I have been chasing a gremlin for months. I've replaced many parts, verified fuel pressure, verified that I have no vacuum and/or exhaust leaks. My car still has a slightly rough idle and seems to idle really rich. My BLM stays at 142 which I think is a bit too high. Ive upgraded the fuel system (pump, hot wire, regulator). I also put in a new coil pack, plugs, and wires. I put in an lt1 MAF sensor and translator. I replaced the o2 sensor. The only thing that I haven't done is replace the original injectors. Can a bad 30 year-old injector account for a high blm?
Can Dirty Injectors Cause Abnormal BLMs?
- Thread starter DaveyX87
- Start date
gunzandgearz
gearzandgunz
- Joined
- Aug 24, 2015
You need to check for injector not firing, if you have a infrared thermometer check for temps on each header tube to see if one is cooler then all the rest[you can also use a spray bottle with water and spray on header]. If you have a mechanics stethoscope put it on injectors and listen for injector clicking, if you find one not clicking you have found your problem. This is where I would start, good luck
- Joined
- Feb 18, 2006
What chip?
- Joined
- Feb 18, 2006
Edited:
Never heard of a classic chip. What's the version #? 5.7 or?
Most tt chips will only go into closed loop idle when first run or after the ecm is reset. It learns where to be then locks the blm and stays open loop.
It's not rich. It's lean. Hence the high blm. The ecm is adding fuel to make up for a slightly lean condition. 142 is not that bad though. The rule of thumb is 10+ or 10- from 128 is acceptable. 142 is a little high but nothing to lose sleep over.
I sometimes will trick the chip by letting it learn with translator base set to 0 then shutting the motor off and turning translator base to 10% rich. That will further enrich idle area without the ecm/chip pilling the fuel out. When you reset the chip and added fuel the chip/ecm pulled the fuel out. Hence blm going from 142 to 138. It made no real change to the air fuel ratio. It just brought down the blm.
Never heard of a classic chip. What's the version #? 5.7 or?
Most tt chips will only go into closed loop idle when first run or after the ecm is reset. It learns where to be then locks the blm and stays open loop.
It's not rich. It's lean. Hence the high blm. The ecm is adding fuel to make up for a slightly lean condition. 142 is not that bad though. The rule of thumb is 10+ or 10- from 128 is acceptable. 142 is a little high but nothing to lose sleep over.
I sometimes will trick the chip by letting it learn with translator base set to 0 then shutting the motor off and turning translator base to 10% rich. That will further enrich idle area without the ecm/chip pilling the fuel out. When you reset the chip and added fuel the chip/ecm pulled the fuel out. Hence blm going from 142 to 138. It made no real change to the air fuel ratio. It just brought down the blm.
Last edited:
Yes, it's the 5.7. I still need to check the injectors. I did, however, make an adjustment on the MAF translator. I set it to run 10% richer at idle and then reset the computer. After it relearned everything and I started it for the second time I got the bl down to 138 at idle.
gunzandgearz
gearzandgunz
- Joined
- Aug 24, 2015
I think your putting the cart before the horse, heres what you need to do, pull plug wires off one at a time see if you get a change in how the engine runs, this should happen with every hole.If you pull one off and there is no change there is you problem cyl. Now you can start troubleshooting why you have a dead hole. Also put a vacuum guage on engine and let us know what it does, ie what is reading at idle, is it bouncing around. I still think its an injector but I could be wrong, its kinda tough diagnosing without car in front of me but if you give some info on some of these tests might be able to help. I see stuff like this come into my shop all the time and if you do some of the basic old school troubleshooting techniques it will about 50% of the time reveal some great information without throwing money at electronic parts that wont fix your problem, my snap on dealer doesn't even carry vacuum gauges on his truck anymore, mindboggling. Any way let us know your findings, good luck.
Will do! I have the day off tomorrow so I will take my time and report back here. Thanks.
- Joined
- Feb 18, 2006
If you suspect a miss fire, start the engine cold, run it for a few seconds and shut it off. Feel each header pipe off the heads. The suspect will be colder than the others. Either no spark, no fuel or too much fuel are all possibilities. No or low compression would be the worst case scenario.
I doubt there is any real issues. The blm would be on the floor or the ceiling if there was.
Also I edited my last post.
I doubt there is any real issues. The blm would be on the floor or the ceiling if there was.
Also I edited my last post.
Update: I am not getting any misfires. Compression is good. I changed the PCV for a third time, but, this time I used an RJC heavy duty PCV and ran a catch can. Whatever the reason, the BLM dropped to 136 warm at idle. The car is running the best it has ever run.
I'm assuming your fuel pressure drops accordingly with the vac line connected to the FPR? Have you verified cam sensor is set properly? And yes faulty injectors can do what you described. Just changed a set in a relatives car and it purred like a kitten after and KR was almost eliminated.
- Joined
- May 28, 2001
30 y/o injs, even at 26K on the clock, can be your issue. I've cleaned stockers at 25K/25 y/o, and found issues. I've cleaned them @ 125K, and found them really close.
No real way to draw a conclusion til they are on the bench.
Being you plan on upgrades, I'd not spend the $ to clean them. I'd replace them, and the chip, with some new pieces, such as a set of 60's...
No real way to draw a conclusion til they are on the bench.
Being you plan on upgrades, I'd not spend the $ to clean them. I'd replace them, and the chip, with some new pieces, such as a set of 60's...
- Joined
- Feb 18, 2006
The blm changed prolly due to the RJC PCV. It flows less volume resulting in less unmetered air entering the engine.
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