zenofspeed

iTrader: (1)

AFRs: 11.5 under load, 14-15 cruising
EGTs: 800C peak. 700C during normal driving.


Ok so the car was running great, idling at 1100rpm and vacuum at idle was -17psi. Smooth acceleration.

Then I pulled out the J&S knock sensor.

Now the vacuum is -10psi and idle is 800rpm and sometimes bounces down to 600rpm.

Upon acceleration (at lower rpm) the car starts going then loses some power, and starts to bog down, but I can power through. Once above 3.5k rpm, I don't really feel any problems.

Could this all be related? What can cause the vacuum to drop so much?

thanks for any feedback,
Ian

spoolage

iTrader: (2)

All you did was remove the J&S Knock Sensor, started the engine and then the vacuum was 10 psi with an idle of 800 rpms???

What was your reason for pulling the knock sensor in the first place?

zenofspeed

iTrader: (1)

The display of the knock sensor got damaged.

It could be unrelated. I drove the car one night, got home. And pulled the sensor the next morning. The knock sensor computer was spliced into the ECU with 4 wires. I just snipped them and taped them up.

What could those sort of symptoms possibly reflect? Could timing effect vacuum? I'm imagining some scenario where the PFc is pulling timing and causing the hesitation on acceleration. But I don't really know how these engines work on that specific of a level. And I have no idea about the vacuum.

The car seems to run and pull fine once over 3.5k rpm. Another change i forgot to mention is that before all these strange issues the max EGTs i were around 700c. Now I get 800c under the same driving conditions and AFRs.

spoolage

iTrader: (2)

Its definitely possible that the J & S sensor was having some effect on the timing which would have an impact on the idle. I dont know anything about the J & S sensor so I really cant comment on it.

I take back what I said about the injectors, did a little reading..

Based on your increased EGT's I think there is definitely something going on with either your timing or you are getting increased fuel delivery.... Are you running the stock injectors?

spoolage

iTrader: (2)

"The unit has a high energy ignition with constant energy dwell controller. The system monitors the coil current, and adjusts the dwell time to achieve seven amps of coil current. Compared to a GM HEI, this is a 62% increase in energy stored in the coil. The system can also be used to trigger an MSD."

Not sure if this has any relevance - but it sounds like the J & S is able to increase the spark?

Have you tried resetting the ECU and having it re learn the idle?

Also... do you recall what your AFR's were at idle before eliminating the J & S knock sensor in comparison to your current idle AFR's?

Ill buy that knock sensor off you if you want to sell it.

arghx

iTrader: (3)

post datalogit logs

djseven

iTrader: (56)

With that low of vacuum on a new engine, I would assume you have a leaking injector. Did you notice an increase in fuel smell? You should not be pulling that low of vacuum on a new engine.

classicauto

iTrader: (3)

I've found AFR will effect vaccum quite a bit. What was it idling at before you removed the sensor, and after removal? A big fat 10AFR idle will sound flatter, and pull less vac then at 12.5-13

zenofspeed

iTrader: (1)

No fuel smell at all. Yeah, the vacuum is what worries me the most. I havent had the time to investigate yet. It will be going into the shop this week.

The injecters are 550/1600

Is there anything else that can cause low vacuum?(other than bad boost gauge reading)

zenofspeed

iTrader: (1)

Since I wasnt expecting the sudden change, I didn't pay much attention to the difference in AFRs at idle. However, it isn't that rich now. It seems to idle around 13-14.

It doesn't sound flat. It sounds like an idle at the correct AFR to me.


As far as reseting the PFC, does that just entail disconnecting the battery? I've really been meaning to do that, but I've been busy this week.

djseven

iTrader: (56)

If you want to go back to the base map you cant do it by just disconnecting the battery. I havent had to do it in a while so I cant remember the exact steps but hopefully someone will chime in and walk you thru it.

David

pluto

Ian,
your leading coils are not working since you removed the J&S. The J&S connects between the ECU and the leading coil ignitor(in series) so that when it detects knock, it would retard the leading timing (ONLY). when you spliced all wires, you will need to reconnect the two wires that connects to the leading coil so that it would work again. Check those wires and make sure you have them connected since your sympton sounds like you are only firing trailing coils.

zenofspeed

iTrader: (1)

Thanks Steve!

Can that explain the vacuum drop?

Busted7

A drop in rpms will lower vacum you said it was idleing at 880rpms down from 1100rpms?

zenofspeed

iTrader: (1)

yeah its at 600-800

pluto

Yes! hard hot start, lost of vacuum (not by much), lower rpm at idle (assuming without ICS), higher EGT, laggier spool up, lost of power are symptons of no leading coils when the engine has good compression.

Don't get on it anymore because you can crack your iron housing at WOT running just trailing plugs.

DriftDreamzSS

iTrader: (4)

Huh? I disconnect my battery all the time when i store my car and it never does anything to the maps on my pfc. I would hate to accidentally go back to the base map tho, does anyone know how exactly that would happen by disconnecting the battery?

spoolage

iTrader: (2)

There is a function select that you can use the commander to navigate to - it will ask a question and you have to select [yes] or [no] then shut down the car and start it back up. This is the only way I know that you can "reset" to basemap

zenofspeed

iTrader: (1)

well, luckily I haven't been getting on it at all really. Because I am still in the break-in period. I think I boosted as much as 5psi once by accident, but I babied it to the shop yesterday, so I think it is going to be OK.