Hi
First of all i wanna thank everybody on this site because of you i managed to do an intake swap, without any knowledge of engines, new suspension and Prom tuning. The last step leads me to my question i have about the BLMs.

Car runs great and idles around 128-129 BLM, during acceleration BLMs are at 130-133 in any gear. So far so good. As soon as i let the foot of the gas and drive at constant RPM the BLMs climb slowly to the maximum of 158. Same in cruise control, for example in 5th gear at 32MPH 1000 RPM. When it goes uphill the BLMs start to drop when it adds gas.

Now my question(s) is(are): Is this normal? Kind of a lean cruise mode or something? Why do i have an injector constant of 20.82 and other 305cui proms like ANZA or APYP a constant of 19.48? My stock prom is a AKFX 2427. Everybody says 305cui have 19lbs injectors. Where there 305 models with 21lbs injectors?


Many thanks for any answer in advance.

BTW My car is a 88 GTA 305 with 5 Speed Manual transmission and 3.45 axle.

Regards
Marc Kemmer (Luxembourg,Europe)

 

Sounds like the O2 sensor is cooling off and reporting lean. There could also be something wrong with the AIR system, and it is injecting air into the exhaust manifolds during closed loop operation.

RBob.

 

Hi RBob
Thank you for the fast reply. I replaced the O2 yesterday so i'm gonna check the AIR system. Could a loose screw on the headers cause this perhaps? I think i better check all the tubes, bolts and screws on the headers and the AIR system. Thank you very much for the advice.

BTW a lot of your posts helped me with my little project and i really appreciate your advice.

Regards
Marc Kemmer

 

High BLM's are almost always a sign of un-metered air (vacuum leak). You will have better power with BLM's at 128 or lower. In fact, sometimes with a malfunctioning o2 sensor, your BLM's will be stuck at 128. Only the 350 models had the 22 lb injectors not the 305's.

 

Hi ninetyone

I had some vacuum leaks when i first had the intake back on. The passenger side runner to base gasket was wrong (Edelbrock intake and runners) and the (new) runners had a crack in them. After i fixed it it was all good. The engine runs nice and stays steady even with the propane test.
Since i have a new O2 installed i checked the AIR system and the small tube on the cat converter that goes up to the AIR system is loose. Not on the cat but on the engine side. It was late yesterday so i didn't took a closer look at it but i will check it out today.
Can that be a problem to?

Regards

 

the connection to the cat coming from the air pump being loose isnt the cause of your problem since the o2 sensor is upstream and the o2 is the source of the blm calc data. the extra air going into the cat is only to help burn the leftover fuel going out the exhaust so the leak there just makes your HC count higher than normal at the tailpipe.

 

I had an ext leak at the interface from header collector to ext pipe flange. Drove up BLM's. But not as severe as you report. Issue was lack of lock washers and it loosened enought to leak.

 

Yes, any air leak past the MAF sensor will drive up BLM's.

 

Hi everyone

Thanks for the hints so far. I'm gonna check those things out when i have the time and keep you posted.

Regards

 

If the headers are un-coated long tubes with the O2 sensor at or behind the collector, a heated O2 sensor is required. A 1-wire sensor will cool, off and report lean.

RBob.

 

I forgot to mention that i have Edelbrock shorty headers (ceramic coated) installed with a 3" Magnaflow exhaust and cat. The O2 sits in the driverside header just before the Y-pipe flange. I couldn't find any vacuum leaks with the brake cleaner past the MAF and intake section but i'm gonna try it with a propane torch.

 

Did u spray down your lower intake manifold?

 

Yes from the MAF on to the TB over the plenum, base, runners, chinawalls and injectors, all good with the brake cleaner test.

 

I have used carb cleaner to check for leaks. I have a question on use of propane? If you were to release propane near the dist on a running engine is there a chance it could go poof? My dist cap I vented with some .0625 holes about midway around cap so i wont try propane. Any way it could get in an unvented cap?

 

Hey I had a problem with my Edelbrock shorties and my regular non-heated O2 sensor! Definitely get a heated 3 wire sensor, wire it to the fuel pump (which turns on when the ignition goes on). It's safe, it's been 2 years since I did this and it goes into closed loop faster and NEVER falls out of closed loop. Either way you will need this to tune properly in my opinion because otherwise it will cool down and fall out of closed loop often (unless maybe you live somewhere with a super hot climate). This could be your problem, maybe not, but a good idea regardless and your car will run better as a result.

I would also check your EGR valve for leaks too maybe unless you did that already..

And what about throttle body? I would clean that too, maybe the throttle blades get stuck open and don't close fully when the pedal is released? Maybe it sounds stupid but just a thought..?

 

Hi Ronny

Good question. I tried the propane test anyway and no leaks so far. And it didn't blew up, yet. :-)

 

Hi hellz-wings

Thanks for the tips. Can you recommand a good 3 wire O2? EGR is checked and all good. Another thing i have to mention is: The car idles fine at 127-129 BLMs but as soon as i rev the engine to 1500 or whatever RPM the BLMs rise. When i release the gas pedal the BLMs drop to 127 and it idles fine. When i drive it's the opposite. During acceleration BLMs arroun 130-133 and as soon as i release the gas pedal the BLMs climb to thr maximum.

 

I don't know where the internet rumor of carb cleaner and brake cleaner came into play? But they both suck for finding vacuum leaks! Starting fluid used to work great but you can guess how dangerous it was. Seems the formula changed and the new stuff won't even start cars let alone find a vacuum leak anymore.

Spray some down intake and motor does not raise RPM, it kind of dies worse. Spray propane down intake and motor RPM rise! This is what your looking for is a rise in RPM or at least idle get's steady.

Yes the propane torch can light because of spark, but that's it, it lights and you pull it away. There may be a small poof. But nothing like a liquid fire. You'd probably have to point it in the vented cap to get fire.

Unlike car/brake cleaner which is a big wet puddle of fuel on engine that lights/ explodes and stays on fire.