Rough Idle, Sputtering, Can't figure this out!

[KDMatt]

So... here I am again with another strange issue I can't pin down.

The other week I was changing sparkplugs again (I usually just go with cheap Autolites, sort of NGK knockoffs, as a bit of oil dripping from the valve stems tends to clog them up fairly quickly) ... The auto parts store was out of my usual Autolite fix, so the clerk sold me some Champion platinums for the same prices (and I was dubious, since I hate Champions with a passion) ...

I put them in and the car ran a bit more rough at idle, but at a consistent speed, so I figured as was well in the car kingdom. I took the car for a spin and I could really feel the different platinums make, I thought I was sold! ... Well sure enough half a week later the idle was still rough, but the speed had gone way down and was varying a LOT ... so much so that the chassis... the car itself was shuddering...

I figured enough was enough, back to business and swapped in some new Autolites like I had before. I quickly gapped them, installed them, but the idle was still way off, slow and with varying speed.

I've been contending with this for almost a week now and it's driving me CRAZY (literally)... I get a sputter (almost going to die) if I do a slow/normal take-off, and it certainly sounds as if it's not running on all cylinders ... At idle I can pull either the #1 or #2 spark plug cable and not hear much difference in the idle.

I pulled the plugs to clean and re-gap, #1 had unburned fuel on it.

Here's the list of relevant parts that have been replaced...

Dizzy Cap and Rotor (Niehoff) about 9000 miles ago

Plug Wires (NGK) also 9000 miles ago

Ignition Coil (Accel Super Stock) approx 2500 miles ago

Fuel Pressure Regulator (Niehoff) 2500 miles ago

Fuel Injectors (Rebuilt, Ebay, Mr. Injector) 2500 miles ago

Fuel Injector Connectors (Ebay) 2500 miles ago

Fuel Filter (engine bay) 3000 miles ago

Fuel Filter (additional, at the tank) 50 miles ago (over the weekend)

Was running great a couple of weeks ago, quiet and smooth! Now sounds and runs terrible and I can smell the unburned fuel. Almost sounds like it's got a huge vacuum leak somewhere, it's just so rough and awful.

I'm getting voltage at the injectors with the engine running, No vaccuum leaks I can spot, and no fuel leaks. My hunch is a spark issue (??)

I'm at such a loss, please help me!

[KDMatt]

Update:

Took a timing light to the plug wires to see if spark was being delivered to all of the plugs, and this is the case, so I'm ruling out the ignition system. Advance also looks good as does ignition timing.

Second, I did a vacuum check from the brake booster line directly off the manifold and my gauge read about 12 Inch Hg (which converts to about 6 psi) ... now IIRC proper manifold vacuum should be closer to 18 or 19 Inch Hg (which is closer to 9 or 10 psi)... So now I'm hunting for vacuum leaks, but haven't found anything obvious.

... Still looking for help if anyone's got anything... I'm getting so annoyed at my car right now

[KDMatt]

Will barely idle now guys! I have the idle adjust screw turned all the way out and will barely maintain 550 rpm at closed throttle.

Still coughs and sputters at partial throttle.

Any leads or insights are really appreciated. Could it be the BCDD? Are there any other tests I can do?

[sblake01]

You say you're getting voltage at all of the injectors but are you sure that they are all firing? Do you hear an audible click from each and every injector? Especially at number one and two where you say pulling the wires makes no real difference. I use a mechanics stetescope to check that. The only other thing I've ever come across with my two efi cars that caused a problem like that was a bad connection at the temperaure sensor but if the sensor itself is bad it can also make it run like that.

[KDMatt]

okay blakey, I figured it out, but now I don't know what to do...

I tracked down a hissing sound in the engine bay and traced it to the vacuum advance on the distributor. The hose itself isn't leaking... if I push on it (i.e. pull toward the advance mechanism itself) I can get the idle to stabilize and increase the engine speed a bit, but the hissing won't cease... in fact I can't even tell exactly where the hiss itself is coming from ... Especially with the engine fan running...

I left the car idling for a few minutes while I looked around for some tools and it actually died on its own... she is not a happy Z right now...

So ... lack of vacuum in the advance explains low vacuum and fouled/wet plugs at the same time ... at least I think so...

[KDMatt]

Fixed er'!!!

Leaky hose near the advance, sealed it up and runs fantastic again!

Alright, again, thanks Blake for your help, I'm glad somebody responded to help me get my head together. I'd be so lost without this place. :stupid: