Misfire!

[dansformula]

Alright I am new to ltx and just purchased my first lt1 a 1994 firebird formula. So heres what I know the car is missing all the time. I just replaced the opti waterpump and plugs and wires and cleaned the (MAF) with cleaner. the car is throwing 6 codes. Car runs and drives but misses constantly and I am looking to fix it ASAP! I appreciate anything you guys can tell me. I checked fuel pressure, injectors all work, I am pretty sure the opti is on correct as well as spark plug wiring. Car is running rich. Like I said I appreciate anything THANKS!!

1. (011) Malfunction indicator lamp circuit problem
2. (015) coolant temp signal voltage low or short circuit (No coolant temp in dash)
3. (029) output driver module (ODM) fault EAS circuit
4. (032) EGR incorrect EGR valve operation
5. (048) Mass air Flow circuit problem
6. (VSS) vehicle speed sensor loss of signal

[Badbird_96]

Check the maf and the egr. Also could be unrelated like on my 94 formy I had a lifter come apart and had a dead cylinder. Saw you changed opti but forgot if you changed plugs. Checking them will narrow it down to a cylinder. Also don't know if the temp sensor means the one for the dash which is on the head. If the other one on the water pump is bad it will cause the car to run rich and flood which will cause a stumble. Would also check the o2s if all else fails. I know it didn't throw a code but sometimes they don't. I would bet though that its the egr or the temp sensor. The maf can be cleaned and sometimes that helps but be super easy doing it. Use electrical cleaning spray and don't just soak it.

[dansformula]

thanks! i baught a new maf sensor and it seems to run smoother but the cheap wires i baught arc so im going.to try and replace those or repair

[Badbird_96]

Oh yeah that would do it lol

[rdx]

I agree with Badbird 96, main suspects are the MAF and the EGR but if your cables are bad they'll cause missfires too. So if now you have replaced the MAF and the code has gone away we can discard it, it was probably part of the problem but not the whole. As you're going to replace the wires I will recommend getting a "DEI Protected a Wire" kit so you can protect the new wires from the exhaust temps and make sure you route them far from the manifolds and cats (if you have) that way you can prevent them from getting melt again.. About the EGR, try unplugging the line that goes from the electrical solenoid to the top of the EGR valve while the car is idling and see if it idles better. EGR can make the LT1 run like crap, trust me on that one :)

[Badbird_96]

Even worse on a 4.3 vortec. It won't idle at all. Egr is a horrible idea anyways

[rdx]

Even worse on a 4.3 vortec. It won't idle at all. Egr is a horrible idea anyways

You bet, once I figured out I had bad EGR, I bought the block off plates inmediatly

[Badbird_96]

Mine was good and I was like hmm egr... toss that shyt lol

[rdx]

Mine was good and I was like hmm egr... toss that shyt lol

LOL, also it is less crap to worry about when chasing issues down

[Badbird_96]

Personally I think air pump/egr/ and rear o2s should be standard deletion items lol

[rdx]

Personally I think air pump/egr/ and rear o2s should be standard deletion items lol

BTW how do you delete the rear o2s without reprogramming the PCM? I saw there are "spacers" that prevent you from getting codes and from getting the car in open loop but you still need to plug the o2s with the spaces back into the exhaust pipe, right? So it is not like a physical delete, Am I right? Or is there a different way to delete them?

[Chris]

They make simulators that send a signal back to the pcm to prevent dtcs. The spacers move the sensor out of the exhuast stream so there is less to sample

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[Chris]

http://fasttoys.net/shop/O2-Simulator-and-Tester-LT1-LS1-V6-Camaro-Firebird-Corvette/
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[rdx]

They make simulators that send a signal back to the pcm to prevent dtcs. The spacers move the sensor out of the exhuast stream so there is less to sample

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But both work right? Except for the fact that with the spacers the sensors will still be somewhere..

[Chris]

I would prefer the simulators myself or having them tuned out of the picture.
The spacers still allow the sensors to sample and create the chance for a dtc
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[Badbird_96]

The spacer tries to simulate the reduced flow of the exhaust from the cat. Really all the downstream o2s do is make sure the flow coming out of your car is said percentage less than the upstream. It really does nothing to begin with. Yes to tune them out the pcm has to be tuned. The simulator just basically lets it think its hunky dory. Spacers as Chris said can still cause a check code and the spacers are still hooked into the exhaust. Basically all the simulator is, is a resistor that puts the correct voltage through to the pcm. Although its not a resistor just best way I could think to describe it.

[dansformula]

well i changed the wires because two are bad but the car seems to run choppy when accelerating and runs pretty smooth at idle. i changed the maf but i think there might be a short in the wiring harness

[Badbird_96]

Very possible. My moms firebird has two shorts I gotta find. One is too the alternator and the other is to the throttle body. 3.8 fbw car

[popo8]

well i changed the wires because two are bad but the car seems to run choppy when accelerating and runs pretty smooth at idle. i changed the maf but i think there might be a short in the wiring harness

I dont want to sound rude... but are you sure the wires are routed properly.....

[Badbird_96]

Hey good call popo didn't think of that. When we got my moms firebird it had a miss and two wires were crossed.

[rdx]

^^ +2 check the wires again :) About the MAF.. did you get rid of the MAF DTC with the new unit?

[dansformula]

well i look on shbox.com for all wiring even tho it is labeled on distributor. never checked egr but will do that when i get home car is a pain in my ass. once i get it in the garage i am going to check all connections for the 4th time on the wires im going to pull the plugs to see if they are fouled i want to egr delete but im not fully sure how. and as for the maf sensor idk about the wiring.
thanks for all the tips and advice! if it wasnt for my limited budget i would probably just run a completely new wiring harness because whoever have the car before me rigged a few things constant fan running broken connections and who knows a few burnt wires.