critter

iTrader: (9)

Can anyone point me in the right direction on this? I haven't made changes that should affect this - just the Nogo big cam idle stuff and IFR table for SVO injectors - but when I mash the throttle I get about 1 second (9 samples with EFIlive) of openloop and power enrichment, and then it goes closed loop and 14.7 AFR. I have checked these obvious things:

TP 100%
Cell 22
ECT 185
IAT 91
COT off
WOT enable 65% TP, 142* (F I assume)
MAP 98-99kPa

Where do I look next?

TIA

Brains

iTrader: (7)

Fuel trim cell 22 is WOT/PE..

critter

iTrader: (9)

Right. So how come the PCM is commanding 11.7 AFR for a second and then switching to commanding 14.7 AFR?? At the same time, the PCM switches from open loop to closed loop, obviously.

Bink

I'll take a shot at it.........Canister Purge is activated. Drops it back to EQ ratio =1.00= 14.7 and closed loop. Scan to see if your Fuel System Purge is active - I'm not sure what the PID is??? Sound plausible? Refer to 2nd page this thread for more info....->
http://www.efilive.com/forum/viewtopic.php?t=474

critter

iTrader: (9)

Thanks Bink! I never thought of that - I will now go study and log tomorrow.

critter

iTrader: (9)

Nope. Canister Purge is inactive during the WOT time. Here is the sequence.
At TP=85%, it switches from CL to OL-DRIVE. Cell is still 15, EQ=1.0, and EVAPDC=90%. Next sample, TP goes to 100%, EQ goes to 1.25 and EVAPDC to 18%. Next sample, EVAPDC goes to 6%. Next sample, cell goes to 22 and EVAPDC goes to 0. Next 7 samples are the same. Next sample, PCM goes to CL, EQ to 1.0. It stayed in CL about 1.7 sec. Next 12 samples the same. Lifted foot. Next sample TP goes to 0. Next sample, cell goes to 3 and EVAPDC goes to 11%. This is really wierd ...

critter

iTrader: (9)

Wow ... nobody has an idea?

gojo

iTrader: (12)

How about raising Closed Loop enable temp to some high value. If it stays in open loop you might have incorrect ECT being reported?

critter

iTrader: (9)

EGT is being logged as 170 to 185, but it sounds like something to try anyway.

Super Sport X2

Power enrich mode will not turn on until all of the qualifications are met.
There is also a timer to hold off PE.

Enable Map
% TPS Enable
Delay mode RPM (Rpm > to bypass the delay)


Ken

critter

iTrader: (9)

The problems is premature turn off of power enrich mode, not failure to turn it on. The car meets the qualifications and goes into PE mode, but drops back out after a couple seconds. But, it appears that this only happens at TP=100%. If I keep TP closer to the min, it doesn't seem to happen. Resetting the PCM doesn't help either.

critter

iTrader: (9)

Here is another clue:

I can go OL-DRIVE with PE as long as I don't use 100% TP. I have gone as high as 90% TP and as long as 9 seconds in OL-DRIVE/PE but when I go 100% TP, it drops back to closed loop after a second or so.

I also have seen this error, but I don't know when it happens in relation to my test runs but it did not happen on my most recent test:

P0123 "Throttle/Pedal Position Sensor/Switch A Circuit High Input"

So, is my throttle blade opening too far and sending too high a voltage to the PCM, causing it to kick out of OL/PE mode? I haven't checked yet since I am not home, but will check later. I don't know what the max TP sensor output is supposed to be, or that to do with it if it is too high.

critter

iTrader: (9)

Well, I found it. I'll report here in case anyone else ever runs into this.

The problem was the sum of several things, but the result was that the PCM was seeing 4.9V at WOT. The manual says it is supposed to be 0.5V to 4.5V and over 4.75V is an error code - P0123. That explains the periodic P0123 code I would get, but strangely enough, I would not get it every time I ran a WOT test. This is probably because the condition did not last the required 10 seconds. However, within a second or so after the PCM saw 4.9V it would kick out of OL/PE mode and back into CL and shoot for stoich. This is counter intuitive to me. I would think if the TP sensor is in trouble you would want to go open loop and keep it rich, but what do I know ...

The reason the PCM was seeing 4.9V was because the throttle blade was going over center a bit. I have a ported TB with the throttle stop mod, and either the set screw backed out or the 2000 cable pulley is a bit different than the 1999 on I had on before. Perhaps there is a bit of difference between the TP sensors. Rather than keep the throttle blade from opening all the way, I slotted the TP sensor bolt holes and adjusted it so that the range was 0.5V to 4.5V, throttle closed to full open. Now my Z28 is a happy camper and I can finally start tuning.

Bink

Carl-Thanks for updating us with the solution.
joel

Super Sport X2

Excellent post critter.

I had no idea you were running a modified throttle or getting
error codes in the WOT process.


Ken

critter

iTrader: (9)

You are welcome. I hope it proves useful

critter

iTrader: (9)

Heh - I thought everybody ran a ported TB. I didn't connect the P0123 code earlier because it did not seem to occur at the time it kicked back into CL and only infrequently.

WOT, 6500, and the PCM is trying to achieve stoich ... thank God for knock retard.

But the bigger lesson is that anyone who has the throttle stop mod on their ported TB would be advised to check the TB sensor voltage PID.

dr.mike

This brings up an interestign question for me. Is there a way I can force the PCM to run in closed loop 14.7 all the time? That would really make my life easier. I can program my LM-1 ( & AuxBox ) to simulate 14.7AFR at any actualy AFR as read by the wideband. So, under load, I could have the LM-1 output a 14.7 signal when the acutal AFR is 12.5, etc. Then, theoretically, instead of fighting the PCM, it would be tricked into doing my biding