upper rpm sputtering

SleeperLS

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Oct 19, 2008
14,355
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West of the Mississippi
I got my e85 conversion done as well as some P&P heads with 1.8rr. The car was running great for about 2 days and then this morning it started to sputter really bad in lower rpm and as the day progressed the car only sputters in the upper rpm range.

My hpt is showing no misfires, and I just checked the plugs and wires and gapped plugs to .045. I just changed the flex fuel filter to see if the other one was clogged, and it hasn't made a difference. The car doesn't lean out when the sputtering happens and there is no loss in fuel pressure or boost. The knock will shoot up if you stay in it too long while it sputters. Anyone have an idea on what I should check next? Thanks, Andy C.
 

M@

Somebody buy this thing
Nov 26, 2007
2,871
2
if you have the P0300 code turned off in the PCM for the cam, the PCM will no longer report misfires when they occur.
So, if that code is disabled for the cam, as I suspect it is, you probably ARE misfiring badly, and it's just not being reported by the PCM.

Misfire issues are generally due to the wires on these things, replace those first and see if that helps. Do you have a wideband? What AFR is being reported?
 

SleeperLS

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Oct 19, 2008
14,355
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West of the Mississippi
thanks for the help, I will see if that code is on or off. I noticed that there is no change in wideband, or fuel pressure readings when this occurs.

This morning I woke up and had to head out in a hurry without letting the car warm up that much and the sputtering occured with just over 1800rpm. As the car warmed up a bit more the sputtering only happened at about 4000rpm or so. As the day went on yesterday, the longer I drove the more rpm I could go up without sputtering.

Any chance of a gasket that leaks and then swells as it gets hotter?
 

Sinister Drag Designs

SinisterDragDesigns.com
Aug 3, 2007
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Chicago, IL
check your coil packs for rust or crap that builds up on them. 97-03 coils dont have the same rust protection on the terminal ends as the 04+ cars.
Take some sand paper or a piece of steel wool and scuff it if there is any. We have fixed quite a few cars that had a similar problem this way after a plug and wire change. You said you checked the plug? Did you replace it or just clean it up and put it back in?
 

SleeperLS

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Oct 19, 2008
14,355
8,187
West of the Mississippi
I checked the plug terminal, it was clean. I checked the plug and it looked brand new pretty much; not noticeably lean at least. It only had about 600 miles on it. I changed and re-gapped the plug and I still have the sputtering.

While I was messing with this, I discovered a coolant leak so I am thinking that is the intake gasket. I haven't located the exact part of the motor that leaks, but could there be coolant leaking into the cylinder heavily when the gasket is cold and allowing a stronger leak to occur? Then, It only sputters in the upper rpm when it gets warm and this is because the gasket has swollen up and is only allowing enough coolant in to misfire #6 at 5000rpm plus. Might also explain why the plug looked brand new, a ghetto form of direct port water injection.

Any thoughts?
 
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