ULTM8Z

Yep, tried a different ECM already.

I'll check the stuff on the EST circuit later today... wiring, HEI module, etc...

That 200 msec value on the Code 42 description vs my 200 msec PE drop out cycling rate... there's now way that's a coincidence... it has to be related somehow...

RBob

iTrader: (1)

Sure the code 42 isn't from setting the base timing? Clear it and see if it returns. The SES/CEL has to be on for a code 42 to be stored.

RBob.

ULTM8Z

I don't recall the last time I had to set the base timing, so I'm not sure how that would play into this issue.

Although, I generally never unplug the ECM after setting the base timing, and I don't still don't get this issue. I just re-plug the EST connector and start driving.

I've done some other work on the car recently where I disconnected the battery, and I don't "think" I've run the car with the EST connector unplugged since then. If that's the case, then it couldn't be a stored code.

But, in the spirit of the scientific method here, I'll be sure to try and eliminate this possibility off the fault tree later today...

RBob

iTrader: (1)

An open EST/BYPASS connector with the engine running will set code 42. A code 42 is easy to set, the tests for it are touchy. Too many items unrelated to it can set it off.

This is why I mentioned a bad ECM is a possibility.

Being a retro-fit brings additional issues. The ECM needs to be both electrically and vibration isolated from the chassis. All ECM grounds go to the engine block, and need to be tight and clean.

Make sure that the firewall to block ground strap is good. Battery cables are tight at both the battery and the block/starter.

If you don't mind email your current PE drop out BIN to me. I'll give a good look-see, there just may be something not quite right with it.

RBob.

ULTM8Z

Rbob, appreciate the offer... will do!

Only thing is, before I impose on your time, let me go inspect the HEI module and wiring and make sure I don't have any issue there. If I have a hardware problem, don't want to waste your time.

I'm extremely confident in my grounding scheme...

I have hefty ground straps from chassis to engine, battery to chassis, battery to engine, one cylinder head to the other cylinder head, a small ground strap from the distributor housing to the cylinder head, ground straps from the O2 sensor bodies to the cylinder heads (since I was skeptical of the ground path through the headers). I've also back probed all the ground wires from the ECM connectors to ensure they're connected... each one has ~.5 ohm to ground.

Yeah, I've been burned by ground issues in the past, so I left no stone unturned.

Every other aspect of the car runs phenomenally... idle, part throttle, AE, cruising, fuel mileage, etc. Matter of fact before I encountered this issue, I was just about ready to put the ECM back up and declare victory finally!

Any rate, hopefully I'll have some more data today or tomorrow (depending on when I get a chance to do the inspection).

ULTM8Z

Well it was too good to be true...

I disconnected the battery and then drove the car. The Code 42 disappeared, but the cycling in out of PE continues...

Not only that, but I verified the continuity of the harness on the EST circuit. Checked the HEI module with my tester (I have an Actron tester). No issues found.

Rbob, ok, now I guess.... if you wouldn't mind PM-ing me your e-mail address, I'll send over my bin and latest data log.

ULTM8Z

Well it's not the ECM. Just ran my ECM on a bone stock 91Z. No PE drop outs. Solid as a rock in PE mode.

ULTM8Z

Problem solved, thanks to RBob who generously took some time and looked at my datalogs and bin file.

Ended up being the 20 kPa I put in for the Min MAP for Power Enrich. I put the stock ANHT value back in per his suggestion (91.9 kPa) and that solved the issue.

From what I undersand (and RBob, correct me if I'm misinterpreting your statement) this value is actually supposed to be in vacuum, not in MAP. Appears that there's some sort of conversion going on when you enter in a value for MAP.

If I put in 20 kPa in TunerCat for Min MAP for Power Enrich, then view the same bin in TunerPro, TunerPro will report that entry as 80 kPa.

The $DA3 bin ('93 batch fire LT1 Camaro) uses 15 kPa, so I used the lowest value in $8D I could get (20 kPa). But I guess this is one instance where the $DA3 value (due to hard-code) makes is incompatible with the $8D.

99% of the time, the $DA3 values for things runs better with this Miniram than the $8D ANHT, but this particular one backfired on me. I was 100% convinced I was making it easier (on the MAP side of things) to get into PE, thereby having the TPS essentially govern entry into PE. I would have NEVER guessed that I was making it more difficult.

Ended up splitting the difference with 50 kPa and the car seems to like that.

I have to update my Miniram start bin as it currently uses 20 kPa. I'll put it to the stock value and let the user tailor it to his liking.

Any rate, hats off to RBob on this one!

BWilcox

Thanks Mike,

I looked at the ANHT hack and the AUJP Hack.

The "stock" PE Enable Minimum Intake Vacuum appears to be ~8.1 kPa.

Assuming close to sea level , the BAR would be ~ 100 KPA. So the MAP would be 100 kPa - 8.1 kPa = 91.9 kPa.

RBob, what is the purpose of this PE Enable function?

Best Regards,

Bruce

RBob

iTrader: (1)

With a large enough TB and low enough RPM, the engine can go into a high load with just a little throttle. Lower the TPS required for PE mode and the mileage suffers (so does the engine as it is always rich).

More important is a boosted engine. It is easy to generate boost with a medium throttle opening. The MAP PE table enables PE mode where the TPS % won't.

RBob.

BWilcox

Thanks RBob,

I think I understand.

PE is enabled for either one of two cases.

1. % TPS.

2. Vacuum (BAR-MAP).

Higher Load implies higher MAP or lower Vacuum.

So the PE enables for either a minimum MAP level or below a maximum Vacuum level.

Correct?

Best Regards,

Bruce

RBob

iTrader: (1)

For $8D it is either above the TPS% vs RPM table, or if the vacuum goes below a certain level.

RBob.

ULTM8Z

now that is interesting... you'e saying its an either/or criterion? I always thought both conditons had to be met before entering PE.

MrWillys

I thought all criteria must be meet to enter into PE?

RBob

iTrader: (1)

I'll go through the $8D code again to see how it works. I have so many code bases in my mind that it gets confusing at times. The other issue is, is that $8D firmware has different code between the various BCC's.

I use AXCN to look at how $8D works ('91 y-body). Should I also look at how AUJP works(?), as it is different from AXCN in other areas.

RBob.

ULTM8Z

AUJP would be interesting to know about (at least for me anyway since I'm running S_AUJP). I'm not sure what I'd do differently knowing if it was counter to what I had assumed previously, but it'd be interesting to know.

RBob

iTrader: (1)

So it really doesn't matter?

RBob.

ULTM8Z

it's certainly not something I'd want you to spend a lot of time on... unless you yourself were super curious...

if someone else has a more pressing need to know i guess they can chime in...

RBob

iTrader: (1)

The PE enable logic between AXCN and AUJP is the same. This is how it works.

If there is a TPS low or TPS high error then TPS% vs RPM threshold to enter PE is skipped. The logic goes right to the vacuum threshold to see if the ECM needs to enter PE mode (vacuum must be lower then the threshold).

With no TPS errors the firmware selects which table to use: normal coolant or a high temperature coolant TPS% vs RPM table.

If the current TPS% reading is lower then the threshold from either table, PE mode is not entered. The logic is done and the rest is skipped.

If the normal coolant TPS% vs RPM table is in use, and the TPS% is greater then the threshold, the vacuum is checked to see if it is lower then the threshold. If so PE mode is entered, otherwise PE mode is not entered. So in this case both the TPS% and VAC qualifier thresholds are used and need to be met.

If the high temperature TPS% vs RPM table is used, the VAC qualifier is skipped. All that is required is for the TPS% to be greater then the threshold to enter PE mode.

In both masks the crossover temperature to use the high coolant table is 116.75°C/242°F. Note that the TPS% threshold to enter PE is lower in the high temperature table. Makes sense to help prevent detonation and to help cool the engine.

My guess when the normal coolant table is used, along with the VAC qualifier, is for fuel mileage. The VAC qualifier will make the ECM less likely to enter PE mode, unless the engine load is high.

And being a N/A engine it makes entering PE mode more consistent regardless of elevation.

With the EBL P4 & SFI-6 systems supporting boost it is done differently. There is the TPS% vs RPM table and also a MAP KPa vs RPM table. Exceeding the threshold of either table causes the ECM to enter PE mode.

RBob.

P.S. a quick check of AXXD (LB9/5-spd) shows the same PE enter logic.

ULTM8Z

Ok, so it is in fact both the vacuum and TPS% that have to be met in order to enter PE.

RBob, thanks for taking the time to look it up!

RBob

iTrader: (1)

Only when the normal coolant temperature table is used.

When the high temperature table is used the VAC threshold is ignored.

RBob.