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‘89 300 i6 running rich.

Old 04-15-2018, 11:15 AM
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Default ‘89 300 i6 running rich.

The motor in my truck is running rich and it also cranks for a long time before starting, and the idle likes to go up and down. The air filter, idle air control valve, MAP sensor, spark plugs, distributor cap/rotor, fuel pumps, dual function reservoirs, throttle plate, and fuel filters have all been replaced within the last two years, but nothing we do seems to fix the problem.
Maybe someone has had this problem before and knows what I’m forgetting to replace. I really just need any suggestions on what could be causing this problem.
Each part we replaced is one that showed signs of wear and age. But I’m guessing there are more parts that I am not noticing wear on. The truck only has 75,000 miles on it so when I first got it most of the parts were originals, and sitting for so long is the reason many of them went bad.

Last edited by Shagg; 04-15-2018 at 05:06 PM.
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Old 04-15-2018, 04:44 PM
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You're forgetting to DIAGNOSE the problem. Replacing parts is NOT diagnosis; and as you're learning, it's not repair, either. Factory parts are generally MUCH more reliable than replacements, so replacing parts often results in MORE problems. And there are MANY grades of replacement parts - are you using Ford/MotorCraft or other high-quality name-brand parts? Or are you buying the cheapest ones you can find? It matters. For each part, list the brand, PN, source, & when (date/miles) it was installed by whom for what reason.

So does the truck's history, and COMPLETE description. Click this, read the whole caption, study your truck, and then fill in your signature so we can see everything with each of your posts:


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Old 04-16-2018, 01:33 PM
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First thing is to check codes.Second which won't cost anything is to see if raw gas is present in the vacuum line going to the fuel pressure regulator.

Last edited by raski; 04-16-2018 at 01:37 PM.
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Old 04-16-2018, 09:10 PM
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Originally Posted by raski View Post
First thing is to check codes.Second which won't cost anything is to see if raw gas is present in the vacuum line going to the fuel pressure regulator.
Ive has it checked for codes, and everything came up fine. But I’ll be sure to check the vacuum line for gasoline. I never really thought to try that.
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