Runs rough, like it's missing

[dnaugtbass]

Hi, First post here. I was wondering if anyone could give me anymore ideas on how to test for the cause of this problem. My truck started missing, engine lost power and running rough. It is more noticeable when you are in 4th gear at slow speed and push the gas pedal a little, not enough to kick down the trans. But it runs rough all the time now. I changed the cps, no change. Is it the UVC harness? How do I test that, with a multimeter?

Thanks for your help.

[dieseldan2005]

Try and get it on a good scan tool. I just picked up an auto enginuity and it can test for all that stuff to see if the whole cylinder bank is misfiring or if its just 1 or 2 cyls.

[dnaugtbass]

I forgot to mention, no check engine light - so probably no codes. I ran it with only one side plugged in then the other side. It almost sounds like one cylender is missing on the drivers side, and two on the passenger side.

[smitty16s]

just because there no engine light doesnt mean theres no codes. have you checked the ICP sensor?

[dieseldan2005]

Well if you can get access to an AE type scanner it will be able to do a cylinder contribution test to verify if you have cyls that aren't working properly. Its not something that would always throw a code. When did you change your oil/fuel filters last? Also welcome to the ORG!

[dieseldan2005]

Originally Posted by smitty16s

just because there no engine light doesnt mean theres no codes. have you checked the ICP sensor?

Exactly they can throw "soft codes" or ones that don't trigger the SES light.

[dnaugtbass]

Thanks for the info, I will look around for the ICP threads.
Can that cause a misfire?

Try to find a scan tool, I would like to get one, but don't have enough cash to get that and the parts to fix the truck.

Thanks again.

[dieseldan2005]

I wouldn't say it would cause a misfire, but it would make it run rough. The icp sensor is run on oil pressure, so thats why i asked about when you changed your oil last. I have also heard that the oil pressure sensor can cause a rough idle, because if the OP sensor is bad it'll affect the ICP sensor.

[dnaugtbass]

Yeah, it does need an oil change, I changed the fuel filter a couple months ago 'cause the fuel heater went out and popped fuses - truck wouldn't run. Maybe I'll change the oil first. That's easy enough, and it needs to be done anyway.

[dieseldan2005]

Yeah, try it first. If it doesn't work then try the other stuff mentioned.