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Sanity Check - Advice

519 views 6 replies 2 participants last post by  Jayare 
#1 ·
I have been working through some maintenance/upkeep items on my 89' 300E for the past year or so and wanted to get a little perspective on my process.

I purchased the car in 2016 and it had a bit of a cold start issue. Moderate fuel economy ~20 mpg with mixed driving and a bit sluggish off the line.

Checked cold start and it appeared to be functioning correctly.

Economy gauge not pegged left at idle or even 1/8 away. Probably 1/3 or more. Researched and figured it was probably a vacuum leak. High idle ~1000 to 1500 at times. Drive took it down to around 800-700 as I can recall.

Completed a few minor maintenance items including power steering hoses, oil, power steering fluid/filter.

Drove the car for a while with no issues and only a little pedal on startup to get it going.


Eventually did a full vacuum check with air filter housing off. Intake and breather hose closed off with latex gloves. Found significant vacuum leaks in at least 3 fuel injector insulator/o-ring seals. Decided to simply replace all injector seals and injectors as I had no idea how old they were or if they were functioning. I decided it was worth it to pay the $180 to just go ahead with all the injectors as well.

Replaced all the 'major' vacuum hoses including the dreaded hose from idle air valve down to intake. Did the air filter and serp belt at this time too. Also replaced some plastic housing pieces at rotor and spark plugs.

Eventually got it all finished and the duty cycle adjusted. The duty cycle had previously been adjusted per the previous owners documentation to 50%. After all the previously noted items had been replaced, the duty cycle was something like 78-80% at idle.

Previous owner noted to have adjusted the EHA 1/4 turn CW (raising fuel pressure?).
The little reading i did on this led me to believe they did this to help on startup or slow acceleration at low revs? I took the EHA off and the screw covering the 'allen bolt' adjuster looked like it had potentially been removed (small wear at screwdriver slot). I turned the EHA back CCW 1/4 of a turn to what I assume was factory spec.

Adjusted the duty cycle, but the range was fairly large at idle with engine warm ~5-10% range (will verify this range again). Currently varying between 43-53%.

Idle rpm down to around 800-850 from the previous 1000-1500.

Economy gauge about 1/4 from left at idle (some improvement). Brake booster checked and does not appear to be the source of the assumed remaining vacuum leak.

Approx mileage improved to around 22 (not 100% on this yet) after duty-cycle update and vacuum fixes.

Starts up almost instantly with no gas/pedal.

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With all that said I am questioning my plan on evaluating the following items in the near future:

Potential bad ECU based on the high range of duty-cycle readings?
Vacuum leak at ECU?
Check all small plastic tube and rubber vacuum fittings for remaining vacuum leak (including ecu)?

Should I realistically expect higher mileage?

Thoughts or advice on the general process/plan that I have taken thus far?
 
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