cheers again mates - so i got this 3.4 all back together, this weekend installed engine. got averything hooked up, gave it crank and started right up, maybe 4 seconds of cranking after complete rebuild, was pretty surprised/happy with that. seems to run pretty smooth, after a few minutes, i'd say close to but no more than 10 for sure, i notice exhaust manifolds getting hot - and i mean glowing hot. i shut it off immedietly, and within few seconds the glow goes from dark orange back to black, so they were just at the point of glowing, but still. seems very hot. wondering what can be causing this - i haven't set the timing yet, i just eye-balled it when putting the distributor in, but for it to start that easily i'm guessing it can't be too far off. would it being terribly retarded cause this? i have no engine warning light, and i know light works. if i had an o2 sensor problem, i'd have an engine light on right? does this seem like a lean condition? these are those thin-walled steel tube style manifolds, wondering how much of this might be normal.....for sure i'm going to get the timing set correctly and go from there. i should set at 10 deg btdc with jumper wire installed?
Some of the typical causes are air leaks on the manifolds, and inconsistent spark.
The spark can be really difficult to figure out. The idea is, once in a while the cylinder doesn't fire, then the air fuel ignites in the manifold. Check you wires at night, and spritz them with a water mist and look for spark discharges.
Being very lean with light up the manifolds. Check the timing and watch the O2 for sitting under 100mV. if it is, the suggestions are good. Too much air or too little fuel.
That said, I put a camera under the hood and went for a drive (the engine was running correctly) and the manifolds will get red hot under there when everything is fine. But just sitting there idling you shouldn't see any glow when the O2 is switching correctly and the AFR is right.
I believe there is an ALDL mode on the V6 ECM where the SES lamp will flash the status of the O2 but I think it only does it when you are off idle. However, it might still tell you of the O2 is dead even when you rev it up. The O2 should go high for a second and then start switching when you hold it steady. If it's still low, something is wrong.
[This message has been edited by TK (edited 11-12-2013).]
yeah i don't remember exactly but it did idle quite high.....cracked tube doesn't sound good. so other than pulling the tube out how would i confirm that? is that tube from valve to intake under pressure or vacuum? what would the fix for that tube? i assume its no longer available.... hoping to get car back in tomorrow night to set timing and measure o2 sensor voltage. any way to check that tube? carefully spraying ether or brake clean or something? (thats assuming that tube is under a vacuum not pressure)
Also check the idle tube and hose that goes from the bottom of the TB to lower manifold. That is the idle air path. Idle air doesn't flow through the upper plenum. I had a cracked line down there that drove me nuts (and it still shows today!)
yeah i don't remember exactly but it did idle quite high.....cracked tube doesn't sound good. so other than pulling the tube out how would i confirm that? is that tube from valve to intake under pressure or vacuum? what would the fix for that tube? i assume its no longer available.... hoping to get car back in tomorrow night to set timing and measure o2 sensor voltage. any way to check that tube? carefully spraying ether or brake clean or something? (thats assuming that tube is under a vacuum not pressure)
Loosen the connection under the intake plenum and slip a thin strip of sheet metal between the bolts and tighten it up... an aluminum beer can is the perfect material. If your idle goes down you know there is a leak in the tube.
edit: tubes are still available.
[This message has been edited by Gall757 (edited 11-13-2013).]
Just a few tips. Being that both manifolds are glowing you can deduce that it has to be something common to all cylinders. Not an individual misfire i.e. plug, wire. However if it was a misfire common to all cylinders i.e distributor, coil, rotor it should run like crap. Pre ODBi, 1.5 and ODBII uses a single or 2 wire O2 sensor(stock Fiero single) without a heater. When around idle PCM does not monitor O2 unless it goes above .45v. In that case you would not get a light/code at idle. Anything that could cause unburned fuel in the exhaust, timing, air/vacuum leaks(brake booster hose disconneted, leaking EGR tube, stuck open EGR at idle), overly rich(fuel pressure regulator) would be the things to look at first.
okay thanks again guys.....well tonight I set the timing, jumpered the A and B terminals, then set to 10 deg.... it was way on the retarded side. I let it warm up, after couple few min idle came down to 900, which I confirmed with timing light (reads rpm). while it was warming up I sprayed ether all around the vacuum lines and egr tube, not a lick of rpm change. I also watched o2 sensor voltage, and this is with multimeter and with sensor connected, voltage between .8 and .2, sort of jumps up and down between there. im not completly sure about the 02 sensor cycling like that seems to be running pretty good to me....is there a chance it was all just from the timing being out? I didnt run it for as long tonight, and the other night when manifolds were glowing I had it up around 2000 rpm (first time running since rebuild) and timing wasnt set.
There is a good chance it was all in the timing. I had the same thing happen to me just after a rebuild and in my case thats all it was. Tons of miles later I never had any issues.
