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01-21-2015
Thanks for this. I'm going to replace all the vacuum lines. I'll keep you updatedOriginally Posted by Scottydoggs
the line from the top of the sc to the fire wall is what powers your hvac controls.
make sure all the evap lines are good and the one to the map. you may have leaned on them and snapped one.
01-21-2015
if you have a advance auto local go there. they are the only parts store that sells the good t's they are small white t's 2 in the pack for two bucks. they sell vac line by the foot. bout a buck a foot.
the t's the others sell are 3 inches long, and suck so bad, one huge T also costs 350 here. so f that. and it to damn big.
the fat hose off the TB to the evap, that one likes to break, if you get a hose that fits that nipple you can then push the smaller line inside the fat one to reduce it to the smaller line.
for the evap solenoid you need the ends, so cut them off, push the hard line into the vac line. all done.
01-21-2015
oh, if you change the lines on the top of the sc tree top the bbv, cut the line off with a sharp new razor, those tree's break all the time, be careful with it.
01-21-2015
I found these but im not sure if they would work on a 97 GTP?
http://hiperformancestore.com/pontiac.htm
01-21-2015
Found this too but it says 98-03 too....
http://www.ebay.com/itm/Silicone-Vac...-/380865733231
01-21-2015
you can spend 5 bucks.....or 75. up to you.
01-21-2015
Pre-cat o2 is giving you constant readings? The first o2 should be rapidly switching when working correctly, but maybe I read that wrong...
01-21-2015
Yea im constantly getting signal, not constantly getting same signal
01-21-2015
you have a t app? can you read your ltft's?
your up stream o2 should dance up and down at idle fast.
01-22-2015
To best understand why boost goes down when you open up flow. It's because boost is the measurement of back pressure within the intake manifold. Headers on an otherwise stock engine will help get some of the pressure through the heads and out the exhaust, as the exhaust is restrictive. Hence.. back pressure aka boost goes down.
Bragging about boost being high is silly IMO, because it's back pressure and not necessarily being used by the engine. However comparison engine to engine with mods etc.. it can be a good indicator of expected power levels.
01-22-2015
Yea I can read the graph of signal being put out out by o2. Yea it goes up and down. I'll replace o2 if vacuum lines dont fix it
01-22-2015
ltft's are your long term fuel trims. then can tell us if your running lean or rich.
01-23-2015
What do you guys think about wideband o2 sensors? Would that help?
01-23-2015
A wideband O2 sensor is only useful if a computer will treat it accordingly.
Essentially, a "standard" O2 sensor is really just set up to read rich/lean. Rich is above 0.45V, and lean is below 0.45V. The computer is really just trying to make sure that it runs so "close" to the correct A/F ratio that the signal quickly goes above and below that 0.45V threshold, which told the computer that the A/F ratio was averaging out about correctly. If the O2 sensor spent a lot of time below 0.45V and didn't go above very often, the computer would try to fatten up the mixture accordingly. That's how the PCM acts.
The voltage is not linear above & below the 0.45V - not even close. It's a wild curve, but 0.45V is pretty much always equates to a 14.7:1 A/F ratio. Look at this:
Unfortunately that graph makes the response look linear and predictable, but it isn't nearly as clean as that graph makes it look. But you get the idea.
In the old days some of the boosted cars (i.e. 1980's turbo Grand Nationals) would pick a particular voltage and tune accordingly. Sometimes 0.810V, sometimes 0.850V, etc., but it had to be reviewed every time the sensor changed, the driver would have to set expectations for the new sensor accordingly.
The advantage of a wideband is that it can give a much more linear signal, so that you can interpret a more precise A/F ratio. That works great on an A/F ratio gauge, or for computers which are set up to read that signal and adjust accordingly. But since the PCM in our cars is set up for the "standard" O2 sensor, the PCM would be confused and would not react accordingly.
I am in the middle of installing EFI onto a 1973 Buick, and that will have a wideband O2 sensor - because the computer I'm using is designed to use it. It will tweak the tune accordingly.
You can't just swap a wideband O2 in place of a standard O2 because the computer won't know what to do with it.
01-26-2015
What about the plugs? I dont know if it would cause the engine to sputter or bog down but if your running stock plugs with headers maybe thats the problem?
01-27-2015
Hey guys, thanks for the input. I appreciate the o2 explanation as well. I am replacing all the vacuum lines today, if that doesnt work, ill replace the precat o2. Then I guess I'll think about plugs? Just out of curiosity, what kind of plugs should be used with headers?
01-27-2015
I'm pretty sure you want autolite 104's with headers, but maybe that is only after you drop the pulley size. And I'm assuming your on the stock pulley. I'm sure some other guys will chime in..
01-27-2015
stock plugs are fine with a stock pulley and headers.
if you put a 3.4 on there you'll want the 104's
01-27-2015
Guys thank you for all your help. This is now solved. check engine light finally came on. Came on after driving it hard, cylinder 4 misfire. Cracked plug. All good now.
01-27-2015
there ya go.
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