torqueaddict

I'm tuning for fuel using the Moates O meter WB and datalogging to my laptop. Small changes to the injector constant seem to have unpredictable results on AFR. I have been at this for about 6 months now so I'm thinking maybe I have bad injectors, or something else? Fuel Pressure is good.

I can't get the car in closed loop. Typical scenario:

1. run car with inj constant = 26.0
2. Do 55 mph cruise - AFRs running 13-14 - no closed loop
3. reburn chip with 26.5
4. Do 55 mph cruise - AFRs running 15-16 - no closed loop
5. reburn chip with 26.3
6. Do 55 mph cruise - AFRs running 18-19????? - no closed loop

Yet the day before 26.3 seemed nearly perfect - closed loop cruise - 12:1 WOT.

I am running LS1 injectors and I am using "known good PROM" for this setup on an 89 L98 TPI. The car has a ZZ4 cam and Vortech heads, SD Intake, and Edelbrock headers. I was told that I should be at 22 lbs but it was too rich there.

Any ideas?

torqueaddict

I kept making adjustments and I think I am somewhat close - It'll go into close loop a little the go out. WB AFR is about 13.5-15 cruising. How close do I need to match the commanded AFR to get into closed loop? Is it easy to log the WB in tuner pro?

If someone is really good at quickly looking at a datalog, I put one here. Does anything look out-of-whack?
http://members.bellatlantic.net/dantill/monday.xls

thanks in advance for any help

pandin

O2 mv at 444 too much, low cross count numbers, the O2's should swing a little (WB feedback or NB). O2 mv stayed low at WOT only one line at 800 mv 2145. should ramp up as injector pulse increases.

Random lean (23 - 25) commanded AFR's, starts at line 22 and 24, goes randomly as data is logged.

pandin

This looks like your 23.6 AFR issue.

Re: MAF goes lean @ PT
Quote:
Originally Posted by Rebuildman
One problem I run into is at PT with low load on motor watching the WB it will intermittently go very lean, like from 14:1 to 20:1. The inj PW drops by 1/2, the MAF LV8 and MAF grams airflow also drop alot, MAF RAW input does not change nor does the TPS.
Suggestions?
Thanks!

It sounds like the ECM thinks that the MAF is bad and is creating a default value. If the MAF raw input is OK, but the LV8 and Gms/Sec airflow drop then the ECM isn't using the MAF input.

This may be being caused by a borderline MAF 33 condition. This is where the ECM checks some parameters to see if it can then check the MAF airflow. If the airflow is too high it will go into default mode. With a modified 400 this can happen.

Check the data log for these values (stock ARAP values):

less then 3200 RPM
less then 14.8% TPS

now if the airflow is > 45 gms/sec, there is an issue

This airflow value is stored at $C210 ($6E ARAP), increase it to a value greater then what the data log shows.

RBob.


Also check to see if Highway mode is enabled, this changes the AFR from 14.7 to 15.3 @ 55 MPH.

PE will change AFR to 12, raise "Minimum LV8 to Enable Power Enrichment" 4FD ($6E ARAP) from 50 to 55.

torqueaddict

Thanks for the information! I didn't think anything of that radom lean commanded AFR.

Could I need a MAF sensor? The wire is intact. I would've bought one already just as a test if they weren't $300.

Last night I got desperate for closed loop and removed the ls1 injectors for the accel 21lb ones that I had used before - at least I know back then I was running in closed loop most of the time. I'll know tonight once I get the injector constant right for 21lb injectors where I am at.

pandin

Read this post

https://www.thirdgen.org/forums/tpi/429791-maf-relay-differences-they-new-post.html

Try these guys

SIA Electronics
730 N. Minnie St.
Tilden, IL 62292
800 737 0915

will test
$68.00 to repair
Fast turn around

I got one fixed, it works fine (It was dead).

torqueaddict

Thanks. I read the post - I will check the relays and the MAF. I guess I could have a "borderline" issue but I have yet to get a code for MAF. I'd like to know before I buy more for this car that there's a problem. I'll check the diagnostic procedures in the GM shop manual.

If I replace the relays - it sounds like for 89 the relays can be the same..

torqueaddict

How close to the target AFR do I need to be to get into closed loop? If I am 16:1 or 13:1 cruising should I be in closed loop?

By the way - tried to do some tuning after replacing the injectors with the 21 lb accel - still couldn't get closed loop for more than a minute.

I started with the injector constant around 22, and I'd lower it about .5 to .1 and then do a short drive. After a few hours, I got it down to 17 lbs - at around 18 lbs I was seeing cross counts but no closed loop. I tried ARAP unmodified and no difference.

I guess it's time to start checking my MAF.

pandin

Closed loop is "determined" by the O2 sensor:

ARAP is the same but at a different line location.





LC55F FCB 45 ; If o2 < 0.199 VDC then o2 is ready

LC560 FCB 50 ; If o2 in window formed by LC55E & LC55F for 10 Sec, o2 state NOT READY ; SEC = (num/5)

;----------------------
; Closed Lp Limits
;----------------------
LC561 FCB 60 ; Closed Lp Corr, Min Value
LC562 FCB 180 ; Closed Lp Corr, Max Value

;---------------------------------
; Closed Loop Fuel Cnt'l Param's
;---------------------------------
LC563 FCB 3 ; Clsed Lp Idle TPS 1.17% Gain Factor
LC564 FCB 16 ; 0.2 sec Added Corr To Int Dly At Idle, (sec * 80)
LC565 FCB 160 ; 0.625, EECC Clsd Lp Gain factor
LC566 FCB 12 ; Diff Value to Make up Rich/Lean Window for Fast o2.(VDC * 226)

"This is stock ECM set at 50mv or 1/2 of the Air offset."

LC567 FCB 23 ; Diff Value to Make up Rich/Lean Window When Air diverted.(VDC *226)

"LC454 ARAP"

"This is the Air pump 100 mv offset which is subtracted from the O2 swing points when not diverted."

LC568 FCB 4 ; 17 mvdc, Min Error To Implement Int.(VDC * 226)
LC569 FCB 224 ; 991 mvdc, Positive Error Gain Factor
LC56A FCB 154 ; o2 Filter Constant when Coolant Temp Low

LC56B FCB 96 ; 43 Deg c, Cool Int Offset Int Gain

torqueaddict

Thanks, it's a little cryptic but I will look that over.

I just wanted to share a few things I've noticed (some uber-guru may instantly see a likely culprit):

1. I always need to set the injector const down a good 4 lbs from what it should be to get the car to cruise at around 14.5:1. This is the case with 2 sets of injectors and 2 proms! Car is at like 19:1 with the stock prom and injectors!

2. I never see closed loops or much xcounts unless I am almost flooring it, at which time I will see closed loop for almost a minute.

3. gm/Sec seems low I think - full throttle - 190 idle - 9

4. no check engine light

I did swap relays and it didn't help. I check fuel pressure and it's great - even while driving. I know I have that random 20+:1 commanded AFR - I can see if the diagnostics help with that.

I don't really know where to start other than the MAF relays since they are cheap.

thanks in advance for any more ideas!

pandin

A 20 year old Maf will read low 190 or so. A Z (Cardone) rebuilt Maf's can also read low (190)

I would send your Maf off to SIA and have it checked.
They also recalibrate to better air flow numbers (higher air flow means more fuel, richer).

If repair is needed it only $68.00 (internet price).

torqueaddict

FYI: It's been a while but I finally got it -
I cut the tan wire and attached it to the body and instantly saw the O2 swinging - thanks for the help

pandin

What he did was ground to the body, the Tan O2 sensor return wire that runs from the ECM to the engine block.

Must have been an open between the ECM and the engine block.

Mine is bolted to the block just above the oil filter, along with the neg battery cable, and other grounds.

This is where the old manual clutch pedal pivot ball was attached, back in the day.