1986 F150 Mystery
11-30-2007, 12:32 AM
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1986 F150 Mystery
Hello everyone, I'm new to this forum, but not new to fords, so hopefully sombody can help me with this
I just inherited an 86' F150 with a 302 EFI, 2 wheel drive extended cab shortbed from my dad.
The reason he gave it to me was because it has a problem no mechanic can figure out. I went with him to at least 15 mechanics and every single one said they can't fix it. But personally I'm not so eager to give up...
Basically, at idle it runs perfect. you can rev it up and sounds great, but when driving it, it's a totally different story. after you start to go above 2000 RPM's it cuts out and kinda sputters with an occasional backfire, with the end result of it dieing. But if you stop and put it in nuetral, it drives fine until you go over 2000 RPM's again. Anybody have a clue?
PS It has a new motor, new transmission, rebuilt I-beam, New rear end, and new fuel pressure regulator Thanks in advance!
I just inherited an 86' F150 with a 302 EFI, 2 wheel drive extended cab shortbed from my dad.
The reason he gave it to me was because it has a problem no mechanic can figure out. I went with him to at least 15 mechanics and every single one said they can't fix it. But personally I'm not so eager to give up...
Basically, at idle it runs perfect. you can rev it up and sounds great, but when driving it, it's a totally different story. after you start to go above 2000 RPM's it cuts out and kinda sputters with an occasional backfire, with the end result of it dieing. But if you stop and put it in nuetral, it drives fine until you go over 2000 RPM's again. Anybody have a clue?
PS It has a new motor, new transmission, rebuilt I-beam, New rear end, and new fuel pressure regulator Thanks in advance!
11-30-2007, 01:41 AM
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do you have fouled plugs? mine ran like crap when i was driving and it was sputtering when i got on the gas...i bought new el cheapo autolite plugs and now its a lot more consistent...mine were sooo disgusting...
11-30-2007, 06:24 PM
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Actually thats the first thing i did, i changed out the plugs, plug wires and rotor cap. I also changed the fuel filters and all the fuel pumps. External and inside the tanks
PS I have a dual tank setup
PS I have a dual tank setup
11-30-2007, 06:55 PM
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might have something to do with your efi module, on a carb, the idle screw controls the fuel flow to about 2k rpms and then another one controls after that, i donno if that second section of your ignition module is messed up or what...i would try a new ignition module if i were you...its under 50 bucks i think, for my 351w it was 25 bucks...
*shrug*
*shrug*
11-30-2007, 07:33 PM
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Have you checked the catalytic converter? One of the failure / blockage modes is that the higher RPMs become limited.
One check is to feel the exhaust - if all you feel is a steady flow with no slight pulsing from the cylinders - much like the breeze from a shop-vac outlet - then the cat bears further investigation.
If it can't get the exhaust out, it can't get the air in.
*edit* but surely any mechanic worth his salt would've checked this???
Also, are you SURE the timing is right with the new motor??? Verify TDC of the #1 cylinder against the timing mark, made sure to pull the SPOUT connector when setting timing.
One check is to feel the exhaust - if all you feel is a steady flow with no slight pulsing from the cylinders - much like the breeze from a shop-vac outlet - then the cat bears further investigation.
If it can't get the exhaust out, it can't get the air in.
*edit* but surely any mechanic worth his salt would've checked this???
Also, are you SURE the timing is right with the new motor??? Verify TDC of the #1 cylinder against the timing mark, made sure to pull the SPOUT connector when setting timing.
Last edited by wde3477; 11-30-2007 at 07:37 PM. Reason: added comment
11-30-2007, 08:09 PM
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I know for sure that the exaust system is good, i had a test run at a local shop and they said it was better than a new car.
I recently had the timing replaced, but since that was done i have had nothing but trouble... and before that the Distributor and ignition module were changed out by the same place.
And at that, I dont feel right about the distributor, the auto shop said they had to jam the plugin on the ignition module for it to work, which sounds to me like they put the wrong one on. the bastards charged me $700 for it too.
I'll check the timing tommorrow, thanks for your help guys...
I recently had the timing replaced, but since that was done i have had nothing but trouble... and before that the Distributor and ignition module were changed out by the same place.
And at that, I dont feel right about the distributor, the auto shop said they had to jam the plugin on the ignition module for it to work, which sounds to me like they put the wrong one on. the bastards charged me $700 for it too.
I'll check the timing tommorrow, thanks for your help guys...
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12-01-2007, 10:53 PM
#8
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Hmm, this is getting to be a challenge - especially since 15 mechanics have looked at it up close and personal.
Fuel, spark, air, timing - pretty much as to fall in one of those categories.
It appears that the problem occurs under load. If I understand things right - it revs freely while under no-load - at standstill.
That suggests to eliminate spark and timing - leaving fuel and air flows. Perhaps check the fuel rail pressure??? Any chance the timing chain has jumped?
Fuel, spark, air, timing - pretty much as to fall in one of those categories.
It appears that the problem occurs under load. If I understand things right - it revs freely while under no-load - at standstill.
That suggests to eliminate spark and timing - leaving fuel and air flows. Perhaps check the fuel rail pressure??? Any chance the timing chain has jumped?
12-02-2007, 12:17 AM
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15 mechanics, eh? I don't think there are 15 mechs in my whole town! LOL
Sounds like weak fuel pressure to me. Hae you checked the pressure and compared it to specs?
Good luck, and let us know what you find out.
Dan Harriman 84 F150 lwb
Orange, Texas
Sounds like weak fuel pressure to me. Hae you checked the pressure and compared it to specs?
Good luck, and let us know what you find out.
Dan Harriman 84 F150 lwb
Orange, Texas
12-02-2007, 01:38 AM
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I think its fuel pressure too, but what else do I need to change out?!?!?
Like I said, I changed out all the fuel pumps, the fuel pressure regulator, and even had all the lines cleaned out. It's apparently not an easy fix.
If I dont figure it out soon, I guess I'll just take it down to Ford, let it sit in line for a month and have them empty my bank account...
On another note, could it be something electrical? maybe theres a short somewhere thats making it cut out? any suggestions?
Like I said, I changed out all the fuel pumps, the fuel pressure regulator, and even had all the lines cleaned out. It's apparently not an easy fix.
If I dont figure it out soon, I guess I'll just take it down to Ford, let it sit in line for a month and have them empty my bank account...
On another note, could it be something electrical? maybe theres a short somewhere thats making it cut out? any suggestions?