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Discussion Starter · #1 ·
Font Screenshot Number Electric blue Parallel

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I'm having a misfire on cylinder 3. I've replaced the plugs, wires, cap, rotor, and distributor, also the upper plenum. No vacuum leaks. Under load it will misfire as seen in the freeze frame photos. When I come to a complete stop, sitting in neutral, clutch out. The idle will start to fluctuate. It'll drop low down to 100 if not lower almost stalling before throwing it back up to 1100. If I'm rolling at all. Doesn't matter the speed it won't fluctuate. But as soon as my wheels stop the idle drops and she wants to die. I've spent a fair amout of time on this forum. Looking into this. It seems to be a wide spread issue but nobody has the answer.
Appreciate you taking your time to read. If you've got any information, much appreciated.
 

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I have no idea why you are in Open Loop while driving, but that might point to the issue. Not sure. You should be in Closed Loop on the highway. If you changed your plugs/ wires and are still getting a specific misfire on a bank I would assume that valve keeper is done for. You can try AT-205 as a quick remedy to help reseal the valve keeper, but if that doesn't work, it might be toast and the engine would need to come apart for it to be replaced. Along with the rest while you're at it...
 

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2001 Spyder GT
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P0303 is pretty specific, so start there. You've already replaced your #3 spark plug, #3 wire, and distributor cap. Next is troubleshooting the injector; then your compression.

Use a noid light to verify the injector is getting electrical signal. Then check the injector resistance is 13-16 ohms.

If that's all normal, do a wet and dry compression check, and then a leak-down check, on all cylinders. That will tell you if there's leaking past the rings or the valve seals.
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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Yeh...I'd go for an electrical problem first, but there are other issues. Should be pretty easy. Just one cylinder to diagnose. ...J.D.
 

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Discussion Starter · #5 ·
P0303 is pretty specific, so start there. You've already replaced your #3 spark plug, #3 wire, and distributor cap. Next is troubleshooting the injector; then your compression.

Use a noid light to verify the injector is getting electrical signal. Then check the injector resistance is 13-16 ohms.

If that's all normal, do a wet and dry compression check, and then a leak-down check, on all cylinders. That will tell you if there's leaking past the rings or the valve seals.
I'll start with that Injector. Appreciate the insight.
 

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2001 Spyder GT. Koni adjustable shocks. cold air intake, ST sway bar.17X8.5 rims. LED headlights.
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566 Posts
The good thing about having a code like PO303 is it tells you what is NOT the problem. You can eliminate anything that all the cylinders have in common. ...J.D.
 
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