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I have narrowed down a strange problem in my stock 89 TPI to using an 89 APYY PROM vs an ABUS 87.
If I put either of my two APYY modules in, the car runs great except for heavy throttle above 4,000 RPM where the engine just stutters and loses power.
If I use my other module, an ABUS, there is no problem and the engine runs great all the way up at full throttle
I recently went through my entire engine and literally replaced everything except the "cam and pistons." Two distributors, caps, two kinds of plugs, fuel system checked, all of it. It did not have this symptom two months ago.
The only difference is the APYY vs the ABUS and it comes in rather predictably. Driving, if I go a little more throttle at 4,000 RPM the "missing" starts, if I back off, the missing stops. I can go back and forth. Maybe there's a table somewhere in the programming? PE mode?
If I rev it in neutral, its fine.
I do not understand PROM burning and tables but am hopeful maybe the expertise here can explain what is going on between the ABUS and APYY (I also duplicated the symptom in a separate ECM chassis, so it is the programs.
Last edited by Tootie Pang; 10-15-2017 at 12:40 PM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Hmmm... that is interesting.
Maybe shoot me the two bins... I can do a bin compare and see the differences. Unless someone who knows the bins already chimes in and gives the answer.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Also, this misfire happens with both the original Multecs in there and my Bosch -710s. BLMs are fine. As a reminder: I can pop in the ABUS prom and the problem goes away. I pop in one of the two APYY's, problem comes back.
There is a finger pointing right at the mapping. Weird.
Also, it did this in both ECM chassis I have.
And, lastly, my fuel system is solid. Checked it three times driving around with a gauge in my lap and a fire extinguisher. Solid pressure at the rails. All ignition components new.
Last edited by Tootie Pang; 10-05-2017 at 09:04 AM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
That's a great article. I did buy a Memcal and have it tuned. But both of my APYY proms do the same thing. Now, when I got my car in February, it came with a Delphi ECM:
I am fairly certain that my car did not exhibit this high-rpm, heavy throttle missing until about two months ago. I just don't have the notes but I do remeber being able to WOT without issue months ago.
This is just weird. In the process of refreshing my motor (changing everything), I picked up this miss. Now both APYY maps cause it (the one that was in the Delphi and the tuned one) and the used 87 Firebird TPI Auto ABUS, that I bought as a double check, runs fine.
Now I suppose I could be the victim of coincidence. Maybe my Delphi memcal is wrong, or the previous owner changed it and the missing was masked by another wrong engine condition but that's just too strange.
Right now all I know is with either APYY I get the miss, and the ABUS (which I believe is an original), does not. Maybe the Delphi has the same issue.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Abus is a $32b mask from a 87 5.0 auto, apyy is the original memcal for your 89 5.0 automatic. Odd your having those symptoms. The 87 uses a ninth injector for cold starts and no vats . I would assumed different fuel mapping and sa.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Here they are. Note the resistor in the APYY and the cut pins near it (Is that an OEM thing or might I have bought the car with a tune on that APYY memcal? That sticker looks misaligned too). The unlabeled is the Tune APYY. I see no jumpers on any of them. Recall the ABUS memcal works fine, the two APYY (labeled and no label) share the 4,000 RPM, heavy throttle misfire.
Last edited by Tootie Pang; 10-06-2017 at 01:21 AM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
In 89 I think gm ran out or change the netress. The two with the 10k resistors are real the one with the sst eeprom is from a v6 and should have a jumper 56-62. You can see where a knock filter use to be soldered on. The sst looks like a friction fit or a really clean solder job.
Last edited by Tuned Performance; 10-06-2017 at 02:32 PM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Thank you! I can do the jumper but am not getting the pin numbering 56-62. Maybe I'm associating the wrong pic? Also, you mean by 10K resistors, in the netres's? I only see one memcal with a resistor. I also found an old thread where you explained the change in 89. Looks like my Delphi has that change.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
I’m curious to hear if there’s much of a change, I have heard the complaint of long craning this can be addressed with the jumper and additional programming for injector pw vs crank ref pulse in some calibrations. Way the sst one suppose to be a apyy with other changes vats , emissions disable , fan on offs changed ect.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Well in my case, I am after a heavy throttle, 4,000 RPM + misfire that I can start and stop precisely and at will every time by depressing the accelerator another 1/8" or letting up an 1/8". This is with both APYY proms and not the ABUS. In my caveman understanding of things, sounds like Power Enrichment trigger, but again, I'm a barbarian- my words.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
Update: No change. Weird weird weird.
Recalling my ABUS memcal works flawlessly:
My next step can be one of two ways: I can put an APYY tune on my ABUS memcal or put an ABUS tune on my Delphi APYY memcal. I suppose a third is I can put a modified ABUS tune on my ABUS memcal. Anyone care to weigh in? I prefer the way the car drives around with the APYY proms.
Last edited by Tootie Pang; 10-06-2017 at 08:40 PM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
So the tuner, Scott Hansen, put the 1987 ABUS programming on the memcal along with the 89 cold start table, and a few other changes, but essentially the ABUS programming.
Problem has been resolved, no more heavy throttle, high RPM misfire that came with the APYY program (regardless of memcal or ecm).
So the mystery continues but now the car runs very, very well.
Thanks everyone for all the help!
Last edited by Tootie Pang; 10-15-2017 at 11:07 PM.
Re: APYY - high RPM/Load misfire, ABUS - runs fine
The ABUS memcal was read and VATS was enabled, fan temps were brought down to 210F on, Cold start table from 1989 was used and the scan ID was changed to APYY in case California reads his ALDL port during smog inspection. When I lived there they were putting my vehicles on a dyno and making sure everything functioned.
10-05-2017, 12:50 AM
