Rusty tuner with VERY erratic AFR

[grover]

Hi folks. I've never been super savvy at tuning my MS, but I just plugged in to today for the first time in a year or so. The car is not my daily driver, but I take it out at least a once a week and it runs well except for a stumble at about 2300rpm and a MAP of 30 or so. Thinking I'd investigate this, I plugged in the laptop and was struck immediately by the completely erratic AFR readings with the needle pegged much of the time at 19.9. The readings dart all over the place even when at relatively steady state cruising (MSQ attached.) Any thoughts on what might be going on here?

Thanks a bunch in advance, looking forward to getting back into this and getting the car running really smoothly again.

Tom

1973 BMW 2002, 2.3L stroker motor, 292cam, MSII and EDIS

[kjones6039]

The first thing that jumps out at me is, why is your tps stuck at -16%? That can't be good.

I also would be checking for exhaust leaks that might be causing the erratic lean indication. Your pulse width also seems quite short at cruise.

Lets see what the experts say but I am sure you need to correct the tps issue before trying to sort out the lean condition.

Ken

BTW... Your log is attached but NOT your msq. I am sure it will be helpful to the experts...........

[grover]

Thanks Ken. Sounds like I'm even rustier than I thought as I didn't even pay attention to the TPS numbers, I was so focused on the AFR. And to add to that I'm getting all the file terminology wrong. Yikes, it's going to be a long road back at this rate. I'll recalibrate the TPS in next couple of days, but it seems very strange that it could be reading it in such a way but still get such varied driving out of the car. Good call on checking for exhaust leaks too. Thanks. Attached is the MSQ.

[Matt Cramer]

What sort of O2 sensor setup are you running?

[grover]

Matt. I'm using the standard Innovate LC1 sensor.

On a seperate note, I went to recalibrate the TPS last night and found that it has zero voltage going to it regardless of pedal position. Bummer. Looks like I'm going to have to track down a bad connection or something.

[Matt Cramer]

Check the voltage at the LC-1's analog output. What sort of voltage are you seeing?

[grover]

Thanks Matt. If I can get my hands on the LC1 wiring diagram I'll try to give that a try this evening (raining here unfortunately and I have no garage).

[grover]

Alright. So I fired the car up this morning and it was like nothing I've ever experienced before with it, the car sputtered all over the place and barely run with the rpm's darting up and down. I grabbed the laptop and plugged it in and the datalog is attached. A couple of things I noticed (I didn't even get around to testing the 02 sensor Matt, but I have it on 0 EGO correction right now anyway.)
1. Before the engine is fired the TPS looks to be working properly and is showing increased rpm through the pedal motion. If I look to calibrate the TPS it is indeed getting a solid voltage.
2. However, after the engine is started I can hold the pedal perfectly still but on the screen it shows that it is moving quite a lot (as is referenced by the first datalog, the second datalog is with my foot completely off the pedal and as you can see the numbers are still bouncing around quite a bit.) Would this indicate some sort of electrical interferance? Aboout 6 months ago I replaced the alternator to one using an internal voltage regulator, vs. the old one I had which used an external regulator. No idea if that's related, just trying to think of any other electrical things which have been touched.
3. A big reason I didn't touch the MS for a while was my old laptop completely died (along with ALL my old files.) As such I had to re-download MegaTune onto a new laptop, and one thing I see when I plug it in is a warning message saying the the file found is MSII Rev 2.88600 whereas the one in the controller is 2.88000. The first time I over-rode this as I couldn't figure out how to change the set-up in my laptop. Any chance this could be playing in to what's going on? Seems unlikely, but thought I'd put it out there as it is an unknown.
Any input or advice would be appreciate, as the car is basically right now.

[grover]

Okay, now I am even more confused. About 10 minutes has passed since my last post and I just went out to see if I could figure anything else out. Got the car started and it actually ran much better (granted it is somewhat warmed up now) but the TPS was showing no response or voltage whatsoever, showed as -16% in the MegaTune read out. What the heck is going on here???

[kjones6039]

Check a couple things:

At the TPS connector, with your voltmeter: (connected , key on, not running)

~5 volts on one side
Ground on the other side
voltage at the wiper should vary with throttle opening

At the TPS sensor: (disconnected, key off)

measure the resistance across the sensor
measure the resistance from the wiper to both other leads
the resistance should vary with throttle opening

If the voltage or resistance does not vary I would be looking at a bad sensor
If the voltage is correct and the ground is ok then I would be looking at the wiring to the MS

Ken

EDIT: How are you calibrating the TPS? The TPS numbers you're seeing in TS?

[grover]

Okay, so I got the TPS back in order today, I found that one of the three wires into the sensor had fatigued and broken. Got that all fixed and I'm back on the road, although the AFR is still completely erratic (datalog attached.) Matt, I did as you suggested and tested the voltage at the yellow and brown analog wires. At the yellow I got about 0.3V (bounced between 0.2-0.4) but got absolutely nothing off of the brown lead when taking it directly from pin 20 on the relay board. After turning off the car I checked resistance between pin 20 and the 6 pins at the outlet of the LC1 and found minimal resistance at all but one of the terminals (same thing when checking resistance on the yellow analog wire.) Any thoughts or advice based on these findings? thanks so much guys.

[Matt Cramer]

Connect to the LC-1 with the LM Programmer. How is Analog Output 2 calibrated?

[grover]

thanks Matt. I'm out of town for business for the next week, will give it a try when I get home. thanks so much for the input, will post here when I have some new findings to report.