MISSING AT IDLE..EXHAUST DEPOSITS

[DMAN302]

Ok my88GT has a miss at idle, kinda stumbles and stays about 1000-1100, if I bring it down any lower it gets really rough, also getting alot of black soot off the passenger side exhaust tip onto the bumper. Any one have any ideas??
Heres my set up as is:
Typhoon intake, new PCV valve, new wires plugs, new AFPR at 40#, new cap and rotor, new act, iac, tps, egr and selenoid..the idle is really picky and does'nt like to be played with much. car is 5spd with 196000 miles..any help appreciated...

 

[ss93cobra]

How are the plugs on that side?

 

[DMAN302]

Plugs are actually really clean and O2's are 2months old, timing is at 12deg.

 

[ss93cobra]

Is fuel pressure setting (40) with vac. off or on?

 

[DMAN302]

vac off

 

[ss93cobra]

Some of it could simply be from the age/mileage of the motor too. Did this just start with the installation of the mods or has it always done it. Plus, depending on how old your plugs are, for them to be "really clean" could also be a concern, such as not firing.

 

[PonyBoy90]

How thick is the deposit in the exhaust tips? Is it thin and powdery black, or are we talking caked on black crap? You could be running a little rich on that side of the engine.

Or, you could be burning oil and your valves are going?

 

[DMAN302]

don't really leave it on long enough to build up but seems like light powder..mixing with exhaust vapour so hard to tell how heavy it could get, I have noticed some oil burn lately but no smoke at start up or idle only when I give revs over 3000 rpm..I kind of think somehow its related to my idle problems I've been experiencing since cleaning the upper intake..all vac lines seem good and connected so I don't see vac leak. I am friggin tired of casing problems with this damn car!!

 

[bjmellon]

Have you tried using 2+2 to find a vacuum leak? It seems like it could definitely be a vacuum leak.. Whats your tps voltage??

 

[DMAN302]

2+2??what is that?

 

[Hydrocarbon]

I'm kinda have the same problem. It surges and misses at idle, especially in gear. I checked vacuum by hooking up a tee to the FPR, vacuum is at 16" and doesn't fluctuate.

 

[DMAN302]

Helll I've got a strong 21Hg and still think I may have vac leak..however tonight I adjusted my set screw and started up the car without adjusting TPS and resetting computer and what do you know...cold start idle started at 1400 and fell to a nice 850-900..so I checked my TPS it was at .96..so I did not reset computer and just drove it for a bit..found idle to be falling nicely though stickin at 1400-1500 for a few seconds before droppingt to 900 when falling between up shifts and falling right to 1000 when downshifting..???how the hell can the car tell the difference!!??.sometimes I just have to step back and laugh. The stumbling idle has me guessing..I just can't narrow it down to anything I can easily find unless it's something like a head gasket, but the oil is clean as can be and coolant is good and full..and clean as well.

 

[bjmellon]

2+2 is a brand of carb cleaner, sorry I guess i'm just so used to reffering to it as 2+2. I noticed the tps is .96v, but did you open the throttle and measure the voltage to make sure it "sweeps" nicely ( doesn't jump, stay at one voltage for a while). Also check to make sure the tps isn't sticking at a higher voltage.