Misfire Problem
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Freshman User
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Misfire Problem
So I bought a 92 F250 and the guy had the motor in the truck that overheated and blew rebuilt. According to the receipt they put new heads on because they were warped and machined the block and did new bearings etc. now I have a misfire so I went and bought plugs, wires, cap and rotor and a coil. I found a melted wire and I just assumed that it was the issue. When I changed the wires I noticed that whoever built the motor did a “custom” firing order and I replicated the same thing. Doing the tune up made no difference. So I then said ok let me pull a plug wire and see if it misfires, I pulled number 4 off of the cap and I heard no difference so I’m thinking the misfire must be worse than before. Question being, are there any common problems? I believe all the gaskets were changed. I do have a high idle issue with the throttle body getting stuck but It goes back manually and I am in the process of rebuilding it. Other thing is a small exhaust leak. But I don’t know if it is causing this. Any thoughts? Thanks
Lead Driver
Joined: Jan 2019
Posts: 5,082
Likes: 865
From: N.W. Alabama
What motor, with motor at operating temp, check for codes, even if CEL(check engine light) isnt on, could have stored codes, most of us use the Innova 3145 OBDI, but you can use a paper clip, see link below.
Fuel Injection Technical Library » How To Run a Self-Test
(16) How to read a check engine light code on a Ford 1983-1995 EEC 4 system - YouTube
Fuel Injection Technical Library » How To Run a Self-Test
(16) How to read a check engine light code on a Ford 1983-1995 EEC 4 system - YouTube
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Freshman User
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Yes I did the self test and the Koer and no codes. Also the previous owner put a colder thermostat so it doesn’t get to operating temp. The other problem I’m having is the alternator isn’t charging but is new, I wonder if the battery cables are causing this because it also was not starting a couple of times, I changed the battery and terminals. Could the cables cause a misfire and charging issue?
Elder User
Joined: Dec 2016
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From: Mid Missouri
These computers go into closed loop at 160* so unless he put a cooler thermostat in it than that (do they even make one cooler than 160?) it’s getting up to operating temp.
Can you expand a bit on the whole “custom firing order thing”? What did he do? Sounds to me he swapped a couple wires and you just need to put the right wire on the right plug/distributor terminal.
Can you expand a bit on the whole “custom firing order thing”? What did he do? Sounds to me he swapped a couple wires and you just need to put the right wire on the right plug/distributor terminal.
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Freshman User
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So it turns out the firing order is not custom I don’t believe. It is written on the cap as 1-3-7-2-6-5-4-8. But, on the cap where it is labeled number one it is actually 8. So it is advanced by one number. Also the wires don’t go to the correct cylinders such as 1234-5678 on the left and right sides of the engine. It goes something like, 1427-5638. I’m wondering what that is because when I unplugged what is number 4 from the cap it made no difference in how the engine was running but when I unplugged number 2 it misfired really bad. Wondering if my best bet is to go back to the original order recommended by Ford and go to number 1 on the cap.
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Any thoughts on the number 1 from the cap? It’s an aftermarket distributor so I don’t really know why it’s moved forward by one?
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And does rebuilding the engine change the firing order in any way depending on a component they could have installed
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Elder User
Joined: Dec 2016
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From: Mid Missouri
It’s not that it’s moved forward, he put the wrong wire on. Remove all the wires, find where # 1 is on the distributor and start there. Then do the rest in order of the rest of that firing order.
What camshaft did he use?
What camshaft did he use?
Elder User
Joined: Dec 2016
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From: Mid Missouri
It sounds like he had to turn the distributor clockwise when he set the timing, which is perfectly fine. I think it now appears that #1 is #8 and that’s throwing you off. Just make sure #1 plug wire is going to #1 on the cap and then follow the rest of the firing order.
Logistics Pro
Joined: Dec 2003
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From: Foothills of NC
According to how the distributor was installed, #1 on the cap may not be #1. If it runs now, then I would expect #1 is where it should be as far as firing goes. Start off by leaving #1 where it is, and change the rest out to the original firing order. Be sure to go in the direction the rotor is turning.
You will need to adjust timing after you get it running.
If you are still getting a lot of popping, then you can try moving everything back one post to the marked #1.
Since the engine will start and run, it would reason that #1 is probably where it needs to be. Easiest way to know is to try and see, unless you know how to achieve TDC on compression stroke, and how to index the distributor to match. If not, start where you are and see.
You will need to adjust timing after you get it running.
If you are still getting a lot of popping, then you can try moving everything back one post to the marked #1.
Since the engine will start and run, it would reason that #1 is probably where it needs to be. Easiest way to know is to try and see, unless you know how to achieve TDC on compression stroke, and how to index the distributor to match. If not, start where you are and see.
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Ok so the firing order was correct but it was just moved one toward. The number one on the cap was actually number 8 so it was advanced by one wire. The engine is a 5.8l a 92 so I believe that means it’s not a roller, (idk if that means anything) the cam is apparently stock and it has new stock heads. Did plugs wires cap and rotor. Also the coil. No difference. Any thoughts. When I unplug a wire it doesn’t seem to make a difference but when I unplug a fuel injector it misfires bad and continues to until I restart it even if I disconnect it. Possibly should I do a compression test and fuel pressure test