Got a quick question? I finally somewhat fixed my split BLM condition by fixing a leaky collector gasket that was giving me a false lean condition. Now I know that a false lean condition will show up as lean BLM's in datamaster 140+ that actually causes the motor to run rich as the computer is dumping fuel to compensate - Correct? Now I am running pretty rich accross the range 2000-4000rpm and the blms are staying below 120 ish and even bottoming out around 108-110 sometimes. For example at 2500 rpm the left bank is reading rich at 108 with the inj BPW at 2.99, inj dc - 6.3, 02 - 346 and tps at 9.8. I know this is just a small example, but is there such thing as a false rich condition and what could cause this? If not what would cause her to run rich as I have the injectors running in the tune at 33.94 when they are SVO 30's to compenstate for the rich, but it doesn't seem to be helping. I am tired of chasing my tail here and want to know could it be a maf issue that is not throwing a code and how can I tell? But, I think I am gonna just bite the bullet in a few months and pay for a dyno tune and do you think that these rich issues could be tuned out with a wideband on the dyno? Any suggestions are much appreciate.

 

bumb. Im would like to know also, i have same thing going on?

 

Please don't "page" individuals in the tech forums. A PM is the way to handle it. I deleted my name from the "topic".

A single O2 reading in closed loop is sort of meaningless. The one you happened to pick (346mV) is actually telling you its lean. But since the O2 readings should be swinging on both sides of 450mV 9 times every second, picking out a single number is pointless.

A 108 BLM does not mean its running rich. It means it would be running rich if the PCM wasn't using that BLM to correct the problem. If its a "true" condition, you have to find out the source. Could be a miscalibrated or dirty MAF. In OBD-I (unlike OBD-II) there is no way for the PCM to check the rationality of the MAF reading.

Is it running rich? What do the plugs look like? If its really running rich, and the BLM's bottom out at 108 and its still running rich, the short terms are going to average less than 128. Have you looked for that condition in the data log?

 

Sorry Injuneer, I appretiate your help. As to your question, yes when the BLM's go 108 and bottom out the STerm fuel trims are avg 115-120ish and she seems to be running rich across the board. I'm really stumped here as I have solved every consevable leak, vacuum, exhaust, etc that I can find. As to the MAF - is there any way to A Acurately tell it has a problem (IE: looking at AFGS in datalog)? and B Clean it without harming it? The only thing I can think is the tune that I got from Bryan at PCMforless is wayyyyy off and I just need to get by before I can get the cash together before I dyno tune her properly. BTW - Do you think that a custom tuner can eliminate all these issues on the dyno - assuming there is nothing mechanically wrong?

 

One possibility may be leaking injectors. A leaking injector can produce enough unburned O2 from a single cylinder to consume the residual oxygen in the exhaust, and make the O2 sensors think its running rich.... that would be a "false" rich. But the fact to appear to have the problem on both banks would indicate that it would have to be injectors on both banks.

You should be able to identify a gross error in the MAF readings, by looking at the AFGS at idle and at max engine RPM.

 

Thanks, after your suggestion I don't think it's the MAF as the AFGS line up across the board (RPMS) that it should and it can't be the injectors as I just had them serviced and cleanded and I have their flow chart, so I am sure it's not them. Could it be the FPR? What are the symptoms of a FPR diaphram leaking? Also, it could just be the tune is wayyyy off, so I am going to take it to Chuck at HPE in the coming weeks, to see if he can dyno tune her.

 

Dyno tuning will not fix anything with regaurds to street driving. Dyno tuning and wot operation are completely different tables from the ones you're driving around on. If you have logging capability post your log so we can see it. I could tune an lt1 for maximum performance wot and the rest of the thing could still be a wreck, the two are not related in the tune.

Clean your maf, you have some classic symtopms of it being ditry. Blms being good at idle and off everywhere else sounds to me like a cammed car with a dirty maf. The dirt changes the thermal resistance and goof's up the coef of convection that they use to figure out the velocity of the air.

Do not assume anything is working in a fuel injected car assume it is all bad and work from that pov. You will have to test and look at a lot of stuff but you will find the problem. You will not if you just arbitrarily rule things out. Your skill level at current is not such that you can just say oh its not this or that.

When running a maf there are only a few things that will make it have to pull alot of fuel. Leaky injectors, a bad fpr, bad input from the maf, or a bad iat reading (causes bad maf input), failed o2 sensors will do it too but i think you'd know in that case.

A bad fpr depending on its failure could puke gas into the vacuum line hooked to it, or it could make the car hard to start and lethargic due to low fuel pressure.

 

First of all I double checked the FPR last night and it is functioning normally (pulled the vac and jumped 5-6 psi and she holds pressure), next I'll clean the MAF today. My skill level is just fine as I think/I DO know what I am doing here, the reason I said it was fine is while logging the car I monitored the AFGS and compared the results to other posts here and on LS1tech and mine line right up with what I should be seeing. O2's are brand new and when switched out with my old AC delco ones (which were functioning properly, just changed out due to running rich for a while) the mV's and readings were the same, so I know that is not my cause. I think my VE tables and MAF calculations are all out of wak with this mail order tune and Gary over at HPE here in Houston is going to have Chuck take care of me on Friday morning. Also, you can tune for street driving as well with a dyno tune session as that is what Chuck does everyday. I'll keep you all posted on what we find.

 

I hope they get you taken care of, typically you do not tune part throttle on the dyno. I wont be checking back in, sounds like you got it all figured out. Sorry you got your feelings hurt, just trying to help you. I do this crap every day and have helped dozens on this board get thier cars tuned. Best of luck.