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1G Mitsubishi Eclipse - Runs Rich, Throws Codes - Point me in the right direction please

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Mar 5, 2018, 12:43 PM

Post #1 of 2 (583 views)
1G Mitsubishi Eclipse - Runs Rich, Throws Codes - Point me in the right direction please Sign In

Howdy! I need a little help getting me pointed in the right direction to properly diagnose a problem(s) with a 1990 Mitsubishi Eclipse (base model, 1.8L) that I've taken on as a bit of a project car learning experience with my kids who are getting to driving age. This car had been sitting in a field for about 12 years. We've got it running fairly good; have replaced the fuel pump & strainer, fuel filter, spark plugs and other basics, but it's running pretty rich: black smoke and unburnt fuel odor from the exhaust and heavy carbon fouling on all spark plugs. Starts easy enough, but rough idle below 1K RPM and can be a hesitant or pulsey at certain RPMs. Seems to be missing too. It's also throwing OBD1 codes for the MAF sensor, intake air temp, air pressure, coolant temp and idle speed control motor position sensor. I believe some or all of these are false-positive as I've replaced the coolant temp sensor and had temporarily replaced the MAF with a new unit and got no better result. Haven't found any obvious vacuum leaks, but admittedly I need to pursue that more.

I have to think that since it's sat so long this is likely a fuel injector issue gunked up with old gas residue (wasn't drained when it was resting for a decade), but don't want to invest $$ in new injectors just to throw parts at the problem without some more qualified advice. Haven't checked fuel pressure as I'm trying to track down a gauge for this (no schrader valve on the rail to make this easy) and I kinda checked the fuel pressure regular to make sure it wasn't clogged (just disconnected the return line to see if it'd flow gas through when under pressure).

'Back in the day' I used to be a bit of a gearhead when the most complicated emissions device on my hotrodded Vega (yes, a Vega with an early 60's Buick V8) was the PCV. Then life and career happened and didn't keep up with cars in this respect until my kids got to the age that they're renewing my interest. But that's not helping the skillset...

Any advice is greatly appreciated!

Hammer Time
Ultimate Carjunky / Moderator
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Mar 5, 2018, 12:53 PM

Post #2 of 2 (576 views)
Re: 1G Mitsubishi Eclipse - Runs Rich, Throws Codes - Point me in the right direction please Sign In

There is no such thing as a false code unless you caused it yourself by unplugging something with the key on.

You need to get to the bottom of those codes. Having a code referring to a specific component DOES NOT mean that component is bad. It merely means there is an issue with that circuit that needs to be further diagnosed.

Unless you understand how these sensors send signals and can read a wiring diagram, this could be a very long and expensive diagnosis.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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