[texholdem]

Results for high speed/low speed:

HC (PPM) 454/445 (Standard = 140/144)
NOx (ppm) 3512/3189 (Standard 984/1077)

According to info sheet the possible reasons are:

- O2 sensor
- EGR valve or hose
- Ignition timing and system (advanced timing and ignition components are some of the most common problems)
- Pirimary feedback sensor failure including oxygen sensor, MAP/MAF, TPS, RPM and CTS sensors.
- Vacuum lines (deterioration of vacuum lines, inlet manifold seats, and become more prevalent causes with age).
- Catalytic converter.

My car has no OBDII how can I narrow down the cause? Is there a pre-OBD device with push buttons somewhere? and why there is no CEL at such figures beyond pass range.

Before the inspection I had fuel system cleaned, I changed spark plugs and coolant.

I've got 14 days to get re-inspected; I'd appreciate your inputs since the spectrum of causes is to wide for me.

 

[texholdem]

I bought the car 2 weeks ago on impulse. Last tune up according to records 01/22/09 with Cat replacement. O2 sensor replaced in 2004. Can it fail again?

I am not sure about spark plugs, bought them (Bosch 7927) from auto zone and checked on Bosch website that they fit my car.

Distributor cap & rotor replaced 2005; air filter just replaced last week after purchase.

 

[POS]

Search on this forum or possibly on the peachparts.com forum for a Dallas mechanic who has an excellent reputation, then take that form to him and ask him for his opinion. Best you can do, I think.

 

[texholdem]

Yes, that's what I have to do eventually, but I'd rather go there with some knowledge beforehand.

What troubles me is that on my 1996 E320 at least I can plug an OBDII scanner in and get some clues, but pre-1992 cars don't have that nice feature.

 

[BRONZEROSS]

two things. are the bosch plugs u have platinum? if u do have platinum plugs u need to get rid of them because they do not fire hot enough to burn up all the gas. and u may have to adjust the lambda, "air fuel ratio".

 

[texholdem]

No the plugs are not platinum, they are Bosch (7927) FR8DC Super Plus Spark Plug with the Yttrium electrode (a Y). Both auto zone and Bosch site list them for my model year 1990 300CE.

 

[bsmuwk]

two things. are the bosch plugs u have platinum? if u do have platinum plugs u need to get rid of them because they do not fire hot enough to burn up all the gas. and u may have to adjust the lambda, "air fuel ratio".

As long as the plugs don't have resistors, he's fine. Adjusting Lambda right off the bad is the wrong approach.

Tex,

Check Peachparts, I want to keep everything to one thread on one forum.

Allen

 

[texholdem]

OK, can anybody confirm this theory? Before the state inspection I put a bottle Guaranteed-to-Pass (G2P) to a full tank then drove 240 miles, the fuel gauge was at about 1/4 mark. I filled up then went to inspection, that means some of the G2P was still in the tank. Some people think that could mess up the emission. Any comments?

Should I drive until the tank is empty without doing anything then re-take the emission test? but if the theory does not hold and I fail the test again, what is the fine for expired state inspection ticker?

 

[Anri_300D Turbo 85]

Hi,
I had the same problem when I used to own 300CE-24 "92 3.0.

Let me ask you how many miles you have on the engine/car?

My recommendations are: Check spark plugs make sure they are brand new, Ignition wires, Distributor cap and rotor, Air Filter, make sure its 91 octane in TX you guys have 93 use that.

In general Mercedes makes there car to run rich! The Smog guy should be friendly to the car and work together.

Its a Must before you put the car on the dyno to rev the car for about 2-4 mins around 2000-2500 rpm in order to cook the cats

Then you will be fine.

I miss my 300CE-24 such a nice car it was replaced with a E24 M6 real machine

Good luck

 

[texholdem]

The car has 169009 miles now. Air filter and spark plugs have been replaced last week. Before I throw money at many more items I'd like to have some clues. Sure it would not harm to change spark plugs wires, distribution cap & rotor, 02 sensor, EGR valve but then I would never know which one cause the bad numbers.

 

[scratcher]

Tex, I had the same issue with my 260 300E. Fresh tune up, the works, and it failed.

I pulled the injector nozzles, soaked them in carb cleaner over night, blew compressed air thru them and bingo, passed with flying colors.

After soaking the injectors, when I blew the air thru I noticed the the carb cleaner blew out in a stream. So I put a little more cleaner in the nozzle and blew air thru again, and again until I got that nice atomized mist.

I was so impressed with the results, I immediatly did the injectors on all my cars, thats like 34 injectors in all. And it's now part of my tune up routine.

 

[texholdem]

Hi scratcher,

I am happy to hear an approach/a solution that does not involving parts replacement. Could you tell how hard it is to remove the injector nozzles? I understand that the air filter housing must be removed but I stare at the fuel distributor and don't know further.

Thanks

Edit: figured it out, at least from the drawings, gonna give iy a try.

 

[neanderthal]

Going through the same thing on my 94. I've been doing a little research and you are the lucky recipient of such. My findings have been thus.

High NOx is typically EGR valve, lean burning/ too hot.

Your most likely culprit is the EGR pipe; it gets clogged. There is a simple test to detect if the EGR valve is opening; you pull the small hose connected to it and blow (or suck) and if it is hard to do so, it is not opening. If it is functioning correctly, the it is most likely the pipe.


Do a search for EGR pipe. One guy has a nice, detailed post with pics on how he cleaned the pipe. Search for "obsidian goop" either here or at em bee world dot org. Specifically, take a look at the DIY sticky there at the top.

Takes a little time and effort and little to no parts need to be changed. I understand newer EGR pipes are modified and don't clog as easily.

 

[texholdem]

Hi neaderthal,

I was trying to remove the EGR valve to test but unable to, it is mounted on the rear exhaust manifold and the is no room to remove the rear nut with not more than 1 inch clearance. I think it can be done only with special tool.

Next step is to try to clean the pipe. Thanks!

Edit: as the picture shows, the wrench when going over the nut is already touching the engine block no room, not 1 cm to wiggle.

 

[texholdem]

Going through the same thing on my 94. I've been doing a little research and you are the lucky recipient of such. My findings have been thus.

High NOx is typically EGR valve, lean burning/ too hot.

Your most likely culprit is the EGR pipe; it gets clogged. There is a simple test to detect if the EGR valve is opening; you pull the small hose connected to it and blow (or suck) and if it is hard to do so, it is not opening. If it is functioning correctly, the it is most likely the pipe.


Do a search for EGR pipe. One guy has a nice, detailed post with pics on how he cleaned the pipe. Search for "obsidian goop" either here or at em bee world dot org. Specifically, take a look at the DIY sticky there at the top.

Takes a little time and effort and little to no parts need to be changed. I understand newer EGR pipes are modified and don't clog as easily.

Hi neanderthal,

I disconnected the EGR rubber tube from the other end connecting to a plastic vacuum line, thus the tube is still connected to the EGR valve. I sucked and blew on it I could hear the valve open, especially at sucking. So I suppose the valve is functioning. The pipe is my next target but one pipe end is at the EGR valve, where is the other end? The pipe goes arong the back of the engine but I can't see where it is go to the other side of the engine, picture attached.

I know that it goes to intake manifold, does that means it lies beneath all stuffs in the picture?

 

[texholdem]

Super Bowl time now

 

[BRONZEROSS]

sorry for trying to help, just in my experiance i've done those things before and they've worked. and especially the platinum plugs have not done well in the cise cars i've worked on. and at least checking the lambda is not the wrong approch especially when it can give u a base percentage of how rich or lean its running. and besides with that kind of mileage on the car who knows if the lambda has been messed with before. probably has, just my guess. in any event just trying to help, i been a mercedes technician for 8yrs now and just wanted to help a fellow enthusiast.

 

[texholdem]

sorry for trying to help, just in my experiance i've done those things before and they've worked. and especially the platinum plugs have not done well in the cise cars i've worked on. and at least checking the lambda is not the wrong approch especially when it can give u a base percentage of how rich or lean its running.

I appreciate your inputs. One has to look at every possibility. I also heard about the platinum plugs not doing well in older cars, therefore I did not use them.

Is lambda adjustment done that way as in the picture:

 

[BRONZEROSS]

I appreciate your inputs. One has to look at every possibility. I also heard about the platinum plugs not doing well in older cars, therefore I did not use them.

Is lambda adjustment done that way as in the picture:

yes, but here's some pics so u can get a reading as well. u need the car at normal operating temp. find ur lambda connector, (shown in the first pic.) its on the driver fender well above the ignition module. find pins 2-3. using ur dmm positive pin in the number 2, and neg in pin 3. set dmm to dc volts. with the engine running watch the voltage, should ocillate from 5.5v to 7.5v. turn the lambda tower screw clockwise to richin, counter to lean. also it doesn't take much when ur turning the screw. after u do that snap the throttle and watch ur readings. also u can tell if u have a bad o2 sensor this way too. if the readings are slow or go open. that means ur o2 sensor is probably bad.

 

[Blago]

Did they give you a reading of CO output or just NOx and HC? And are you sure the catalytic converter has been replaced? Because those readings look like you have a bad convert.

High HC means that the engine is running rich, ie is spitting fuel out. High NOx means that the engine is running lean. But when they're both so high, it usually means a bad catalytic converter.