Misfire in Cylinder 8... need some more input

[daftphunk]

Sup guys, so I've read a few topics about misfires on the board, etc. and got a good idea of what I'm dealing with but I just want to go through some of these options with you guys.

I saw the guide on how to Ohm injectors, and haven't had any luck. I have a 1997 Q45 and when going to Ohm the injectors, I don't come up with anything at all, across all 8. I am using a Fluke 115 to check this also. I can't tell if I am just not testing the correct plug, but I do have the ignition set to 'On' and I am not getting anywhere with that method. There are also no other 8 pin plugs in the general area of the plug that I am testing.

I pulled the spark plug in cylinder 8 and it was pretty wet with fuel and burnt oil and what not. Replaced it with a brand new plug which yielded no difference. I don't actually have an OBD2 scanner handy, so I have to do a lot of guess and check work obviously. Anyways, I've read that the coil packs on these cars don't really ever give out... To check my coil pack I had the car turned on and unplugged the harness to the coil pack in cylinder 8 and it made no difference to the idle of my car. Pulled some of the other harnesses and obviously the idle dropped while the car's idle got a little bit more rough.

Figured that it MIGHT be a coil pack so I just went out to go get a new one. Replaced the coil pack, but nothing changed. Swapped the coil pack with another one and did the same kind of test with the harness. Cylinder 8 is still not responding to the different coil pack when plugged in our out.

That leads me to believe that the coil pack harness at that point is dead. I obviously haven't been able to rule out the dead injector or not since I couldn't successfully Ohm the plug, but I don't see those two issues being related (please correct me if I am wrong). Is that what I am actually looking at here? And if so, what are the next steps to get this going? I need to get my car running on all 8 cylinders again, I try not to drive it, but when I do the gas mileage is terrible.

Thanks

[paranoidjack]

Nono - coil packs are a weak point of these cars. Injectors rarely fail.

Swap coil packs and see if problem follows coil pack.

[daftphunk]

^ I swapped the 'bad' coil with a brand new coil pack and nothing happened. I swapped that new coil to another cylinder with no changes either. I disconnected the coil from the harness at Cylinder 8 with no change in the performance of the car - leading me to believe that it is the harness with the information I have gathered thus far.

I am going to go get an OBD2 scanner tomorrow to see if the misfire code moves with the coil pack but I mean, if the idle isn't changing at all (not getting worse or improving) with the coil pack on cylinder 8 unplugged/plug, does that not seem like my culprit?

Thanks

[Skibane]

I saw the guide on how to Ohm injectors, and haven't had any luck. I have a 1997 Q45 and when going to Ohm the injectors, I don't come up with anything at all, across all 8. I am using a Fluke 115 to check this also. I can't tell if I am just not testing the correct plug, but I do have the ignition set to 'On' and I am not getting anywhere with that method.

I'm not familiar with the guide you mentioned - but are you absolutely sure you're supposed to have the ignition switch on while you're measuring the resistance of the injectors?

Typically, the resistance of a circuit is measured while it is unpowered. Your ohm meter is supposed to supply the only voltage necessary to make the test - If there is also voltage coming from somewhere else (i.e., the ignition switch) while you're making the measurement, you'll get a wildly inaccurate reading on your ohm meter.

if the idle isn't changing at all (not getting worse or improving) with the coil pack on cylinder 8 unplugged/plug, does that not seem like my culprit?

Only if the coil pack is actually causing the misfire on that cylinder. For example, if an injector isn't working, you'll still get the same misfire, regardless of whether or not the coil pack is plugged in.

[Skibane]

Reminds me of a story:

Once upon a time, a group of scientists taught a flea to jump whenever a bell was rung.

After the novelty of what they'd accomplished started to wear off, they got bored, and decided to see what would happen when they removed one of the flea's legs.

The flea still jumped whenever the bell was rung.

They continued to remove the flea's legs, one-by-one. Each time, the flea continued to jump, until after they removed his last leg.

Upon observing that the flea no longer jumped when the bell was rung, they concluded that removing all a flea's legs makes him go deaf.

[daftphunk]

I was referring to this guide right here:
http://q45.org/ohminjectors.html

Though I am aware that the guide states this is specifically for 90-96.. but I swear I read somewhere that someone did something very similar in their 1997.

If this isn't the appropriate way to go about checking resistance on the injectors, what else should I do to check and see if the injector is still alive? I feel like that the actual problem but I want to make sure before I go out and buy more stuff

[goody90q45]

On the 90-96 engines you can remove the connector from the #1, #2 and #8 injector (and pull the injector) without removing the plenum and measure the resistance directly on the injector pins without having to measure at the FI harness connector. Is it the same for the 4.1 engine?

[daftphunk]

So I went ahead and checked the resistance on injector 8 and it came in at 10.6ish which is in spec no? Car still misfires and pours gas out like no other. I'm at a dead end here.

Still think it's the wiring to the coil since unplugging it does nothing. Any more input?

[daftphunk]

I did that screwdriver test and could hear the injector pulsing. I haven't pulled them, but that was cylinder 8. Went ahead and replaced cylinder 8 with a new coil pack again and now I am getting a code for random/multiple cylinder misfire. When I had the old coil pack in there I was getting cylinder 8 misfire but with the new one it's random now, what gives?

[Q451990]

and pours gas out like no other

What do you mean by this? I wonder if you have a bad lower o-ring on that injector that's causing excess fuel in that cylinder?

Heath