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Another rough idle / P0303 Code thread

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  #1 (permalink)  
Old 07 Jan 2012, 10:45 pm
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Posts: 13
Default Another rough idle / P0303 Code thread

Hello fellow Cruiser Owners.

My 2004 Cruiser (105,000 miles/non turbo) has the rough idle/P0303 code syndrome. Check engine light flashes while sitting on idle, solid check engine light while driving.

I've had the spark plugs and wires replaced, PCM updated at the dealership ($115.00) to see if that helped, as I've read that there was a TSB indicating that an update on PCM could possibly fix. Still rough idle, still P0303 code.

Dealer wanted another $115 to run a full diagnostic on my cruiser, to see if it was the PCM itself that was malfunctioning and in need of replacement. I declined the full diagnostic as the dealer said that the possibility of the PCM to be at fault is very high and I can purchase a refurbished PCM on the web for $199 and replace myself rather than pay the dealer to replace (but I am waiting to see if I can do other lil repairs prior to having to buy the refurbished PCM.

This weekend I will be taking my cruiser to the shop to have a compression test done and see if its a burnt valve or injector that is causing the rough idle. I'm having him check for vacuum leaks as well as I read that it can also be the cause for the poor idle.

I've read about the carbon deposits that are also common amongst cruisers and dumped a slick50 fuel treatment on a full tank of premium fuel and hope that does something for this problem while I wait for my mechanics visit next weekend.

Anything else I've missed that I can do?

Done list:
- PCM updated
- Spark plugs replaced
- Spark plug wires replaced
- Fuel injector cleaner
- High and Low fan relay replaced (cause I have the "A/C makes my Cruiser stall while on idle problem" idk if that has fixed it as I'm not currently using the A/C)

To do list:
- Compression test
- Vacuum leaks to be checked
- PCM possible replacement
- Maybe throttle position sensor replacement
- Timing belt and water pump will be replaced also very soon as I have 105k miles on it :/

BIG FAN of this Forum, I'd appreciate any advice for my precious wagon!

Last edited by Depeche878; 07 Jan 2012 at 10:56 pm.
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Old 08 Jan 2012, 12:19 am
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Join Date: Mar 2011
Posts: 2,943
Default Re: Another rough idle / P0303 Code thread

Did you take the throttle body out and cleaned it? specially the IAC ?
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Old 14 Jan 2012, 01:31 pm
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Join Date: Jan 2011
Posts: 13
Default Re: Another rough idle / P0303 Code thread

Well, I have checked for vacuum leaks, spark plugs, spark plug wires and the IAC, they all check out fine, still rough idle, did compression test and found that cylinder 3 marks at 90 on the gauge versus 180 of cylinder 1 and 2.

I was told by my mechanic that the engine is going out basically

I think that its time for the wagon to be sold...
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Old 29 Jan 2012, 12:17 am
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Join Date: Jan 2011
Posts: 13
Default Re: Another rough idle / P0303 Code thread

Ok, so I'm not selling my wagon! With my tax refund I am aiming to have valves checked and rebuild my engine if necessary, since the compression of cylinder 3 is 90 units below the other cylinders. So I should have a great Cruiser with a rebuilt engine shortly.

How much would that run me on average? I'm in California.
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Old 30 Jan 2012, 03:42 pm
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Default Re: Another rough idle / P0303 Code thread

With over 100,000 miles, you need timing belt and water pump replaced anyway, ballpark $1,000. With belt off have them take off the head and see what's wrong - probably valves. Rings usually aren't the problem, must likely valves either burnt or not seating right.
"Anti-intellectualism has been a constant thread winding its way through our political and cultural life,
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Traded in '02 Silver Touring Edition w/87,000 miles
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Old 01 Feb 2012, 08:39 am
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Default Re: Another rough idle / P0303 Code thread

Thanks quicksilverdon, yeah I'm hoping that it is a valve problem, Cruiser has been in the shop all day yesterday, hopefully I get some good news today, it's with a trustworthy mechanic, so I am sure that whatever it is that's wrong will be an honest diagnostic.

I will be having the timing belt replaced and other miscellaneous preventive maintenance parts replaced as well.
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