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Discussion Starter #1
need help guys. my 1990 5.8 is running really rough and rich,i mean rich!! this just started about 3 days ago. egr valve, fuel pressure reg. iac valve, tps, and everything related to air- fuel has been replaced exept fuel pump and injectors. it sounds like it is missing but when i get on the gas it responds. it will also start jerking and at hwy. speeds. steve 83 mentioned something about a loose timing chain. i tried adjusting the timing to see if that help. it raised and lowered the rpm's but didn't help with the missing. also spark plugs and wires and rotor and cap are about a year old. thanks in advance for any help.
 

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Ex Navy Nuke
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5,420 Posts
What about the O2 sensor? That's the most likely cause of a rich condition(also the ECT). Have you pulled codes?
 

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Discussion Starter #3
forgot about that. i changed it around the same time as everything else
tried pulling the codes but didnt have any luck. think it has something to do with my ignition. i'm having to jump it right now because my ignition is screwed. i've been waiting for this warm weather to fix it. if it isn't one ting its another:banghead
 

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maybe a fouled plug my bronco did the same thing the jerking replaced plugs that was only 8 months old and havent had any problems since
 

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Discussion Starter #5
i'm leaning toward the spark plugs or wires myself. a friend of mine said he had the same thing happen to him. hope it's something simple like that.
 

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Check the vaccum line to the MAP sensor to see if it has vaccum(it should).The map sensor is located at the left upper area of the heater plenum with a 1/4" plastic vaccum line with a short piece of rubber vaccum hose attached to it,the other end is attached to the upper intake manifold beside the brake booster hose.
 

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Discussion Starter #7
listen guys. i really appreciate all the suggestions. cant tell ya'll how much time and headache this site has saved me.
 
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