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1996 Eclipse GS Code 300/1255: Is It Fuel Quality or Engine Misfire?

Model: 1996 Eclipse GS Fault Code: P1255 Posted: 2010-04-05 17:26

My 1996 Eclipse GS started stuttering and popping about a quarter mile after filling up. I managed to drive it home, but had to feather the throttle to avoid stalling. The check engine light came on during the drive (code 300, also referred to as code 1255). I've already replaced spark plugs, ignition coil, wires, and checked all wiring connections. I recently purchased a new ECM, hoping it would resolve the issue—but the problem persists. I'm now wondering whether bad fuel could be causing this misfire. Can poor-quality gasoline trigger code 300? Is it more likely a fuel-related issue or a spark problem? Additionally, how can I properly inspect the EGR valve? If it's stuck, would that cause multiple cylinder misfires (code 300)? I also noticed a hum from my ECM after replacing an 80-amp fuse near the unit—this occurred when I accidentally shorted hot wires while changing the alternator belt. The car had been running perfectly until then. I'm now concerned about whether the fuel system or electrical components are at fault.

Related fault codes

P1255

Comments (5)

Anonymous 2010-04-06 11:01

If the issue started after refueling, it's worth checking the fuel pump and pressure before replacing the ECM. Does your fuel look unusual in color? Both poor fuel quality and a stuck EGR valve can trigger code 300—so both should be considered.

Anonymous 2010-04-07 04:14

The fuel pump is only three weeks old (Walbro 255 HP), and the fuel filter (Blox 12:1 FMU) is also new. The engine has a T3/T4 turbo with 7 psi boost via wastegate, a Blox MAP bypass valve, and an AEM wideband kit for air-fuel ratio monitoring. During a late-night repair on the side of the road, I accidentally shorted two hot wires from the alternator, blowing the 80-amp fuse near the ECM. The next morning, I heard a humming noise coming from the ECM—something I hadn't noticed before. That’s why I replaced the ECM. There are two relays on the firewall near the brake reservoir—I’m unsure of their function, but they may control fuel pump shutdown. The car had been running perfectly prior to this incident.

Anonymous 2010-04-07 21:38

Finally found the root cause—$1200 and three days later under the hood. I removed the fuel pump and inspected the tank. There’s about an inch of gasoline floating on top of a layer of water. On Sunday morning, I filled up to drive to a family gathering about one hour away. The car stalled after just one mile into the trip. I’m now waiting for the insurance adjuster from the station to arrive so they can assess damages.

Anonymous 2010-04-08 05:25

That sounds like exactly what happened—great to hear you finally found the issue! Sorry about your bad luck, but thanks for keeping us updated. It’s clear this is a solid car with some serious mechanical challenges!

Anonymous 2010-04-08 14:31

For reference: we’ve seen similar issues before. In cold or warm weather conditions, fuel can separate due to thermal shock—especially since U.S. fuels must contain at least 10% ethanol. When stored fuel (e.g., at 50°F) is exposed to colder outdoor temperatures (like 10°F), the ethanol may separate from gasoline and cause engine failure because most vehicles won’t run on pure ethanol. The common fix involves adding dry gas and aggressively rocking the vehicle to help reabsorb the ethanol into the fuel stream. I haven’t tried it yet, but this is valuable information for others facing similar issues. This doesn't confirm what happened here—but it's worth sharing as a potential cause.