97 F350 460 missing. Need help!!
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97 F350 460 missing. Need help!!
I know there are tons of threads on this here and I’ve stolen advice from them. I’m at a loss though...
Details:
Rebuilt the engine (460) 600 miles ago. Raised compression to 9.5:1 and put comp cams efi compatible cam in, everything else is stock. Engine assembly went great with nothing out of tolerance and EVERYTHING checked twice. The engine never has impressed me after the build and then this misfire showed up and is getting worse. It’s a constant miss, idle or cruising. Very pronounced when loaded..
- Compression test 170-180psi on all cylinders.
- New map sensor
- New tps
- New ICM
- New IAC
- Pulled and checked ECM internals (nothing stood out)
- Vacuum test holds 18.5 in hg (drops to 18 when the engine misfires)
- Fixed all vacuum leaks (two small leaks)
- All injectors are “ticking” (haven’t bench tested them)
- Blocked off EGR to eliminate it for testing
- Only codes I’m getting are 311 (air pump deleted) and 622 transmission solenoid fault. Had both codes on previous engine.
- No shavings in oil indicating a worn off cam lobe.
- No out of the ordinary valve noise
- Spark plugs are all snow white (not sure why it’s running lean but would assume that’s why it’s missing...)
- Fuel pressure checked good at idle with vacuum hose on and off of regulator (aftermarket adjustable unit). Haven’t tested pressure while driving.
- All plugs, wires, cap and distributor are new
Thanks!!
Last edited by Jcstanton; Aug 1, 2018 at 09:02 PM. Reason: Add more info
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By good I meant 40psi with vacuum, 45psi without vacuum.. I don’t have the capabilities as of right now to drive and check at the same time...
Fleet Owner
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40 PSI at idle with vacuum on the fuel pressure regulator is too high. Should be in the 32-35 PSI range. Make sure the plug wires are correctly set for the firing order. Should be 15426378. Keep the wires for 4 and 2 separated as well as 7 and 8 to prevent crossfire.
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wires have been confirmed and have plastic separators on them
Fleet Owner
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Just like the small blocks you need to ensure they are not running directly next to each other. Just because they are in a separator does not necessarily prevent cross fire.
Similar to this:
But for your 7.5L engine make sure 4 & 2 and 7 & 8 are moved as far away from each other as you can.
Similar to this:
But for your 7.5L engine make sure 4 & 2 and 7 & 8 are moved as far away from each other as you can.
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Just like the small blocks you need to ensure they are not running directly next to each other. Just because they are in a separator does not necessarily prevent cross fire.
Similar to this:
But for your 7.5L engine make sure 4 & 2 and 7 & 8 are moved as far away from each other as you can.
Similar to this:
But for your 7.5L engine make sure 4 & 2 and 7 & 8 are moved as far away from each other as you can.
Fleet Owner
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From: Kentucky
One step at a time. I remember my old 460 was prone to crossfire on 7 & 8 due to the sequential cylinder firing. Once I separated the wires further apart I had no more issues. Cheap plug wires tend to make the problem more prevalent. May not be your root cause, but something to verify.
If the problem is still there then start removing a plug wire one at a time to narrow it down to one cylinder, if possible. Swap plug wires if you find the culprit. Could be a simple random misfire from a bad plug wire.If the problem stays to one cylinder then swap plugs. If the problem stays to only the one cylinder then you could be facing a bigger problem.
If the problem is still there then start removing a plug wire one at a time to narrow it down to one cylinder, if possible. Swap plug wires if you find the culprit. Could be a simple random misfire from a bad plug wire.If the problem stays to one cylinder then swap plugs. If the problem stays to only the one cylinder then you could be facing a bigger problem.
Thread Starter
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One step at a time. I remember my old 460 was prone to crossfire on 7 & 8 due to the sequential cylinder firing. Once I separated the wires further apart I had no more issues. Cheap plug wires tend to make the problem more prevalent. May not be your root cause, but something to verify.
If the problem is still there then start removing a plug wire one at a time to narrow it down to one cylinder, if possible. Swap plug wires if you find the culprit. Could be a simple random misfire from a bad plug wire.If the problem stays to one cylinder then swap plugs. If the problem stays to only the one cylinder then you could be facing a bigger problem.
If the problem is still there then start removing a plug wire one at a time to narrow it down to one cylinder, if possible. Swap plug wires if you find the culprit. Could be a simple random misfire from a bad plug wire.If the problem stays to one cylinder then swap plugs. If the problem stays to only the one cylinder then you could be facing a bigger problem.
Fleet Owner
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From: Kentucky
If the fuel pressure is 40PSI at idle and climbs to 45 with the vacuum hose removed then you should be running rich.You need to see what the fuel pressure does under load.
Does the truck have two tanks? Try running on the other. Fuel filter?
Does the truck have two tanks? Try running on the other. Fuel filter?
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2 tanks and the filter has been changed. Nothing changes when I switch tanks. I’ll have to buy an adapter for my fuel pressure gauge to see it in my cab. Filter was pretty nasty when I changed it