mblackey

We are having LEAN issues with a 305 TBI that we're prepping for this summer's road racing season. The engine runs WAY lean (headers are turning red) and idles refuses to drop below about 1500-1800 rpm. It will only run about 2 minutes before we have to shut it off to prevent overheating.

Here's what's been done to engine:

Stock 305 TPI engine and heads
TBI rebuilt
New TBI manifold gasket installed
Ported TBI installed with slightly ported stock TBI intake
Stock TBI fuel pressure regulator modified and is now adjustable and enriched as much as possible.
New IAC installed and reset, along with ECM
New IAT installed
New MAP installed
TPI fuel pump installed
EGR removed, block-off plate installed
Air pump removed
Associated emission vacuum lines removed & capped on TBI/intake
Headers installed with 12" racing muffler
Timing set at -6 degrees (we're at 6,000 ft elevation in Colorado, so this should not be a factor)
Idle screw is full out, butterflies are completely closed
IAC cam just touching butterfly tab but not causing butterflies to be open.

Will getting a programmed chip solve the lean/high idle issue, or are we missing something else????

Any help appreciated.

Mike
Frustrated in Colorado

ex-x-fire

Get a ohm meter & thermometer, place the tip of the coolant temp sensor in hot water at different temps, measure the restistance at different temps. You can find the temp/resistance values on line under GM CTS resistance. A cts thats way off will cause problems. Have you checked the fuel pressure? Does it adjust higher?

UnderCover89TBI

iTrader: (25)

Sounds to me like you have a big vacuum leak. Check the tbi gasket intake gasket etc.

RBob

iTrader: (1)

+1 on the vacuum leak. And set the base timing back to 0* on a warm engine with the EST/BYPASS connector open.

Note that without the EGR it needs to be disabled in the calibration. Otherwise when the ECM enables the EGR valve it will add timing and remove fuel. Tends to cause detonation and throws off the WOT fueling.

RBob.

mblackey

Right on and thanks on the leak. Found it.

RBob, on the EGR, are you saying we need another chip?

RBob

iTrader: (1)

Sorta', can always do the tuning yourself and not be buying chips. Although for a one time change/charge, getting a stock calibration with VATs, EGR, and the speed limiter turned off can be an advantage.

RBob.

UnderCover89TBI

iTrader: (25)

glad you found the leak. was it on the intake or tbi base gasket? Im always curious!

RBob

iTrader: (1)

Missed this the last couple of times: "Stock 305 TPI engine and heads"

Will also want to change the main SA table for the TPI heads. Can grab the values from a TPI calibration such as AUJP.

The L03 engines run swirl port heads which run at very low spark advance values. Whereas the TPI heads are not swirl port and require more spark advance.

Also, raising the fuel pressure will also require additional tuning. DIY on the tuning is looking better and better (I know, but I had to say it).

RBob.

mblackey

UnderCover - leak was from wrong base gasket.

RBob - Wow, talking way over my head now. "SA tables?" "AUJP?" Part of the ECM reprogramming?

We are planning on about -8 low spark advance (just being in Colorado at 6,000' we figure another -6 on advance)

Haven't taken fuel pressure reading since we made regulator adjustable, but it is "maxed" out (spring is fully compressed) and still running lean. Figure we're around 15.5 psi? Does that sound right?

Fast355

iTrader: (2)

The ECM already adds additional advance for the altitude based off of MAP sensor readings.

TPI heads need more timing, but not everywhere across the board. With the 601 head 305, I ran 6* more timing and a VAFPR and no tuning for over a year. Ran well, but the fuel pressure under load was 18 PSI with 350 injectors and a stock 305 chip.

UnderCover89TBI

iTrader: (25)

[QUOTE=mblackey;4922814]UnderCover - leak was from wrong base gasket.
QUOTE]

Thanks for telling me. It seems like so many people take advice fix thier problem and then never let anybody know what it was. It really helps everyone on the board, help everyone better! Thanks.

mblackey

Fast - thanks for the input. You folks are a wealth of info!

UnderCover - a pleasure to converse with all of you. Thank you for taking the time to help out!

We'll check fuel pressure on next run. Will stock TBI injectors flow 15.5 psi?

Will probably leave advance at -6 and see how it does.

RBob

iTrader: (1)

I'd like to ask a favor. When you post -6, I see that as 6 degrees of less spark timing (minus sign). As in 6* ATDC, not 6* BTDC, as the base timing. Better to use BTDC to define the setting in gear-head terms.

Putting it to 6* BTDC isn't that bad. Not the right way to go, but with no way to tune the ECM it is a viable but limited method.

RBob.

mblackey

That's reasonable and easy... we're talking 6* BTDC...

UnderCover89TBI

iTrader: (25)

That's good. MAN Rbob one of these days im going to cough up some money for the EBL!

RBob

iTrader: (1)

SA is spark advance, there are tables for it in the ECM calibration. AUJP is the broadcast code (BCC) for a 350 f-body TPI engine (L98). By opening that calibration in an editor (Tuner Pro), you can copy the values into your TBI calibration.

That will give you a good start for the spark advance due to the difference in head design.

On a 305 LG4 engine I had to go with 350 injectors (61 #/hr versus 55#/hr) to provide enough fuel. Of course it also meant additional tuning. Getting into the tune is what makes the engine run right.

Once one starts to mix & match engines/parts and EFI, have to get into the calibration.

RBob.

mblackey

RBob: we have one of your ECMs, already, so we'll be taking on the tuning issues shortly. Any recommendations on initial settings, based on the setup we told you about?

Mike

RBob

iTrader: (1)

Well shoot, that makes it easy. I'd start with the base calibration (EBL_F_TB2.BIN) and go from there. That one is for a LG4 engine with the '416 heads, which are similar to the L98 heads.

Could also copy the SA tables (Main & Extended) from one of the provided TPI calibrations.

Adjust the BPC vs VACuum table for the proper injector flow rate, check that the EGR and CCP are disabled and flash it in.

Note that the initial (base timing) is set to 6* BTDC in that cal. So while messing with the distributor set it to that value.

RBob.

mblackey

RBob - the settings you recommended worked great! We're doing more tuning now, thanks to your product and the software you recommend.

Can't say enough about the flashable ECM and software... it has outperformed our expectations.

Likewise, your and others here on the forum have been very helpful and generous with your time. Thank you ALL!

Mike, Shawn, Brandon & Sean

Fast355

iTrader: (2)

I have a spark map for a 1983 LE9 305 HO Van/Truck engine if you want. Worked great when I swapped my mildly cammed LE9 305 to TBI. I also found that I had to run 350 injectors at elevated pressure to feed the 305. Made something around 240 RWHP.

mblackey

Sure! Much appreciated: UFlyMike@gmail.com

Hope we can get air/fuel to work without going to bigger injectors. The 6,000 ft altitude will hopefully help.

Checked fuel pressure with modified regulator cranked to max (and TPI fuel pump). Only getting 13.5 psi... thought we'd get more????

Mike

morgsie

iTrader: (1)

I also put a TPI pump in my car and even with an adjustable FPR, I couldn't get it over OR under 16 PSI... This has been a problem for about a year now (car hasn't been driven much) that I would like to start working on it again in the next few weekends. I am thinking maybe the spring is too stiff?

BTW, this is an '89 Caprice and I am taking the readings from the supply (3/8") line on the R/H frame right before it goes to the flex hose and then to the engine (less than a foot). This is all at the front of the car.

Sorry to hijack, just reporting a similar problem.

mblackey

We're still not getting the power we expect. Engine Power falls flat around 3700 rpm. We put in 61# injectors. A little better but not much.

We're thinking about trying a BBC TBI next (1990).

What do you guys think?

Mike

UnderCover89TBI

iTrader: (25)

im kidn of battling the same thing now. my engine bogs down (I believe a lean bog) hopefully due to lack of fuel pressure still have stock tbi pump. So I am getting a TPI pump and seeing if I can bump the fuel pressure back up with the holley tbi unit on there.

mblackey

We've run two setups now, still having problem with engine falling on it's face:

First setup: Mildly ported stock 305 TBI 61# injectors and 14.5 psi fuel press... No power above 3700 rpm.

Second setup: Stock 454 TBI 61# injectors and 20 psi fuel press... Bogs badly at any open throttle setting.

Haven't messed with any table values other than basic setup of injector size, fuel press, etc.

are we totally on the wrong track going with the bigger TBI? Should we go back to stock TBI setup and try to tweak the AE tables or work on the bogging issue with the 454 TBI?

The car had no power when we were running in the race during the day (85-90 degrees) but seemed to have much more power at night when temps dropped (60-65 degrees)... this was with stock TBI and 61# injectors. It ran slightly rich the whole time, particularly during the day. Engine temps during day 190-200, at night 180-190.

RBob

iTrader: (1)

Need to find out why it isn't making the power. What does the O2 read at this point? Checked fuel pressure at this point? Are the injectors max'd out (WUD gives DC%)?

The other thing is, I'm not sure why the BBC TBI but with the 61#/hr injectors.

RBob.

mblackey

Rbob,

Indeed we do! Having those Hondas pass us was not a pleasant experience...

O2 readings appear normal, fuel pressure steady at 18 psi, Injectors top out at 75%.

We're running the 61# with the BBC TBI thinking we need more air not more fuel at this altitude (6K). It's been running rich.

Problem now is mainly at WOT at any rpm. Open the throttle, and the engine bogs and starts missing, ease out of the throttle and it clears and runs smooth all the way to 5500 rpm. It accelerates fairly well if you slowly feed throttle in as rpm rises. We get the "PE" light on the "WUD" display when we go WOT.

We have some files we could send. Could we do that?

Best Regards,

Mike
Colorado Springs, CO

RBob

iTrader: (1)

You can send a data log. It is helpful to place markers int eh data log at the points the issue occurs. Just tap the space bar to do this.

Can use the MAP value to see if the intake system (including TBI) is a restriction.

Bogging is usually a sign of too rich. On the surface it sounds like there is to much AE. This is due to you stating that when hitting the gas it bogs, but when slowly rolling into the gas it is much better.

RBob.

mblackey

RBob,

Will do on the data log.

How do we use the MAP to see if intake is restricting?

Which AE tables would we adjust and settings?

Thanks very much,

Mike

RBob

iTrader: (1)

Start a data log, key-on, engine-off, pause. Start engine and continue logging. When reviewing the log note the MAP KPa at engine-off, that is barometric pressure.

Now look at locations within the log at higher RPM and WOT. Note the MAP KPa. Subtract that value from the barometric value and the difference is the drop through the system.

The larger the difference, the larger the drop. IIRC, 6 - 8 KPa difference is OK at high RPM and WOT.

AE: to reduce, lower these two tables:

AE - MAP PW
AE - TPS PW

There are other tables that can be used for fine tuning. But these are the 'rough in' tables.

Go by the data log, there is a ton of information in there.

RBob.

mblackey

RBob,

Sure appreciate the help!!!!!

Will do on all above. We'll be at the track this weekend, so hopefully will be able to apply some of your advice above.

Think we're on the wrong track with the BBC TBI with 61# injectors?

We're still using the 305 intake manifold with a 2" -to- 1 11/16" adapter spacer, i.e., the manifold is still restricted to the smaller bores.

Mike

RBob

iTrader: (1)

> Think we're on the wrong track with the BBC TBI with 61# injectors?

A data log will let you know.

If you have any logs of the bogging check them out. That will give you a head start on this weekend.

Can also check the MAP values for intake system restriction.

RBob.

mblackey

RBob, Have the data file. Could I email it to you? My email: uflymike@gmail.com

MAP is at 79KPa ignition off and tops out at 79KPa WOT, 42 at idle.

When at WOT the DC goes to 106% and this is where it stutters. We are running a VRFPR at 18psi base.

RBob

iTrader: (1)

You can email it to me. Is there an O2 sensor in the exhaust. If so check what it is reporting when the engine is stuttering.

RBob.