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So, my car broke down on I95 in Stamford, CT, 100 miles from home. Acted just like it ran out of gas, but the tank was 3/4 full. Had it towed to a nearby shop, where they said the evap canister was leaking and the fuel filter was clogged. Got totally ripped off, but the car was running again and I needed to get back. Right away, I noticed the idle was a bit rough, and as soon as I got back on the highway the Check Engine light came on. Just wonderful. I made it back without incident but the gas mileage was now horrible. Dropped it off at my regular mechanic at home and a scan revealed that 4 oxygen sensors were bad (open circuit). They are booked up and with the holiday weekend, it's gonna be laid up there for a while.
What are the odds of all 4 going? Could this be related to the evap and fuel filter problems?
So, my car broke down on I95 in Stamford, CT, 100 miles from home. Acted just like it ran out of gas, but the tank was 3/4 full. Had it towed to a nearby shop, where they said the evap canister was leaking and the fuel filter was clogged. Got totally ripped off, but the car was running again and I needed to get back. Right away, I noticed the idle was a bit rough, and as soon as I got back on the highway the Check Engine light came on. Just wonderful. I made it back without incident but the gas mileage was now horrible. Dropped it off at my regular mechanic at home and a scan revealed that 4 oxygen sensors were bad (open circuit). They are booked up and with the holiday weekend, it's gonna be laid up there for a while.
What are the odds of all 4 going? Could this be related to the evap and fuel filter problems?
Here's a diagram of the W208 Evaporative Emission System (EVAP) control system.
Basically, it's function is to prevent gasoline vapors from being released into the atmosphere and will throw an emissions related CEL, but does not store an ECU fault condition diagnostic trouble code (DTC) and won't affect engine performance, (e.g. such as a clogged charcoal canister, a loose or forgetting to put the gas cap on etc.).
If gasoline gets into the canister, typically by overfilling the gas tank, the charcoal will break down and clog the system and very little air will be able to be displaced in the gas tank. If air can’t leave the gas tank, gas won’t go in. The canister will also clog due to old age because gas fumes will break down charcoal too.
However, the first shop's diagnosis suggested a leaking canister. Perhaps, the description of system flow will provide additional insight.
BTW, most states now exempt older vehicles (MY's older than 2005) from having to pass the OBDII emissions test, but must pass the safely inspection (e.g. steering suspension, brakes, tires, exterior lights, horn, wippers etc.). However, vehiclescan fail a safety test if there is smoke coming from their tailpipe.
Additionally, note that the fuel pressure regulator is integrated into the fuel filter and if it's clogged, the correct filter was not used or the 4 port lines were not installed properly, your fuel trim could be out of kilter, which may be the cause of the current CEL.
It's very difficult to troubleshoot without more diagnostic DTCs via the internet (e.g. could be caused by a fuel rail pressure issue, a stuck fuel injector etc.).
However, IMHO, odds of all 4 oxygen sensors suddenly being bad, on both engine banks, is highly usual and indicative of a fuel problem.
agree w/serendipity about fuel issue...sounds like bad pump or filter filter...check fuel rails to be sure that you are getting fuel. Bad MAF throws O2 sensor malfunction codes.
Thanks guys. The fuel filter was an aftermarket unit that always made noise, so maybe that's it. Oddly enough, the check engine light went off, and it's running smoothly again. Will post an update.
OK, it's it's still running, but with a rough idle and running much hotter than normal. Hooked up a fuel pressure gauge. 58 PSI, holds within +-1 PSI from idle to 3k RPM. Stayed within a pound of that pressure for 1/2 hour after shutting off the engine.
Come to think of it, the shop that did the work in my OP said after sitting overnight it started right up, and died 20 minutes later. Ever since the mileage has been bad, it idles rough, and doesn't accelerate properly. Bad crank position sensor perhaps? Cheap enough, but a ***** to get to.
I am having a similar problem. After replacing the four O2 sensors on my CLK320 W208 I am still receiving malfunction codes for all of them and, additionally, for the purge valve solenoid and for the secondary air pump. My motor also runs a bit roughly in idle. I will probably start replacing the fuel filter as indicated above and then come back to you and tell if there are any improvements. Rob8, have you been able to solve your problems? Thanks a lot for you advice.
I am having a similar problem. After replacing the four O2 sensors on my CLK320 W208 I am still receiving malfunction codes for all of them and, additionally, for the purge valve solenoid and for the secondary air pump. My motor also runs a bit roughly in idle. I will probably start replacing the fuel filter as indicated above and then come back to you and tell if there are any improvements. Rob8, have you been able to solve your problems? Thanks a lot for you advice.
I would go with a new OEM MAF...get it less from autohauzaz...no ebay/China knockoffs...be sure to seat the rear of the airfliter before lowering the the front onto the clips...while you have that off, check that none of the vacuum lines are cracked
I would go with a new OEM MAF...get it less from autohauzaz...no ebay/China knockoffs...be sure to seat the rear of the airfliter before lowering the the front onto the clips...while you have that off, check that none of the vacuum lines are cracked
Many thanks for the quick reply. I have already replaced the old MAF by an original new one from Bosch some time ago, with no effect on the 4 O2 sensor fault messages. So it's definitely not the MAF. Also, these are circuit faults which should not be indicative of a leak in the vacuum lines. Thanks for your help anyway.
Many thanks for the quick reply. I have already replaced the old MAF by an original new one from Bosch some time ago, with no effect on the 4 O2 sensor fault messages. So it's definitely not the MAF. Also, these are circuit faults which should not be indicative of a leak in the vacuum lines. Thanks for your help anyway.
I'll just go with the easy fixes that others have found...if you don't seat the airfilter securely into the MAF housing, it will throw O2 faults...double check it
05-24-2019, 12:59 PM
All 4 Oxygen sensors?
