ZEX-Z

iTrader: (4)

I have a 95 LT1 and one day my car started backfiring. I have a 584" lift cam. STAGE 3 ported heads and intake. LT1 edit tune. 32lb injectors, 255 walbr fuel pump with regulater, Brand new tpi sensor,maf sensor, and optispark distributor, coil pack,ignition control module. My car is still stuck in open loop mode. The only things that I can replace is the coolant temp sensor and the O2 sensors. The O2 sensors are reading right at open and closed loop mode. But the only way to go into closed loop mode is a scanner. my idle is up another 250 rpms and smells like it is running rich. What is my problem. I really need help.

brad8266

iTrader: (23)

I would just start checking everything out under tyhe hood to see if something is not right. Start with plugs, wires, filters, optispark.

ZEX-Z

iTrader: (4)

Replaced all of that.

brad8266

iTrader: (23)

Di you replace the coolant temp sensor? And did you listen for an intake leak and for a possible valvetrain problem?

Your issues can be caused my many different things, its really hard to tell you what to look for.

Doc

iTrader: (9)

What about the wiring at the base of all those connectors. Temp sensor is prone to getting chaffed just enough to cause problems like this. Wiggle them around while you have buddy watch the scanner.

ZEX-Z

iTrader: (4)

Alright. I will do that. The only one that I did not replace is the coolant temp sensor and the O2's. I messes with the idle screw on the throttle body right before my car started acting up. I rolled it in because I wanted my idle to go down a bit. It dropped to 700rpms down from 1100 and even when it dropped to 700 it just picked right back up to 1100 again. is the idle programmed by my tuner and could this be the problem. The computer is just trying to get back to the idling point and it cant?

ZEX-Z

iTrader: (4)

Does the temp sensor show the temperature on the scanner or does the temp guage sensor show the temperature on the scanner.

ZEX-Z

iTrader: (4)

My car made very impressive #'s on the dyno. I took it back to g-force and my tuner is the one who pointed it out to me that it was stuck in open loop mode. With the power I make on Juice I should be a 10 second car if i learned how to drive on the track a little better. Little over 600hp and 700 Tq on spray bhp and TQ

brad8266

iTrader: (23)

The O2's should have nothing to do with you being stuck in open loop. The coolant sensor does though. I would pull your tune and see what the idle is set for in there. Youy may need to tweak all the idle stuff like speed, throttle cracker ect...

ZEX-Z

iTrader: (4)

So that does have an effect on the computer?

brad8266

iTrader: (23)

When the engine warms up, the coolant temp sensor tell the computer what the temp is. Once it reports a certain temp, the computer will enter closed loop operation and then your O2 sensors will start working for ya. While you are in open loop, the computer will fuel based strictly on the fuel tables, with no realtime fueling corrections, also known as LTFT's.

So basically your coolant tamp sensor can be keeping you from entering closed loop. Check out the circuit to the sensor as well as the sensor itself.

ZEX-Z

iTrader: (4)

Well check this out...... I replaced the O2 sensors and it went into closed loop. But it is still doing the same thing. Backfiring and spitting and popping at 3000 rpms and more. I talked to g force and they told me to check the plugs. I checked the plugs and They were white. So i instantly knew it was running lean. So I went back to recheck the fuel pressure..... 42-44lbs at idle and 46 at wot? No check engine lights nothing. Just a 1350 rpm idle backfiring and the bakfiring is a lean backfire. Could this be my injectors or the tune on my computer. It feels great in open loop mode. I can stomp all over it and drive the hell out of it when its cold but when it warms up and I can keep an eye on the scanner at the same time; the instant it goes into closed loop mode the car freaks out......... Any more ideas? what sensors work primarly in open loop mode?

ZEX-Z

iTrader: (4)

I replaced the pcm and had it reflashed and still the same problem. It will go into open and closed loop mode though.