Did you test the injectors with teh PCM firing them?
Pull the fuel rail out and put some blue shop towels under the injectors. Unplug the coil packs and try to start the car for a couple seconds and see if the towels are wet under all the injectors.
BUT have you verified that they are actually spitting out fuel, when fed by your pump and your PCM?I've checked the injector wiring with two different sources. Once with a noid light. Secondly with a computer safe test light. It's simply a 12v powered test light with resistors and LED's. Attach it to positive it lights red. Attach it to negative it lights green. The fact that it has LED's allows it to be used like a noid light to read the negative pulse from the computer to the injectors. The non firing ones all have positive from battery and are getting a pulse from the computer.
I'm of the belief that the problem is in the fuel supply ... What I'm trying to discover is "why" the injectors are not firing (when being fed 12+ and Neg pulses from the ECM).BUT have you verified that they are actually spitting out fuel, when fed by your pump and your PCM?
Makes perfect sense. I wonder if they do use transistors that share a trace on the circuit board. Seems low tech but I bet it's cost effective. I would think the whole thing were microprocessor controlled (but you'd still have trace on the circuit board for the mcp as well).I believe there are discrete transistors driving the sink to ground for each injector. If it turns out that the problem does reside within the ECM, it may well be that those 4 transistors share a common circuit element or board trace that may have failed.
Yep Yep, it would. I plan to get out of here (the office) early enough to get home and ohm test the injector wires. If they all are in balance with each other, the only other possible cause will have to be in the ECM. I'm not totally sold on that (again, I have never seen an ECM fail in this manner ... But this is the first GM product I've owned in over 15).While it's low probablility that all 4 transistors crapped out at once, the failure of a common element would explain the problem and put a big bow on it.
Well, I can't argue that point (as I have no experience in this area). Have you seen them fail in this or a similar manner?I still bet money its the ECM. I have seen them go bad.
Not with this particular symptom, but given how complex the ECM is its not surprising.Well, I can't argue that point (as I have no experience in this area). Have you seen them fail in this or a similar manner?
http://www.jegs.com/i/Edelbrock/350/7118/10002/-1?CT=999...and I'd much rather have a simplified platform...
Jeff I hate to say this but...It's actually rather refreshing to know I'm not the only to have this happen (as forked up as that may seem).I find this post most interesting because I am currently troubleshooting almost the same thing on my '04... same symptoms: rear 4 cylinders are cold to touch like they aren't firing, but I get spark and gas. It happened when I was cruising @ 50 or so, just like you.
I'll follow along on this post to see if anything turns up for you, and if I come up with anything new I'll post back as well.
Nothing that archaic (I wouldn't put a carb on shyt anyway).
I never did update this but since it's at the top ...Sorry if I'm digging this one back up, but I finally got my issue straightened out and felt I should include this for the archives or if the OP is still having his troubles. I took it to a garage once winter cleared out and I had some time. They found the #6 cylinder exhaust valve sping was broke, and that's it. I guess that was enough to throw the rest of the cylinder's timing off because I was really dumbfounded how multiple cylinders just went dead. So yeah, new valve spring and it's good to go. It never threw a CEL code on any sensor pickups.
I guess I'm "lucky" in the fact the valve didn't fall and meet the piston BUT ... I had the supposedly fixed Comp 918's on the heads. I put a stock spring on it and ran it like that for about 2 months until I installed my L92/LS3 combo on.I'm wondering if the beehive design of the springs I was running allowed it to sort of catch itself and not allow the valve to fall completely down to contact the piston.