My sister has a 97 automatic neon with a cone filter...

My mother was driving it and it started acting funny and back firing and bogging down pretty much, around 116K. Since the head gasket was common, and it leaked oil down the back of the block, I replaced it, even though it had the MLS gasket already. Stopped the major oil leak and let me clean all the carbon buildup, replace the timing belt, water pump, tensioner and other belts, ect....

When we started it, it did the same damn thing before I took it apart. So I found out, if I unplug the 4th cylinder(closest to the drivers side wheel) if I unplug the 4th cylinder injector wire, it didnt change at all. So I decided to drive it a mile and plug it back in. I did that, and it started working great besides gas mileage being poor. (18ish city)

About 2K miles after replacing the gasket, it would back fire out of the intake occasionally. Mainly when you hit the gas to go, it would pop and then go.

Well it started losing oil and the backfiring got worse. We changed the oil and it did fine again, no leaks. Back firing didnt change. Just almost everytime at a light it would spit and sputter before taking off.... Brings reality to the term "**** and get"..... The weird thing, is when you hit the defrost, at like a stop sign, the backfiring got worse.

Yesterday, while on the highway, it started backfiring and smelling like gas, and acting like its running on three cylinders... I unplug that 4th injector wire, and it didnt change a damn thing, besides the mess of fluid on the header and block cleared up, plugged it back in and it returned. So I got it home, and unbolted the fuel rail and stuck empty water bottles on each injector to measure the flow and watch the spray pattern, ect. I cranked it over for 5 seconds and looked. The cylinders 1-2-3 had like a teaspoon of gas in them. The number 4 cylinder had about a 1/8th of the bottle filled. It was wide open, full duty cycle. I put the connector of the #4 injector on the #3 injector to determine if it was the wiring or the injector. The #3 injector did the same thing. So I know its the wiring.

I took out my digital volt meter and read .3~.7 on all the injectors while cranking. The #4 injector read 13.7.....

Sorry for the long post, just wanted to get all the details out there. I dunno why only that injector wire would send that much voltage. I reset the computer. Nothing changed. Has anyone had this problem? Anything I can do to fix it? I dont see any shorts. I dont have a manual, so I cant test to see if its the ECU sending that much signal, or its getting sourced from somewhere else. Any help is appriciated.

Thanks, Andrew

 

It is probably the PCM or if it happens to have a separate module an injevtor driver module. But just to be sure you need to see if you have ground always available in you harness for #4.

Basically your injectors always have voltage on one wire and the PCM (Injector Driver Module if Separate) grounds the injector to allow it to fire. So if you have a chaffed wire allways grounding you will have a complete circuit and thus spray. This would occur even if the PCM was not intending to fire the injector.

Try checking your Injectors buy seeing what voltage is available and on what pin.
Also check that pin with a test light. This checks load carring ability (Probably not a problem here).
Check the other wire for ground. With ignition(key) on and egine OFF (KOEO) you should have NO GROUND.
While Craking you should get a little bit of Ground due to resistance of the wires and PCM and it should vary as it is cycling on and off with the PCM. If it has constant ground you will obviously get constant spray. The only question is the is it the PCM or wire.

Basic Check...

Wiggle the wires slowly moving back to the PCM from the inector and see if readings change. If you find a spot that changes the readings you probably have a wiring issue at or neer that spot. If not the disconnect PCM and check for ground again. If gone you probably have a PCM problem.

ANY check engine lights???

 

Thank you, I will check that in the morning. Had a looooong last 8 hours...


But the check engine light is always on, saying number 4 cylinder misfire..... I pulled the plug and the tip was gone.... so the injector has been messing up for awhile... I shaved the head bolts a millimeter on the ones around the common leak place, and that helped it, so it seemed...

But I know something is shorting out somewhere, guess Ill track it down in the morning and leave some feed back....


Thanks, Andrew