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95 3.4 wont idle, misfires bad

152 Views 9 Replies 2 Participants Last post by  Injuneer
So I replaced the headgasket, used the Lisle tool to remove and install the pushrods so no valve adjustment needed, pushrods are all in correct spots. Check compression and its good. All gaskets/seals that were removed for the job were replaced. Used ARP studs and torqued to 80 ftlbs in three steps per ARP.

Car starts for around 2 seconds after excessive cranking but misfires badly and shuts back down, shuts down even quicker if you give it any throttle. Swapped the ICM and coils with another and same thing. Plug number 6 gets very black and wet others are dry, any ideas on a starting point? Anything to unplug that if bad would allow it to run to narrow down a trouble point without throwing parts at it?

Plug wires seem to be correct, injector wires seem to go to correct spots as well. Everything appears to be plugged in.

With the 94/95 V6 scan tool with a red devil fiero cable it doesnt seem to show anything I would believe abnormal. Everything seems plugged back in correctly.

Did see the cam sensor wire looks a little rough (damaged by something) but from what I've read it should run but throw a code if it were to be bad, this hasnt thrown any codes yet and essentially doesnt run. The cam sensor would not cause it to misfire bad and shut down immediately, correct?

Car ran fine before the job but overheated and puked out overflow (was leaking into cooling system, didn't burn or mix fluids)
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#6 injector might be leaking so bad it’s screwing up the fuel pressure. Check the pressure.
got about 35psi with a battery charger hooked up to the battery and around 15 key cycles (keeping voltage around 13.x to help) and drops to around 25 in a 2-3 minutes and 10psi in around 15 minutes.
You have a leak somewhere. The pressure should build to at least 40 PSI with the first turn of the key. Turning the key 15 times was pointless. Should not drop more than a few PSI in 10 minutes. Possible sources of leaks:

- faulty check valve in fuel pump

- leak in a supply side fuel line, including the flex hose in the tank

- defective fuel pressure regulator

- Leaking injector(s)

I don't know the detailed layout of the V6 top top side fuel components. Most likely cause is a leaking #6 injector. Next would be a leaking fuel pressure regulator. If the regulator is vacuum compensated, where is the vacuum port located on the intake manifold. If it's closer to #6 than any other cylinder, the pressure regulator diaphragm could be torn, dumping fuel into the intake manifold.
Two plugs ended up being wet and black, took injectors out and two work but leak and 4 seem to have given up so ordered new injectors. I used 12v and a can of tb cleaner sealed to back of injector to test, the two that had dirty plugs worked but leaked and the other 4 seem stuck shut. Would explain it not wanting to run lol
New injectors did the trick. However I did notice after running for about 10 seconds the temp gauge starts to rapidly peg past 260. It has a new sender in it as the original one got damaged when removing the head. Any easy tests (ohms at various temperatures) to determine if the sender is bad or if there is a wire issue? Was searching the factory manual but doesn't seem to detail it so far, although 4100 pages is alot to dig through lol
This procedure covers testing sensor and system voltage. It's specifically for the LT1 V8, so the locations of your sensors will be different. But the sensor resistance and circuit voltages will be the same.

Runs great, however currently have no thermostat in it so I could bleed it easily and see if it was fixed. Does not mix fluids, doesnt smoke and doesn't push coolant now, however after driving it around (temp gauge stays below 160 with no t-stat) and letting it sit turned off the gauge is pegged, guessing from heat soak from no circulation. Assuming it did overheat any ideas? would not think head gasket again since there are zero symptoms (other than overheating) Was vaccum bled and then extended funnel bled with cycles of idling to help it bleed.

So if gauge is accurate (new carquest sender, the old new one was faulty) what would be a decent starting point for overheat with no coolant bubbles, no mixing fluids and no smoke? Guessing maybe an underlying issue which could've caused the blown gasket in first place? Clogs or weak waterpump? More air yet? Held a vaccum just fine so cooling system seems to be sealed well

Cooling system related it has new aluminum radiator, new headgasket, arp head studs, new serp belt and tensioner, new hoses

Like the car but it has been extremely frustrating lol

Thank you for the help so far!
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Update, got a mechanical gauge and it gets up to 190 degrees and stays around 185-210 degrees driving around with the A/C full blast, was around 80 degrees outside, probably 20-30 minutes of driving on a loop with hills and fair amount of corners to accell out of. Park it and with heat soak (engine off) it reaches around 228 degrees. Assuming this is all very normal and within spec? Guessing I have a gauge or wiring issue that I'll have to track down.
Everything seems good. The engine was designed to run @ 210°F, to yield the best combination of low emissions and high MPG.

Watch the temp gauge when you are driving at high speeds on the freeway. If the temp start to climb, heading for the red, check to see if the black plastic “air dam” is still under the front bumper. If it’s missing, it screws up air flow to the radiator at high speeds.
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