XrayTedd

Back ground on the engine first.
TPI SD fresh built 355 from the ground up.
Dart eagle iron SS heads .202/.160 valves 72cc fastburn chambers. Crane 2040 flat tappet cam with 1.6 roller tip rockers. Hyper flat top pistons. Long tube headers with ACdelco heated 3 wire O2 sensor.
EGR delete. 24lb inject. SFI adj fuel press reg. Delphi fuel pump. large cap HEI dizzy. 7730 ECM. Prom has been tuned for the engine upgrades. Stand alone wiring harness from Larrys Electric.
The engine is in an 87 K5 Blazer that was formerly a TBI engine mated to a TH400. Running a VSS from Jagsthatrun.com. Fuel pressure is around 36 at idle and 48 at WOT.

This issue wasn't always present. it was only occurring every now and them during the tuning process. Now its occurring more often than not. But will tend to go away then come back. Engine idles fine. Low RPM is good too. But once it hits 2400 RPM It breaks up and wont go much over that. It wont stall out nor do I get any codes. once the trans shifts and the RPM comes down it runs fine until that 2400 mark again. when its not acting up its a delight to drive. Runs fantastic with tons of power. Then the gremlin will show up again. Running a TH400 I basically cant do over 55mph. I've triple checked wiring and grounds. Had the ICM tested several times its an ACDelco and new. The MAP sensor is gently used but bench test show its functioning fine. I'll probably change it next though. All other sensors are new. Does anyone have ANY suggestions?? If I had the money sitting around I would've already ripped this system out and went FiTech. But for right now that's not an option. Thanks in advance for any help!!

Tuned Performance

iTrader: (92)

Not sure what to suggest since it’s intermittent.
you might try the suggestion on this thread about monotering ignition voltage.
https://www.thirdgen.org/forums/tpi/...t-3000rpm.html

XrayTedd

Yeah I saw that earlier. Its the closest problem to what I'm experiencing that I've seen yet. Except I don't lose my RPMs. It almost seems like the timing isn't advancing like it should. I'll go ahead and take a look at that suggestion and see what it's doing.
Thanks for the input.

ULTM8Z

Can you datalog? With Tunerpro or something else? It's always easier to diagnose based on data...

XrayTedd

I have some logs on TunerPro. I was able to get a log while it was running good and I took one while its acting up. I don't really know what I'm looking at with them. I sent them to my programmer and he said he thinks I have a sensor sending false data. He seemed baffled over the phone. Didn't have much direction for me. I'd be happy to send them to anyone that would like to take a look at them!

I tested my pickup coil with a multimeter and it tested normal. May still be something I revisit later. Is it normal for timing to jump around at idle with est connected? It smooths out and advances as you roll the throttle, but at idle it bounces around?

84Elky

Are you using a ZIF socket for the chip or possibly for an AutoProm cable to the ECM. If so, check connections and/or chip seating. A less than solid connection can cause just what you are seeing. Been there , done that! Intermittent ain't fun.

XrayTedd

This is part of the reason I'm considering switching to the Holley Sniper EFI. LOL I'm not well versed on these TPI systems. I believe my setup is just a burned factory prom and ECM, Whats a ZIF socket and AutoProm??
Thanks for the input!

Tuned Performance

iTrader: (92)

A autoprom is a emulator. A zif socket has a latch that snaps down on the legs of the prom vs a dip a push in socket.

84Elky

Sorry for the overkill. It's as Tuned said. But the point is that if there are any loose connections in or to the ECM, there can be (note: "can be") intermittent issues. May be more overkill, but if you were using S_AUJP v5 and its ADX file, you would be able to see if you are getting an ECM Data Out of Range error. If so, that can cause intermittent issues as well. I'd explain how to do it otherwise, but very detailed.

How about your posting a log that has the problem. Be sure to export it to a .csv file as the TunerPro xdl log file is useless unless you also post your adx file.

ULTM8Z

Ok, couple of things I'm seeing...

1.) You're stuck in BLM cell 4 (the idle cell). Something is up with your CCP settings in your bin... my guess is someone flipped the switch for "Force BLM idle cell duty cycle threshold" to 0% and disabled the CCP? Your CCP is never becoming active (duty cycle is showing 0%), so the BLM cell never gets out of 4. It should be varying during different driving conditions.

2.) Your IAC position is stuck at 87. Not sure what that's all about.

3.) There's a large voltage drop between the keyed ignition and the fuel pump (about 1 volt). Sometimes this can cause issues with how the ECM fires the injectors (injectors seeing a different voltage than what the ECM thinks they're getting, which means the injectors could be firing at a different pulse width than what the ECM is commanding).

I don't know that any of these would cause what you're experiencing...

How's your fuel pressure? I exported your data to .csv and pulled it into excel. When I filter the data on >3000 rpm and TPS% > 60, I'm noticing the O2 sensor seem to be tending toward the lean end of the voltage range. Granted it's a narrow band sensor, so I'm not inferring an actual AFR from it, just that it may indicate a lean condition, which could point to something with the fuel pump, filter, etc... can you get hold of a pressure gauge that you can monitor while driving?

84Elky

1. Has a log been posted? ULTMZ commented on one.
2. Yes, timing will move around at idle with est connected.

XrayTedd

Awesome. Glad to hear that. I've never had any experience with that before. I haven't posted a log yet. I would need a little more info on how to do that. I emailed a couple logs to ULTM8Z over the weekend.

We'll set #1 aside for a min and take a look at everything else first. With the IAC, was this the same results in both logs, and would you suggest replacing the IAC? I will check out the voltage drop today after work. I assume you're talking about voltage before and after the "key on ign" to the fuel pump? Also the fuel pump was an Ebay special in those logs. Shortly after, it was pulled and tossed in the garbage. Replaced with the Delphi. Not sure if that could be part of the voltage issue. I'll also "borrow" the fuel pressure gauge from Oreillys and tie it up under the hood and slap the go pro under there and go for a short drive. Thats about the only way I can think of to view it while driving.

Greatly appreciate all the info and help I'm getting. I really would rather keep the TPI system in if i can get it working properly.

ULTM8Z

Edit: Disregard on the IAC... I must have had a filter on in Excel... when I went back to look again, the IAC voltage is in fact varying.

On the fuel pump voltage, it could be an excessive voltage drop across the ignition switch. What I would do is measure the voltage at the injectors and see what the injectors are actually seeing. Basically take a voltmeter to the pink/black wire and then to chassis ground. That would be the important thing... if the voltage at the injectors doesn't match the fuel pump voltage being reported in TP, then yeah there could be issues. If they're seeing the higher keyed igntion voltage being reported in TP, then we you either chase down the voltage drop, or simply change the tune to base the injector offset table on the keyed igntion voltage rather than the fuel pump voltage.

In terms of the fuel pressure, yeah you'd need to know what the pressure is at the time you lay into the throttle and over ~3000 rpm. If you can correlate go-pro footage back to those conditions, it could work.

XrayTedd

I ran through everything I mentioned above with the exception of the IAC. I did install a new MAP sensor just because it came in the mail on sunday. I had ordered it around the time of my original post. My voltage at the injectors, while idling, was 14.2. I took it for a drive with the pressure gauge and gopro under the hood. I havent had a chance to upload the footage to my computer yet, but it looks like there is only parts of it where it wasn't too dark to read. I couldn't find a light that I didnt care enough about should it fall out. LOL Also looking at TP it looks like my fuel pump voltage was 13.2 and dipped down to 12.7 at times while driving. That is an improvement from the log that ULTM8Z was looking at. However during the entire 10 min drive, my BLM stayed max lean at 160. I did record that log. I still dont know to to upload them here in the .csv format.
My "intermittent" issue I think is now "just and issue". The last time it ran good, it only did so for about 30 sec. Then it was back to crap.
I'm starting to think I may need to just start back at square one with tunning?

ULTM8Z

What injectors are you running? As in the manufacturer and p/n?

XrayTedd

I had to get under the hood to check. I couldn't remember. They are Bosch 0280-150-947.

ULTM8Z

Maybe post your bin... it could just be something in the tune

EDIT: found this on your injectors for the voltage offsets

http://forum.efidynotuning.com/viewtopic.php?t=464

ULTM8Z

Yeah, the problem with the voltage drop is that within the injector voltage offset table, the injectors may be operating in one voltage range, whereas the ECM is commanding them thinking they're in a different voltage range.

One range is 12.8 to 14.4. If your injectors are seeing 14.2 then they're actually in this range of their performance curve. However, if the ECM is seeing less than 12.8 (I'm seeing as low as 12.4), then the ECM is commanding them thinking they're actually in the 11.2 to 12.8 voltage range.

XrayTedd

With help from 84Elky. If I did it right. My log from yesterday should be attached.

XrayTedd

So is that something that can be tuned out?

ULTM8Z

Yeah, you would take the voltage offsets for the injectors and input them into the voltage offset table. Would need to do some interpolation to get these values to line up with the voltages in the factory table.

15.94 0.50
14.00 0.50
13.00 0.59
12.00 0.81
11.00 0.91
10.00 1.31
9.00 1.50
8.00 2.00
7.00 3.00
6.00 5.00
5.50 7.00
0.00 7.00

You would also either have to rectify the voltage drop issue in your engine/EFI harness, or as a work-around you can change the voltage that the ECM looks at to make the calculations...

In Tunerpro, the flag at Bit 6, Voltage source for Injector Voltage Offset, check the box (it's unchecked in the factory calibration). This sets the voltage source to keyed igniton voltage (which appears to match what your injectors are seeing).

I don't know that this is the root of your issue, but it's something that needs to get cleaned up.

XrayTedd

Looks like I'm gonna be investing in some chip burning equipment. In the mean time I will take a look at my fuel pump wires and make sure they are all good. I really appreciate everyone's help. You guys have been great. I hope I can get this thing going. I really don't want to spend the 1k for a different EFI system. I'll report back once I get the equipment and some changes are being made. If anyone thinks of something in the mean time. I'll be happy to check it out.

PS I wrote this response a few days ago but for some reason it didn't post...

XrayTedd

We finally got this issue resolved! It did need so adjusting on the tune, but that wasn't the cause of my problems. Turned out to be a bad ECM ground. I had tested the grounding points to the battery several times and didn't find anything. It was until I back probed the wiring at the ECM that I was able to find it. The builder of the harness had connected all of the ECM grounds into 1 that I had mounted on the intake manifold. After replacing that everything was back to normal! I also went ahead and added an additional ground from the intake to the batt.
It's nice to finally drive it. Thanks to everyone that commented and offered up advice. Great group of guys on here and an over abundance of knowledge!

84Elky

Glad you got it fixed. And you have solved a problem that causes so many similar issues. Solid ECM ground(s) absolutely essential!