Scanned my car two weeks ago after doing a bit of tuning, everything looked good (no knock, BLMs are close, no unusual codes). Lately car has been acting up, breaking up at ~4500rpm and up and whatnot.

Scanned car and realized alot of the time the BLMs are WAY OFF sometimes even 115/160, other times they are fine (Left BLM always seems to be rich while Right BLM seems to always be lean). Also I noticed the car would jump from closed to open loop every now and then, for no reason that I can see from my logs. Today I got a couple of codes (43, 83, 84, and the usual 77) that showed up right before I shut it down. All this along with an unhealthy dose of knock retard.

The problems seem to have started since I pulled the throttle body to swap a new one in, but the new one was a POS so I put the stocker back on. Everything looks good, all connections are tight. Also today I changed the plugs but its seemed to actually make the problem worse. However all this with the TB may be coincidence cause I don't see how removing & reinstalled the TB could have caused all this.

Any ideas? Bad gas, O2s, opti, ignition, leaks??

 

if its jumping in and out of closed loop its usually a dead or slow O2

when u scan look at ur O2 readings .. if one is slower than other or is dead .. then u know what to do.. bust out the 22mm wrench and goto work

 

Ok, now I'm getting mad. I checked my logs for a slow/dead O2, but I don't see anything that really looks like its slow; all Sterm counts are moving quickly as well as BLMs.

What makes me mad is that I saw my Sterm counts as far off as 99/196, how the hell is that possible?? Min. and Max. O2 counts are 108/160, so how is the computer seeing counts as low as 99 and high as 196?

 

The 108/160 limits apply to long term corrections (BLM's), not the short terms.

If you have known codes, why not get rid of them so you can concentrate on the problem. 77 if fan realy, 43 is knock sensor, 83 and 84 are tranny related. None of those should cause split BLM's or dropping out of closed loop.

If the O2 sensors aren't the "open/closed loop" culprits, check the coolant temp. Is it dropping below 140degF at any time?

 

Check all your grounds for the ignition system. Disconnect your pcm plugs ans plug them back in. Do the same with any other ignition/emmission components. Also disconnect the battery for a few mins. to reset the pcm. If none of this works you could have a fried pcm.

 

Fred said exactly what I was about to. I had a friend whose coolant temp sensor was bad and it would bounce back and forth from open to closed, it would run like a champ in closed, and like a dog in open.

 

Coolant temp is steady throughout, 195+*F.

Just started the car and as soon as it went into closed loop it wouldn't idle at all, rpms drop to 400-500 (900rpm is normal idle). I put in some old O2 sensors and now the car won't go into closed loop. I let it run for about 8 min. up to 235*F and no closed loop, idles good in open loop.

Should my BLMs be changing during open loop? I thought they should be locked at 128. With the first set of 02s both BLMs fluctuated in open loop, with the 2nd set just the right BLM would go up (lean) when I reved the engine.

Thanks for the help so far.

EDIT: Also my fans are not coming on by the PCM or manual fan switch. Just one problem after another.

 

TTT

 

When you are in open loop, on cold start, the PCM needs 3 things to go into closed loop... 1) hot O2 sensors that work, 2) coolant above 120-140degF (varies), and 3) timer - about 2 minutes.

If your "old" O2 sensors are faulty it isn't going to go into closed loop.

In open loop, it will use Cells 16 (idle), 17 (coastdown) and 18 (load). It will use the BLM's it stored for these cells during earlier closed loop operation. Cells 17 and 18 appear to be "calculated cells", based on some sort of algorithm that derives them from Cells 1 - 15. The BLM's will change as you move the throttle, because you are changing "cells". Only the short term corrections are "locked" at 128 in open loop. And, "learning" is locked. Since there is no accurate feedback from the O2 sensors, the BLM's can not be changed.

 

Put the other O2s back in and it goes into closed loop again, but still drops out often. I switched the sensors the opposite way they were before but the left side is still rich and the right is still lean. BLMs are maxed 108/160 all the time.

 

I have been having a similar problem, in which I narrowed down to being the ECM.

What does you IAT sensor read?

I show the same symtoms as you, car struggles to go into closed loop, and cycles in and out like it cant make up its mind. I also have split blms.

I never payed attention to my IAT, but when I did it read 155 degrees farenheit on a cold start and 332 degrees farenheit with the IAT sensor unplugged.

Normal readings should be ambient tempatures (90-95 Degrees in Texas) at startup and -35 degrees with sensor unplugged. It works the same way as the ECT sensor.

I them proceeded to check my sensor, but it was good. And then I found voltage on my ground wires with the ignition key on. The entire loop of MAP, IAT, and other insignificant A/C sensors had the same problem.

There is no ground point physically anywhere on the engine bay area and it was concluded that that would be inside the ECM.

Check your grounds, and check your for any abnormal readings in other sensors.