dbarkley

Mine is about 150-160, however the Intergrator stays around 120-130. Exhaust smells rich.

dankhound

The blm's can take a while to change. All they are is a long term fuel trim. With the integrator right where its supposed to be the exhaust shouldnt be rich. I would keep checking on the blm to make sure its going down.

dbarkley

That's the thing... it isn't I've even reset the computer and the BLM goes right up there. And even tho it's been stated here several times that the BLM maxes out at 160, I've watched mine go to 168.

Since you have a 305, can you tell me what g/s your MAF detects at 1000RPM? I'd like to compare to see if my MAF is working correctly.

dankhound

Tbi's are speed density not maf. That problem almost sounds like a programing problem. The only way that the blms can go up is if the integrater goes up. Since the exhaust smells rich i would guess the intergrator numbers are incorrect. Have you tried doing anything to richen up or lean out the mixture and then see how the two react?

dimented24x7

iTrader: (2)

Hes got TPI. Replace the O2 if you havnt done it in awhile and check for exaust leaks near the O2.

dbarkley

I have replaced the O2 about a week ago. BLM still high. When you say check for exhaust leaks near the sensor, you mean upstream, right? I only have 1 O2 and it's right under the left manifold. There isn't too many places to check for a leak. I did make sure the AIR valve was working correctly.

I was thinking about replacing my MAF sensor but it seems to be operating fine with readings between 7 at idle and 100 at WOT.

I think I still have a Hypertech chip in the ECM for the lower thermo in the car. I'm thinking of digging up an old stock chip and going back to basics. With all the other stuff I have going on I can't get into prom burning.

Dustin Mustangs

iTrader: (1)

The O2 sensor compares the amount of unburned oxygen in the exhaust stream with the amount of oxygen in the ambient air inside the engine compartment. It's the difference in these two values that makes the sensor produce a voltage which the ecm monitors for the aproximate AFR. If you have exhaust gasses in the engine compartment from a leak located anywhere (up or down stream of the sensor) on the exhaust, it will thow off the ambient O2 readings and corupt the O2 sensors signal.

High BLM's means your car 'thinks' it's running lean. This doesn't mean it is though. An exhaust leak like mentioned above could trick your ecm into thinking it needs to add more fuel when it really doesn't. This would make it run rich, just like you said you could smell. There is also the chance that it actually is running lean, albeit small becase this is happening at idle where the demands on the fuel system are the lowest and because you said you could smell a rich condition.

FWIW, the maf on my 350 idles at around 9 grams/sec. It sounds to me like your MAF is not at fault. If your BLMs are staying high at idle that means whatever is causing it is also at idle, and your MAF idles right were it should.


Have you pulled the codes yet? Regardless, my money is on an exhaust leak.

dbarkley

I disagree with that. Where is the sensor that detects the oxygen content in the engine compartment? The O2 detects the oxygen in the exhaust. If there is any it increases the pulse width to richen things up. When it see's little to no oxygen it considers the burn rich... There the tetter-totter game begins.

I'm leaning more toward a faulty ECM or prom. Maybe a bad connection from O2 to ECM. (I need to look into that... does higher resistance equate to a lean condition?)

I also question if the Hypertech chip forces the BLM up with that crazy voodoo that it does!

Thanks for the reply tho.

dimented24x7

iTrader: (2)

By the exaust smelling rich, does it smell like raw gas? A missing cyl. on that side of the motor can dump alot of oxygen into the exaust causing a false lean condition. The fact that the O2 volts are dropping so low means that either something is dumping alot of oxygen into the exaust or there is a fault with the O2 circuit. A bad maf could cause a similar problem if it wasnt reporting the airflow correctly. This would cause the ecm to incorrectly calculate the engine load and then it would attempt to correct for the lack of fuel. At WOT around 4500 rpm the airflow should be something like 180-200 grams a second.

One thing that might help is to look at the O2 volts when the motor is completly cold. The O2 will behave as an open circuit and the voltage will be around .45 volts. As the motor warms up the voltage should then begin to vary. If its just real low all the time then there is a short somewhere. If its ok but then dumps real low then there is either a problem with the fueling or there is alot of oxygen in the exaust for some reason. Do you still have AIR? Ive never heard of this happening but perhapse its still delivering air to the manifolds even when you go into closed loop. The air pushes the O2 volts to almost nill when directing air to the manifolds in open loop. As for the hyperjunk chip, its basically a stock one with the temp threshold for closed loop bumped down a bit and a fancy sticker on it. Some things you could also check for are maybe ignition problems or a bad fuel injector causing a dead cylinder. This stuff would show up though because the motor would run uneven with a dead cylinder.

dbarkley

It really only smells rich when it's running cold. Just this afternoon I got to thinkin' "Maybe my car is really running a little lean!" and the BLM is getting set high. So I looked at the BLM while in open loop and the BLM was 128 and slowly rose after the system went closed loop. Odd thing is, I thought the BLM would stay at it's last known value even during open loop.

I did check the AIR system and it's okay. I even took off the belt and plugged the hose with no effect.

I've got the AFPR bumped up in the high 40s now and I put a new pump on last year. I didn't change the filter tho.

I pulled the injectors and sent them to Cruisin'Performance a couple years ago and he got me a good set.

The ignition has me wondering. There was an occational pop, only at idle. I just put new plugs in it last week with the new O2 sensor and the wires are a relatively new set from Summit.

Going down the road warm it runs smooth. After an hour or so of driving it may set a lean code but that symptom has ALMOST vanished since I put my old MAF sensor on.

I guess I'll put in a new fuel filter and go over the basics such as base timing, TPS adjustment, etc...

onebinky

iTrader: (1)

You know that loose metal sleeve on the rear side of the o2 sensor? That's where it brings in the fresh air to compare the oxygen content of the exhaust. The o2 sensor works like a battery. The fresh air is brought inside a tube, and the exhaust stream runs past the outside of the tube. IIRC, the tube is made of zinc. The hydrocarbons in the exhaust react with the fresh air and the tube material, and create a voltage reading. This is transmitted to the ecm as a 0-1v analog signal, with 1v being richest, and 0v being leanest.

Since you're looking at the scanner, check out the crosscounts. You want them to vary between 200mv-800mv, with the swing point being approx. 450mv.

Have you done any modifications to the car that will increase airflow? With only shorties, duals, and a gutted airbox on my old setup, my BLM's were consistantly 150-160.

Might also want to check for an air leak after the MAF, or a vacuum leak. Any false or unmetered air will have the car running leaner than it should be, because the ECM can't adjust for it.

dbarkley

Mod to airflow include gutted cat, SLP cat-back exhaust, and a 1988 GTA airbox with K&N filter... oh, and one of them foils too.

Since I have the stock ECM in an '85 the scan rate is pretty lame but I can see where the 02 occationally drops down to 50mV or lower.

P.S. thanx for the explaination on the O2 function.

dankhound

The o2 has noting to do with hc in the exhaust. It just compares the air outside the exaust and inside to create a small voltage. It doesnt really tell you rich or lean just the difference in o2. While gennerally above .45 is rich and below is lean that is not necessarily the case. A misfire could cause the o2 to see a false lean signal due to the fact that no o2 was used in combustion in that cylinder.
The car smelling rich at startup is normal. Thats just the way its programmed to work. Since the integrater is reading where it should i wouldnt worry too much about the blm being high unless there was drivability issue.

Vader

Just a few casual observations, but if the ECM is truly cleared, the BLM numbers probably shouldn't be that high on the initial startup. The integrator is likely a better guide to what is happeing in the immediate world.

• You've capped the AIR tubes to eliminate that as a possibility - Good.
• You should verify that the air intake ducts are sealed, and not loose/split/damaaged.
• You should inspect the O² connector and check for the 450mV bias at the connector in KOEO.
• Just for now, get rid of the airfoil.
• Is the MAf altered or does it still have both sets of screens?
• Are you using the stock PCV air supply tube and NOT a breather-type oil filler cap?
• What is the fuel pressure?
• Are injectors clean and spraying a round, atomized cone of fuel instead of streaming fuel out the tips?

Dustin Mustangs

iTrader: (1)

Not for long you won't.



Oxygen content is relative. Is Denver going to have the same O2 content as Miami?

dbarkley

My humble apologies... :hail: :hail: :hail:

dbarkley

I'll check the ducts again. I have 100 times.

According to my AutoXray the O2 sensor often visits the double digit mV range.

The MAF sensor is missing 1 screen (outgoing)

The PCV hose is stock. seems to work fine.

I cranked the FP up to 50 today and now the car occationally 'chuggles'. I'm going to move it back down.

The injectors were serviced by CruzinPerformance less than 2K miles ago (i.e. 4 years ago). I took then out to try and get rid of a cold start idle hunt going on. No change when I put them in but he swapped me an ECM and it cured the problem... for a little while. It's back again and I think it has something to do with this lean run condition.

I've aready replaced the CTS but the temp looks goofy on the AutoXray. The temp should be the same as air by morning and I'm going to see how far it's off.

And my engine bay get's VERY hot... I'm wondering if I do have an exhaust leak. It's seems that the manifold-to-y-pipe connection would be a candidate but I figured I hear a lot more noise.