Engine stumbles slightly at start of throttle opening up

[gnonyx]

Personally, I think UR4 is getting pretty hot.  I would go UR-5, myself.

I see many people are going to very tight gaps.  I have never had a problem running 25 psi on 0.035" but I often set them at 0.032".  For normal boost, I don't think you will have any problem.

If you want to read what Earl statement on his Ebay item:
This heat range is correct for stock cars with minor upgrades to modded cars with basic bolt-ons.  If you're serious about tuning and getting every last little bit out of car that runs a little hotter than usual, the UR5's might be worth trying.(NGKs heat range is 'backwards'. Higher numerically = colder on a scale of 1-10)

I don't know about these spark plugs other than reading and hearing about them

https://www.ebay.com/itm/163122170495?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649

[gnonyx]

Hi Steve, If you read what I found, all came true of adding fuel, but then didn't changed as it got worse after finding an air leak between the throttle body and plenum.
I put a very little smear of RTV on the Throttle body gasket, and the next day checked with about 15# input air into the intake manifold and on air leak.

Installed the MAF pipe, started the car and started to read the scanmaster readings, it was great to see the numbers looking good, until the engine got hot showing CLT 173.

The BLM was at 130, and then started to climb to137, so I increase the BLM parameter from default setting of 08 to 10 on the Commander Chip, and still the BLM was increasing.

I then disconnected the MAF system and while the engine was still hot and again input 15# of air into the intake manifold and found a smaller air leak between the throttle body and plenum where the very little smear of RTV on the Throttle body gasket I just replaced.

The worst came true of finding the TB or plenum is slightly wrapped.

I removed both throttle body and plenum, and used a squared piece of flat glass, Emery medium sandpaper, and started to sand down the throttle body and plenum until smooth and levelly flat.

[Steve Wood]

I don't understand either your problem nor Shimy87's.

I have had all kinds of air leaks and never had one cause a stumble.  If it was a carbureted car, I would say it needed more accelerator pump shot.  That feature is in Fuel injected cars as well but there is nothing that  can be adjusted in most chips.

Shimy87's car is showing low o2's but adding more fuel thru pressure or the Translator has made a difference.  Usually if the leak is large, the car will idle faster than is programmed in the chip.

Leaks such as you are chasing are so small they should not really show up in normal operation.  You find them by adding a lot more pressure than normal vacuum would be sucking during idle and off idle.  I don't think they are problems.

We consider blms to be normal if they are plus/minus 10 from 128.  At those levels, the ecm has plenty of room to correct the fueling back to the 128 level.

I am assuming that you all do not have old gas in the tank that does not vaporize well.

[Shimy87]

I have been watching this thread as well looking for a new "lead" on what might be causing my issue.

[gnonyx]

I don't understand either your problem nor Shimy87's.

I have had all kinds of air leaks and never had one cause a stumble.  If it was a carbureted car, I would say it needed more accelerator pump shot.  That feature is in Fuel injected cars as well but there is nothing that  can be adjusted in most chips.

Shimy87's car is showing low o2's but adding more fuel thru pressure or the Translator has made a difference.  Usually if the leak is large, the car will idle faster than is programmed in the chip.

Leaks such as you are chasing are so small they should not really show up in normal operation.  You find them by adding a lot more pressure than normal vacuum would be sucking during idle and off idle.  I don't think they are problems.

We consider blms to be normal if they are plus/minus 10 from 128.  At those levels, the ecm has plenty of room to correct the fueling back to the 128 level.

I am assuming that you all do not have old gas in the tank that does not vaporize well.

Be sure you clean up the throttlebody and get all the varnish out from around the throttleblade and clean the IAC passage well.
[/quote]
Hi Steve,
As you mention before on Reply #1: Be sure you clean up the throttlebody and get all the varnish out from around the throttleblade and clean the IAC passage well.
[/quote]
I see where I forgot to add the part when I removed the throttle body and before sanding I removed the newly IAC unit, and saw inside the how dirty it was. Even if you spray constantly you would never remove the built up inside the IAC and it's passage way. The only way to really clean this is to remove the throttle body, heavy spraying of carb. cleaner and I also used Q-tips for the passage way, and on the IAC seat.
 I see where I forgot to add the part when I removed the throttle body and before sanding I removed the newly IAC unit, and saw inside the how dirty it was. Even if you spray constantly you would never remove the built up inside the IAC and it's passage way. The only way to really clean this is to remove the throttle body, heavy spraying of carb. cleaner and I also used Q-tips for the passage way, and on the IAC seat.

[Steve Wood]

you may try swapping mafs if you have not

[gnonyx]

you may try swapping mafs if you have not

You're in the wrong business Steve, you should be in the physic world
I'm waiting for an 3" LT1 MAF to arrive
Right now I have a new Delphi AF10056 - 3-1/2" which is a newer model of the old style LS1 3.5"
Once I finish with the flat sanding of both throttle body and plenum, assemble the existing MAF, recheck for any air leak. Start the engine warm it up, and see what are the scanmaster readings. If the numbers are good then I will remove the MAF and put in place the old style but 3.0" LT1 type and see how the scanmaster numbers reads.
I'm wondering if the newer MAF being it's 3.5 requires more fuel since it's drawing in more air, or will the 3.0" LT1 will give me a better scanmaster numbers.

[Steve Wood]

the translator should take care of that.  You just have to change the settings for the 3.5

[gnonyx]

the translator should take care of that.  You just have to change the settings for the 3.5

Right now I'm using the 3.5" and the translator MAF base is set at 0, and when the 3.0" MAF is being use I will change translator MAF base setting to 3.

[gnonyx]

Hi Steve, I know I haven't written nothing since I finally installed the heater hoses, sanded, and flatten down both throttle body and plenum surface flat, installed with new gasket, started the engine and again found the BLM up around 128 then climb to 143. I knew it would happen since I believe one of the plenum bolt was stripped since adding the power plate, I placed the fuel rail bracket hole underneath the bolt instead of placing it on top of the bolt after torqueing down the plenum bolt, which cause the bolt to stripped. I went to check on the suspected bolt and not tried to loosen it but I tired to tighten the blot and found it loose.
Right now I'm waiting for longer bolts M8x1.25x50mm to come in so I can replace all of the plenum bolts.
I didn't tried to swamp the MAF since I have to take care of this air leak first, and then see where I'm at.
I will post again after replacement with scanmaster readings

[Steve Wood]

You may have to install a helicoil in the stripped hole if a longer bolt does not solve the problem.

Remember that if the battery has been disconnected or the orange memory wire has been disconnected, the chip has to relearn and the the car needs to be driven around for ten or 15 minutes and then the key turned off and the engine restarted before the blm readings are really meaningful.

Reread this article https://www.gnttype.org/techarea/faq/BLMINT.html and then this one  https://vortexbuicks-etc.com/blms.htm

Note how small the rpms bands for each cell are and understand a blm reading for idle may be a bit off, but the next cells may be much closer and that should not be a reason to obsess over not being exactly 128.

Be sure your maf reading at idle is correct.  Normally, with the key on and engine off, the maf will read 3.  With the engine running at warmed up idle, the range is normally 4-6.  Sometimes, with a Translator, it might be one number off.

When using a Translator, I prefer to leave the box set to the defaults and use the chip and fuel pressure to make any adjustments.

[Shimy87]

With the stripped bolts in the doghouse, use some, not a ton, of black silicone on each layer, the intake, the powerplate ( both sides) and the doghouse. let it cure before starting and you will eliminate any potential leaks. Makes removal harder but if you do it right you should never have a reason to remove it again. Even if you take out a headgasket in the future you dont need to remove it to remove the intake.

That bolt on my car was stripped also, used the silicone and put a slightly longer bolt there and its all good.

[Steve Wood]

I misunderstood what was stripped.  I helicoiled a couple of stripped ones in mine.  The best solution is to use studs rather than bolts.......im o anyway

[Shimy87]

Steve's solution is the right/best solution with studs.....I cut corners🤣🤣🤣

[Steve Wood]

I did not say I used studs....but I should have LOL