Engine will not stay running

1998 FORD F-150
245,000 MILES • 4.6L • V8 • 4WD • MANUAL
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CLINT2DUNN
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Truck will start up fine but seems to idle only on the driver side of the engine and will backfire and shut off if I touch the throttle. But if left rough idling it will sometimes surge up to maybe seven cylinders... This only started happening after a hard rev followed by a loud pop ever since the truck has done the above. It was bought as a Toy half of the exhaust is gone on passenger side due to rust.
Nov 28, 2021 at 3:47 AM
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KASEKENNY
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Let's start with the basics unless you have already changed a number of different parts.

However, if you have misfires then we need to start with checking the plugs, wires, and injectors.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

However, the fact that you just got this truck, and the exhaust is in poor condition, I would suggest with just changing all your ignition components, fuel filter, air filter and then recheck the operation of the engine.

https://www.2carpros.com/articles/how-to-tune-up-a-car-engine

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

If none of this checks out, we are going to need to move onto a possible vacuum leak. So here is a guide that will help with this:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let's start with all this info and based on results we will have a better idea what the issue is but we will then need to check fuel pressure, but I don't think that is the issue which is why we need to start with all this.

Let us know what you find. Thanks
Nov 29, 2021 at 7:05 AM
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CLINT2DUNN
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Okay, so, everything you mentioned was replaced when i first got the truck I had it running like new, then one day I was mudding and hit redline and made a loud bang. ever since then the passenger side barely fires, and when it does i can't touch the gas or it backfires and turns off. I also took a can of brake cleaner and sprayed around the intake plenum while trying to run and it doesn't seem like there is a vacuum leak.
Dec 3, 2021 at 8:37 AM
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KASEKENNY
  • Experienced Mechanic
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Great video. That helps a lot.

We need to jump straight to compression checking because I bet you have some bent valves that are no longer sealing, and you are going to be low on compression in more than one cylinder.

https://www.2carpros.com/articles/how-to-test-engine-compression

This engine has a timing chain so I doubt it jumped a tooth or slipped like a belt can. I think that the bang was pistons hitting valves and did some damage.

However, if the compression is ok then we can dig further but I bet that is going to tell us what is happening.

If I am correct, then unfortunately mudding may have claimed another engine.

Let us know what you find with this, and we can go from there. Thanks
Dec 3, 2021 at 10:44 AM
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CLINT2DUNN
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I have not done a compression test but turning it over without coils plugged in doesn't sound like it lost compression and I have pulled all of those spark plugs out and they have no damage. is it possible I made a valve stick?
Dec 3, 2021 at 11:02 AM
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KASEKENNY
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No. A sticking valve is caused by carbon build up or not maintaining the vehicle properly among other things but not over revving the engine.

The red line and bang event most likely bent the valves. I understand it does not sound like it has no compression, but you are going to be down on compression and that is why you have such a bad misfire, and it backfires when you rev the engine.

We need to do a compression check and at this point and at least confirm they are ok. However, I am pretty confident that we are going to find the issue here. I hope I am wrong but everything you told me is pointing there. Which means we need to do a compression check.

Let us know what you find. Thanks
Dec 3, 2021 at 11:24 AM
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CLINT2DUNN
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Thank you so much I don't like asking for help it makes me feel useless. But I will do a compression check and see how it goes, I had just went through everything. Stumped I sucked it up and turned for some advice.
Dec 3, 2021 at 11:57 AM
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KASEKENNY
  • Experienced Mechanic
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Haha. I am no different. I don't even like reading instructions. I want to figure it out myself and when I can't I get frustrated.

Thanks, is why we are here. If you need help, we are here for you. Let us know what you find.

Thanks
Dec 3, 2021 at 9:47 PM
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