nigel45

I have a 1997 Mercedes E420 with 3 readiness monitors at not ready, Secondary Air, Evap and Catalyst. I have completed numerous drive cycles, replaced the battery (in case low voltage was the issue) driven hundreds of miles. I checked the secondary air pump and it is blowing at cold start.

Other issues (may or may not be related) car sometimes has inconsistent idle at stoplights. Also, my A/C unit will sometimes blow cold air, then hot humid air, the go back to blowing cold air. Sensor readings as follows:

1-26
2-35
3-8
4-7
5-59
6-89
7-11
8-42

E FF

Any suggestions for a fix on this?

kajtek1

35C outdoor in February has to be Australia?
Your refrigerant shows low, but for full testing display #7 mid-day when entering hot car and observe how it changes in next few minutes.

nigel45

Ha actually I'm in Texas (no clue why my readings are in Celsius), so not too far off temperature-wise, I actually took additional sets of readings one after the car idled for a few more minutes and again after my drive home form work (about a 20 minute commute). What reading suggests my refrigerant is low? Is it also possible my evap temp sensor (#5) is bad? Since it's saying its like 60C/140F?

After Longer Idle

1-21
2-26
3-14
4-14
5-59
6-65
7-11
8-44

After Sustained Driving

1-23
2-20
3-21
4-21
5-60
6-85
7-05
8-20

kajtek1

The working refrigerant pressure is variable, but 5 bars is low even with compressor off.
you need to follow my above advice for final confirmation.
Evaporator sensor shows strange, but not knowing all parameters can't do final verdict.
Read all the sensors in the morning before engine start and before sun warms up the car.
If it reads 60 then, it is shot, however those car do have default programs and can run ok with shot sensor.
I had 2 of W210 from the same year, same engine. One would read in F, the other in C.
Both read the pressure in bars. Could never figure it out, but I spend 1/2 of my life in metric system, so don't even need to covert the data.

Plutoe

Regrettably mr mumbo jumbo has been leading you around the may pole with his HS.

FYI:

1=in car temp
2=outside temp
3=L heater core temp
4=R heater core temp
5=evap temp sensor
6=engine coolant temp
7=refrig pressure inbar
8=refrig temp

The data point number 5, 7 and 8 are the indicators---both 5's are consistent and very high--should be in the low 40's

The 7's are low and very low(11 and 5) should be 15-17

The 8's on earth are relational and the correct temp for 11 should be 115(F)---for 5 the correct temp should be72

All the data together suggests that your compressor is not making pressure or you are low on refrigerant ---the corroborating test is placing gages on the system and watching the H and L pressure

PS: you do not have an issue with the evap temp sensor

fabbrisd1

Well.. please reread the OP (original post) and you might think to address the earnest question(s)... rather than blowing hot and cold air..

Plutoe

You may want to re-read the original post ---FYI there are two questions asked, I addressed the second question--are you going to try to contribute and answer the first question or is more of your buddies mumbo jumbo tactics!!!!

nigel45

I actually replaced the evap sensor and the A/C seems to be working fine now.

However my readiness monitors (CAT, EVAP and Seconday Air) are still not ready. I have no codes, no CEL. Have gone to the mechanic, replaced the Sec Air cut off valve, reset DME Adaptions, checked for vacuum leaks (none found) and these monitors are still giving me trouble. Plus I've completed numerous drive cycles since the last reset. I've done the drive cycle ohlord had posted on here, plus the official Mercedes one on that .pdf that's been circulated around the boards. Also my daily commute is a 35 minute drive with stop and go traffic and some highway time as well.

After all this I'm still not able to pass inspection in my county. It's getting frustrating. So I have to wonder, is it possible I have a slowly failing O2 sensor that still completes readiness and doesn't throw codes, but is somehow messing up the other tests (I replaced one a couple years ago, but the other three are quite old)? It would explain the occasional rough idle. Or something my mechanic might have missed?

I should mention that I've encountered this computer stubbornness in previous years with the same three monitors not resetting, but usually after a couple drive cycles the secondary air becomes ready and I can pass inspection. No such luck this year. So any suggestions? tips? additional insight?

dirtymike72

did you ever figure it out getting the monitors ready?

nigel45

I did, the saga of this issue took a few more turns so bear with me.

After my initial mechanic replaced the secondary air valve, reset DME adaptions and checked for vacuum leaks, my car's readiness monitors still had not ticked over. I then proceeded to another independent shop to get some additional opinions on the matter, they ran some tests, found nothing mechanically wrong with the car, and did some drive cycles and had no luck with the readiness monitors. They advised me to go to the dealership where they have Star Diagnostic Systems/SDS (they thought something might be wrong with my ECU). Thankfully they didn't charge me for this diagnostic work they did since I had been to this shop a few times with other cars.

I went to the dealership (Mercedes Benz of Austin) and they checked the car with SDS. They told me the car was mechanically fine, ECU working properly. They did an ECU reset and suggested some additional driving tips to get the monitors ready. I drove the car all over (put about 200 miles on the car), did drive cycles etc and still no luck. Again, thankfully the service rep there was a solid guy and didn't charge me the usual diagnostic fee of $150.

By this point I was resigning myself to the unfortunate reality of having to get a one year safety inspection exemption for my car and contacted the local Texas DPS office to inquire about the waiver process. I told the gentlemen there the whole story, the three different mechanics (including the dealership), the driving, the repairs etc and he suggested I visit one more shop in town, Ben's Workshop, an independent shop that specializes in just Mercedes and BMW cars and has Star Diagnostic equipment.

Took it to Ben's, explained the situation to the guys there and dropped the car off. The called back later that day and informed me of two issues; 1) that my intake temp sensor was unplugged with a resistor taped into the terminals of the cable (something that had occurred prior to my possession of the car). This was causing the ECU to think the intake temp was -14 degrees Celsius. 2) My throttle position switch was not responding at idle. Both of these issues would keep some readiness tests from running. They removed that resistor and adjusted the throttle cable/re-calibrated the throttle actuator. Charge was for 2 hours of labor. Immediately noticed my car wasn't idling oddly anymore and lo and behold within 24 hours of regular commute driving and some additional idling ALL OF THE MONITORS were ready. My E420 was inspected and registered within 48 hours of getting the car back.

The absolutely bonkers part of this story is that these two issues slipped past the dealership. I'm willing to give the other shops a pass since they aren't SDS equipped, but the dealership has no excuses. I'm pretty upset that they didn't do their due diligence with a whole staff of trained techs and didn't notice two glaring things like an off the chart temp reading or a non responsive throttle switch. At least they didn't charge me for the diagnostics, but they had all the equipment and know-how to fix the issue and could've solved the problem right then and there. I'm definitely going to inform my two local independent shops to send any Mercedes drivers with mysterious car issues to Ben's Workshop in South Austin instead of the dealership. They have all the equipment the dealership has, but a much more caring, thorough approach to diagnostics and a lot more knowledge about older Benzes. Also the whole staff there were awesome, informative and very helpful.

The moral of the story is: find a good mechanic. If you drive a Benz (especially an older one) a good mechanic makes a whole world of difference . I'm glad that this process has at least led me to discover a kickass shop with a very knowledgeable staff, that does good work and doesn't charge an exorbitant rate. I fully intend to take my car there for any repairs I cant DIY. One trip to those guys and they fixed issues no other mechanic had spotted or been able to fix in my 3 years of driving this car. Now my '97 E420 is driving better than it ever has. It's a spectacular feeling.

kajtek1

Good to hear end of long story and car ready to
Just becouse the dealer did not charge you for doing nothing is not good excuse at all.
I would still report them to MB USA.
There is no reason to put up with this crap.

dirtymike72

I wouldn't be surprised if the dealer simply hooked up to it and checked to see if there were any pending codes, and upon seeing none just assumed everything was ok.

kajtek1

Electronics are not my expertise, but I had my car scanned couple of times and in just seconds it come with +- 10 codes on perfectly running car.
The amount of sensors on W210 is amazing.
You will have a code becouse 2 years ago PSE pump worked 10 seconds too long. .
Bottom line I will have hard time to believe that proper scan did not discover crucial elements on the engine malfunctioning.
But than it takes somebody who knows DAS beside owning one to troubleshoot the car, not just shoot you something he doesn't know.
My feeling is that the dealer just plug OBD, while W210 takes 38 pins plug to read sophisticated codes.

Plutoe

Would you be so kind to post a picture of the invoice from the Austin MB dealer--thank you!!