[gator68428]

Seeing some weird things in my ECT signal. The measured temp drops suddenly and randomly but only for a second or so.
When this happens of course the car stumbles and the mixture goes super rich (have WB O2). Its annoying!!
I realize this could be from a faulty connection to the sensor: a brief open circuit would cause the detected voltage to rise, [C. O. Probst, Ford FI and EEC] and therefore temp to fall.

I have tried setting the ECT default to my thermostat temp. I pulled the wire to see what would happen, and at first the ECT defaulted to that temp, but then after a minute or two started mimicking the ACT sensor temp (which was much cooler)... why?

Two questions:
1. Has anyone seen this issue before, any resolution?
2. Why won't the EEC stick to the default ECT in the event of sensor failure?

Other info:
Got the system from Mass FLO EFI back in 2006. So comp is at least that old, but car is driven very infrequently <1k mi /yr.
Also seeing very intermittent anomalous MAF readings (all the while MAFV is FINE)???
Maybe the EEC is the issue?

[decipha]

ACT/ECT always track each other when one fails no worries

if maf is dropping out too you prob have a bad ecu, first step is to replace the ecu relay and see if it stops

[gator68428]

Thanks decipha.
Went ahead and replaced the ecu relay and the issue is much better.
However it did have ONE hiccup over the course of 30min of driving or so... (normally would have had at least 10 hiccups during this time before replacing relay). But this time all sensors read 0 or default for two logging entries, then all went back to normal instantly. Except for the ect sensor--it took a few seconds to come back to temp (linearly rose from the bottom--which was 60F)
Attached is the log showing the hiccup. It occurs at 4.04s ET.

Oh and no anomalous MAF readings... YET :) so that's better

Want to make sure i give the ECU the benefit of the doubt before scrapping it... and dropping few hundred bucks. But like cgrey8 said its helpful to have a backup to rule out in these types of situations... so maybe i will consider it.
Based on the data, it looks like the relay blipped for some reason. Any guess as to why?

FYI before replacing the relay the ECT looked the same as in attached, BUT none of the other values changed before... Maybe it was just too brief of a blip before and this time it got recorded?

[gator68428]

Turns out the relay didn't help. Just a fluke it only hiccuped once the first half hour. Got worse the next day. Car was almost undriveable. Found that when it hiccups the relays are flip flopping back and forth. So I dug further and checked the wiring: grounds looked fine. found some possible damage in the keyon ignition wire to the relays, which could cause the issue if supply voltage is teetering on the threshold. I replaced the wire thinking that would fix it. IT DIDN'T... Relay flip flops randomly. I even monitored the KEYON wire during the hiccup and its voltage didn't move off 13.6V... only until after the engine died did it droop to 12.5V... which is still above the 10.5V requirement.

How can the relay switch if the supply signal doesn't change and the ground is good???

Not giving up tonight i tried one last thing. I swapped the Tweecer for the Moates F2A (programmed from Burn 1 and EEC Editor) to see what would happen. F2A is what i used before Tweecer. AND like MAGIC the problem is fixed!

This is good progress but I don't understand how the EEC can switch the relay if the power comes from the ignition switch (which is hardwired directly to key power, separate from EEC). Something is happening that i'm not understanding. But i would love to. Any ideas?

Also, the Tweecer has been problematic for me from the get go. Wasted hours trying to get it to work when i first bought it and turns out some of the memory chip pins had lifted and needed resoldering... So it has a history of being unreliable for me. Recently it's worked OK but now seems it's the culprit again. Using the F2A as i have learned to do, in the meantime...

Anyone else have reliability issues with the Tweecer? That sounds like the culprit right? Thanks!