Running like crap, odd spark readings

[Gollum]

So my L28E in the daily never runs superb, but it was free and I don't feel like messing with it often. The other day it started running bad, as though it was only running on 4 or 5 cylinders, and this was pronounced when cold. Once hot it was better, but not a ton.

 

This morning while it was cold I fiddled with the AFM and noticed it didn't like how rich it was running. Leaned it out, and the idle went from almost dying to a good 1100. Then once it's hot it's running slightly lean (probably my fault, I've been purposely running it lean in the colder weather, and now it's warm again). Idle when hot goes up about 100-150rpm when I enrich it a bit.

 

So today I noticed that this tank of gas is flying by, which I figured as hinted by the terrible gassy smell... Usually I'm at around 300 miles at 1/8, this tank I'm at 210! So I pulled my spark plugs since I know I have a slight oil leak, thinking I had some fouled plugs that were oil saturated. Nope, here's what I found.

 

(I took a pic but it's on a phone, hopefully I can post it later)

 

#1-3 were completely white on the tip insulation part and white on the upper portion of the arm.

 

#4-6 were black, but they didn't look oil fouled. They just looked carbon fouled.

 

So 1-3 look too lean/hot and 4-6 look cold.

 

Can anyone guess if I'm having a fuel or ignition problem? My injector wiring is normally kinda iffy, and the engine was running on 5 cylinders when I got it, and cleaning up the contacts fixed that. You can also fiddle with some of my injector wiring and cause injectors to cut out without disconnecting them (scary, I know). Could spotty injectors be my issue here? If so, why does leaning out my cold mixture help? Unrelated maybe?

 

Or maybe worn cap/rotor not helping an old engine with bad oil pressure and compression? Just seems weird for it to be all of the sudden like this. Last tank I got 350 miles out of, I'll be lucky to see 250 out of this one.

[Gollum]

Hmm, so I got home tonight, after having cleaned the plugs off right before posting earlier, and starting tinkering. So #5 and #6 aren't combusting. I pulled the injector plugs on them and the idle didn't change a bit. It was dark, and late, and for some reason this caused me to not think about pulling the plug wires to see if they'd arc. I'm pretty sure they would. So it must be some issue with my injectors, or injector wiring.

 

Damn. The worst? I have to drive to oakland first thing tomorrow morning, on 4 at best cylinders dragging at least 2 behind.

[Gollum]

So I've got arc at the plug wires, and I tested the injector plugs with a probe and they seem fine. So either I've got contact issues between the injector and injector plug, or I've got bad injectors...

 

Based upon the stumbling nature of how it's been driving, I think it's badly sticking injectors. I have spares, but man that's a headache I didn't want to deal with. I'll update this once I've done the work of replacing the rear injectors.

[woldson]

Good to see you Gollum! Seems like you are on the right track, good luck!

[Dtsnlvrs]

Fire the motor up, then take a LOOOONG screwdriver and place the tip of it on each injector housing while placing your ear on the handle....if you hear it clicking (very loud) it is working. Listen to all six injectors, the dead ones will be very noticable.

 

Another thing to try...remove the fuel rail and CLEAN it, i mean really clean it...use pipe cleaners and such (gun brushes work well)....make sure every pasage and opening is clean and free of obstructions. Hope this helps

[Gollum]

I'd heard of the long screwdriver trick before, and it actually worked quite well. My only issue is that to isolate the tick noise and be certain on some of them, I had to pull the plug off to hear the noise disappear.

 

So all my injectors were opening at least. That proved that I had good electrical connection, so either it's clogged somewhere in the rail or the injector, or it's not the injectors.

 

I thought about the off/on nature of the way the car was stumbling, and couldn't imagine it being a clog/debris in the system so my next thought was the fuel pressure regulator. Luckily I had a spare lying around attached to my spare fuel rail, so I pulled it off and low and behold it's now running better than it ever has since I got it. It now skirts 2nd no issue, which it only did before on heavily damp pavement.

 

Still has uneven exhaust pulses at idle, but it idles smooth. The pulsing is either badly worn valvetrain wanting a valve adjustment (quite likely) or the fact I have two cylinders bellow minimum compression spec (also can't be helping).

 

Now we'll see if I can get 400 miles to the tank!

[Dtsnlvrs]

Good job, now get that valve lash set, and enjoy the car