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Discussion Starter #1
Noticed the kids car runnng rough so started looking into it and after a little while checking things over, replacing some vac lines I’m becoming stumped or just crazy staring at it.

1990 gt ., 5 speed ( think it was converted, few hints and a a9p)mostly stock , cobra intake, headers,exhaust , no smog stuff, timing is at 12, fuel pressure with vac off/ running is 41 with vac on 39’ish, Cannot find any vac leak per say. No cel light on, car passed cylinder balance test, twice

Act, ect, Maf all check out test/volt wise , all plugs are really white/lean

Now car runs rough on cold start, usually takes 3 times of starting then dying until it will hold a ####ty rough idle, 800’ish with vac around 14.5-15.5

Now trying to probe the computer while running to see what volts I’m getting, I am getting nothing on either pin 29 & 43 , tried 2 different times and nothing

So to test for resistance or a break short what do I need to test from those pins on computer ( hooked up or not?) to the body side o2 harness?

Also what wires get power and how much at the actual #o2 connector? Whites ?

Any help would be great , I’ll try to get back ASAP but leaving for vacation in a few days
 

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backprobe the 02 connector's signal wires, while engine is at operating temp

what is the voltage at both banks?

no resistance tests, they are pretty useless

going to assume the maf, and injectors are stock
 

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Discussion Starter #3
Sorry for late reply-family stuff
Ok back on this
Reset everything and warmed it up and took for a drive to see if codes were there
Spitting and sputtering at low speed and cel on about as soon as I left driveway so around the neighborhood and back

Running rough at idle, 14 lbs of vacuum off intake.

Yes stock 19# injectors , stock maf with bbk kit , air filter in fenderwell

Found and checked power at o2 harness from gt/y wire and down to each o2?

Now I get these for codes

Koeo
0= 81 & 82
C= 31 , 41 , 91

Koer
R= 41 & 91

The 81 & 82 is for the smog stuff which is gone I’m assuming

The 31 is new and is for the evp?

What can I check there?

Also 41 & 91 lean both banks, low voltage or no switching detected

Again back probing computer at pin 29 and 43 I’m barely getting any
29 was bouncing from 0.0 to .01
43 was steady at .03

Rechecked at took off orange ground on back of head( it was bolted to head) clean it and added ground from there to firewall

Smells like a vac leak and or electric gremlin

Help please
 

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Indy- back probe what wires?

With them hooked up and car running?

What should I see?
02 signals at the ecm

in order to get the 02 to read the exhaust, the engine must be running, no?

you tell me what you should see
 
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