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Removing plug wires at Cylinders 4 and 6 reveals no loss of performance; Engine starts barely and will stay lit; removing plug wire at 2 will stall engine. Spark strong when pulling 4 and 6. New plugs, some soot on 6 and nothing on 4; 4 plug is totally clean when pulled. I think I smell some unburned gas from tailpipe, but not sure.
Fuel pressure good (a few pounds more than on my K8 in fact), pump leak-down is gradual, faster than on my MX-3 GS, but don't see cause of problem. Tried swapping a fuel regulator from yard off MX-6, no difference, and pulling vacuum hose caused a difference.
Fuel filter and O2's x 4 are new (o2's are ebay cheapo's, but, don't see how they would come into play before engine actually warms up if they suck); Ignition wires and plugs are new as well.
Compression good at all cylinders, ranging from 196 - 209 psi.
Resistance good at crank sensor, knock sensor, etc. Not sure if I checked the VAF for other than voltage present.
I shipped out fuel rails for service, pre-flow testing showed all good, from -6% to -11%(#4). Guy tonight suggested pulling rail and moving injectors around. Suppose I would have already done that if I hadn't had them serviced and it had occurred to me. Did back probe wires after rails re-installed for proper resistance and voltage. I have a 'stethoscope' and pretty sure I hear clicking at injectors 4 and 6.
I assume timing belt is non-issue as compression test went as expected, and, if say it skipped a tooth on the front side bank sprocket, cylinder 2 would also be out of play, correct?
I know it's gotta be something dumb I just can't think of. Don't want to pull the rails to swap around injectors for another effort in futility until I get some feedback. Thanks

assuming your getting spark and compression like you say id think it would have to be fuel injector related. try cranking the engine once with the plugs out and see if you can smell raw fuel in those cylinders. how old is the disty cap? are plugs 4 and 6 sparking? i cant think of anything that would only affect 2 cylinders other then compression problems, injectors or spark delivery. soot on plug number 6 indicates a rich mixture, perhaps the spray pattern is bad and the fuel isn't vaporizing?

any smoke or fuel smell coming from the exhaust?

Disty cap decent; scraped off only a bit of residue. Will pull 4 and 6 plugs to smell for fuel, thanks. Yes, pulling Ignition wires 4 and 6 spark strong to the sidewalls of the valve cover all the way out. I think I smell fuel in exhaust, will try after running longer. Don't think there is smoky exhaust.

Half a--'d wondering myself if I got legit service I paid for for the injectors; place in Houston, InjectorRx of InjectorDR...

But, thinking pulling fuel rails again likely in my near future, so tedious!

id confirm fuel first by pulling the plugs. if there is infact fuel id try shuffling the injectors in the rails which would tell you if they are spraying properly. its possible they are just sitting in the rails crooked or something...

Before I shipped injectors out, I tried to remove them from the rails, found it impossible, which was one reason I decided to have them serviced (they had trouble removing them too; they called me and told me, because they said they would have to charge me an extra $5/injector for their extra time and effort, which they said really didn't pay for all the extra time).
Anyway, I remember putting bottom of injectors on something to try pushing them up while trying to grab also from the top and pulling, and figuring I would end up damaging them. I suppose if they really got serviced, they should come out easier now, but, is this typical for our cars? Are there any write-ups regarding these removals?

i dont remember mine being that hard to get out. i gently grabbed the outside of the top with some water pump pliers and worked them back and forth while pulling up. some wd 40 should help get them out aswell. keep in mind if you do take them out youll probably want to replace the o rings. did they give you a printout of the before and after flowrates? usually service entails complete disassembly flushing/reverse flushing and then reassembly with new pintles and new caps/o rings, which is usually fallowed up by a flow test. if you take them out be careful to not touch the tip of the injectors, they are sensitive and if they get damaged they will have a bad spray pattern.

They supposedly did all that you mention. Looks like rails coming out; I did spark plug out test; no smell of gas from #4, do smell gas #6. Will use WD40 as you suggest after prying them up a bit, hadn't thought of that. I included a pack of new O-rings for them, and they returned rails with the old rings.

Think I will move #2 injector to #4 position, #4 to #6, and #6 to #2 . . .

valentiner wrote:They supposedly did all that you mention. Looks like rails coming out; I did spark plug out test; no smell of gas from #4, do smell gas #6. Will use WD40 as you suggest after prying them up a bit, hadn't thought of that. I included a pack of new O-rings for them, and they returned rails with the old rings.

Think I will move #2 injector to #4 position, #4 to #6, and #6 to #2 . . .

UPDATE: All above work done, same result! Not thinking injectors anymore.

Would have thought distributor (bad coil) long ago if I thought sparks were bad. Plug wires arc to valve cover! How can that be weak?

Aw shyte; on hunch just swapped ignition wires of the two bad cylinders. One now works!

Yes, I must have been sloppy installing new ignition wires. Didn't pay attention to the numbers on the cap, bottom of cap, counterclockwise, is 1-2-3, so I assumed wrong, the top would be 4-5-6, when in fact it goes 6-4-5.

Still messes with my head, why, if firing order is 1-2-3-4-5-6 ???

Anyway, I am so relieved. But now, I have a pronounced ticking noise, after running engine for 5 minutes, and revving to 3500 rpm to move the oil. I haven't driven the car for months; 2.5l V6, think I may have done damage to the engine using the improper firing order?

Good catch. Gotta pay attention to the numbers on the cap. The firing order is 123456 but the cap is built for ignition cables to be connected differently. See this link for a picture of the ZE versus DE cap and the DE cap has a wire built into the cap to route the spark to the correct cable.

Ticking is almost certainly hydraulic lifters that have been bone dry if not run for a long time. You didn't hurt anything by firing in wrong order. Hopefully they quiet down as the engine warms and they build oil pressure. You might try some synthetic oil for the next 3 - 5K miles. I'm high on Mobil 0w-30. Its not magic - no claims of super mileage or added power, but I rarely hear hla tick ever.

If the ticking is around #1cyl it could be the timing belt is a little sloppy (tensioner).
Because of the bad parts I've gotten in the past every time I work on my engine I swap out parts one at a time. Wires only, start the car. Plugs, start the car, etc. That way you'll know if one of the parts you installed is no good.

Well, whomever buys this car will have minty clean injectors I didn't intend for them to have; lol.

What screwed me up for a long time too was the anti-theft system that disables the fuel pump if the key and remote are not together.

In all of this stuff I did all at once (and never again) I also took the remote off the key ring to clean the contacts inside, too many coincidences!

I had checked my firing order several times before, but didn't know about the goofy order on the cap.

I have been gravitating toward the oil you suggest lately anyway, and I am aware of the problems with our HLA's. I think the HLA's on my '93 GS are almost total crap, now with 260k miles, and can't believe it still runs as well as it does.

Ultimately would like to do a swap, but, it really just needs head gaskets (they aren't really even that bad for as much as I cooked them once) and the stem seals pass oil. Probably won't go to all the bother, just do the swap when forced to. And oh ya, could really stand to fix the two cam washers that are so noisy.

Thanks for all the follow-ups, got me to concentrate a little more clearly.