surging idle switching from sync to async

[mike65]

Hello fellow Gearheads, I've been visiting this great forum for a couple years now and have always been able to get most of my answers by just reading post........up until now. My project is an 87 Jeep YJ with a Chevy Vortec 350. The project started around two years ago with a TBI350 from a late eighty G2500 van. Then last November the motor lost a cylinder so I decided to go with a rebuilt Vortec 350. I figured from all the hours and hours of reading on this forum that I would be able to make the required changes to the fuel/spark tables etc. and have a good running stock Vortec 350. At first things seemed to go well with the stock injectors 61.2# but I always had a slight miss. So while pondering on the reasons for the miss I convinced myself that the old injectors must need cleaning or be replaced so I threw down the cash for some rebuilt 65's. At first all was going well. I used the TBI calculator to set the new BPW and injector bias then data logged to set the VE table. This is when I started having problems that I haven't been able to solve. The main issue is at idle, it switches between sync and async. This is causing a surging idle that I haven't been able to figure out over the past few months. To make a long story short I decided to set the BPW and Injector bias back to stock 135/0.42 (I know 0.42 isn't stock but close to 0.396) and started over today. Things seemed to be going great with two data logs....idle was good and BLM were getting close to 128 after a few adjustments. Then I decided to take a break and came back two hours later and now the problem with the sync/async switching at idle started again. So now I'm bowing down before the TUNING GODS asking for leniency on my retribution for a failed Tune. Seeking any help or direction to a thread discussing this issue. The vitals are has follows:


Fuel pressure at 15psi (verified by gauge)
TunerPro (purchased)
Moates Hardware
350 vortec stock L31 bored 0.030”
Edlebrock performer dual plane intake
TBI/intake adapter is 1/2” thick aluminum (I've verified no vacuum leaks)
Shorty Headers

1987 jeep around 3300lbs
4:56 gears 33” tires
custom Dana 44 front ARB locker
custom Ford 8.8 rear ARB locker
TH350 custom built mated to Early Bronco Dana 20 Transfer Case
Hydro Boost Brake system disc front/rear
High steering with Performance unlimited steering system


Bin:
Started with ADYR $42
Spark table is modeled off Dave W Vortec table listed on this forum
Some changes have been made to the IAC setting to bring down idle a little quicker
Included are two data logs and Bin File
Data logs included are: Last data log for setting VE table and idle log showing the switching between Sync/Async.


One other thing I noticed on this last log was an Error code on the VSS. For some reason this pops up from time to time. I can sometimes disconnect the battery or change the Chip and it goes away. I do utilizes a 2 pulse VSS sensor from JTR. I think I'll check the connection at the position switch to make sure I'm getting a good grounded connection in park position.


Thanks for any suggestions

[dave w]

Have you looked at these parameters?

See pic

dave w

[mike65]

Thanks Dave for the reply.
Yes I did switch those parameters. It would start and idle okay but when I tried to accelerate the motor would cut out and fall flat on its face. Perhaps I did the adjustment wrong?

[dave w]

Thanks Dave for the reply.
Yes I did switch those parameters. It would start and idle okay but when I tried to accelerate the motor would cut out and fall flat on its face. Perhaps I did the adjustment wrong?

Vortec heads like lots and lots of AE. Maybe your going lean would you try to accelerate the motor? Maybe you have access to a Wide Band O2 sensor to see what the AFR's are doing when you accelerate the motor?

dave w

[mike65]

Not sure what happened I replied to your last comment Dave a few hours ago and it appears it didn't post. Anyway!!

In the early stages of the project I did set the AE tables and the motor responded well under acceleration. I even used a WB O2 to verify. My sync/async switching problems started after I changed the Injectors to 65#er. Initially no problems then when I got to the fine tuning the sync/async switching started. My first step to eliminate was trying the parameters changes you mentioned above. These changes caused the motor not to rev above 1000rpm....couldn't even get out of the driveway.


Today because of your suggestion I tried to make the changes to the Async setting again. The same thing happened today as before. Would idle but wouldn't rev up....pig rich! I did notice that the units in the Asnyc note didn't match the units in the scalar (Usec vs Msec). Has anyone noticed this before? I'm using $42-1227747-V5.9.3 xdf.


Mike D

[dave w]

I noticed the Microsecond (Usec) vs. Millisecond (Msec) differences. The conversion is: 1000 Microseconds = 1 Millisecond. Let's cover the basics, then work from there.

dave w