I want to test my coil packs. I have heard that you can test them with a ohm meter.

Also, how would one test a fuel injector?

I took my 2000 5.4 Excursion in because it felt like it was skipping when you put a load on it ie: accelerating. Well, they put in new plugs, new coil packs, fuel filter and did a fuel injection service. It has a slight rough idle. Nothing that shakes the truck. Before you did'nt know it was running, now you can feel it ever so slightly. They said it is in the fuel injectors themselves. I want to test them myself. Also, I want to test the coil packs they took off to see if they really were the problem.

Thanks in advance.

 

The DC resistance check isn't that reliable an indicator of a COP's actual performance since that measures only if the internal primary coil has continuity. If it shows as "open" that's an issue, assuming you're testing at the COP body and not through a wiring harness or connector.

Someone more experienced with testing a COP's in-vehicle performance can give you a good, safe way but I've always used an old fashioned method myself. Typically if a COP is faulty it'll throw a code for its particular cylinder. If you don't have the old COP's you probably can't determine whether they were at fault originally.

HTH

 

I have the old coils. It makes sense what you are saying. I'm leaning towards a injector issue. I floored the truck this morning and it stumbles. Normal driving it does fine. A little skip in the idle after it is warm though. I just was looking for any tips to start with when I start checking thing this weekend. The odd thing is no check engine light or codes. And the light works and it never threw a code when the shop had it.

 

A quick test that's helpful would be to begin disconnecting each injector with the engine running, after its up to normal operating temperature. Paying close attention to the idle, each injector disconnected should cause a slight change---the suspected one won't if in fact it is an injector.

Someone with more knowledge should come along soon but I'm not sure what code would be thrown should one (or more) of the injectors act up.

I have heard using the Techtron fuel additive can be helpful---I used it myself for general purposes and it cleared up an issue with my fuel tank sending unit----pretty amazing stuff, worth a shot.

 

Finally got the thing to give me a code. Misfire on cylinder 8. I've taken the connector for the fuel injector off and can notice it run rougher. I removed the plug for the coil pack and can notice a difference. It only sputters when I get up to 40-50 mph, 1600-1800 rpms. I'm thinking I'll try the coil pack connector and then a fuel injector. Dont know what to do after that. I'm thinking maybe a intake gasket? One thing is I noticed a smell from the truck when I got home. Kind of a sooty smell.

I have one of thos pocket scanners. It shows the things it monitors and two things come up incomplete all the time. O2 sensor and O2 heater. No matter how long I drive it those two come up incomplete. The book says that if it is not driven enough those will show up but I drove the thing 25 miles. Those should have registered by then.

 

More fiddling same results. Sputters upon a load and a little sputtering idle. I've put a new injector in cylinder 8 so that makes new motorcraft platinum plug, new msd coil and now a new BWD injector. Still, P0308 misfire. I'm begining to lean towards intake gasket. I've looked everywhere for a vacuum leak and cant find one. I dont know how to check for that though. It runs so smooth when it is not sputtering. I guess once this saga gets figured out the thing should run like a top.

 

Some aftermarket coils are known to be bad out the box, switch COP with another cylinder to see if code moves, they can ohm fine and fail under load and when EGR system is activated.
IF code doesnt move and your sure your connectors on the COP and the injector are good a compression test for that cylinder is recommended ( which is a PITA)
Burnt valves are common with cylinder 8

 

I was told about the burnt valve thing and to put a paper towel up to the exhaust. I'm not getting any suction but I did notice very low flow coming from the exhaust. I've got the old cop's and i'm going to try moving the #8 like you suggested. It took forever to get that code to come up though. I drive about 50 miles a week. It took a week and a half to get the P0308 to come up. I'm going to see if I can get a "test" pipe in place of the cat and see if the trouble goes away. I may have ruined the cat with the misfire though. If so that is going to hold me back finding the route cause of this issue. I did'nt replace the plug ends though. I can unplug them and get a noticeable difference and it smooths back out when I plug them in. I dont know if that means anything or not.

I guess I'm going to have to have the fuel pressure tested and a compression test done. Fun.

Did a test of the fuel injectors with a meter. Getting between 15 and 16 ohms. I checked the old coil packs and between the terminals i'm almost getting a short 1 to 2 ohms. Between the postive terminal and the wire in the boot I get 5.45 ohms.

The other thing I found odd is the truck would not run without the tube coming from the air filter connected to the throttle body. I did have the tube from the drivers side valve cover disconnected as well. I dont know what that is but should'nt it have at least run without that connected?

 

Took your guys advice and moved the coil pack from 8 to 5. I tested them with a meter when I swapped them. They were the same across the plug prongs but the #8 had 5.93 from the postive prong to the part that touches the plug. The good one had 6.30 with the same test.

 

The MAF is in that hose. Needs reference from it (MAF) to run.

 

Just a update. Still no code since I moved the cop. But it still sputters like crazy. Going to put in a new fuel filter seeing that the original one was plugged up. Maybe there was bad gas that has not got out yet and has plugged up the new filter. I may bite the bullet and buy a fuel pressure tester and test it. I've got new plugs to put in the drivers side bank just to see.

 

Just a thought after you do all that and you still have a bucking, sputter at 40 -50mph, turn off OD, if it clears up you still might have a weak COP, this is the risk with aftermarket COPs, then you have to buy one and play musical COP, until you find the weak one, it will not throw a code, PCM does not see this as a hard miss
On another note im sure you already checked the pcv valve and hosing to throttle body for leaks and your engine vacuum is about 18 to 20ingh
And a quick check of your fuel regulator vacuum line, the red one for gas wettness

 

Thanks, I checked the regulator line. No wetness and no change in idle when I removed it. I was running without the overdrive but eventually that did'nt matter. Today I pulled the fuel rail an to my surprise the number 5 injector had its o-ring crooked in the rail. I fixed that, pulled and replaced the plugs, tested each cop with the ohm meter and got anywhere from 5.95 to 6.23. Well, after that it idles nice and smooth. Took it up the hill and got no sputtering or bucking. I'll check vacuum to see what it is pulling. I have a vacuum gauge. I'm starting to think I have a bad cop. I left the one from #8 in #5 so we'll see if I get a P0305 instead of the P0308.