goes from 600 to 1400 rpms... checked for vacume leaks around engine, intake and tb but no changes.... so i thought maybe its the timing or something so i pulled the dizzy wire to set base timng and idle smoothed right out,,, with the dizzy wire pulled car idles perfect at 600 rpms... WHY??????????
also checked timing and its set to 0

 

Have you tried the factory setting of 6* BTDC ?

Have you set minimum idle and TPS idle voltage ?

 

Would setting minimum idle mean setting the IAC pintail? Also im having a hard time finding the diy for setting TPS and setting IAC?

 

The IAC does not need setting, the ECM takes care of that.

Read this on setting minimum idle and TPS idle voltage.

http://www.lbfun.com/warehouse/tech_...ch%20Paper.pdf

Why do you have your timing set at 0* ?

 

i guess when i reinstalled the dizzy i moved it a bit. i set it to 8* and it seems to be running better... still surges like the TPS thinks its accelerating and tryes to compensate. i checked the TPS its at 0.501 i looked in the manual and it says 0.525 - 0.075 so i guess its within that range barley. what sould it be set at?

 

ok my timing is set to 8*, my minimum idle is set per tech tips advice (set it at 450-500rpm even though it seems like it wanted to die at 450-500 rpms), set my TPS to 0.538. car runs and idles way better but it still wont stay steady at 600 rpm it surges from 500-800 rpm... i checked for vacume leaks with propagne couldnt find any. hey at least it will idle and not die now.... but why wont it hold contstant... i have a new fuel pump, new fuel filter, deleted the pulsator on the fuel filter and i have a new fuel pressure regulator diaphram in there.

 

When exactly does it do this mild surge?

The ECM changes the idle as temps change, a/c comes on/off...as the ECM shifts from open loop to closed loop. Mine starts up and idles at 750 everytime for about 5 seconds then sets to 600 and stays. When cold it idles at around 800-850 then settles at 600 the instant the temp hits 150.

If yours is going up and down on its own, no pattern, its almost always a tuning issue. Timing needs to be 6btdc if its stock, fuel pressure 40psi steady, and all injectors should be ohms tested. If the inj do not test all the same, and pass a leakdown test with pressure that should hold for an hour within 5 psi of the normal pressure, there are bad injectors.

 

it surges on its own randomly with no apparent pattern. what are my injectors supposed to Ohm out at (im going to Ohm test tomorow)? in order to find out if the injectors leak can i hook up a fuel pressure gauge to the schratter valve on the fuel rail, fire the motor up, shut it off, take a reading then come back in an hour and take another reading to see if its leaked down fuel pressure? Also maybe this is unrelated but my oil pressure usually sits in the 40's at idle. after making all my adjustments today i fired up the motor and was idleing it up to operating temps. oil pressure was in the 40's then once the motor got up to 205 degrees or so it dropped to as low as 16 but when i would step on it the oil pressure would shoot back up to the 40-50's then as the rps came down it went back down to the 20's. i shut the car off let it sit for an hour, came back fired it up let it idle the oil pressure was in the mid 30's

 

Injectors should show about 16-17. If they are more than a couple pts down, they are bad or on the way out. The stock injectors are junk in several ways.

Connect the pressure gauge, start up, shut off and note the pressure. Leave it as it.
Come back in 30 min and note pressure, again in 1 hr.
You should not loose more than 5 psi in that time, do not key ON when doing this test. Keys stays OFF until done.
If you can, see how much pressure it holds over several hrs. A good fuel system will hold 20 psi a day later...

The oil pressure is behaving normally.

 

ok Ohm'd the injectors most are 16.4 some are 16.2 and one is 15.8.
i adjusted the timing to 6* and it seemed to help a little bit. I am running the fuel system pressure check now.
i hooked the fuel pressure gauge up and it was right 38-39psi at idle and goes up a bit when i step on it. how ever i do notice that at idle it seems like the fuel pressure wants to climb and go up over 40 psi, thats when the rpms surge and then it feels like the computer is trying to correct this because the fuel pressure goes back down a tiny bit right away and the RPMS drop
I will let you know about the fuel pressure leakdown test

 

ok did the fuel pressure leakdown test.... within 10 minutes the pressure has leaked down from 43psi to 35 psi after 30 min. its all the way down to 22psi. SOOOOOOO..... i have a fuel pressure leak, but where? I charged the fuel system turrned the key off and clamped off the fuel return line @ the gas tank and the fuel feed line @ the gas tank with some vice grips (think the lines were all the way clamped off or at least almost all the way clamped off) i then took my fuel pressure reading 43psi,,,, within 10 miniutues it had droped to 35psi. any ideas where my leak is coming from

 

well..
if the return was closed off the only place that fuel can possibly go is thru an injector. Makes sense.
A roaming idle or loping used to always be an injector problem, but as EFI has advanced there are more and more things that can cause this.
The presssure is the result of eng intake vac, and floats up/down slightly with the vac level.
In order to confirm leaking injectors, IMO the next step would be to look at spark plug colors and find the cylinders that have plugs that are more carboned or dirty than others. That will confirm a cyl(s) that run rich, if any. Between some dirty plugs and injectors that are leaking fuel past, is a fair amount of evidence for a set of new injectors. Not to fear, $250 covers everything at FIC. The rest is just some wrench time...a good job for a Saturday.
Your leak down is not horrible, but its not great either. After I did inj and filters, mine would hold within 5 psi of normal for a couple hrs and it was all day before it dropped to 20...
Yours ohm ok, but that only means the electrical solenoid is in good shape, the nozzles can plug, stick and get gummed up and leak, and not spray very well. Poor nozzles drip fuel in and because these L98s are bank-fired, the fuel MUST be atomized since there can be a full cycle before its actually drawn into the cylinder. It has to 'hang' in the intake port as mist until the intake valve opens. Since the inj all fire together, there are always several that are spraying fuel at a closed intake valve...or dripping.
For more info on that, go to youtube and search fuel injectors.

 

DONE!!! Thank ya'll so much for your help. I learned alot and fixed the problem thanks to the cool cats on this forum, thanks again.
I ran a vacume check and discovered a vacume leak that I hadn't previously found. I fixed the leak and the car idles solid a 700 rpm. Thank you two again

 

 

I was wondering if the varying fuel pressure was a clue...knowing that it the direct result of intake vacuum...

Good job !

 

Cool. Ya done good.

 

can you exactly tell me where is the leaking was ? I have the same problem on my vette.
Thanks!!!