3.8 CCC Diag help

[a.graham52]

hey guys, new here. iv owned an 85 cutlass supreme for about a week now. bought it not running. previous owner bought it, put an aftermarket carb on it to fix w/e concern he was having and pretty much the car never left the shed because it didnt run right.

Complaint: will not idle. runs great at 1k plus but anything below that its very lumpy and will stall all the time.

unsure if dtcs are accurate or if i have caused them. codes set are 21, 23, 43. i did notice tpms voltage was about 2v. i read how to adjust that and im going to look into that when i get a chance. i also noticed on my scan tool (snap on motis) that coolant temp was -40, rpms was like 3k even with engine off and its always in open loop. i unplugged the coolant temp sensor and it still showed -40. i put a paper clip between the two terminals and it still showed -40. iv checked fuses and iv also cleared the computer several times.

where should i start?

 

[a.graham52]

little bit of an update. first issue, scan tool data was fixed once i found the proper engine selection :/ computer is showing on average 30 dwell while running at 1000 rpms. oxygen mv is around 100 so its seeing an issue, i also installed new sensor today just in case. nothing changed. tps voltage is .56, once again at 1000 rpms.

 

[a.graham52]

i think i have done all the easy things here, i checked and verifid spark plugs are good. replaced spark plug wires. inspected cap and rotor to make sure it looks good (plugs cap and rotor were done by last owner with zero miles on them), i have blindly adjusted lean stop and air valve on top of carb with zero change. O2 sensor always reading around 100mv and car will not run below 1000rpms. i removed and disassembled carb completely even though it is a fresh reman. could not see any issues there. last thing i did was spray carb cleaner around intake and found drives side rear has a bit of a leak. i guess i might as well throw come intake gaskets at it and see what happens. its interesting because map sensor shows nearly 18" and the thing runs great anywhere over 1000rpms.

 

[a.graham52]

no one has any input? i removed the pcv valve from the block and verfiifed there was no vacuum at the hole in the block. i also sprayed carb cleaner around the intake and the vacuum leak is not present. sounds like in intake port not to blame for the leak but the valley its self. not too worried about this. i thought i could hear an exhaust leak until i clamped the smog hoses with vice clamps. the sound i herd went away but no change in oxygen sensor mv. last thing i want to do is remove the intake and find out that doesnt fix it without probable cause.

 

[1bad79]

So I am looking at these codes 21 tps 23 mc Solonoid 43 esc module looks like the esc and mc are powered by the same wire and all are conned to the ecm maybe your missing a ecm ground?

 

[1bad79]

The coolant temp being -40 will make it go pig rich

 

[1bad79]

I haven’t worked on this system in 20 + years

 

[1bad79]

Also it looks like there’s 2 ecm fuses may want to check those even if your scann tool is working

 

[a.graham52]

i have since corrected the scan tool data by finding the proper engine selction (had 3 v6 options). once that was done all the data looks plausible. its not running rich as i can have it running in the garage and there is almost no smell of rich exhaust. if chose is closed then 02 mv is up around 800. fuses: checked. dtcs havnt returned since i cleared them a few days ago. suspect faults dtcs from me trying to figure this out.

on another note, im trying to figure out firing order and plugwire/cylinder relation just to verify previous owners work. however i have seen a bit of contradictory online with even fire/odd fire/ years ect.

 

[1bad79]

I’ll find it be right back