Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
HiCustomer I see from your previous posts that you've been battling this problem for awhile. It's absolutely necessary that a CIS fuel pressure gauge be connected to the fuel system to monitor all three of the system pressures in order to diagnose this problem. The CIS fuel injection is highly dependent on fuel pressure. Loss of fuel pressure or incorrect upper and lower chamber pressures can result in loss of power on acceleration. With the gauge connected you can see if you're getting the proper acceleration enrichment from the warm up regulator. It's also possible that the overvoltage protection relay is acting up. This would be noticeable by the anti-lock warning light coming on in the instrument cluster. You could also try disconnecting the CIS control unit and resetting your fuel mixture with it diconnected and see if it still bogs on acceleration with the control unit unhooked. We're focusing on the fuel system right now because from your description that's what it sounds like. Let me know if you have any questions.
The anti lock light should never come on while the car is running. If it does then the relay may be bad. The relay is located above the fuse box. I've attached a diagram and picture of the relay for you.
The CIS or Lambda control unit is located in the passengers footwell underneath the carpeting. There will be a plastic panel in the footwell area. The control unit is located behind the panel.
Ok, when you disconnect it you will need to readjust your mixture. I really think a fuel pressure test is necessary however. We need to know what the fuel pressure is doing when it runs bad. I'm thinking it's also possible that our idle control valve is shutting down for some reason. We can disconnect that next and drive it with it unhooked. We'll need to choke down the air through the valve so it doesn't idle too high. Let's do one thing at a time though.
HiCustomer you can drive the car with the frequency valve disconnected. You'll just need to readjust your fuel mixture. By doing so you will rule out the lambda control system as the problem. I'd be suspicious of the warm up regulator but you'll need to test the fuel pressure to diagnose it. Intermittent problems are the worst to try and figure out. It takes patience and persistance. Please let me know if I can be of further assistance.