190E EHA/Fuel Problem?
 

Hello,

I discovered that my 190e was running to lean (70%) Using the guides from this forum i was able to adjust the mixture to 49% which is perfect. She is running a lot smoother.

I still have a problem though. When i rev my car to 2500rpm the value doesn't go down 10% like it should. It constantly stays at around 49%

I tried another EHA valve and lambda sensor but it gave the same value. What could the problem be?

Thanks guys

I would first check the spark plugs first. If it is browny red with no fouling then I will not care about whether if the duty cycle goes down 10% at 2500rpm. Another thing to judge the AFR is to feel when you drive it. If the AFR is right then you should see her accelerate without hesitation.

The car doesn't hesistate and is good to drive. But, it is lacking power and has poor fuel consumption (~20mpg) The duty cycle seems to stick at 49.2%, it doesn't change at all when the car has heated up and when your rev her (even further than 2500rpm).

Again, check the spark plugs. They tell a lot about the engine's condition.

Checked the spark plugs a few minutes ago and they look grand. They were only put in a 1000 miles or so ago.

If the spark plugs are good then your engine should be fine. I am out of ideas for your problem, if you call it problem.

The car is lacking power and mpg. I adjusted the fuel mixture as it was off but there's still something wrong. I'm going to replace the OVP but i doubt it'll sort the issue.

Any other idea's guys?

Your duty cycle at 2500rpm is supposed to be +/- 10% of the idle value. Which means it should fluctuate on either side of wherever your duty cycle is. Sounds like your EHA is most likely functioning fine.

Is your duty cycle the same with the engine cold, hot, and at RPM? If so, it sounds like you could possibly be running in open loop all the time. With the key to "on", the one right before cranking, what is your voltage measurement at the diagnostic plug? The duty cycle should be fixed with the engine cold, once it warms up and goes into closed loop the duty cycle will start fluctuating fairly quickly.

You need to establish that the car is going into closed loop before you can accurately diagnose the problem.

My duty cycle stays the same either cold or hot. When the ignition is on but the engine isn't, the duty cycle is at 70%. I'm unsure of the voltage but i can check soon if you want.

Before i adjusted the fuel mixture, when the car was first started the duty was 50% then fluctuated between 67 - 70% I adjusted it to and it read 49% which was grand. But it seems stuck at 49.2% now even when the car is cold so I'm assuming the car is stuck in an open loop? :(

Cheers for the help

What do you's think the problem could be guys? sorry for double post

Have you considered fuel injectors. May be a longshot but they don't last forever despite what some might tell you. Not such a pain to remove and spray test, not really that expensive to replace either. Also, have you given any thought to checking diagnostic trouble codes. If there's a problem in the Jetronic it will help you immensely to pull codes. Trying to hazard guesses with the fuel injection is a waste of time and money.
also
-Vacuum leaks
-plugged catalyst

I assume you have the m103 powered car, correct?

Injectors were changed a few weeks ago, the catalytic converter has been removed for better sound and power :)

The car is a w201 and it doesn't have a proper diagnostic tool. There's a few pins for a multimeter to read values but it doesn't give you codes :(

Mine gives me codes
?

Oh right. No codes from mine unfortunately. I'm running out of ideas :(

Well you have established the car is not going into a closed loop operation.
First and foremost establish if the O2 sensor is functioning. Pull the passenger footwell carpet back and you'll find the O2 sensor plug in there. Use a DMM on it when the car is warm and see if it reads any voltage. 0 is lean, 0.9v is rich. You should see it fluctuate around ~0.45v. If there is no voltage -- replace it. I read you did replace it, but did you replace with a new one? Either way you should check for operation so you can definitely rule it off.

Here is a link:
http://www.landiss.com/mixture.htm
#5 at the very bottom.

Bosch MB sensor costs ~$125, but you can splice in the same Bosch O2 sensor from a 1990 Mustang GT for ~$40. You pay quite the premium for the 'plug'!