Data Logging OBD 1.5 Sketchy data

[cdcollins1]

Hello,

I'm finishing up the V6 conversion into my 78 MGB convertible. 3.4 Iron head from a 95 Camaro, mild cam (260h), bored +.020, running the SFI from a 95 Camaro.

I'm having problems with the engine dying at idle once it gets hot. I'm using TunerPro RT to edit my bin file and have bumped the idle speed up to 850 and pulled some of the timing out using the idle spark vs. MAP and idle spark vs. Coolant Temp. I'm using the P66 mask for the .bin file and the 16184737 .adx file for the data stream (ECM is out of a 95 Camaro with an automatic). Programming the PCM is done with CATS WinFlash.

I recorded a data log and have been using the dashboard in TunerPro to watch engine speed, IAC steps, coolant temp, L and R O2 sensors, etc. to watch for anomalies that would help me figure out why it still dies when it idles down at a stop, or if sitting at a light for a long time.

I'm thinking I've got something quirky going on from my sensors or in the ECM. The values seem to jump all over the place and not by just a little. coolant temp almost always reads minus (-)38.6 degrees, with occasional flashes of what looks like the correct temperature. The cooling fans do come on at 225, so I know the sensor is working correctly. Engine speed is reading double what I think it really is (possibly due to the waste spark DIS system(?) but is still all over the board with displayed values.

I view the data log which was mostly just idling in the drive and the data trace shows things bouncing all over the place when I watch the Main VE table, Idle VE table, Main Spark Table.

Looking at the item list and watching the various parameters during playback, it seems to be constantly bouncing in and out of closed loop with some of the parameters that aren't even applicable flashing off and on (clutch switch, A/c clutch, brake pressed and these aren't even in place)

Overall, it runs great on the highway, but without having a reliable data log and seeing steady data, I can't tell where I might need to tune things. (probably need to back out some VE at low rpms and add some at higher due to the mild cam)

What would cause the data to jump all over?
Does this sound like I have a short somewhere in the wiring?

I trimmed out a lot of wires when I installed the harness since I deleted EGR, A/C, all transmission connections, etc. that I didn't need and shortened/lengthened others to layout nicely in the MG.

Thanks,

Doug

[robertisaar]

https://www.dropbox.com/s/q10dtjezoecezrm/P66%20V6.zip?dl=0

try that ADX, it's the one I use and have 0 issues with. if it still logs errors, you have a wiring/PCM issue or cable settings require adjustment.

[cdcollins1]

Thanks Robert. I'll give that a try tonight.

[cdcollins1]

Robert,

That ADX seemed to make the display a little less erratic. I also found that my coolant temp sensor wire wasn't completely seated which was the cause of the (-) temperature reading.

I'm still at a loss as to the engine speed showing twice what it should. I've got the target idle set at 850 and the engine speed shows 1700.

What sensor does the ECM get engine speed from?

I'm wondering if that particular sensor wire is lying too close to a plug wire and picking up the waste spark which make it look like it's running twice it's speed. IAC never moves above 15, so I'm thinking that with the engine speed signaling 1700 and possibly a worn throttle body or air leak, the ECM doesn't know to enter into idle settings and so it dies when it's hot instead of backing out the timing and using lower VE.

Any diagrams of wire routing available?

Thanks,

Doug

[robertisaar]

if the ECM thought engine speed was that much higher than what was being commanded, it should have been closing the IAC down to 0 steps and reducing advance to bring it in-line.

engine speed is via the 24X sensor when below ~1250RPM with a FWD calibration and ~2000RPM with a RWD calibration(this setting is able to be changed, but every calibration I've looked at shows roughly that pattern), above that, the 3X signal from the ICM is used. if the 24X sensor drops out, 3X only. if the 3X signal drops out, the engine quits running.

if the ECM thinks the throttle is being opened(TPS% above 0 or 0.39%), then engine speed control transitions away from idle settings and goes into throttle-follower mode.

[cdcollins1]

Thanks Robert. That's good info. I'm going to test my 24x and 3x sensors this weekend.

So here's a question. What is the source of the engine speed that is output on the data stream? 24x or 3x

If I had a bad 24x sensor and it was sending twice the pulses to the ECM at speeds below 2000 rpm, then why would my engine speed not display correctly once rpms went high enough for the 3x sensor to drive the process? I'm wondering if the ECM is really not getting the right engine speed input or if it's just a data stream issue.

I'll test both sensors and then disconnect the 24x to see how it affects things. Testing the output pulse voltage of the 24x might make it seem like it's working, but it might be doing something wonky (like counting leading and trailing edge changes or something)

Thanks,

Doug

[robertisaar]

Thanks Robert. That's good info. I'm going to test my 24x and 3x sensors this weekend.

So here's a question. What is the source of the engine speed that is output on the data stream? 24x or 3x

as far as I can tell, it's the 24X at low speed and 3X at high speed, the ECM gives no indication as to which it is using at any one time, if you look at the "filtered 6X" value(which may or may not be defined in that ADX), you'll see where the ECM quits updating after x RPM.

If I had a bad 24x sensor and it was sending twice the pulses to the ECM at speeds below 2000 rpm, then why would my engine speed not display correctly once rpms went high enough for the 3x sensor to drive the process? I'm wondering if the ECM is really not getting the right engine speed input or if it's just a data stream issue.

it shouldn't be a stream issue..... you're using the same ADX that I created/use and I don't have that issue. not much else could cause the wrong value to be displayed.

I'll test both sensors and then disconnect the 24x to see how it affects things. Testing the output pulse voltage of the 24x might make it seem like it's working, but it might be doing something wonky (like counting leading and trailing edge changes or something)

Thanks,

Doug

see above.

and I don't know, this is kind of odd, the stock plug wires actually run super close to wiring that I would otherwise consider really sensitive to voltage spikes. you're not running anything crazy like non-resistor plugs or solid wires, are you? the lowest resistance plug wires I've used were taylor spiro-pros, which were probably in the ~250 ohm/ft range. I didn't have any issues running them, but no real benefit either.

[cdcollins1]

Some success this weekend. Tested my 24x sensor and it's working fine. Did some research and the 3x sensor is what tells the PCM and tach what the engine speed is, put my freq counter on the tach leads and it is in fact 3x what my expected idle speed is. I also fixed a major exhaust leak on the right side header which could have been throwing the right O2 sensor off and causing problems.

It's idling much smoother now and only died once in stop and go traffic on the way to work this morning. Fixing the ECT sensor seemed to help as well.

Now I'm hoping to get good data log from some driving and start tweaking for the cam.

Thanks,

Doug