jedwards156

hey guys just purchased my 1st ls1 converting from a carburated 355 rx7, but any how i have an issue trying to sort out someone elses headaches.. car is a 98' formula has had lts added the egr deleted th400 swap. the scanner obviously reads no trans.. but amongst other issues i can sit in idle all day and the car runs and fires great no issues... a few blocks down the road under light throttle heavy throttle whatever, soon as the car warms up it starts to stutter and backfire... had car scanned at local chevy dealer and they said the cars computer is reading the ect as -39 degrees..so i swapped out the ect with a new one no change... drove it around with my own handheld scanner and the temp never changed, runs rich stutter and backfires still... so i unhooked the sensor an tried to trick the computer by putting a paper clip in the plug.. changed the reading to the opposite parameter to +283 car ran less rich but few blocks down the road did the exact same thing.... i am lost, i know i need to go have the car tuned yes but i want everything to at least be partially working before wasting money to fix nothing... i would greatly appreciate if someone could please give me more insight on this issue... i have cleaned all grounds....currently at a loss please help

JRENIGAR

iTrader: (37)

water temp sensor in drivers head at front will cause similar issues when bad. Its $20 or so and would be a good place to start. have you changed plugs recently sometimes the sensor gets damaged during #1 plug changes. BTW the paper clip reading is probably out of the specified range for the comp and it started causing bad things on the other end of the spectrum. This is only a guess...

PlatnumStatuz

iTrader: (6)

check the wiring from ect connector to ecm

jedwards156

yes i have already replaced ect (temp sensor) wiring looks good still protected in plastic no cuts or burns or rubs around bends... ive been most everywhere hunting this down... plugs look good electrode has very little corrosion..plugged in or unhooked the scanner still reads -39 untill i bypass it with the clip then it hits the other end of the spectrum.. its not one single misfire its like they all stutter out at once because the ecu is reading incorrectly... cannot get it to read properly i have a good ground through plug in, also have 12v for the temp gauge and 5v for the ecu power.....have no vaccume leaks.. have good battery and charging system... almost wish this thing had a carb...giving me a huge headache

jedwards156

just removed my ecu no corrosion no faulty wires everything looks good....is there a way to have it looked through while out of the car...just curious...and if i replaced it would it have to be the exact same year an model... or will i have to change my wiring harness and multiple sensors to adjust for updates over the years.....know i have alot of questions but im ready to get this thing rollin ...dedicated

ez2cdave

Faulty computer ?

After all, this is a 1998 unit . . . The "Orphan".

Russ K

iTrader: (1)

With the yellow & brown wires jumped together at the connector, turn the ignition on & twist and pull on the wires at the connector while looking at the ECT temp on the scanner.

Only the coolant temp gauge on the dash requires the temp sensor to be grounded.

Russ Kemp

luigiandme

iTrader: (2)

Pull the ECU connector and check continuity on each wire. One of them should be O.L. or Out of Limits. (Open Circuit)

LS1-450

iTrader: (33)

Have you confirmed that you are using the 98, 3 wire sensor & 3 wire harness? The 99+, 2 wire sensor will not work w/ the 98 PCM.

jedwards156

yes guys i have made sure of all of this.. i am a newbie to the ls1 world but as far as wrenching i do this daily ... work on diesels all day long...i have actually tried 3 different ect sensors all the 3 wire plug... chased the wires alll around the harness... and tested them ... i am getting the correct 5 volts to the plug in from the pcm ....i just cannot get the thing to read anything other than -39 ???? finally pushed her a little further on my last test drive and ckp crank sensor code came on.... so im pretty excited now that i can swap that and have this thang taken to get the crank sensor relearn procedure done, but then again ... i have no clue how to get this damn thing to read the right temperature...its like the sensor is being plugged in and just not reading i think itd be pretty impossible to get 3 new faulty ect sensors....what a headache

LS1-450

iTrader: (33)

Only other that I can think of is to check the female metal connectors in the ECT plug & @ the PCM to see if a wire has come loose from one or maybe one has been damaged. If nothing found, run a single wire from the ECT pin that sends voltage reading back to the PCM to the pin on the PCM that receives it. If this solves the problem, then it's in the wiring or a plug. I'd say to do the same for the 5v ref, but you said that the 5v ref is there.

If after doing these additional checks & still an issue, it's likely the PCM.

Notsoobs

what did it end up being

G Atsma

jedwards56 hasn't been here for over 8 years. Check post dates....

Notsoobs

So it should be fixed by now mine reads -38 on the hp tuner new sensor new thermostat kind of baffled

Notsoobs

[QUOTE=Notsoobs;20462875]So it should be fixed by now mine reads -38 on the hp tuner new sensor new thermostat kind of baffledIt ended up being the male side of the temp sensor if anyone else has the same issue

LilJayV10

iTrader: (39)

You have a broken wire somewhere. That's the default temp that is displayed when there is an open circuit(sensor unplugged or broken wire)