Bucking issue cured with 89 octane?

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jseabolt
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Bucking issue cured with 89 octane?

Post by jseabolt »

For awhile my '03 Baja has developed this bucking issue between 2500 to 3000 rpms in 3rd gear puttering along. As if I am taking my foot off the accelerator. It only does this under cruise. Under accelerator it runs smooth and idles smooth.

If I shift and drop the RPMs down a bit it tends to go away. Which requires more foot pressure.

For some reason the problem tends to show up worse after topping off with gas. I thought it might have been water in my fuel but I would think it would have been gone by now.

The other day I decided to try 89 just for the heck of it and it seems to run better.

I've heard everything. faulty TPS, dirty MAP sensor, bad evaporator canister, coked up EGR valve.

I have replaced the fuel filter. Not long ago replaced the spark plugs and plug wires.

This car is a 5 speed and has 77,000 miles on it. Check engine light is not coming on and my ODB II reader is not showing any stored codes either.
http://s222.photobucket.com/albums/dd148/turbofiat/

2003 Subaru Baja
1968 Ford Fairlane 500
1980 Fiat 124 Spider (turbocharged)
1987 Yugo GV (1500 turbocharged)
1981 Trabant 601 S
1987 Citroen 2CV
1977 MGB
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kamesama980
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Re: Bucking issue cured with 89 octane?

Post by kamesama980 »

Why were you using high octane in a NA in the first place?

Running higher octane than required (within what's available at the pump) shouldn't cause any production vehicle issues, I'm just curious.
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
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jseabolt
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Re: Bucking issue cured with 89 octane?

Post by jseabolt »

kamesama980 wrote:Why were you using high octane in a NA in the first place?

Running higher octane than required (within what's available at the pump) shouldn't cause any production vehicle issues, I'm just curious.
I've always ran 87 octane since day one for the past 77K miles. I did run 93 octane to the beach 10 years ago to see if it made any difference.

The only reason I tried 89 was to see if it made any difference.
http://s222.photobucket.com/albums/dd148/turbofiat/

2003 Subaru Baja
1968 Ford Fairlane 500
1980 Fiat 124 Spider (turbocharged)
1987 Yugo GV (1500 turbocharged)
1981 Trabant 601 S
1987 Citroen 2CV
1977 MGB
w.rohr
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Re: Bucking issue cured with 89 octane?

Post by w.rohr »

Mine does the same thing after I fill up and sometimes when I am almost out of gas. I was told it is the fuel purge solenoid (or something like that) but you have to replace some line from the engine to the filler hose. We are going to take a look when I do my suspension hopefully soon and will let you know if it makes a difference.
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kamesama980
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Re: Bucking issue cured with 89 octane?

Post by kamesama980 »

jseabolt wrote:
kamesama980 wrote:Why were you using high octane in a NA in the first place?

Running higher octane than required (within what's available at the pump) shouldn't cause any production vehicle issues, I'm just curious.
I've always ran 87 octane since day one for the past 77K miles. I did run 93 octane to the beach 10 years ago to see if it made any difference.

The only reason I tried 89 was to see if it made any difference.
Oh, OK I misread. I thought you meant you usually run higher octane and recently tried going down, 89's the lowest octane most stations around here.

As for why it made a difference, I doubt the octane did it. maybe the added detergents cleaned up some gunk from the port or chamber? (most stations mix low and high octane juice in the pump to get the mid-octane so they only need to maintain 2 tanks)
-Russell
"You don't get to judge me for how I fix what you break"
03 sport 5mt
05 turbo 5mt vf39 and other STI bits, 3" turbo-back
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