Too much fuel
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Junior User
Joined: Feb 2009
Posts: 85
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From: Mountains of VA.
Too much fuel
I have a '90 f-150 with 300. It is getting too much fuel. Puffs black smoke at idle and when you step on the gas pedal it sputters and puffs smoke. Has been in the shop for 4 weeks. Mechanic has about 30 hrs on this problem and can't figure it out. He has changed ALL sensors and even took a computer out of another identical truck and nothiing changes. He says injectors are staying open about 8 miliseconds at idle compared with 4 miliseconds on another truck that was running normally. He says if you create a vacuum leak idle smoothes out but still can't drive it. When vacuum leak is corrected you can watch the computer gradually call for injectors to start staying open longer.He is a good mechanic but this one has him stumped. Anybody have any ideas?
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
I hate to ask, but what is the fuel pressure? Has the FPR been checked for to high of fuel pressure? I've heard of people having similar problem but with 90psi fuel pressure. This sounds plausible hence swapping PCMs didn't change injector pulse time. Have you and mechanic opened your PCM and checked the main circuit board? Throw us some more info and we'll try to help ya out.
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Junior User
Joined: Feb 2009
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From: Mountains of VA.
Pretty sure he told me he had checked fuel pressure and it was normal, however I don't recall the exact pressure. We have talked about it so much I can't remember all the stats. Truck does not act up all the time. You might crank it up and drive it a couple miles before it craps out. Next time you crank it it runs crappy from the start. When we drove it to the shop (about 5 miles) it ran good about first 1 1/2 miles then crapped out. Had to go to 2nd gear for a ways because it wouldn't pull itself in 3rd then it cleared up for 1/2 mile or so then back to sputtering again then cleared up and ran good last couple miles to shop. Mechanic has had same results while test driving vehicle.
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Junior User
Joined: Feb 2009
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From: Mountains of VA.
PCM has not been taken apart. Mechanic could not talk to first PCM that was in the truck. Truck originally had E4OD in it. We swapped tranny to 5 speed manual. Had been running truck for about 3 yrs with the E4OD selector switch still on the truck fixed in the neutral position. When his test equipment couldn't communicate with PCM we took PCM from another parts truck same yr model with 4.9 4 speed manual trans. Truck runs as bad with one PCM as it does with the other. He also says that even with truck flooding itself out the O2 sensor is showing a lean condition.
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