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Old 09-23-2012, 10:42 PM   #1 (permalink)
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Hard start and poor gas mileage!

I have an 03 mdx with about 140,000 miles and i have replaced spark plugs (double checked gap), newish air filter, good battery and good alternator. I am getting horrible gas mileage and it is really hard to start. I have to hold the key over and give it gas. Cranks fine and idles smooth once it's started. No check engine light. Trying to change the pcv valve tomorrow. The fact that it takes so log to start makes me think it may be a fuel thing but I read there are no fuel filters? Any ideas? Has this happened to anyone else?

Thanks guys!
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Old 11-02-2012, 01:23 PM   #2 (permalink)
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Well it looks like I am on my own on this one. I changed the PCV valve and adjusted the valve lash which fixed my poor gas mileage problem. The exhaust was CRAZY tight and intake was loose. I took the car to a shop because I still had the long cranking issue and they ran a computer diagnostic for $40. Came back as having too low fuel pressure on start up. Good news is, all I have to do is prime to fuel pump a couple times and it starts right away. Bad news is this means I likely have a bad fuel pump or bad regulator. The fuel pump/filter/regulator/fuel level sender are all one assembly in the gas tank. I ordered a new assembly from here: 17045-S3V-A50 - Acura MODULE ASSY., FUEL PUMP and it came out to be around $235 shipped. I'll try to take pictures along the way as I replace it.

I checked the FSM and it looks fairly straightforward. Remove the rear seat, cut a hole in the carpet, remove access panel, use custom tool to unscrew fuel pump, remove, replace, reassemble.

Hopefully this fixes it and can serve as a future reference for anyone else who has this problem.

Cheers.
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Old 11-02-2012, 01:32 PM   #3 (permalink)
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A leaking fuel injector would cause fuel pressure to decline while engine is off and result in initial hard starting. If fuel pressure is declining w/ engine off, suggest checking injectors for leaks.

good luck
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Old 11-02-2012, 01:42 PM   #4 (permalink)
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Yeah that was the other option I was considering but the fact that the pressure bleeds off immediately after I turn the car off I'm thinking hints towards the fuel pump and not an injector. If an injector was leaking that bad, I'm sure I'd have some crazy idle problems. It doesn't matter when I try to start the car: hot engine, cold engine, hot outside, cold outside, parked all night, just drove around. Every time I try to start, I get a long crank UNLESS I prime the fuel pump 2-3 times first.
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Old 11-03-2012, 11:47 PM   #5 (permalink)
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any pics of the fuel pump change you can share?
and more importantly, did it solve the problem? let us know
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Old 11-05-2012, 09:02 AM   #6 (permalink)
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The fuel pump hasn't come in yet. I'm hoping it will get here sometime this week and I will put it in this weekend. I'll be sure to take some pictures along the way so people can see. The trickiest part is going to be trying to figure out how to unscrew the thing without the special tool. I may have to do a little fab work :-/
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Old 11-12-2012, 05:40 PM   #7 (permalink)
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tagged lookin fwd to pics
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Old 11-12-2012, 07:00 PM   #8 (permalink)
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Quote:
Originally Posted by Smeddy2 View Post
Well it looks like I am on my own on this one. I changed the PCV valve and adjusted the valve lash which fixed my poor gas mileage problem. ....
Cheers.
What's poor gas mileage? I get 14-15 mostly city. 04 mdx 130k - never had a valve adjustment
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Old 11-12-2012, 08:29 PM   #9 (permalink)
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Originally Posted by CODOG2 View Post
What's poor gas mileage? I get 14-15 mostly city. 04 mdx 130k - never had a valve adjustment
That sounds bad. Our 01 with 185k gets 20 mpg, 06 with 110k get 17.1 mpg
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Old 11-13-2012, 12:33 PM   #10 (permalink)
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I'm interested in doing a valve adjustment..can someone explain to me, the steps to do it? I did timing belt, ect. Just have not looked on how to do the valve adjustment. Would love someone who did it first hand to give me a few tips first.
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Old 11-13-2012, 09:38 PM   #11 (permalink)
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Check ericthecarguy videos on youtube. He has a video on Honda V6 or Acura V6 that shows procedure.

good luck
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Old 04-09-2014, 01:44 PM   #12 (permalink)
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I have a 01' MDX that will not start. I have change the fuel pump and still has the same problem. After changing the fuel pump it worked for a couple a days, but went back to the same issue. Please help how to solve this issue.
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Old 04-10-2014, 09:05 AM   #13 (permalink)
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You'll get better response/help w/ your own new thread.

You don't say if it turns over, but if it does, then following may help.

Suggest trying to determine whether fuel or spark is missing. Easy way to check is to attempt start w/ 10 sec spray of throttle body cleaner into air intake duct.

If car starts briefly, then fuel delivery is problem, fuel relays would be prime suspects.

If car fails to start, then spark is missing. Look for a ignition switch problem (no power to ignition).

good luck
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