Hi guys,
I have a 2003 f-250 v10 with 78K. I recently noticed that if I am driving and stop at a stop sign or light, the engine feels like it runs kind of rough - almost like one cylinder is not firing or is weak. If I take it out of Drive and put it into Park the rough feeling goes away.


I have changed the air filter, fuel filter, and spark plugs within the last 6 months, so I think these can be ruled out.

Any ideas on what could be causing this? Anyone else notice this type of problem?

 

Check to see if there maybe a vacuum leak.

 

thanks. I checked this morning and couldn't find anything. PCV valve also seems to be ok. Weird thing is, at idle in neutral or park the problem doesn't happen. When it's idling in drive the rpm's drop just slightly and I begin to notice it.

 

Mine was doing the same thing. COP was on its way out. It completly stopped working a few weeks later and caused what felt like driveline vibrations al low RPMs at speed.

 

Any thoughts on how I could find a bad COP right now? I figure when the check engine light comes on I can hook it up to the computer at autozone to find it. Right now I have no check engine light.

 

I beer had a check engine light, but there were codes when I scanned it.

The code will tell you the cylinder, or you can just unplug the COP's one by one untill you find the one that doesn't cause a change.

I scan it first though.

 

Well, I tried autozone yesterday afternoon. Nothing showed up, but the kid there told me they normally don't show anything unless the CEL is on. He did say a lot of auto shops have better scanners and may be able to tell more. I guess I'll need to take it in and get a diagnostic check somewhere. I hate like hell to start unplugging the COP's to test this because it has got to be in gear for the problem to occur, and I'm just working by myself in the driveway.

 

Update:
I took a gamble that it was a bad COP. Ordered 10 new ones from AIP off of Ebay for $153. They arrived yesterday. I replaced the coils in cylinders 1 - 5, then decided to test. I started the engine and the problem was gone! I guess I won't replace the other 5 until I start noticing a problem again.

I tested the resistance of all 5 cop's I pulled off the motor with a multimeter, all of them seemed to have the correct ohm readings from b- to b+ and b- to the spring. But one or more of them had to be bad.

 

Mine didn't throw a code and my Scan Guage II only showed one code and the rest were 0000. Advance Auto had a much nicer one one with a big sceen that said which cylinder was misfiring.

 

Sometimes its not the Coil On Plug, but the boot itself. Usually a COP will show oil on the body when it is going bad as it is leaking oil (fried). Check the old ones and if you have a lot of oil on one of them, throw it out and save the other 4.

 

Yeah, I was thinking that it may be a boot as well, but they all looked fine. I'm pretty sure one or two of those coils was beginning to go bad, probably allowing some spark but just not enough to get good combustion in the cylinder.

 

A word of caution on e-bay COP. Mine lasted a year. Then three went out. I replaced all 10 with Motorcraft units. I searched the web and found all 10 for $399.

 

Lots of luck with those AIP COP off ebay never again, though it seems you have enough spares for when they go bad!! There are companys in China posting on ebay a price of $15/each, even less in volume. Remember you get what you pay for!

Bought a spare COP from AIP for my GXP Northstar, at one point I decided to make sure the spare was good and how well it worked compared to OEM ACDELCO. BAD choice, the unit from AIP lasted only 9 days which translates into 700 miles for me, unit went stone DEAD, no spark, nothing. Considering the AIP for the Northstar are $26/each with only 90 day warranty, the OEM ACDELCO are a steal at $36/each with 1 year warranty from Amazon and other ebay suppliers.

Other AIP customers have posted feedback on ebay that their COPs have been dead out of the box. My advise from first hand experience with these people would be go with the OEM parts not the Cheap China made imitations, you pay for it in the end. 4 days/emails later I'm still waiting for AIP to be honorable/ethical and do the right thing... still waiting???

jspringator - Just curious were your COPs also from AIP??

jspringator
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A word of caution on e-bay COP. Mine lasted a year. Then three went out. I replaced all 10 with Motorcraft units. I searched the web and found all 10 for $399.
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I'm not sure. I'm guessing they are all made in the same place anyway. These COP were the only problem area on the truck. They should probably be replaced at 125,000 miles as preventive maintenance. I've got the fuel pump in my back seat waiting to be put based on the same principle.

 

The folks on the Caddy forums for the Northstar engine are suggesting that one will have the first failure around 75k miles. Which was the reason I was looking into having a spare onhand.

AIP claims to be selling "NEW" units but with no label most likely from China. The question becomes are the units originating from a reputable manufacturer or are they a counterfeit? I am an electronic engineer in the industry and we are having problems getting brand label ASICs from our suppliers, in some cases the suppliers are providing counterfeit inferior ASCIS (prone to failure) units believed to be originating in China.