400E running "rich"

[Gatorblue92]

I'm a bit stumped with my new (old) 93 400E. The car is running beautifully but it smells like its running very rich. I also took it for inspection today and it failed the emissions test. They actually didn't even start the test because they said the CO2 level was reading too low to begin. Doesn't seem to be any exhaust leaks (my first thought for the low CO2) and the car wasn't displaying any codes. Appears to have recent F8DC4 plugs with Beru wires and what appears to be Bosch caps. Haven't removed them yet. The one plug I pulled didn't look fouled but it was a bit white looking. I swapped in 2 different LH modules including the original one from this car and the known good one in my other 93 400E.

Possibly bad O2 sensor or plugged cats?

 

[Gatorblue92]

 

[gsxr]

Spark plug in your photo looks normal.

If the O2 sensor is old, I'd consider that first... then reset adaptation on the LH module. Bad MAF could cause this too.

Plugged cats would cause a power loss at high RPM + full throttle. Do you have access to a digital scanner to view live data?

 

[Gatorblue92]

Spark plug in your photo looks normal...

I actually might have access to the digital scanner. Is it part of the Chinese version of the Star diagnosis system?

There doesn’t appear to be any power loss at all and I would actually say this one runs better than my other 400E (the salvage title car) I’ll go ahead and order a new O2 sensor and see what if anything it does. I doubt it’s been replaced.

I was also poking around the engine bay and broke the EZL vacuum line. Not exactly jazzed about that

 

[gsxr]

Digital scanner = anything that will show live data from the LH system, but yes, the Chinese SDS will show you everything there is to see.

Read the O2 sensor replacement threads, I'd soak the oil one in Kroil for a few days before attempting to break it loose.

Check ALL the vacuum tubes in the engine compartment, if one broke, the others may be brittle as well. Very cheap to replace all of it.

 

[a777fan]

While i haven’t had the time to test out or prove my theory, I recently had a similar problem on my e420 (rich smelling exhaust), but my issue was combined with a warm stalling/no restart condition. I looked at many different things, and finally ended up at the distributor caps. The factory diag manuals have a spec for the cap resistance. When I tested mine with a multi-meter they we’re practically in open circuit territory. I replaced both and I have noticed that the rich smelling exhaust has largely disappeared.

I recorded data for the secondary ignition voltages prior to the cap change, and I need to take more data with the new caps to see if secondary voltages are up relative to the original readings.

So nothing more than a qualitative assessment/suggestion for you, but might be worth checking out if you have a multimeter and 10 minutes.

 

[gsxr]

Jon, I had forgotten about your issue... were your original caps very old? I believe spec is ~1000 ohms.

Also... make sure to clean off the residue on the inside terminal to get a good connection & accurate reading, if the VOM probe can't touch the brass, it may read abnormally high resistance. The high-voltage spark punches right through the residue, but the VOM battery can't do that.

 

[a777fan]

Jon, I had forgotten about your issue... were your original caps very old? I believe spec is ~1000 ohms.

Also... make sure to clean off the residue on the inside terminal to get a good connection & accurate reading, if the VOM probe can't touch the brass, it may read abnormally high resistance. The high-voltage spark punches right through the residue, but the VOM battery can't do that.

Indeed dave, the caps were old (not sure how old, but I hadn’t ever changed them and the appeared quite beat up), and I did remove the burnt material in the interior of the cap connections before testing. I really couldn't believe the numbers i was getting, but the new caps tested out a-ok! IIRC, you are correct at ~1k ohms.

 

[Gatorblue92]

Finally got the car in the garage this afternoon and discovered a hole in the exhaust. That would explain the low co2 reading at the inspection station. I’ve also got a new oxygen sensor set to go in this weekend along with some new plugs. I’m also going to pull the distributor and check the condition of the insulators. I doubt they were done when the rest of the ignition parts were replaced. Once that’s done I’ll see if it’s running better and worst case I can borrow some parts from my other 400E to get this one through inspection.