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Started By
Message
Misfiring Engine on Older Truck
Posted on 5/2/24 at 8:00 pm
Posted on 5/2/24 at 8:00 pm
There is no automotive board, so I figured this board would be better than the OT. I don't feel like hearing "that'll cost you tree fiddy" over there.
I have an old arse early 2000's truck that is misfiring. At idle the engine revs up then almost cuts off, then revs up again, etc. While driving, it is very "rough" and you can feel vibrations. It's obvious something is going on.
I took it to a mechanic because it wasn't starting (despite having a brand new battery). It turns out my brand new battery had to be exchanged under warranty, so he replaced it. While I was there, he said "hey your engine is misfiring" and I said "yeah I noticed it was driving rough." He said "Well since your battery was dead when you came in, we weren't able to get OBD codes, so just drive it until check engine light comes on."
I've driven it today and no light came on. I have been reading that you should not drive an engine that is misfiring. So I guess my question is what should I do? Does the check engine light HAVE to come on to get codes?
I have an old arse early 2000's truck that is misfiring. At idle the engine revs up then almost cuts off, then revs up again, etc. While driving, it is very "rough" and you can feel vibrations. It's obvious something is going on.
I took it to a mechanic because it wasn't starting (despite having a brand new battery). It turns out my brand new battery had to be exchanged under warranty, so he replaced it. While I was there, he said "hey your engine is misfiring" and I said "yeah I noticed it was driving rough." He said "Well since your battery was dead when you came in, we weren't able to get OBD codes, so just drive it until check engine light comes on."
I've driven it today and no light came on. I have been reading that you should not drive an engine that is misfiring. So I guess my question is what should I do? Does the check engine light HAVE to come on to get codes?
10
Posted on 5/2/24 at 8:10 pm to AUstar
First thing I'd check would be to wait until nighttime and start the engine. Open the hood and move the spark plug wires around a bit to see if they are arcing to the block.
I've had wires go bad like that on a older vehicle that caused misfiring and a simple plug wire change took care of it. If your wires are original to the truck, it is possible that could be an issue.
Be careful handling the wires though because that spark will smarts if it hits you. Best to move them around with an insulated tool.
Oh, and do this in total darkness if you can-----no outside lights, flashlights etc.
I've had wires go bad like that on a older vehicle that caused misfiring and a simple plug wire change took care of it. If your wires are original to the truck, it is possible that could be an issue.
Be careful handling the wires though because that spark will smarts if it hits you. Best to move them around with an insulated tool.
Oh, and do this in total darkness if you can-----no outside lights, flashlights etc.
This post was edited on 5/2/24 at 8:11 pm
Posted on 5/2/24 at 8:10 pm to AUstar
Check spark plugs, pull plug wires until you find the dead cylinder.
Check engine light bulb might be blown or removed
Check Distributor cap
Does it have coils on each plug? What brand truck?
Check engine light bulb might be blown or removed
Check Distributor cap
Does it have coils on each plug? What brand truck?
This post was edited on 5/2/24 at 8:12 pm
Posted on 5/2/24 at 8:13 pm to AUstar
Have had it happen 3 times in 2 different vehicles- 2 were bad spark plugs and the other was bad spark plug wire.
Spark plugs threw a CEL, wire did not.
Spark plugs threw a CEL, wire did not.
Posted on 5/2/24 at 8:17 pm to AUstar
My old 2003 F-150 gave me misfiring codes with the specific cylinder that was misfiring. It turned out to be a coil pack.
And some codes do get stored that do not turn on the check engine light in some vehicles.
You could pick up a code reader online or at harbor freight or AutoZone and check yourself.
https://www.autozone.com/test-scan-and-specialty-tools/code-reader/p/innova-obd2-code-reader/1090295_0_0
https://www.harborfreight.com/obd-ii-code-reader-64981.html
https://www.amazon.com/MOTOPOWER-MP69035-Universal-Diagnostic-Protocol-dp-B08P6VTY52/dp/B08P6VTY52/ref=dp_ob_title_auto
And some codes do get stored that do not turn on the check engine light in some vehicles.
You could pick up a code reader online or at harbor freight or AutoZone and check yourself.
https://www.autozone.com/test-scan-and-specialty-tools/code-reader/p/innova-obd2-code-reader/1090295_0_0
https://www.harborfreight.com/obd-ii-code-reader-64981.html
https://www.amazon.com/MOTOPOWER-MP69035-Universal-Diagnostic-Protocol-dp-B08P6VTY52/dp/B08P6VTY52/ref=dp_ob_title_auto
Posted on 5/2/24 at 8:27 pm to AUstar
I'm also thinking it could be coil pack but check plugs and woresr first as they're cheaper.
Posted on 5/2/24 at 9:04 pm to White Bear
quote:
What brand truck?
Early 2000's F-150.
Posted on 5/2/24 at 9:17 pm to AUstar
quote:coil pack(s)
Early 2000's F-150.
Posted on 5/2/24 at 9:20 pm to White Bear
quote:quote:coil pack(s)
Early 2000's F-150.
My first thought exactly. But that should generate a code.
Posted on 5/2/24 at 10:14 pm to AUstar
The truck will have to run xx miles before the computer generates a code. Especially since u changed the battery. Whatever cylinder it says is the one needing a coil pack. Takes a few minutes to change it. About $60
Posted on 5/2/24 at 10:52 pm to AUstar
Possibly just the ignition coil boot.
Posted on 5/3/24 at 7:19 am to AUstar
90% chance it is one of 2 things.
Cheapest, easiest and a good idea to do anyway: Replace the spark plug wires with decent quality ones. Pull/clean and/or replace spark plugs while you are at it.
Second is a coil pack.
I'd start with the first.
Cheapest, easiest and a good idea to do anyway: Replace the spark plug wires with decent quality ones. Pull/clean and/or replace spark plugs while you are at it.
Second is a coil pack.
I'd start with the first.
Posted on 5/3/24 at 12:42 pm to AUstar
vote for coil pack
that should throw a code immediately and your ecu stores codes a 15 dollar code reader will tell you that, even if the CEL is not on.
that should throw a code immediately and your ecu stores codes a 15 dollar code reader will tell you that, even if the CEL is not on.
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