Stuck Injector, or My Fault?
 

I had MS out last night working on the fan and AC outputs, and when I put it back in, I get symptoms of a sticking injector.

Idles fine, then bogs down and sounds like 3 cylinders for a few seconds, then smells strongly of gas, then comes back to running fine. Then repeats. This happens while driving too, though I can't smell the gas when the car is moving. It's much less noticable at higher RPMs and loads, presumably since the fuel provided by a stuck injector is much closer to the actual required fuel. Poking at my harness makes no difference, so it's not a loose connection or intermittent short there (that's the only thing I actually changed yesterday)

I took the MS back out this morning and opened it up, and nothing looks out of place, which makes sense because all I did yesterday while it was open was check voltages on a couple pins while it was on the stim.

So, do you guys think it's something I did while I had it apart last night, or just a coincidence that the problem showed up when it did? I've got a bottle of some random injector cleaner I'll run through it I think, and see if that fixes anything.

Oh yeah, here's a log of it happening. I marked the spots.

make sure the ms3x ribbon is seated well. I had a similar issue where I was only running on 3 coils, one was constantly held to 5v.

I checked that this morning. I pulled it off, blew in the connectors (like the old video games) and put it back on firmly. Didn't fix.

Bad coilpack?

use the test mode and run through each coil, make sure they are firing.

I haven't used this test mode before, do I just pull the spark plugs out one at a time and see if they spark while grounded, or is there a "better" way to do it?

I just tested them, and without pulling the spark plugs, both coils tick as they are supposed to. I found the bolts on the fuel rail were VERY loose (backed out between 1-9 mm), so I tightened those, but it didn't fix the problem. I'm going to go add some fuel injector cleaner to the gas tank.

I added some lucas fuel system cleaner and drove about 10 miles, and no change. I don't really know how that stuff works, but I'm still in search of the answer.

First locate the offending cylinder by using the spark method - remove the plug wires until there's no change. Once you are certain on the cylinder, swap injectors like this:

1) If the cylinder is 1 or 2, swap these injectors around.
2) If the cylinder is 3 or 4, swap these injectors around.

If the problem persists, the problem is with the injector harness or with the MS injector driver.
If the problem moves around, the problem is the injector.

I will start on that after the rainstorm passes, but is there any similar way to do it without pulling my injectors? It's not nearly as convenient to pull the injectors on this car as it was on my NA.

Not really...removing the upper manifold is a 20' job on the EUDM manifold, dunno about the USDM.

The rain looks like it might be slowing, should I clean the injector with something (carb cleaner?) while I have it out and am switching it?

Apply 12V and see it if clicks.

I just checked with test mode and they all click. The problem is that this issue is intermittent. I will go remove spark from each cylinder and see if any make no difference.

Do that while the problem is actually occuring. Try that several times to make sure that the problem persists on a specific cylinder - don't just assume it.

Well, cylinders 1, 3, and 4 sill exhibit the problem with the plug wire removed, but cylinder 2 doesn't SEEM to. I've sat with it idling with that plug unhooked for quite a while and I dont' seem to get the stumble, or at least it's not the same. (it doesn't help that my idle is still unreliable and seems to hate me)

I'll pull the injectors and swap 1 and 2 and see if anything changes. I will also spray some carb cleaner on inj2 while it's out, just for good measure.

Ok, just switched inj 1 and 2 (and lost one of those spacers even though I was being very careful. I have no idea where it is), and nothing changed. It also doesn't seem to be confined to one cylinder, since it will do it with any one of the plug wires disconnected. I'm relatively certain it's not a sticking injector at this point. So now the question is: what is it?

I just tried reloading the firmware and had no change, so I'm open to suggestions. I can only assume it's something I did while trying to fix the fan and AC outputs, but I can't imagine what would cause this.

Well, after all that, I loaded an old msq and it ran fine. I was late to dinner so I didn't play with it much to see which of the things I did on Friday screwed it up, but I'll investigate further. Now I need to find one of those fuel rail spacers. Any bets on whether I can find one locally? I don't have high hopes.

i have a spacer or two..