My buddy has a 93 z auto, and the blm's are rich. We cleaned the throttle body put in a new iac and o2's and plugs. He has headers and cat back sys. When the car is first started it runs great in open loop, but in closed loop the blm's go down to around to the 100's. Rightside is even worse. We checked for exhaust leaks and didn't find any. That would leave the plug wires, opti or injectors. We also checked the fp reg. map, all good.

We also adjusted the throttle blades, no good.

The thing that gets us is when the car is in open loop there is no rough idle and it runs smooth, but when it's in closed loop it runs like crap. We know in closed loop that the o2's take over and the o2 readings look good except for the richness.

If the wires were bad, wouldn't the car run rough in open loop at idle as well?

Can anybody shed some light for us?

Scott/Justin

 

Anybody?

 

TTT

 

Yeah I get you, i have the exact same problem with my 93T/A. I do not think these computers can handle the changes in my car.

What are you IAC counts/position in idle?

My LT BLMS go to 108 (left/right).
STBLMs hover around 40-90BLMs (with the right worse than my left) Split BLMS.
I also adjusted my Blades, but no change. I am trying to convert to heated 0'2, to see if that changes anything.

Good Luck

 

That wont change anything.. you need to reprogram your PCM.. that is it...

 

That wont change anything.. you need to reprogram your PCM.. that is it...

 

The IAC count now is 9, before we put a new one in it was 0.
The BLMS are just like yours.
Do you have a rough idle as well, when in open loop?

 

Ok, what do ya mean reprogram the PCM. You mean to tell me that the this is the way it came out of the factory? I find that hard to believe that the problem is PCM related and not some sensor or mechanical issue because of headers and a CAI.

Then again, who knows anymore.

Does anyone else have any ideas?

Thanks.

 

Sorry I thought you had a cam change in there and dont ask me why I thought that.. I just did...

Anyways... change the O2s. They can go crazy and get damaged... specially if you ahve used leaded fuel or something...

Maybe that should solve the problem.. if the car is rich for very long periods of time is very possible that you have bad sensors.... try and see if the fuel pressure is not spiked up and or that you do not have a leak after the MAF or even a damaged map sensor.. Those would be the key things to be checked out...

If there are absolutely no air leak after the maf you should check your sensors if they are oscialting from 450 very frequently.. if they are static always.. change them. As soon as they get filthy they just dont measure up correctly.

 

Highlander,

I apologize but I also thought that the car was modified. Still, the problem between my car and your car are similar.

I would love to believe that my 02's are the culprit to my problem, but then I just have to wonder why it would read perfect 400-500 Mv for both 0'2's under Open loop conditions, then completely go nuts once it enters closed loop. I just do not understand why it would do that. I know my problems lie as it idles because as a stab the trottle blms never go higher than 128. But at idle it runs so rich, that it makes my long-terms got to 108.

It could be 0'2's, but it could also be another wacky reading from another sensor.

I asked about the IAC counts, because mine read around 50 at idle and as high as 120 in idle but with load.

Anyways, listen to highlander, he has good points although there is no MAF sensor.


Good Luck.

 

try this to see what happens....

first close those throttle body blades and see what the IAC reads..if its under 100 then just leave it alone. if its above 100 then crack the blades a little.

next you are running way too much fuel pressure if the BLMs are 108.. just back it off and that should bring them up. 128 is ideal but anything close to that will work fine.

its the split BLMs that give the rough idle btw. is there any stumble indicating a burnt wire or bad plug? exhaust leak can give you a split... so can a large cam... so can a bad O2 sensor (happend to me).

 

Please re-read. we've done everything that was mentioned.

 

Someboy must have tampered with the program... can you send a log for us to see it???

If they read perfectly in open loop.. in a speed denisity car, it should read almost perfect in closed loop... so CHANGE THE O2s AGAIN and see... I had that same problem with mine.. they lasted one month and I installed again the old ones and problem solved..

I changed the O2s simply because they were old... but I didn't have to.. so I put the old ones back and problem solved.. I had a 160 right BLM and 128 left blm all the time.. no matter what I did with the program that always happened... I had a bit rough Idle..I changed the right O2 and perfect!!!!!!! DO THE SAME and try it out.. for me its a faulty O2.. not any othersensor.

Also disconnect and reconnect the battery when done to clear previously stored blms...

 

you closed the throttle blades and the IAC is still 9?!.. i find that a little hard to believe. and if in fact it is then something is wrong with the sensor or the harness or you have a vacuum leak somewhere.

then you say you "checked" the fuel pressure.. i said back off the fuel pressure.. not quite the same thing there.

i think you are the one who needs to "re-read"

 

I dont really think a vacuum leak will cause a big difference in a speed density car as it does on a maf car, so even if that may be happening i dont think it will be the culprit of the problem...

BAD O2s I think that is what it is... but turbo Z you are also right with the IAC count.. it should change if you do ANYTHING to the throttle blades... but then again I think that would make the car stumble, not go rich?? what do you think?