# WATER PUMP SWAP BUT NOW i HAVE A MISFIRE



## Weisberg16 (Jan 5, 2011)

Okay so I swapped my water pump today and now my car is saying I have a misfire in the #7 cylinder. I had a problem once before with my number seven cylinder but when it misfired last time it shook pretty violently and this time I can't even tell it's misfiring but my aeroforce gauges are saying it is misfiring and it is pretty random at that. Like 2 to 6 misfires a minute..... Not sure but if anyone has any info on this I would greatly appreciate it. Thank you.


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## Weisberg16 (Jan 5, 2011)

Anyone??


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## jetstang (Nov 5, 2008)

Replace the spark plug. If that doesn't work, replace the coil/wire for that cylinder. Nothing to do with the water pump swap unless you swung your arms like crazy. May be a weak/oily cylinder that eats plugs.


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## Weisberg16 (Jan 5, 2011)

I just got the plugs replaced but I am going to move that setup tp another cylinder and see if it still does it. Thank you


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## Poncho Dan (Jun 30, 2009)

Could be: low compression, grounded out coil, broken/corroded plug wire, high plug resistance, clogged injector, or poor connection to the ignition module. Throwing parts at it without finding the root cause is gonna be hard on your wallet.


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## Weisberg16 (Jan 5, 2011)

So what do you think my best option at finding the root cause of this? This is the second time within a month that my number seven cylinder has misfired...


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## jetstang (Nov 5, 2008)

You got it, swap all the components 1 cylinder to another, preferably an easier access cylinder and see if the problem follows the coil and wire or if the problem persists with the same cylinder. Do change the spark plug as I would consider it fouled.


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## Weisberg16 (Jan 5, 2011)

If I change the one don't I need to change all of them?


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## jetstang (Nov 5, 2008)

No. If cylinder 7 is misfiring, swap the coil and wire with cylinder 1 and see if it fouls. If it does, then replace the coil/wire on 1. If 7 still misfires, then it's an internal engine problem, valve seal or rings, or injector is dumping fuel. I have a Lincoln LS and I do this all the time as that car eats the COPS/Coil packs. That's the nice thing about OBD II cars, it tells you which cylinder is bad. If it is the coil, it may be time for new ones, but you have to figure out what the actual problem is first.


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## Poncho Dan (Jun 30, 2009)

Well there's really no good way to check primary resistance on these coils so, yeah, swapping a coil is going to be the next best option. You can check the resistance of the wire, it shouldn't be more than 7000-9000 ohms. When I checked all of mine as an exercise in class, they were all between 7400-7700. Don't swap everything at once... you might end up overlooking something then. Do one component at a time.

You can clean the spark plug and regap it. Before replacing it I'd check the resistance against a known good plug on a different cylinder before condemning it.

If swapping coils doesn't work, then that's going to narrow it down to poor compression, no fuel delivery, or an open in the ignition module wires to the coil. I'm almost wondering if it isn't fuel delivery, since #7 sits at the end of the fuel rail, which is where crap tends to collect the most. But run a few tests, you'll get it.


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## Weisberg16 (Jan 5, 2011)

Okay so now 2,3 4 and 7 are misfiring......


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## Poncho Dan (Jun 30, 2009)

What happened to cause that? Or did it just start happening? If that's the case, I'm really leaning towards the switching device (which is PCM output, we have an integrated ignition module) Check your wiring back to the PCM for corrosion, loose connections, or opens.


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## Weisberg16 (Jan 5, 2011)

It started right after I changed my water pump. The weird thing is that it doesn't feel to rough beside an occational hick up.


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## Weisberg16 (Jan 5, 2011)

Oh and I am smelling more and more fuel under the hood.


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## Poncho Dan (Jun 30, 2009)

Do you see any fuel leaking from the rails or injectors? Or maybe your supply line has the infamous cut from the engine covers.


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## Weisberg16 (Jan 5, 2011)

No I don't see any leaks or any cuts on the fuel lines. I am going to check everything out today since I have some free time. I am also going to change my oil in the procharger. One member recommended I take a look at my crank position sensor. He says that if coolant got on it whem the water pump was done then it might be the cause of random misfires.


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## Cass007 (May 5, 2011)

Any solid resolution to this issue? I'm trying to track down a similar issue. Thanks.


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