my cell 0 (idle) is running way lean, BLM's 150-158.
every other cell is running normally.
I just went from 19 lb to 21 lb injectors, so I'm baffled. The runner gaskets went in properly, I can't see or hear a vacumme leak.

car runs great, and even idles great. just that the idle BLM's are way high.


any clues ???

 

There is a whole bunch of things that can cause this issue. You didn't mention whether it was SD or MAF. If SD, the vac leak typically doesn't cause a high BLM. On a MAF system it will. Any unmetered air can do it. Even a slightly leaky PCV.

If it was caused by the injector change, and the o-rings aren't leaking air, then it may be that the injector compensation tables need a little rework.

There are typically two tables: one table is vs. vehicle voltage, and one based on PW (short PW compensation).

RBob.

 

1989 MAF, factory prom, ANYX. all stock, except 3" cat back.
the high RPM cells are pretty good.
cell 0 150-158 way high.
cell 1 140-145 (just off idle)

I don't think it's a vacumme leak because the fuel pressure at idle is 37psi.
which is identical to what it was before the injector swap.
46 PSI if I pull the vacumme hose.

The car runs too good to pull it apart, it even idles great at 158 BLM

If there is something wrong, it gotta be on the side with the O2 sensor....

 

I found my IAC counts way high. like 30's-40's.
I havn't figured out why they are so high, but they are.
maybe becase of the heat wave???? or running with the A/C on.
but I will reset the IAC tomorrow.

 

An IAC count of 30 - 40 on a TPI setup is normal. Even more so if there is a load on the engine (backlight heater, A/C, in drive, fan running, etc.).

I think you may be misunderstanding a lot of what I posted. On a MAF system there can be unmetered air that is not a vacuum leak. A very small leak between the MAF and the TB will cause the BLMs to increase. More so at idle when the airflow is already low.

As for the injector compensations. You changed the injectors, 99.9% of the time the opening rate will be different. This requires changes to the compensation tables.

On one hand you state that the injectors were changed from 19 to 21 #/hr, then you state that you are using a factory stock PROM. This doesn't add up. Factory injectors for a 5.7l is 22#/hr, a 5.0l is 19#/hr

Have you changed the injector constant?

RBob.

 

It's the factory prom, 1989 OEM.
I went over the car with ether, I couldn't find any source of a leak. I still have to try the propane method.

The proper injectors for my car are 21lb, not 19lb. I'm not arguing about it.
But my car with the N10 dual cats did not run above 4000 RPM with 19 lb injectors. 2 sources say 1989 + LB9 got 21 lb's, so I went with it, and the car runs great. It revs to 5000 rpm without starving for fuel. It's doesn't surge anymore in open loop. In fact, all my BLM cells are still above 130 with 21lb injectors, so that just goes to show I could have gone bigger than 21 lb on a stock LB9.

 

Larry,

My mostly stock 89 TPI car does the same thing, BLM’s are all pretty good, except at idle in cell 0.
One thing I noticed is that if I pull over and let it idle, the BLM’s slowly climb from the low 140’s to 150 and even higher, but the exhaust smells a little rich, which does not add up. Does your exhaust have any odor at idle?

I also have a dual cat car (now high flow aftermarket), and I suspect that the stock, single wire O2 sensor runs a little too cool at idle to be accurate, and may be falsely reading lean at idle, so I am in the middle of a project to add a heated 3 wire O2 sensor to see if it will help. Of course a wideband sensor would tell the real story, but I want a heated sensor anyway for a future engine project.

I will let you know if the 3 wire sensor makes any difference.

 

That's exactly what mine does. idle cell 0 will begin at 150 BLM, & then she'll climb to 158 and stop there. The exhaust doesn't smell though. But I'm inside the car running the A/C, so I can't be sure. I'll check it out.

Do you still have your original multitec injectors ????
I bet if we flow them, they are 21's.
I have the N10, 3:45 rear, ws6 package, etc. seems like the same car.

 

The Multecs went in the garbage can 3 years ago and I never flowed them. For what it is worth, the stock bin for my car, ANYX, has 19.5 lbs for the injector constant. Car now has 19lb F*rd Racing injectors, and I did have add a little fuel across the board and add some Vbatt pulsewidth to even things out.

 

So then you would have to agree 19 lb with a stock prom, just ain't cutting it.
My factory fuel pressure is 46 psi, and 19# still wasn't enough.

The strange part is, when I had #19's, cell 0 was pretty good.
Now that I have #21's, cell 0 BLM's went way higher....... too strange.

 

I don't find it strange at all. If you re-read my posts in this thread note what I posted about the injector compensation tables, and about un-metered air.

Then again, maybe the MAF is on the way out.

As you are not doing any DIY_PROM tuning, and admit that you can't even read a PROM, maybe you would get better answers in the TPI board. . .

RBob.

 

2 guys with the same car, same exact problem, it's highly unlikely we both have un-metered air. It's also highly unlikely both our MAF's are on the way out. It's obviously something specific to 1989 with the package we both have.

Before I dive into prom burning, I want to car to run perfect in factory stock configuration....

 

Before I dive into prom burning, I want to car to run perfect in factory stock configuration....

But you can't do that as you already tossed the stock injectors in the trash can. See, not so stock anymore, is it?

Not only that, but formula_pilot changed an injector compensation table. Gee, just like I mentioned that you may need to do.

Guess there just may be too many trees in the way for you to see the forest, eh?

I really don't understand why you post here. You ask a question, then don't like the answer. And then even make up stuff about how an engine operates.

RBob.

 

>>Not only that, but formula_pilot changed an injector compensation table. Gee, just like I mentioned that you may need to do.<<
<<<<<<<<<<<<<<<<<<<<<<<<<

He changed his injector compensation table, and he still has the cell 0 problem. gee, guess that is not the solution.

and I never said my OEM injectors went in the trash,
never made up stuff about how an engine works.

obviously the answer isn't here.

 

the stock injectors on the 5.0 are 19, the 5.7 has 22s.
the factory injectors are not very good, they get dirty very easily & flushing doesn't always clean them. when these cars were still new i replaced a lot of injectors because they couldn't be cleaned good enough to run right.

with bigger injectors & not changing the injector size in the chip, its running rich.
being too rich at idle can a false lean condition. you'll need to check the tail pipe readings with a 4 gas analyzer to be sure.
if it isn't rich at cruise, then there is something else wrong.
a wrong PCV valve will cause all kinds of strange driveability problems, especially on the older MAF systems.
there is a reason why i went with a speed density system on my car & not a MAF system.

the answer your looking for probably isn't in here, this is after all, the chip burning section, so we pretty much expect to see a data log.

 

Formula Pilot.
Today my car was idling at blm 158 cell 0, and the exhaust didn;t smell at all.
so it's not running rich. it's actually running nice and idle's nice. If I wasn;t data logging, I would never know.....

 

I am into chip burning (Prominator) and have the same issues with the Idle. Tried 3 different single wire NB O2's, then Added a heated O2 and have tried 3 different ones of those. All the O2's were bench tested and read okay.

With a "stock, no cat" 2-1-2 exhaust, blm's rode at the 158/160 in cell 0. After the duals were installed, it went even more to the rich side (black plugs, exhaust pops, smells rich, stalls at low speed, ect....).

The O2's read low and "lean" so the car runs rich. I set the injector constant to 25#, 24# injectors @ 50# FP, max blm to 140. From past data logs the IBPW at idle should be 2 ms or less, it is at 2.3 ms.

I also wanted the car to run "well" before installing the WB, found I had exhaust leak at the manifold/exhaust pipe flange. Still am testing to see if this is "fixed"

Also use 4 different maf's and no maf, 4 different ECM's, 4 memcal Chips (plus 4 programs based on BUA, BUC, ABTK, ARAP just to check and verify.

 

did you ever solve the problem?

 

The reason for my BLM's slow rise is the "low O2 volts" showing the ECM that everything is lean (exhaust pipe AFR) when it is not (cylinder AFR), it soon is running way rich. I set the max BLM to 133/140 to stop this slow rise in richness, while working on/looking for the "cure"

I was working at sealing up the manifold to down pipe leak. The spring/bolt that was used didn't seal. So I went back to reg bolts (grade 8), refiled the pipe seam, and then tightened the bolts (3/8 bolt to 100 ft/#) after re-centering the pipe. Manifold to head, gasket is a new SS vortex one.
After each ride to/from work the O2 seems to be getting away from the 0 mv output when idling.

I wanted the exhaust pipe connection to be able to give when torquing the motor to save on broken parts.

The O2 reading low is the real issue, and changing to a WB is not a real good idea yet, because a WB includes a NB sensor as part of it's make up.

So if the NB is reading low the WB will read lean also.

After chasing issues in CNC machines for 30 years, I choose to follow the bad/improper output, and see if it is,

A: bad/improper input (cam overlap, revision, exhaust pipe AFR, not cylinder AFR), senor okay, ECM/eprom okay, bad output,
B: Good input, bad/improper sensor reading (defective part/wiring), ECM/eprom okay, bad/improper output,
C: input okay, sensor okay, ECM/eprom bad (can be wiring or the tune), output bad.
D: a combination of all three.

Since the O2 sensor is the "big dog" on running the fuel, if it's readings are "improper" (reading lean when cylinder is rich) then everything else (injector PW) will be wrong. Changing to SD will be no "cure".

If I wanted to read plugs and make manual changes, I could go back to being a carb man.

I have a "garage queen" stock pretty 1986 vette, a work 1986 vette for gas mileage, and then I picked this car, because it was a cheap base to build a hotrod, they all came with the TPI and MAF. (same year, same parts).

The next area of calibration (ECM/eprom to car) will be disable air pump (was removed) in the tune (get rid of the 100 mv offset) location 31E to 328 ($6E), and lower the r/l mv in the O2 tables (location 459 to 4BA).

There are a lot of different tables to consider.

 

Just finished installing the heated O2 sensor and am pleased with the initial results.
There was only time for a 15 minute datalog, but I am happy to report that the idle BLM’s were down to 124-125 vs 140+ before. After driving to get the car fully warm, I let it idle for several minutes, the BLM’s did not start climbing like they did before, just stayed at 124-125.

The original dual cat setup is gone and was replaced with the dual 2 ½ Magnaflow kit going into 3” catback , so perhaps the stock single wire O2 was not running hot enough at idle with the less restrictive exhaust. Some more datalogs will confirm the improvment.

FYI, The O2 sensor used is a Delco AFS-74. RBob and others reported good results using that sensor.

 

my car also has a cat back, so maybe the exhaust is running a tad cooler. just how much cooler, IDK. how fast can the o2 sensor cool off ?

But in my case, bigger injectors, it will run cooler than with the smaller inectors. What I need to do is run the car real hard, & then watch it immediately when it comes back to idle. not when i'm mosying around town.

have you data logged since ?

 

There are two problems I see.

1. Install larger fuel injectors and you'll need to change the fuel injector constant and injector compensation tables in the PROM as RBob has suggested. This is a given. If you want to rule out things like air leaks and malfunctioning sensors and such, then return your engine configuration to the factory condition. This also includes factory setting for distributor advance in case you've changed it. In your case though, this is impossible though since you have a low-restriction catback exhaust already installed. You're also assuming the factory PROM settings are perfect and in most cases, they're not. Might explain why others have had similar problems.

2. If you have an exhaust leak (or any unmetered air leak after the MAF sensor), the ECM (via the O2 sensor) will register a lean condition and add fuel. This seems to affect idle BLMs the most because the engine is generating a lot of vacuum, has low MAF airflow, and short injector pulsewidths. Engine vacuum can suck in even a small amount of unmetered air, but will be relatively large compared to the MAF's expected air flow at idle.

If you've ruled out leaks, then it's time to start DIY tuning as there are two non-stock conditions at play: different injectors and modified exhaust. Three, if you've advanced the distributor. Install a heated O2 sensor and get 'er done.

 

The headers had small cracks in the welds at the 4-1 flange area, rewelded to repair. These cracks let exhaust out and air in, worst when hot, when the cracks would open up.

To buy some time to sort this issue out, I locked the BLM's and Intergrator to 128. This held the Injector pulse to the correct range at idle (2 ms) till the O2 issues could be addressed.

 

is the o2 sensor at the collector, or on 1 header pipe.

 

The O2 is in the "down" pipe just past the 4-1 header flange.

The port in the, 2nd from left, tube is for the air injection/egr (hole is bigger threads are different), see picture.

The "down" pipe is a 90 degree bend with a flair 1" from the mandrel bend, the O2 is mounted horizontal in this 1".

This exhaust system can be seen at Corvette Central, C4 2.25 dual exhaust.

Any leak in this area will send the O2 to "lean land" (350-200 mv) and the idle BLM's to 160 (black smoke, eye burning rich).

The headers are a direct replacement for the "stock" 1 1/2" tube 4-1 vette manifold/ header. These are LT1, LT4, Hooker 2061, 1.75" tube, shorty headers for 1992-1996 c4 Corvettes. A "better" match to the 383.

These were picked to help the upper RPM area as the low end torque on my set up is 400 plus. Torque peaks at 3000 RPM, HP at 4500 RPM

 

Hello All,
I have been reading through as many threads as possible to find answers to my questions and I have learned quite a bit. To make a long story short, I have an '87 IROC 305 TPI, Auto with stock ACXT bin. The car is stock with no mods. The car had many issues and I finally have it running like "new" if that is any consolation. I switched to a "APYM" bin ($6E and disconnected the 9th injector) just as an experiment and it seems to run OK. Maybe a little better. We will see.

My BLM's are always at 158 (max in "Constants / Scalars). I read where TGO member "pandin" indicated to reduce the "maximum allowable BLM" to 140, but I want to tackle this at the right level. From everything I have read, I need to adjust the MAF table correct? (not MAF Scalar) My INT value looks good and it always a few beats away from 128, if not at 128. At idle my vehicle is random jumping between open and closed loop. At idle or cruising, the BLM is always 158. Ocassionally, while driving, the BLM will drop to 150, 148, but usually hovers around >155. My O2 voltage at idle is around 100mV,but then jumps to 750mV sometimes.

CG

 

To flatten (lower) the low cells BLM's to match the cruise, I lowered the maf tables in the Idle and off Idle area.


Arap Maf table 1
22.28
17.70
13.93
11.41
8.98
7.10
5.12
3.68
8.36

New Maf table 1
22.28
17.70
13.93
10.87
8.36
6.20
4.49
3.23
8.36

This change keeps the BLM's together idle, off idle, and cruise (55 mph).

Then when changing the Injector constant in the bin, all of the cells blm's change by the same amount, 128 to 116.

Remember that all maf's read a little different new, rebuilt, and old ( I have seen a 35% difference between rebuilt and old, at max air flow), so there will be variations to the exact numbers.

A heated O2 really helps the open/closed issue.