'87FAKE-IROC-Z

I'm still running the 19# injectors on my 356, so this might be part of the problem.
But at idle the car runs way rich! I've tested with fuel pressure and lowering it doesn't seem to help, I'm guessing the computer just increases the opening time on the injectors to compensate for lower pressure.
The computer is for a TPI305, but to my knowledge the computer is the same as in a L98 car, but the chip is different-my chip is for the 305 too.
I know this is alot of stuff that needs to be switched.
I fuguered that the computer would correct the air/fuel ratio, since the 350 and 305 have the same idle air/fuel ratio (i think).
I'm thinking a chip would definately help, along with a new O2 sensor.
Thoughts or suggestions appreciated.
thanx.

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'88 RS (originally 2.8)
New 350, .040 over, ported vette L98s, ported stock tpi.
Old 305 injectors & chip
TES headers, 3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
(Damn the 2.8!)

The ODB

You do not have to change ECM, chip, or injectors. Those things are not the problem.
The 19lb injectors will support over 400 horsepower.

Check the readings from your TPS, temperature sensors, and your O2.
Diacom or a good scanner will make these checks much easier.

Also if you do not have a catalytic converter you will smell some fuel in the exhaust.

If you want to run leaner than 14:1 A/F ratio in closed loop, then there are some guys on here that can tell you how to change your ECM programming. Generic chips are not the answer though.
The ECM experts on here didn't like my methods of tricking the ECM for control. I have to agree that if you can do it a smarter way and it's affordable then do that.
I would ask them if you find no problems with your sensors.

ODB

Grim Reaper

87, how do you know you are running overly rich? A scan tool will show the BLM/INT values and this will let you know. But when you are in closed loop, the ecm will correct for anything. The only time you can be running rich (if your sensors are working properly) is when you first start the engine and are in open loop.

BTW, adjusting fuel pressure has minimal effect at idle when you vacuum is the highest. Adjusting fuel pressure has the greatest effect at WOT (low vacuum).

Your O2 sensor might do it or possibly your engine is not getting warm enough to go into closed loop. A weak thermostat or a weak CTS can do that.

But if your ecm goes into closed loop and your sensors are working properly, your ecm will compensate properly.

BTW, with 19# injectors and a stock 305 eprom, you would more likely go lean, not rich. ODB is right, you are looking at the wrong spot.

Grim Reaper

Personally, I think the stock 22# injectors are too rich on a basically stock L98. 19# are a better match IMO to compensate for GM's overly rich programming. I agree with ODB on that point also, I think your injectors, ecm and eprom are fine as they are and probably closer to being optimal based on what I have seen with the stock GM programming. GM is way too rich and the biggest reason these cars are slower than they should be.

BadSS

Yep,, make sure all the sensors are in good working order,, but before you spend the money for a scan,, make sure you have no vacuum leaks. Cracks in the valve cover grommets, a PCV not sealing fully, bad valve cover gasket leak,,, I've seen folks run after market breathers in the valve covers,, right there at the PCV. I think ODB said already to check the TPS and set the IAC. A few things a little off,,, stacks up quick.

The ODB

hey I have friends here.

yep, I can verify
the ECM programming is too rich.

forgot to mention this:
an exhaust leak near the heads or collector can throw off the O2 reading.

yeah I see you have TES headers & probably a hollowed CAT too. I would not be surprised at the fuel smell in the exhaust.
Pull a sparkplug out and rub your finger across the tip. If it leaves black soot on your finger then you have an over-rich problem.
Dead or weak sparkplugs will also cause those same symptoms. Test those with an ohm-meter.

ODB


[This message has been edited by The ODB (edited February 22, 2001).]

'87FAKE-IROC-Z

Thanks,
I'm gonna check all the sensors. The plugs do verify a rich condition when removed, they are a little black, but not too bad.
My cat is hollowed, that would explain the smell. so maybe i'm making too much fuss over a little problem.
Thanx for the help.

------------------
'88 RS (originally 2.8)
New 350, .040 over, ported vette L98s, ported stock tpi.
Old 305 injectors & chip
TES headers, 3.73 gears, 700r4.
Best with 2.8-17.4@77mph
Best with 305-15.0@93mph
Best with 356-13.7@101mph
(Damn the 2.8!)

Grim Reaper

ODB, what makes you think that you don't have friends? I think a lot of the more knowledgable members respect your opinion.

I can't speak for others, but I can hardly wait for you to overcome your shyness and come out of your shell.

JETHROIROC

Count me in with Glenn.

LeeH

iTrader: (2)

Yeah ODB - what Glen said.

I like your non-ECM workaround on the sensor.
I forgot which one you were modifying, but I think it was the MAT? Anyway, if you don't plan on going into chip burning, it's an innovative way to bypass the ecm limitations...




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89 Firebird Formula
WS6 package,ZZ4 Crate engine
SLP 58MM TB, Edelbrock TES Headers
Random Tech 3" cat, SLP 3" stainless exhaust
9 bolt rear, Hotchiss swing arms, Lakewood panhard rod
Corvette 2/4 servo, kevlar band, full poly rear.
Centerline 16x8 rims, B.F Goodrich drag radials

Grim Reaper

LeeH, it was the CTS.

Grim Reaper

MAT will also work with a potentiometer (sp), but its a bit more subtle and has a narrower band of effect on the pulse width.

But for the average engine, it would easily be enought to make you overly rich or overly lean in its own right.

But, personally, I'd rather spend the time to get a GOOD algorithm so my engine will ALWAYS operate optimally at any elevation and any temperature; once you got it "dialed in".

The other way, you are always trying to "dial it in" because the temperature change or the elevation change makes all your "tuning" incorrect. Kind of the pits needing 6 runs to dial it in, when you can only get 5 runs in and then all your testing is no longer valid for the next weekend.

But the CTS and MAT is effective and ecomical. It just isn't efficient. I just prefer the 3 E's, but some guys don't care about that. Different strokes for different folks.

LeeH

iTrader: (2)

Yeah, I am going the ECM route too.
I have already ordered the stuff I need to burn em (tunercat, etc), and I will be playing with all the variables.

After going through my boxes of eproms I have discovered that I have tons of 27256's and only a couple of the 27128's. Sicce I have the 165 ecm, I need the 128's. Know anybody who'd want to swap some around? Seems a waste to have to buy them when I other stuff to trade