Engine stumbles slightly at start of throttle opening up

[gnonyx]

Hi Steve,
You and I have been through some converse time in order to solve my high BLM, and during that time I have welded both headers, installed them without gasket just used high temp RTV. Replaced both upper and lower ball joints, replaced front and rear bushings, and all coil springs.
My ScanMaster reading:
02-527-679
AF-04-05
LB-32
BAT-13.4
INT-137
BL-133
NPH-0
CLT-173
ATS-88
R-825
TPS-.42
IAC-25
CC-58-106
NAL-0
OIL PRESS-23-34
VAC-16-17
A/F-15.2-15.4
VAC HOSE OFF-44
VAC HOSE ON-37
I will change the regulator fuel adjustment as per my Commander chip 45
Even though the fuel press maintain it's pressure for over an hour I felt the stumble may come from a dirty fuel injector.
I removed all fuel injectors and found the regulator O-ring not in good shape as you can see in photo.
I also clean up the manifolds injectors holes very dirty as well as you can also see in photo.
In the photo that shows only 2 O-rings, the one on the right is from the fuel regulator and the one on the left is from the other end of the fuel rail.
The other shows the fuel injectors I'm using Siemens DEKA IV ( DEKA 4 ) Mototron 60lb/hour High Impedance Injectors
The other photos shows how dirty the fuel injectors holes are
I already ordered the injectors O-rings, clip and also the regulator O-ring.
I will put all together, and make final fuel adjustment to see and hear engine response.
I will post again once all is final

[Steve Wood]

I'm not much help with Bob's chip when it comes to adjustment because I have forgotten whatever little I knew about them.

The numbers look okay to me.

The lower o-rings on the injectors can cause a vacuum leak if they are cut or chewed up.  The upper ones can cause a fuel leak.  The fuel pressure regulator can cause a fuel leak.

If the injectors are dirty, that can cause a problem as well.  Only having them flowed and cleaned can resolve that.

Be sure you clean up the throttlebody and get all the varnish out from around the throttleblade and clean the IAC passage well.

[gnonyx]

Hi Steve, I for got to add this to the ScanMaster list:
INT-137
BL-133

I'm also going to use the same way this guy on YouTube cleaning method of cleaning the fuel injectors
https://www.youtube.com/watch?v=-eDcY0WhALI

[Steve Wood]

I would spend the money and have them done professionally

[Shimy87]

I tried that way of cleaning injectors and they wouldn't spray, had to get them done at a shop....didn't cost much

[Steve Wood]

Yep...that not only not clean hard deposits from the nozzle of the injector, but, it will not tell you if the injector is spraying the correct amount of fuel each time.  Bad idea.

[gnonyx]

Hi All, and especially to you Steve, I really do appreciate and respect you guys opinions, and I did inquired injectors service shops for price and found the cheapest is $20.00 per injector.
unfortunate right now we're recovery from home project expense, and I'm saving to get the GN digital dash repair from Caspers to which the cost is around $500+.
I already did my DIY injector cleaning and it did came out better good, and I will see if I can tape a short video of it.
I will take another pictures of the manifold where the injector is inserted showing how clean it came out.
Thanks Again

[Steve Wood]

Time to do something free. Program some additional fuel at idle...try about 5% more

Put it in open loop idle if it's not already there

[gnonyx]

Time to do something free. Program some additional fuel at idle...try about 5% more

Put it in open loop idle if it's not already there

Several years ago you posted a thread of using a propane bottle gas to detect if any vacuum leaks was present.
I used your method especially around the upper and lower injectors O-rings location, and also around the intake manifold, and found no leak and the engine idle didn't change.
I have tried many times to upload a short video of how the DIY cleaning injector with Gumout product and also showing a strong stream coming out of the injectors exit port.
I already ordered both upper and lower injector's O-rings, and clips, but I can't find the Fuel pressure regulator O-ring and also the of the fuel return rail O-ring.
Do you know who has both fuel return rail O-ring and fuel pressure regulator O-rings?
Thanks

[Steve Wood]

Again, it is important that the injectors be cleaned properly so that they not only spray a proper pattern, but also to insure they all spray the same amount of liquid for a given injector pulse width.  When you have them professionally cleaned, each one will come back marked to show how much it sprayed so you can compare them to one another to be sure they are doing what they are supposed to be doing.

Having said that, I doubt there is anything wrong with yours.  I think you need to adjust your fueling as I suggested above by programming the chip.

Here are the various o-ring part numbers

NAPA #730-4912 you get 2 of each one and they are correct.
NAPA #2-18416 for a package of one of each size.

STANDARD MOTOR PRODUCTS SK27 Fuel Rail O-Ring Kit
STANDARD MOTOR PRODUCTS SK26 Fuel Rail O-Ring Kit

borg warner or neihoff search part # 27478 , its a kit of both o-rings for the fuel rail

standard motors brand in a 10 pack.. sk27 feed , sk26 return

Fel Pro ES 70599

For the FPR to rail connection it is a standard GM injector O-ring.


I used to have these saved some place but I googled for the results this time

Oh, I still do.  From my site   http://www.vortexbuicks-etc.com/injectorswap.html

[gnonyx]

Again, it is important that the injectors be cleaned properly so that they not only spray a proper pattern, but also to insure they all spray the same amount of liquid for a given injector pulse width.  When you have them professionally cleaned, each one will come back marked to show how much it sprayed so you can compare them to one another to be sure they are doing what they are supposed to be doing.

Having said that, I doubt there is anything wrong with yours.  I think you need to adjust your fueling as I suggested above by programming the chip.

Here are the various o-ring part numbers

NAPA #730-4912 you get 2 of each one and they are correct.
NAPA #2-18416 for a package of one of each size.

STANDARD MOTOR PRODUCTS SK27 Fuel Rail O-Ring Kit
STANDARD MOTOR PRODUCTS SK26 Fuel Rail O-Ring Kit

borg warner or neihoff search part # 27478 , its a kit of both o-rings for the fuel rail

standard motors brand in a 10 pack.. sk27 feed , sk26 return

Fel Pro ES 70599

For the FPR to rail connection it is a standard GM injector O-ring.


I used to have these saved some place but I googled for the results this time

Oh, I still do.  From my site   http://www.vortexbuicks-etc.com/injectorswap.html

Thanks for the info Steve
Yes I know you're right of getting the injectors done professional, I wanted to see if the spray was clogged of uneven spray for me to warrant it to be done professional clean.
In a way I glad I removed the injectors and removing the fuel rail to realize the O-rings needed to be replace, and if I have been driven the car it might have leak and caught on fire.
I have read many times over on your "HOW TO" info, and honestly, the injector swap is one I read once and forgot about, and that includes the O-rings sizes. Thank You for reminding me
Why would the O-rings replacement surjects four O-rings replacement when there are only two location, one on the fuel regulator end and the other at the fuel return rail end.

[Steve Wood]

probably because they cost a penny a piece and people tend to screw up them by not using grease on them or such

[gnonyx]

probably because they cost a penny a piece and people tend to screw up them by not using grease on them or such

TOUCHE' on that one

[gnonyx]

Steve, a while ago just after the welded headers I replaced the spark plugs to NGK UR4 6630 gap at 30, manufacture claimed to set at 35, yet reading other members claimed to gap at 25.
What is your opinion on this type of spark plugs and about their gap?

[Steve Wood]

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.