3100 Bad Idle, Sputtering

[Dallas_95GT]

Hey guys.... Recently I noticed one of my injectors leaking, so I pulled the fuel rail yesterday and changed out the o-rings. I put everything back together, started the car up, and it runs like crap! It's idling about 300 rpm too high, and sounds like it's missing on acceleration. Going down the highway it does ok, put when you try to accelerate, it jerks pretty bad. It also seems to have a rich smell to the exhaust.

I've checked all the plug wires, all vac lines are ok, fuel pressure regulator is fairly new, no fuel leaks. No service engine lights either.

Any suggestions?

[mattcow]

Since all you originally touched was the fuel rail, I would say that you have a vacuum leak at the injector.
This would defiantly cause your car to run rough, but with decreasing vacuum pressure (highway driving) there would be less air getting in, so you may not notice it then.

[daman]

Did you make shure that the injector O-rings seated in to
the LIM good and didn't roll out a little???

i use oil on the o rings and coat the intake holes so
everything slips into place good..

[rixGAphx]

How did you "...notice one of the injectors leaking.."?
Specifically, was it leaking fuel from the rail onto the LIM? or,
Was the injector leaking into the intake and thus into the cylinder?

On each injector, there are 2 O-rings:
* Upper (from the fuel rail to the injector); this is ALWAYS under pressure from the fuel.
* Lower (from the injector to the LIM); this is NEVER under pressure from fuel or air, it is always under VACUUM form inside the manifold.

As you remove the fuel rail, you kinda 'rock-and-jiggle' it to release from the LIM.
All 6 of those O-rings must be properly reseated (and preferably replaced) when the rail is reinstalled.
As Mattcow said, it is very easy to cut or mis-seat one of those lower O-rings, and that would result in a massive vacuum leak to that one cylinder (or multiple cylinders, if multiple lower O-rings weren't right).

If you had sen fuel leaking from an injector (and IIRC, only #2 and #4 are visible until the UIM is removed), then you may have decided to replace that leaking O-ring.
Good.
Mebbe others were also leaking? I dunno.
Are you sure you got the clips on properly? It is the clips that hold the injectors tight to the rail; the O-rings merely seal the gap.

And as Daman said, always use a spot of oil on the O-rings as your install them.

Fuel can only leak from the upper O-ring, never the lower.
It leaks onto the LIM, where it poses a fire hazard and evaporates, and causes poor fuel consumption, but doesn't cause any drivability problems for the engine.
* * *

Finally,
On the 3100, injector leakage is only past the upper O-rings.

The needle inside the orifice of the injector itself becomes blocked by a microscopic grain of sand, which holds it partway open.
So 100% of the time that the fuel pump is on, a trickle of fuel is leaking into the MANIFOLD, where it flow and pools at the back of the intake valve.
Off-the-shelf injector cleaner only dissolves varnish, won't dislodge these micro grains.
Mebbe somebody can 'bench clean' the injectors, I dunno.
IMO, the only solution to this stuck injector is replacement ($75-130 EACH :eek: ).

The engine runs very rich and very rough.
If it's a rear injector (1, 3, or 5), then the exhaust is very rich (lacking in oxygen) when the O2 sensor read it, so the PCM *may* lean-out the other cylinders in response.
Causing further crappy running.
Meantime, that one (or more) rich-running cylinder(s) is creating a lot of power and pollution.

Personally, I would redo the O-ring job, completely.
And while the injectors were out, I would have them tested for leakage.
Mebbe find if somebody local has a good price for a reconditioning/cleaning that is capable of cleaning a stuck orifice.
And prepare for rapage for new injector(s) that can't be cleared.

Good luck.
-Rick