Evap system Engine light started flashing?

2003 CHEVROLET S-10
71,000 MILES • 2.2L • 4 CYL • 2WD • AUTOMATIC
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ROBERT WALBROEHL
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Long time battle. Engine light for awhile and then started flashing months ago and code came up for purge solenoid valve which I changed. Truck was not getting past 4000rpm in park and would hang at 45 with no acceleration. Checked for water in fuel and was ok. Changed fuel filter anyway. No help.i did have a cat, evap and O2 sensor fault which I put a fuel additive in the engine with high test gas. Light reset and did not come back.Still no acceleration past 45 mph. Exhaust has a smell. Went to do my weekly run around the block and engine started missing violently with the check light and now code po300. Reset everything and erased code. Ran it again with bad missing at idle and engine light came back on with po303 which is cylinder 3 misfire. I'm wondering if the evap system caused excessive fuel to the engine. Also I cannot fuel truck without the pump clicking off immediately.what can I do to check the evap system. The fuel pressure meter back then was about 60psi which appears good. Someone said to check for blocked vent valve at fuel canister. I am providing a picture of that area with hoses. Should I disconnect some and check for a blockage. If so which ones. Im totally lost with chevy crap. Thanks Bob
Mar 7, 2026 at 4:28 AM

What to check next

Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.

Stop driving while the engine is misfiring severely or the warning light is flashing, and arrange diagnosis. Have the cylinder-three concern investigated through ignition, injector and mechanical checks. Treat the refueling difficulty as a separate diagnostic branch until evidence links the problems.

Guidance references and applicability

2CarPros: Original discussion 1712287 https://2carpros.com/questions/evap-system-60707862 Source for reported history and outcome. Contributor suggestions are not independently confirmed diagnoses. Attachments were not verified. HELLA: Ignition diagnosis https://www.hella.com/techworld/uk/technical/car-electronics-and-electrics/check-ignition-coil/ General misfire diagnostic support, including electrical and mechanical contributors. Example-vehicle values are not specifications for this discussion.

Read the replies · Discussion summary and reported outcome

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CANNON1349
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Hello, these and many other Chevrolets are bad about the carbon canister sending chunks of carbon throughout the EVAP system, and it will prevent you from filling up at the pump. You will very likely need to replace the carbon canister, and any other solenoids you have in your system, and try to blow out all of the EVAP lines while they are disconnected. If you can't clean them out then you will need EVAP lines too. Hope this helps!

William
Mar 7, 2026 at 11:38 PM
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ROBERT WALBROEHL
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So how would the give me a po303 code. Cylinder #3 misfire and what do I do about that. Thanks
Mar 8, 2026 at 1:53 AM
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CANNON1349
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A clogged EVAP system can cause some weird things to happen, but you also mentioned a catalytic converter issue / o2 sensor issue. Both problems can cause sluggish performance but only the EVAP issue will cause the issue at fill-up. With the age of that truck and how strict they were with the emissions at that time, I would just do the catalytic converters with new O2 sensors and be done with it.

William
Mar 8, 2026 at 3:01 AM
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ROBERT WALBROEHL
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Tried one more thing and again things changed. Cleared codes and disconnected the battery for 2 hours. Reconnected it. Started truck again and was missing again but kept it running. Slowly get up to 2000rpm and became pretty smooth. I let it run there for about 7 minute and then slowly brought it black top idle and it intermittently miss again. So Im going to wait till it gets dark and run its and see if any ignition is arcing in the dark. If not I may need to run its a few more times until the code comes back as it did not come up on the last run. What's your thoughts.
Thanks Mr. Williams
Mar 8, 2026 at 7:05 AM
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CANNON1349
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Let me know if you can see anything. The EVAP codes and emissions codes will usually take 2 to 3 trips before they come back on. If you have a vacuum gauge, you can hook it to the intake and put the engine at wide-open throttle to see if the vacuum goes down or not. This would pinpoint whether you have an exhaust restriction or not.

William
Mar 8, 2026 at 10:42 AM
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ROBERT WALBROEHL
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Saw no arcing in the dark. Service engine light came back on with po303 cylinder 3 misfire. What would you do next. Thanks Bob
Mar 8, 2026 at 10:01 PM
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CANNON1349
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Pull the wire off the plug and see if the engine responds. If not then replace the wire(s). I would pull the plug and check the condition also.

William
Mar 8, 2026 at 11:50 PM
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ROBERT WALBROEHL
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Ok thanks
Ill let ya know. Probably time to change wires and plugs anyway
Mar 9, 2026 at 3:31 AM
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CANNON1349
  • ✓Experienced Mechanic
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Just let us know, we'll be here.

William
Mar 9, 2026 at 3:45 AM
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Discussion summary

Evap system Engine light started flashing?

The owner reported poor acceleration, a flashing engine light, difficult refueling and later recurring cylinder-three misfire code P0303. Replacing a purge valve and fuel filter did not resolve the concerns. No visible ignition arcing was found, and plug and wire inspection was proposed.

Reported outcome: No completed ignition inspection or successful repair was reported.

The reported fuel pressure lacked verified test conditions. Neither EVAP blockage nor exhaust restriction was demonstrated. Referenced hose imagery was unavailable, so no hose-disconnection procedure is supplied.

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AI-ASSISTED SUMMARY · REVIEWED BY 2CARPROS
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