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2001 ml430 744 silver
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150 Posts
Discussion Starter #1
My wife complained of the truck of losing power randomly while driving. It has happened approx 4 times in the last month. One time it stalled but started right up, the other time it just coasted slightly then kicked on again. No CEL. Then the other day she complained it took a few tries to start the truck and then was ok.
Then suddenly the CEL came on ,P0455 was the code. I bought a new dealership cap. CEL still on, it won't clear at all. P0455 constantly. No other codes. She complained a few more time of starting from cold, and 1 more loss of power.
I have read the forum very carefully and want to know if the evap problem could have anything to do with the power loss problem. (fuel filter changed 2 years ago btw). The purge valve feeding into the manifold is definitely pumping.
Someone on the forum was sure the next definite weak link would be the charcoal canister valve back near the exhaust pipe. I want be absolutely sure the power loss problem and the evap error are strictly independent. I want to tackle the powerless problem because that can be dangerous in traffic and the evap error I can tackle later, I would probably take it to the dealer later to narrow the failed component down. Is the evap something they can diagnose quickly? I don't want someone guessing what to change, I can do that myself!
Any opinions are welcome. Oh yeah I am about to change the spark plugs the others have over 100000 mile on them. Always use 93 octane from same station. Swapped mafs also, no change.
Thanks for any thoughts or guidance.
 

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I had a near similar thing happen to me on my VW Beetle. After trying everything I could, turned out to be the battery was on its way out. Check your battery, just in case.
 

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2001 ml430 744 silver
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150 Posts
Discussion Starter #5
Ok, I am still getting the power loss randomly. The first one in 3 weeks, actually stalled and started up immediately. Plugs, fuel pressure sensor , wires & crankshaft position sensor were changed 2-3 weeks ago.dealer diagnosed p0455 error as bad fuel pressure sensor, I am guessing they were wrong.
Cel is on constantly with p0455 error. I checked the purge valve and it is operating correctly. I guess my next step is to have a smoke test done.
I checked the fuel pressure at idle and it is 55 psi.
Any suggestions?
Also, what should the smoke test cost me?
Thanks for any guidance. My emissions testing is due (of course) and I need the p0455 to be fixed ASAP.
 

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2001 ml430 744 silver
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150 Posts
Discussion Starter #8
UPDATE:
It seems something interesting has occurred. After a full tank fill up and 6 local drives the CEL is not illuminated anymore. I didn't think changing the fuel pump would effect the p0455 error. Anyone have a good explanation? Could it be just a coincidence? Thoughts?
 

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2001 ml430 744 silver
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150 Posts
Discussion Starter #9
p0455 still there

Another Update:
Even though the CEL went out; When I check the codes I still have the p0455 code there. My innova 3100C can't seem to clear it. Did I really solve my Evap error by changing the fuel pump? Maybe my scanner is broken. Is there an easy way to clear the codes w/o a scanner?
Also after many drives long and short the CEL is off.
Any suggestions?
 
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