1996 Q45 Missfire Cylinder #8 & #4

[Dave96Q45]

I recenty was given a 1996 Q45. It has a bad missfire in #8 & #4 cylinders. I started with a Tune up. Still having the missfires. So i swapped the coil packs around. The coil packs work in other cylinders. I also did a spark test. The cylinders are getting spark. So I did a ohm test on the injectors. I did not ohm them through the harness. I did it directly at the injector. both 8 and 4 injectors ohm out at 11.2 and they have power going to them. so then i tried a compression test. I did this to all cylinders. all where 205 to 210 dry and 220 to 230 wet. I tried to check the timing... but the marks on the harmonic balancer are gone... im not sure what else i can try... Can the injectors be clogged? any help is greatly appreciated.

[qship96]

have you checked the obd2 codes?

[texasoil]

Well, the good compression test eliminates mechanical damage anywhere in the engine--cam timing, broken valves etc.

A bad injector wiring harness can cause the problem. Yes the fuel injectors can be plugged--especially since this has been going on for a while. You should be able to get a 'mechanics stethoscope' on to the flat top of those injectors to listen for the nice sharp 'click'.

Also can be very leaky gaskets between manifold and intake pipes.

[Dave96Q45]

@ qship96 i did check the codes. i got p0300 and knock sensor code. i forget the # and a temp sensor code. for that the wire was not making good contact, it was a lil corrored.

@texasoil i had a friend mention the wiring harness aswell. saying they do go bad. and he has seen it many times. i have tried the stethoscope. and i cant notice a diff between the good and bad ones... how would one go about testing the injector wiring harness? i do have a multimeter, but im not very skilled with it. now lets say the injectors are clogged. i should just replace all 8. since 2 of them have clogged and its only a matter of time before the rest fail. i was thinking of pulling the plugs and using a scope to see if the injectors are spraying fuel. what do u think of this method? me and my friend that told me about the injector harness will be taking a look at the car friday. if it turns out to be the harness. i pray our local junk yard crazy rays has one. im assuming i will have to pull the plenuim to replace the harness...or it might be possible to repair the harness?

about he manifold and intake pipes. would spraying that area with say brake clean or throttle body cleaner make that leak very noticeable?

thank you for taking the time to give me some advice!

[Q451990]

Q45 injector harness failures are very rare. In fact I can't say that I've ever heard of one. Knock sensor harnesses are a very different story...

You should be able to ohm test your injectors through the harness. Use the method here http://www.q45.org/ohminjectors.html

A clogged injector can probably be cleaned using a pressurized rail flush. That said, I don't hear of many that completely clog - so I don't know for sure that if that's the case, they could be cleaned. If you're getting any flow at all, I suspect a pressurized rail flush/clean would work.

Heath

[AZhitman]

about he manifold and intake pipes. would spraying that area with say brake clean or throttle body cleaner make that leak very noticeable?

Do NOT use either of these to trace intake leaks.

Starting fluid works well.