idle idle idle sputter idle

I guess anything's possible, but it sure doesn't make much sense that a plugged filter would be more evident at idle than on acceleration...

I'm bettin' they haven't found it yet. Sorry. :-)

That happens on my mechanical pump system sometimes just before all heck breaks loose. When my rpm come up, so does the pump flow and it will push by the blockages.

I suppose the power could drop to the electric pump at low rpm causing the same effect maybe?

Mike

bllsht wrote:

bllsht did pass the time by typing:

That was my thought as well, but it is running a lot better now. They also ran heavy duty decarbonizing/cleaning stuff down the injectors to clean out carbon buildup. That may well be the cause of my rough idle. The ZJ was running way rich due to a cracked exhaust header and weak O2 sensor. Oddly though when I had the exhaust header off the valves looked real clean, only the intake rail had some oil/crud buildup which is your usual CCV caused buildup.

Even if it didn't fix the stumble it sure brought back some noticeable power. For right now it idles quite a bit smoother. Not perfect, still has some vibrations, but no where near what it was doing.

On the bright side they did fix a few buzzes under the hood, a hose that was rubbing, and spotted an interference between the ABS pump and my supercharger. That last one I'm afraid is due to a busted motormount isolator. Jeep only sells the damn things as a whole part and there are no aftermarket parts. :( Oh well, it's a Jeep thing and "they" understand.

Gonna have to let the motor cool down and put a prybar on the mounts. Should be easy to tell and fairly easy to fix. Wonder if I could mill a new mount out of poly? Or more precisely have the local plastics shop do it for me. Its only a glorified rubber donut.

Mike Romain did pass the time by typing:

Dunno.. At boost levels the Kenne Bell boost-a-pump module ups the fuel pumps voltage and by that the pressure, but that's only when the rail goes above 2psi. Othewise it should stay stock.

Overall performance had been going down along with fuel milage. First thought was vac leak, but a few passes with the propane wand didn't find any leaks.

Checked and cleaned every single connector also. Even checked the sparkplug wires for crossfire or leaks and the cap for arcing.. Spent so much time under the hood I figured it was time to let another set of eyeballs look at it.

That and I don't have the equipment to properly clean the injection system.

Guess my next project will be to install some more electronics. A O2 sensor and electric sending fuel pressure gauge.

Well, I would never say never, but it's not really likely. :-)

That sounds more like it. Dirty injectors would be much more likely to cause idle problems than a plugged filter. If you couldn't get enough fuel through a filter for proper idle, it's not likely you'll be able to do it on acceleration.

It would be interesting to see what the fuel trim is doing. Why don't you go buy a scanner and let us know what it looks like? :-)

Actually, I don't know if the aftermarket OBD I scanners will show you this. The OBD II ones will.

That was the primary reason for taking it in. I just don't have anything to do that type of work even though the Strap^WSnapOn guy will sell one to me "For a small phenomenal fee." :]

Been tempted but the OBD I types are fairly expensive compared to replacing a few parts here and there. Most of the electrics are easy enough to test with my lab gear (Fluke 87 Multimeter, Tektronics TDS2002 O-scope, etc) Then again I've probably got more money in electronics test gear than a scanner would cost. :)

Dunno either, I'll drop by the dealership and take a gander at the service book. Those OBD II scanners are all over the place, I've even seen shareware versions for a laptop and PDAs.