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  #1  
Old 07-18-2005, 12:40 PM
DavieGravy DavieGravy is offline
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Rough engine, bumpy idle, poor gas milage and no pep

Hi folks.

Just recently, the old svx has started acting up all of a sudden. At idle and RPMs below about 2500, the engine shakes and runs really rough. If I'm on the highway and hit the gas, the whole car vibrates. When I let my foot of the gas, it smoothes out.


On my 40 some odd mile trip to work this morning, it emptied about a 3rd of its tank of gas.

Taking off from a stop, there's no pep what so ever.

My first thought was that it's mis-firing, but I filled it up at a gas station I don't usually go to, so I'm wondering if it could be a bad tank of gas. I've had bad petrol before, but it's never caused problems as severe as this.

Does this sound like a familiar problem to anyone?
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  #2  
Old 07-18-2005, 12:54 PM
red95svx
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It could very well be a really bad tank of gas. It also sounds like a bad O2 sensor. Do you have a check engine light on? It could also be some sort of intake leak. My mom's Legacy had similar symptoms from a worn intake gasket.




Dave



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  #3  
Old 07-18-2005, 03:53 PM
DavieGravy DavieGravy is offline
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Thanks for the reply. I have no error lights nor does the power light blink during startup.
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  #4  
Old 07-18-2005, 04:11 PM
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My friends car had similiar symptoms when he had a bad MAF.
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  #5  
Old 07-18-2005, 05:40 PM
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it sounds like a misfiring coil to me. it could also be bad gas, a bad maf or maybe your timing belt skipped a few teeth. just somethings to check. good luck
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Old 07-18-2005, 07:04 PM
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Sounds like a bad MAF to me too.
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  #7  
Old 07-18-2005, 07:48 PM
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Let us not forget simple things either. Maybe, you're looking at poor spark plugs, dirty air filter, dirty oil, worn fuel pump and/or filter. You might also want to check your idler pully; that could cause rough idle .
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Old 07-18-2005, 08:16 PM
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I'd be more inclined to look for things that would affect all cylinders rather than a spark plug, a coil, etc. Individual cylinder failure wouldn't cause near the problem you're describing. A bad MAF or a hose falling off between the MAF and t-body are likely candidates.

A bad air filter, dirty oil? Come on. I know the idler pulley was a joke but actually it holds more plausibility than the air filter and the oil.
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  #9  
Old 07-18-2005, 09:31 PM
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Have you tried pulling codes from the ECU?
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  #10  
Old 07-19-2005, 04:42 AM
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Quote:
Originally Posted by Beav
A bad air filter, dirty oil? Come on. I know the idler pulley was a joke but actually it holds more plausibility than the air filter and the oil.
Actually, I wasn't joking . Those things could be definite causes though. If you think about it; if your engine is running rough, that could be due to the air/fuel mixture being injected into the combustion chamber being to thick or too lean, and that would cause a misfire (in a performance car like an SVX, that would defintely be noticable). Or; if your spark plugs were toast, the spark used to ignite that mixture could not be enough to cause full combustion of that thick or lean air fuel mixture. (It would be a thick gas mixture in the case of grimy nasty airfilter)

I threw dirty oil in b/c if the oil is nasty; the crankshaft could not move correctly and this could cause shuddering. (Mind you, we're talking oil that is years old; not months)

I may be a bit on the younger side. However, I find that a lot of car problems are caused by simple things; not by problems that require $400 worth of work.
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Mods: DDM Tuning 4500k 35w Low Beam HID, 100w H3 Bulbs, Extra Ground Cables, 15 minute $12.96 mod,
svxfiles designed transmission mount (), sporting a "new" tail light bar,
silver BBS rims, custom power steering cooler (one that doesn't dump ATF constantly), new negative lead cable, no more third or fourth gear
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Last edited by Manarius; 07-19-2005 at 04:49 AM.
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  #11  
Old 07-19-2005, 06:34 AM
red95svx
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Originally Posted by Manarius
Actually, I wasn't joking . Those things could be definite causes though. If you think about it; if your engine is running rough, that could be due to the air/fuel mixture being injected into the combustion chamber being to thick or too lean, and that would cause a misfire (in a performance car like an SVX, that would defintely be noticable). Or; if your spark plugs were toast, the spark used to ignite that mixture could not be enough to cause full combustion of that thick or lean air fuel mixture. (It would be a thick gas mixture in the case of grimy nasty airfilter)

I threw dirty oil in b/c if the oil is nasty; the crankshaft could not move correctly and this could cause shuddering. (Mind you, we're talking oil that is years old; not months)

I may be a bit on the younger side. However, I find that a lot of car problems are caused by simple things; not by problems that require $400 worth of work.

Dirty oil? Dirty air filter? Old spark plugs? Come on. I see dirty filters and rotten spark plugs all day long. They don't cause problems like this. They cause excess fuel consumption and higher emissions, maybe a rough idle but not rough shaking at highway speeds.The sudden onset also points to faulty sensor or an intake leak of some sort....something that can happen suddenly and instantly cause problems. Dirty filters and plugs gradually decrease performance. And I've never heard of dirty oil causing crankshaft "shuddering"



Dave (running to add crankshaft anti-shudder additive to my oil)
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  #12  
Old 07-19-2005, 03:41 PM
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Quote:
Originally Posted by red95svx
And I've never heard of dirty oil causing crankshaft "shuddering"

Dave (running to add crankshaft anti-shudder additive to my oil)
I said in extreme cases. He didn't note had long it had been since he changed oil. If ithe oil is years and years old, who knows how it's going to act.
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(8/23/07-Present) 1995 Subaru SVX LSi (197k) Polo Green (#1102) 03/95
Mods: DDM Tuning 4500k 35w Low Beam HID, 100w H3 Bulbs, Extra Ground Cables, 15 minute $12.96 mod,
svxfiles designed transmission mount (), sporting a "new" tail light bar,
silver BBS rims, custom power steering cooler (one that doesn't dump ATF constantly), new negative lead cable, no more third or fourth gear
(1977-Present) 1977 Chevrolet Corvette (81k) Silver
(12/01/2011-Present) 2005 Subaru Outback 2.5i Limited 5MT (97k)
I have a bad feeling about this.
-Obi Wan Kenobi
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  #13  
Old 07-19-2005, 05:51 PM
oab_au oab_au is offline
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I might be a bit on the older side, and still make mistakes.

Becides all the things that Manarius suggested, I would check the ground wire at the back of the engine, below the throttle bodies, it runs to the firewall below the ignitors. The MAF meter could be suspect, along with the air pipe between the MAF and throttle bodies.

Harvey.
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  #14  
Old 07-20-2005, 12:31 AM
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plugs or coils my problem was similar 6 months ago.
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  #15  
Old 07-20-2005, 02:16 AM
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i'm still aiming towards coil.
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