Transmission? Diagnosing problem
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Transmission? Diagnosing problem
Ive got an 86 bronc 351FI.
Engine and transmission are still stock.
Heres the symptoms, When I start the truck in the morning, It turns over and idles around 1200 rpm for a few seconds...then it all of the sudden dies. In order to keep it running I have to keep the rpm up by reving, around 1200-1500rpm or so. After about 10-15 minutes the engine all of the sudden picks up rpm. I dont move my foot, Keeping it steady around 1500....then all of the sudden it jumps to 2000. At this point, I can drive it. Drives around fine, but at the 40-50 mph area when it shifts into over drive (last drive gear), Its still running good until I come to a stop...then the truck starts putting and will die. In order to prevent this...I shift into neutral for a few seconds...then its fine again. If i dont make it to that gear, it runs just fine. It seems like its having trouble shifting out of the lower gears. Does anyone know what these problems are? It seems to me that its an unusually long warm up time. Maybe give me a starting point? I just bought the truck, so fluid flushes are still to come. Thanks alot.
Engine and transmission are still stock.
Heres the symptoms, When I start the truck in the morning, It turns over and idles around 1200 rpm for a few seconds...then it all of the sudden dies. In order to keep it running I have to keep the rpm up by reving, around 1200-1500rpm or so. After about 10-15 minutes the engine all of the sudden picks up rpm. I dont move my foot, Keeping it steady around 1500....then all of the sudden it jumps to 2000. At this point, I can drive it. Drives around fine, but at the 40-50 mph area when it shifts into over drive (last drive gear), Its still running good until I come to a stop...then the truck starts putting and will die. In order to prevent this...I shift into neutral for a few seconds...then its fine again. If i dont make it to that gear, it runs just fine. It seems like its having trouble shifting out of the lower gears. Does anyone know what these problems are? It seems to me that its an unusually long warm up time. Maybe give me a starting point? I just bought the truck, so fluid flushes are still to come. Thanks alot.
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Transmission problem?
What makes you think this is a transmission problem? Sounds to me more like fuel injection problem. My son's 90 Bronco with the 351 FI had a similar problem...turned out to be the IAC...a simple repair...I think I paid about $15 for a new one, but partsamerica shows it at about $85, so shop around...I think you can clean those out...check the fuel injection threads and you might get a better idea...good luck.
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I figured tranny, because it seempt to be sticking...even though if driving in first and second gear is normal, then going into gears any higher than that...it dies... How is that fuel injection problem.? Maybe its right under my nose. Anyways, Thanks for the lead.
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I'm no mechanic, but just by the sounds of, I would get it would be a fuel injection problem as well. On my newer 5.4L V8 I had a similar problem and it was one my injectors. After my dealership fixed it the first time it ran fine until 40-50mph where it seemed to have trouble shifting into overdrive, and I would either have to give it a lot of gas or slow down to avoid the shift. That was one of my coil packs, I think that your '86 351FI would still have spark plugs though. When my coil pack went it was actually my heater core which made my computer act up causing the coil pack to go. But on the older ones you don't have to worry about that so much.
I don't know if I've been any help at all, but there you go.
I don't know if I've been any help at all, but there you go.
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From: just outside of Phila.
I would give it some Seafoam through the gas tank. It's a metal can and it's about $5. It's a start, and a much cheaper start then taking things apart...never hurts. Give it a shot, and if it doesn't work--and it may not...who knows--then start with parts and stuff.
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Why a fuel injection problem instead of maybe a transmission problem? I just figured that anytime the rpm dropped (which can happen for a variety of reasons...computer adjusting to cold, rapid drop in rpm due to delay in upshift/downshift, maybe even heavy load) if there isn't enough air getting into the combustion chambers, it's gonna stall...lots of gas, not enough air maybe due to a malfunctioning or clogged IAC (Idle Air Control)...equals stall. Hey, what if you spent a grand replacing the tranny, then it still stalled? All I'm saying is I got a year of good performance after changing the IAC before the real tranny problems started up...vibrations, shudders, etc. Best of luck! For all we know, it could be something totally random, like a clogged fuel filter (passenger side, midway, on '90s...couldn't hurt!).
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Originally Posted by farklevill
Why a fuel injection problem instead of maybe a transmission problem? I just figured that anytime the rpm dropped (which can happen for a variety of reasons...computer adjusting to cold, rapid drop in rpm due to delay in upshift/downshift, maybe even heavy load) if there isn't enough air getting into the combustion chambers, it's gonna stall...lots of gas, not enough air maybe due to a malfunctioning or clogged IAC (Idle Air Control)...equals stall. Hey, what if you spent a grand replacing the tranny, then it still stalled? All I'm saying is I got a year of good performance after changing the IAC before the real tranny problems started up...vibrations, shudders, etc. Best of luck! For all we know, it could be something totally random, like a clogged fuel filter (passenger side, midway, on '90s...couldn't hurt!).
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Posting Guru
Joined: Jun 2004
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From: just outside of Phila.
the fuel filter? Just pop it off and get a new one. It doesn't require any tools, and it is easily explained in the Haynes manual. Just be prepared for gas coming out, and pop the inertia switch underneath of the dash on the driver side (also explained in the manual) to relieve fuel pressure before hand. I'd still run some seafoam in the tank, especially if you're going to change the filter. It's cheap and it works.
BTW-just read post date, did you do this? how'd it go?
BTW-just read post date, did you do this? how'd it go?
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