Thanks mate

Will post updates as soon as I have more info.

 

Just came back from the garage.
Without alternator connected, the SES still comes on the first time. Subsequent restarts do not trigger SES.
Swapped alternator with the old one that I had > dash lights dont flicker and I can exceed 3000RPM in N and P.
Went out to try it on the road. ALMOST no stuttering.

When I say almost, it is because lets say it did it for 10% of the times I tried to exceed 3000. Previously it was doing it 80% perhaps more of the time.

Definitely there was/is something wrong with the charging circuit as now I had a lot of variations in the problem behavior. I saw that the old alternator doesnt bring the voltage up more than 12.8V while running so the old one might also not be perfect.
I will take the chrome powermaster alternator to an auto electrician who specializes on alternators to get it checked. Sending it back under warranty is not viable where I live.

Apart from the above, I should get the EGR blockoff plate really soon. This will eliminate any possibilities of vacuum leaks as I will also remove the EGR solenoid and plug the plenum port going to the EGR solenoid. If this also fails, I am seriously thinking of disabling Code 34 diagnostics from the PROM using $6E. There isnt anything more I can try on this aspect.

 

https://www.thirdgen.org/forums/afte...lternator.html

If you could , have your alternator guy look at General Disorder's post in the link above . The General tears down and repairs the faults he found in a Powermaster alternator and it's a great , informative thread

 

What is your RPM at cold startup? The code 34 must be related to low MAF voltage. Have any modifications been done to the PROM that would not allow cold start high idle?

GD

 

RPM at cold is around 975 with Airflow not less than 9. Definitely not 2.5. PROM is stock AKXZ with EGR disabled. Checked the airflow both via ALDL and backprobing with a mtimeter.

 

There may be noise in the MAF voltage signal that you cannot pickup with a regular meter and the ALDL update rate is too slow to allow you to see. Probably have to use a graphing storage scope to find it. That is the only thing I can think of that would account for your variables.

GD

 

I only have a basic old CRT scope without storage. I guess I am going to start doing for a Chinese scope. Was looking at the hantek ones that you plug in to a PC.

 

I haven't used the Hantek one's but the primary difference between those and like the Picoscope products is in the software. Pico has their interface dialed in for professional automotive diagnostics where I think the Hantek one's are more universal and more basic in their software setup. I would say it will probably work just fine for your purposes.

GD

 

UPDATE
Yesterday I got the EGR Block off plate so I headed to the garage. Took the plenum off and while I was removing the EGR Valve I noticed the diagnostic wire (black from the temperature sensor) got pinched while I was installing the runners the first time. For sure this signal was permanently grounded not sure what that would mean. I think the ECU would constantly think the EGR is hot.
Anyway I removed the Valve and solenoid. Looks much tidyer now. Couldn't try the car yesterday as I wanted to leave some time for the instant gasket to dry.
This morning I went to start the car and I got no SES. went out with the car and no stuttering. Started multiple times no SES.

So far so good still running with stock alternator. I am noticing that when they coming fan kicks in, voltage while running drops to 12.75. I hope battery is not also on its way out. Currently it's very hot in Malta (32C) so most of the time fan is on.

Will report back tomorrow. Fingers crossed I get no SES and will work on getting that powermaster alternator checked.

 

That is definitely a low voltage reading while running. Is that he same voltage you see when the fan is off?

 

No fan off is +1V more curve 13.7V. yes it's low.

 

Very strange, your alternator should be putting out plenty of power to keep your voltage up with the increased amp draw. Well, at least to say your radiator fan should not cause a full Volt drop.

Are you seeing other reference voltages drop?

 

Sad news...
After two consecutive days without SES from cold, today I went to check again and there it was. Code 34 ...

The only thing left for me to check is replace battery due to the lowish voktage.

As now I completely gave up and I don't have access to a scope with memory, if I were to buy a new MAF can anyone suggest known good brands? I normally buy from rockauto. They are very reliable.

 

Rather than buy a MAF, it would be better to switch it over to speed density with the EBL Flash II.

https://www.dynamicefi.com/EBL_Flash.php

This way you don't have to worry about the MAF sensor (good one's aren't cheap) - you can just run a $15 MAP sensor instead.

GD

 

Well that surely if in my wish list but will have to wait for now. Been spending way too much money on this car and have to slow down for a bit. Going MAP would make for a less error prone system but I think I can achieve that result with some repinning and 89 BIN also no? I am also looking at the possibility of using a more generic/ cheaper MAF and adapting the voltage table in the BIN. I think that is also possible.

 

89 is still MAF. 90 to 92 is speed density using the 7730 ECM. Yes it is possible to repin for the 7730 but doing so is a lot more work than the EBL and the EBL is pretty cheap ($475 or so) for all the features you get.

Most modern MAF's are frequency based so are incompatible with the ECM hardware. There are still some analog 5V hot wire systems being used - mostly in the asian cars like Subaru for example. You could adapt them but it's not really going to change the cost of operation (they are still $250), it's going to need considerable tuning, and you still have the ECM limitation of 255 grams per second which is about 250 HP.

GD

 

Didn't know newer MAFs use Frequency. Also didnt know that 90 to 92 models use different ECM

Will keep an eye on EBL but will surely not be something I am going to do in the immediate. Anyway the car feels a lot better with the other alternator and I suspect that the battery also needs a replacement. Will try another one soon.

 

The battery is a load once running, a sub par battery could be puling a constant drain on the electrical system. I would be surprised it would cause so many issues (Might have been what bit your old alternator)

While going EBL or to the 89 computer will have it's benefits and something I am looking into, getting something back to the way it ran previously shouldn't require so a major change or re-tune. I would assume in your country, parts stores still load test batteries. I would charge it up on a slow charger overnight and take it and have it tested before buying a new one.

 

Good idea. Will take it to the battery store anyway it's still under warranty.

 

I am really curious to see how this comes out. Any updates? Did you change the battery?

 

Battery is currently on a CTEK charger with AGM mode. Will try to find some time to give it another try this weekend and will surely update you. In the meantime I also checked current draw from the cooling fans. It is at 9.5A which should be quite within normal range so the fans overloading the battery/amp is definitely not the case.

 

Guys,
Am working a bit on my $6E based BIN which I am basing on AUJM (1989 FBody 350 Auto) and loaded the $6E_expanded definition.

1. Are you sure the NO flag for the fan needs to be changed? Description is 'Cooling Fan Request Normally Open'. This is 'Set' in AUJM and I think that my relay is a NO Relay and needs a signal (+ve) to energise the relay's coil. From the description, if I unset it, it would mean that the switch is NC and when the ECM requests fan ON, it then Opens the relay's switch.

2. There is a flag called 'MAF Sensor' and when it is 'Set' it represents 'Analog'. AFAIK my car uses and Analog MAF but in AUJM, this flag is unset. Should I enable Analog Maf flag?

Thanks in advance

 

Here's an excellent video showing diagnostics on a GM frequency MAF. It's not exactly like your analog MAF but has a similar problem in that it has a sensor glitch which can only be found with a scope:


I don't think that MAF sensor flag is important.

As for the Normally Open fan relay request - you want it whichever way makes the fans turn on when you hit the fan set point. So monitor the CTS and if the fan doesn't come on, change the flag and try again.

GD

 

I think the no/nc fan request is based on the ac pressure switch type not the relay.

 

Just burned a fresh AUJM with $6E and went to try it out.
- After 2 days of having the battery disconnected, i plugged in the chip, started and all fine. No SES.
- During these 2 days, the Optima was on an AGM charger (CTEK) and got up to 12.7V.
- While running, the alternator brings this up to 13.6V however as soon as the fan kicks in, the voltage drops to 13V. Not sure if this is correct or not. When I rev the engine, I can see the volt meter in the dash cluster go up to circa 13.5V again. Is this correct?
- Went to drive the car, and it really drives great. Can't say I saw HUGE differences from the stock $32B based bin but idle feels more steady. Also dont have that stuttering yet while driving around 3000RPM but that might be due to the chrome alternator problems which I am now using the stock alternator until I get it checked.

Also FYI, re. the $6E N/O Fan flag, for my transam it has to be 'Set'. This is the same as it was on the AUJM Bin by default. I am assuming this has to be set for F-Bodies and not set for Corvette BINS such as the ARAP.
Re. the Analog MAF, from some research that I did, this flag is valid only for 85 Cars which were using a frequency based MAF. Probably the expanded definition file is exposing this incorrectly and this flag should PROBABLY not be touched (Not Set by default).

 

Really interesting. As I said I dont have a storage oscilloscope handy but if the problem persists I think I will go ahead and buy a handheld scope with storage functionality. There are these cheap [ish] Hantek 2D42 models which also have a signal generator thus can also be used for things such as simulating signals to the instrument cluster.
Thanks for the info GD

 

It might be that $6E is desensitized for the code 34 or something along those lines. There may have been advances in the code used to ignore glitches in the sensor signal. Someone more familiar with the hac would have to chime in. I'm not that good with the assembly code used for these ECM's and I've only looked at bits and pieces of the $6E hac and never looked at the $32 at all.

Any scope is better than no scope. They are super useful. I have about 4 different kinds for various uses.

GD

 

Will surely update you in the next few days to see if SES comes out again.

 

Posting this not to leave this thread pending resulting in it not being concluded and serving no purpose.

I still didnt get any news from the alternator guy to see if the unit is faulty or not, so I am currently still using the stock alternator which drops to high 12V when there is load like the coolant fan.

But for the last 3 days from when I put in the new AUJM based PROM, SES didnt come up yet (Code 34) and I can say that the car is also taking longer to reach higher temperatures. I am aware that I decreased the FAN ON temperature in the PROM but here I am talking about the time it takes to even reach the FAN ON temperature so it looks like this tune is more refined in terms of timing that the engine is also taking longer to reach FAN ON temperatures which I am very happy of.

Will let you know outcome from the alternator shop but currently there are a lot of people on vacation so work slows down.

 

Got some news from the electrician who I took the alternator to.

He said that the alternator is not exhibiting any particular faults. I saw him testing it on a bench test machine and could see that it is outputting a constant 14.7V and such voltage is steady both off-load and on-load at all RPM. This isn't the same behavior I was seeing when it was on the car as with the Fan ON, I was getting 12.7V at the battery terminals. He said that the load this testing machine applies is quite high but he didn't tell me the exact current that it draws. I am assuming it is similar or more than a Fan load (mine was using 9 Amps after a 14 Amp starting current surge).

When I kept on pushing for opinions, he said that what he can perhaps suspect is that 14.7V was on the high side and following this I requested for changing the regulator. This is especially after the negative comments I got from here on powermaster components.

I am really not convinced this will solve the problem but if it doesn't I'll start looking at the wiring on the car related to the charging system. Perhaps the lamp signal which is used by the regulator to keep on outputting voltage is somehow dodgy in view of the fact that my dash is a digital dash and doesn't have a visible alternator light?

In the meantime I can say that SES has not re-appeared till now but I didn't get to try the car on the road again due to bad weather. To be honest, I double checked the BIN to ensure I didn't disable Code 34 SES by mistake

 

Sorry for the lack of updates. Wasn’t actually working on the car. Alternator regulator was changed but still not installed in the car thus still running on the stock one.

Revs were still dropping at 3K with the stock alternator.

Coil and distributor cap arrived in the meantime.

Swapped the coil and bingo... 3K problem in N and P vanished immediately. Tried it a dozen times till now.

Tried it on the road. Feels much better BUT i still have some stuttering. Lets say before it was doing it 70% of the time, now it’s at 15% so big improvement.

Next planned change is the distributor cap.

Will update soon