Strange intermittent misfirE

[03Alerosil]

hey,
I have an '03 Alero with the 3.4. 210,000 on it. I have a misfire on cylinder 2 that only happens at high rpm, usually past 5k, and only happens on the 2nd to 3rd shift if the shift delays. If the shift happens right away there is no misfire on that cylinder. I've ruled out the fuel pump and filter. 55psi even while misfire is happening. ICM and Coil packs are all good, plugs are brand new, wires are new. I tested every single sensor under the hood and they all check out. I did an exhaust backpressure test and the Catalytic Converter checks out so it's not plugged exhaust. I will mention that the intake is barely seeping at all 4 corners, again

Any thoughts would be good. it still runs and drives fine unless i am accelerating hard, like when you go to pass someone.

Thanks

[03Alerosil]

I think I finally figured out what's going on with my car. I noticed I have a lot of issues when it's wet out which automatically made me think an ignition issue. Well as it would turn out there is a connector on the ICM with a purple and a yellow wire going to it that was partially melted to the rear exhaust manifold. Loom is melted or so brittle its falling off. Well I looked up the wiring diagram for it on my repair software. Turns out the yellow and the purple wire are the outputs from my crank sensor! So that explains a lot. That means the signal from my crank sensor was grounding out before it ever reached the ignition module. SO i am picking up a pigtail today and installing it tomorrow when the engine is cold and hoping for the best. I sure hope this fixes it because I've done everything else and tested everything else. I am about ready to scrap my Alero.

[riceralero]

Originally Posted by 03Alerosil

I think I finally figured out what's going on with my car. I noticed I have a lot of issues when it's wet out which automatically made me think an ignition issue. Well as it would turn out there is a connector on the ICM with a purple and a yellow wire going to it that was partially melted to the rear exhaust manifold. Loom is melted or so brittle its falling off. Well I looked up the wiring diagram for it on my repair software. Turns out the yellow and the purple wire are the outputs from my crank sensor! So that explains a lot. That means the signal from my crank sensor was grounding out before it ever reached the ignition module. SO i am picking up a pigtail today and installing it tomorrow when the engine is cold and hoping for the best. I sure hope this fixes it because I've done everything else and tested everything else. I am about ready to scrap my Alero.

Keep us updated!

[03Alerosil]

I cut the ends of the harness and made it longer. Routed it so it runs on the firewall away from the manifold. I did not fix my problem. Oh and the top side stud on the #2 exhaust runner is rusted/ corroded off so I got an exhaust leak now. I am not fixing it. The only solution I have found to my issue is leaving the EGR unplugged so i say F*CK the EGR valve. It's brand new Delphi unit and Im still getting codes. The wiring harness checks out as well. All the values are good when i test it. So I'm going to drive it for the winter without the EGR and get a new car in the spring. Looking at a Jeep Cherokee. 98 to 2000. Build it up with tires and a lift then run that piece of shit Alero over before sending it to the crusher. It's been never ending issues for over 2 years now. I've dumped more money into it in parts alone than i paid for it and it's still a piece of crap.

[03Alerosil]

Still working on the stupid piece of shit.

I unhooked my EGR tube from my EGR valve in an attempt to see if my cat is indeed plugged. Well I can tell you the cat is most definitely plugged. Car ran and revved like it should.....until disaster struck. All the excessive exhaust heat from the cat being plugged got blown out the EGR tube and into my engine bay where it completely melted my throttle position sensor, all the wire loom on my spark plug wires, some of the engine wire loom harness, both vacuum lines for my HVAC and my fuel pressure regulator. i limped it to O'reillys and picked up a cheap sensor for $32. Limped it back to my work. Put the sensor on and repaired the vacuum lines with vacuum tubing, cut all the melted plastic off everything and went the eff home. So it cost me roughly $44 to find out for sure that my cat is indeed a clogged piece of shit. I picked up 2 exhaust gaskets and on Sunday the Cat is getting gutted. I'm not dropping the money into this car for a new cat. Not gonna happen. More than likely getting driven to the salvage yard before spring anyway.

[03Alerosil]

Ended up cutting it off and just sticking a pipe in there. What a world of difference. The Alero lives some more. Feels like I gained 100hp, transmission shifts better, and i don't get choked out by exhaust while driving, plus that squealing sound went away.