TP355Z

Alright - most of you guys know me enough so here's my prob.

I've got the 670 holley unit and i'm still running my 305 computer with the 330hp 350 i built - my problem is that the idle seems too high. With the idle screw turned all the way out (the tbi valves are nearly completely shut) the car still idles around 900rpm. I've replaced the pcv valve, checked my TBI mount bolts, played w/my fuel pressure. The only thing i haven't looked into is the intake bolts - thats my next step. Has anyone else encountered this problem? I'm running out of stuff to check. I've already traced all my vacuum lines and made sure they're ok.

PCV valve
intake bolts
tbi mount bolts
vaccuum lines
valve cover grommets (could stiff/worn grommets do this?)

Please help.

tyler

NJ SPEEDER

start with all teh vacuum lines and vacuum ports on teh tb. the odds are pretty good that something wasn't pushed all teh way on or is a little loose and allowing a leak. just follow them around one at a time and push them all on tight. if it is only at 900 it is a small leak.

good luck

later
tim

TP355Z

well - its still idling at that rate w/the tbi nearly shut - i'll look into it. I've got all my plugs on as far as i think they can go - maybe one of the egr lines is bad or something - i'm not quite sure. I didn't mention this - but i made a 1/4inch spacer outta teflon and used home-made gaskets above/bellow it - so maybe they're leaking (its gasket material - but its not thick and fibery like they normal stuff, more like thin cardboard). Thanks guys

Tyler

MightyMouse

To find a leak, hose down the suspected area with carb cleaner. If there is a leak in that area, the idle speed/quality should change.

Tom91Bird

iTrader: (5)

try retarding your timing just a little bit

TP355Z

well - i pulled all my plugs today. 4 or 5 of them look decidedly sooty (brown or black from over richness?) but two of them were whitish colored and one of those two had white soot on the base of the electrode (looked like white carbon). I'm not sure if i fouled the plugs and they're just not working right or what so i'm replacing them. Also - i think my thermostat was bad, either that or the 180' one which was in the car didn't work well with the computer b/c it ran real rich. I've got to figure out how to better guage how rich/lean i'm running by adjusting my fuel pressure regulator. One last thing - when people (like Z28boy) say they installed an fuel pressure gague, like on the fuel lines, is that measuring the fuel pressure going to the injectors (which can be adjusted on the TBI) or is it just measuring the pressure the fuel pump creates? I'm sooooo in over my head. lol


tyler

oh yeah - i pulled my codes, got a 43 and 42 and the one for "inlet air temperature" because i had the sensor just laying on the wires by the distributor - could that throw things off?

TP355Z

PPS - I'm also contemplating whether my O2 sensor could be bad (100,000 on the car and its an old sensor) or maybe if my Knock Sensor module could be hurting me - I got a new sensor for a 350, but never changed the module.

Tyler

JPrevost

How about you take a look at the IAC. Make sure it's all the way in when you set min idle on the TB. You could hook up winaldl or a scanner of some sorts and read out the IAC steps BUT that doesn't tell you exactly where the pintel is on the IAC. BTW, the IAC is basically a vacuum leak controlled by the ecm to prevent stalls and help warm up the car etc.
Put the key into the on position, you should hear the IAC move. Have a buddy look down at the pintel to verify it's movement. Next you want to use the paperclip in the aldl to put the ecm into ALDL mode. Don't start the car, just keep the key in the on position until the pintel on the IAC is all the way closed. Unplug the IAC plug and remove paperclip, start car, adjust min idle with the engine at operating temp. There, now you've got min idle set. Turn off the car, plug the IAC back in, start car, watch the idle go down and use the scan tool to verify about 5-20 "steps" on the IAC. The idle should be stable and low, if not, vac leak and/or running a bit on the rich side.
The fuel pressure is measured on the supply line. It's rather simple really, the fuel pump pushs the gas down the supply line, through the fuel filter (no effects), and then the next in line is the injectors. After the injectors is the fuel pressure regulator, it's located on the return line. This way the supply line has pressure. Anything the injectors don't use go back through the regulator (hence the name) and through the return line back into the tank.
When you install a fuel pressure guage it has to be on the supply line, doesn't really matter where but the closer to the injectors the better. I don't think it's as important considering what you should be doing is just setting the pressure at a constant engine load/rpm so it doesn't matter where it is. I installed mine on the rubber flex line (drivers side frame rail above power stearing box). The larger metal line is the supply line, return line is smaller.
Shame on you, look at what you just made me do....I wrote all that when I should be studying for my last final!!!

TP355Z

Thank you Jon Good luck w/the finals - I'm clawing desperately to get my car going so i can do a smoke show come graduation...hehehe

tyler

JPL87SS

hey we have a suburban that used to idle fast a heck i hated it but we (me and my dad)replaced the tbi gasket and it idled just fine after that. i'm only 15 and i don't know much but i know that completely fixed our problem

JPrevost

Classic example of a vac leak.
To find a leak, spray carb cleaner (the stuff in the spray bottle/can) around where you think there might be a leak. If the idle goes up even more then you've found the leak .
You can also use the smoke trick but I find that harder considering the engine usually sucks in most of the smoke having an open element .
Anyway you look at it, there has got to be more air getting to the engine than what's being adjusted at the throttle blades. Sometimes the bushings on the side of the TB get worn out. It's rare, but can happen.

TP355Z

Jon - the tbi is brand new (holley unit) so i think the bushings are ok - i'mna have to try the carb cleaner solution in a few days. However - this is what I'm fixing on the car b4 I start hunting around.

Throttle Position Sensor - I never adjusted mine so i'mna hook the car up to a scope and adjust it to the .65volts or whatever.

Fuel Pressure - I've been toying w/the regulator blindly on the holley unit and i'm sick of it - i'm installing a fuel pressure guage soon. My only problem is the cheapest way to do so. I looked at Z28 boys site and it was really helpful - but I dont want to spend $150 on fuel line and anadized hardware - I'd rather put the gague in for the time being - is there a cheap way to do that w/stock fuel lines?

Air Inlet Sensor - I just had mine sitting (hooked up) by the distributor (just laying on top of the motor) and i think that could have caused some problems - so i'm installing that in my 14X3 unit.

Plugs - I pulled all my plugs out and they all looked either really sooty or whitish w/carbon build up so i'm def. running rich (I think). I'm changing those.

Thermostat - the car had a 180' unit in it so i pulled that for a 195' thermostat, i'm thinking a faulty thermostat could have made the car run in rich mode when it was really warmed up?

Valve Cover Grommets - The breather and PCV grommets are really junk (they're hard and leaky) so i'mna def. replace those.

I think i'm on the right track somewhat - thanks for the help so far fellas!

Ty

TP355Z

holy hell - i'm a senior member? I guess that means that those designations are worthless - lol - I def. don't know enough...

nsimmons

the tps could be your problem, set it to 0.54v, if its too higher the cars gonna think your opening the throttle

TP355Z

well fellas - i replaced the pcv grommet and valve itself, changed my plugs, ran a scan-computer on the car - only to find out my home-made teflon tbi spacer was cracked. An aluminum one was fabricated and the car runs like a champ now - *** I love it. Thanks for all the help anyway. I just wanted some closure. lol.

tyler