98 Mustang GT...Running rough, tailpipes black with soot

sanitarium16

New Member
Oct 17, 2004
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My car was perfect up until a few weeks ago. My car is modified with the following: Mac CAI, FRPP 70mm Throttle Body, BBK Intake Plenum, FRPP PI Intake Manifold, Mac Off-road h-pipe,Flowmaster super 40 catback, Trans-go shift kit, Diablosport predator tuner premium fuel tune.
I have my rear o2 sensors shut off via the predator tuners so i am not throwing any codes or CEL. All 02 sensors were replaced with Bosch last year and the car has brand new plugs, wires, MAF sensor,IAC,cleaned the EGR Valve, cleaned throttle body and new fuel filter. Using the diagnostics feature of my diablo predator i am able to read multiple things. My tail pipes are black with soot and have always been since i put on the off road h pipe. My 02 sensor readings fluctuate from 0.1 to 0.7. I was told this is normal. My MAF voltage is .76 idle. My idle is jumpy....goes from 620,650,700 and fluxuates in between there. There is no pinging or detonating going on that i can hear and i fill up on 93. Do i have to buy a new h-pipe with high flow cats in order to fix this problem? Another note is that my spark advance is jumping around too. 17 to 18 to 19 at idle. I have it raised a little (8% throughout entire rpm range) but i have always had it on this setting. Another thing to mention.....there are no vaccum leaks...sorry for the long post but im trying to be as detailed as possible.
 
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I can feel it through the steering wheel and that drives me nuts cause it never did it before. On an off releated topic, do you guys know anyone who does custom tuning for the diablosport preadtor?
 
Yes, i have changed everything. spark plugs are brand new motorcraft, wires brand new frpp 9mm and new motorcraft fuel filter. Every matainence item is perfect i am tedious when it comes to that. It doesn't feel like a misfire and when i rev the engine it is perfect.....just idle....it is driving me nuts. It just started happening all of a sudden!:bang:
 
Tps is reading .097 volts.
Here are some other readings in the "gas fuel" selection. not sure what they all mean

31.84V CAS GRND
2.26V FLI V
2.7V FRP V
5.0V FTPV
3.6-3.7MS FUELPW1
3.6-3.7MS FUELPW2
2.69V IAT V
.94V EGR VALVE
2.32V EFTA
100% FP
 
if fp is for fuel pump duty then your dumping a LOT of fuel in at idle... our car uses the fuel pump to adjust flow instead of a regulator so thecontrol for the pump might be shot causing a lot of fuel to be dumped into teh engine and the car probably burns it just fine off of idle but it struggles at idle...

<---- took a wild guess.
 
sanitarium16 said:
My car was perfect up until a few weeks ago. My car is modified with the following: Mac CAI, FRPP 70mm Throttle Body, BBK Intake Plenum, FRPP PI Intake Manifold, Mac Off-road h-pipe,Flowmaster super 40 catback, Trans-go shift kit, Diablosport predator tuner premium fuel tune.
I have my rear o2 sensors shut off via the predator tuners so i am not throwing any codes or CEL. All 02 sensors were replaced with Bosch last year and the car has brand new plugs, wires, MAF sensor,IAC,cleaned the EGR Valve, cleaned throttle body and new fuel filter. Using the diagnostics feature of my diablo predator i am able to read multiple things. My tail pipes are black with soot and have always been since i put on the off road h pipe. My 02 sensor readings fluctuate from 0.1 to 0.7. I was told this is normal. My MAF voltage is .76 idle. My idle is jumpy....goes from 620,650,700 and fluxuates in between there. There is no pinging or detonating going on that i can hear and i fill up on 93. Do i have to buy a new h-pipe with high flow cats in order to fix this problem? Another note is that my spark advance is jumping around too. 17 to 18 to 19 at idle. I have it raised a little (8% throughout entire rpm range) but i have always had it on this setting. Another thing to mention.....there are no vaccum leaks...sorry for the long post but im trying to be as detailed as possible.



JP i thought you fixed this with the coil packs! :eek: