I have an 89 GTA, 5.7 TPI. I have no engine codes - did some mods (heads, cam, intake, injectors) and can't get closed loop. Been trying to tune this for about a year and just can't get it. Bought an AF ratio gauge/ WB sensor, put back the stock injectors, no luck. I am thinking that a bad sensor may be keeping me from getting the car set up.

One guy said I may have a questionable MAF sensor. No codes, but I have a few random 22-23 commanded AFRs in the datalog. Also, It seems my AFR is kind of unpredictable. I can get it at say 15:1 then after 10 minutes of stop and go, it may settle down at 17:1 or 11:1.

 

What cam did you put in it? Did you reburn the prom for the new cam?

 

ZZ4 cam - I was told it was mild for a TPI. I acquired a PROM from another member who had my exact setup and I also tried tuning from arap.bin myself. Either way I can't get it right.

 

His setup is a ZZ4 cam running under a stock TPI?
Check the coolant temp that the ECM sees. It won't go into closed loop until the engine reaches about 180, I believe.

 

Maybe your o2 sensor doesnt get warm enough to reach operation temperature ? If you got headers the exhaust gases cool down too much at idle and will not activate the O2 sensor, the ecm then "sees" this and goes into "open loop" and causes the engine to run rich and idle rough, even though the engine may be fully warmed up.

 

Good Suggestion - unfortunately I've been through that. First I swapped to an AC Heated unit, then to a Innovate Wideband, using a simulated narrowband for the ECU.

Doing those things is no different than the old original sensor. Also, it will go into closed loop for a little on full throttle so I figure it's ready. Something else is keeping it from going in.

I've been getting some interesting advice from another member to have my MAF checked - which I am thinking of doing. But, since it's not completely dead, could that be keeping me from closed loop even if it is weak?

I am thinking there's come clues to the problem, like needing to have the injector constant down 3-4 lbs than it should just to have the AFR in the right range.

Thanks for any other suggestions - getting ready to give up on it

 

Ive seen some threads lately where odd problems and error codes was due to faulty or arching sparkwires. Low voltage in wires from sensors gets disturbed by high voltage in the ignition system...
Have you tried a known good ecm?

 

Thanks for any other suggestions - getting ready to give up on it..Quote

Hey!! Donīt give up , Itīs a Gta, and its a beautiful car , you just got to love it...even if it lets you down once in a while...

 

FYI: It's been a while but I finally got it -
I cut the tan wire and attached it to the body and instantly saw the O2 swinging - thanks for the help