coolant temp to the gauge and also used for fuel injection system) got a new one coming
Any other suggestions?
Background:
1995 C280 160k km
My regular fuel consumption is about 10.3 L/100 km, at some point about 2 month ago I noticed my car running rough and fuel consumption gone up to abot 12L/100 km, no CEL so I plugged an OBD2 scanner and it gave me a misfire on one of the cylinder. Changed one coil - that fixed it, in about a week after that another coil went bad. So I pulled 3 coils from my 1997 S320 and replaced all of them. I thought that should bring my fuel consumption back to normal, but it still stays high (also outside the temperature dropped below freezing I guess it doesn't help either)
Now I noticed I have hard time starting the car if I leave it for 1/2 hr -1 hr, It cranks but no start. I have no CEL, I have no problem starting cold or hot only if I leave it for a period of time. I watched my temp gauge and I can see this problem occures when coolant temp is below 70-75 deg C. If I floor accel pedal it starts but the RPM goes up and down for a sec untill settles.
When it starts cold my RPM goes up and down for a sec until settles at high RPM as it should at cold start, I do get a blip once in a while, but the RPM goes down as it warms up. When hot RPM goes up and down for a sec until settles at~600 -650 rpm.
I've check throttle body linkage and seems to work OK, it doesn't bind.
Another thing that I've notice and not sure what to make out of it: using ELM327 OBD2 adapter I get a reading on the LTFT (long term fuel trim) and it always stays at minus 3.9. There's no reading for a STFT (short turm fuel trim). I feel that LTFT should change a bit as I open or close the throttle, not sure if it reads the correct port. This car is 1995, pre OBD2 so limited info is available.
Im not really sure what systems are involved during the car start, anyone would give me a suggestion where to start the troubleshooting.
This is a plan I formulated so far :
1. Check/test Crankshaft position sensor
2. Check/test Camshaft position sensor (got a new one coming)
3. Clean MAF sensor (I can see it working OK on OBD2)
4. Clean Intake temp sensor (I can see it working OK on OBD2)
5. Replace OVP relay (I had some problems with it so I have a new one coming)
6. Check all available systems for faults at 38 pin diagnostic plug. The ELM327 adapter for OBD2 port doesn't give much info.
7. Run a diagnostic on the A/C control module for potential faults.
7. Replace coolant temp sensor (4 pins one, I think it sends coolant temp to the gauge and also used for fuel injection system) got a new one coming
Any other suggestions?