Surging...

[Superdave]

While crusing between 5 and 9% TPS around 40kpa(Plus or minus a little) i get an RPM surging in the 3500Z.. the wideband bounces all around so i'm thinking the ecm is cutting fuel. The surging only happens while crusing.. never under acceleration.


BLM's are 119.. i've allready pulled fuel from those cells, also backed off the spark timing a few degrees.. the Injector PW bounces between .8 and 1.14.. around 35 degrees spark advance, IAC is at 64, no knock counts.


i can post a snippet of the log if anyone wants..


thanks,
Dave

[85_Olds_Ciera]

While crusing between 5 and 9% TPS

Just general comments...not specific to data changers...


1. Does TPS fluctuate at a steady speed?

2. Got your muffler on?

3. O2 Sensor OK?

[Superdave]

Just general comments...not specific to data changers...


1. Does TPS fluctuate at a steady speed?

2. Got your muffler on?

3. O2 Sensor OK?

nope, TPS holds steady in the log..

muffler.. if you wanna call it that..

running a WMS wideband o2 with the simulated NBo2 hooked to the ecm.

[IsaacHayes]

Can you try putting the MAP inline with a fuel filter to buffer out the pulses? It may be just the cam that even at cruise like that it's pulsing the MAP too much.

[Superdave]

Can you try putting the MAP inline with a fuel filter to buffer out the pulses? It may be just the cam that even at cruise like that it's pulsing the MAP too much.

with a fuel filter??? lol


i'm using the stock 3500 MAP so it's stuck directly into the plenum. I could go back to the stock MAP, i did leave the plug in the harness...


i'm going to be doing some hardcore tuning on Friday, we'll see what happens when i get the BLM's back to normal.

[sprucegagt]

Have you always had the problem with the new cam or is it recent?

[Superdave]

Have you always had the problem with the new cam or is it recent?

It started late last month, pretty much when we started bumping up the BPC to get the WOT fuel in order..

[Superdave]

forgot to add, it's only in closed loop.. in open loop it's fine.

[SappySE107]

What injector size and what BPC are you using.

[sprucegagt]

Did you check for a vacuum leak?

[Superdave]

Did you check for a vacuum leak?

Yah, didn't find anything...

What injector size and what BPC are you using.

36lb/hr and BPC is like 130.. it needs to go a little lower, at WOT i'm running around a 10.8 AFR and commanding a 12.6.


with the old FPR @ 32lb/hr i was hitting 92% duty cycle at WOT.. running 11.9 AFR and commanding a 12.6

[85_Olds_Ciera]

It started late last month..

If it was running fine before the twitching...and if you go back to where you started twitching it and it still has this problem...then

1. Sensor, wire, unplugged, etc.

That's the only way to rule out a defective part...or computer program "glitch."

[SappySE107]

I am using 140 for the stock 3400 injectors.

[Superdave]

I made a quick vid if it.. this is with no load but it does it with load too..

BPC is at 129 right now...

http://media.putfile.com/Closed-Loop-Surge

[Superdave]

I am using 140 for the stock 3400 injectors.

my old "stock" 3400's BPC was at 136.. pretty close.