Need help please, new motor, now pings bad

[Tuffy]

SilverXJ,

So you are recommending the Neon 703 injector over the other 2 you mention? I really only want to do this one time if possible. I plan on purchasing new injectors so I know they are good. Where is a good place to purchase these 703 neon injectors? Do you feel they will flow enough fuel for my application? What do the stock 4.0 injectors flow, keep in mind I am running 49 PSI? Seeing as how I have bright white plugs indicating a lean condition, it is obvious I need more fuel, but do you feel these 703's will flow enough?

As stated above, the 258 was bored .030 over, has a freshened 4.0 head, some was shaved off deck (not sure how much though) and the head was shaved just enough to be straight, very very little. The rest of the MPFI is stock from a 94 Grand Cherokee with single fuel rail running at 49 PSI. I have a cold air intake, stock exhaust. New stock 4.0 coil, plugs, cap, rotor.

Thanks for the help, keep it coming.

[SilverXJ]

I only recommend them because they have the EV1 socket, so you don't need an adapter. I am basing the recommendation on flow numbers I have researched. I feel the numbers are fairly accurate, but I have not tested them myself.

Plug color is a poor indication of AFR on a fuel injected engine.

[Tuffy]

Silver XJ,

I will be placing my jeep on a wide band O2 sensor possibly tomorrow, what numbers should I be looking for? I will post my numbers as soon as I get them. Should I test at idle, while driving, or both?

Thanks.

[SilverXJ]

Yes, idle, cruise, medium throttle, WOT, etc. Any where you can. In closed loop you should be looking for around 14.7:1, in open loop around 12 to 12.5.

[Tuffy]

SilverXJ

What exactly is closed loop mode vs. open loop mode?

[SilverXJ]

They are operation modes of the PCM. Open loop the PCM is relying heavily on the MAP sensor and to a lesser degree the IAT and the CTS. Closed loop is when the PCM relies on the O2 sensors to prvide feed back to achieve 14.7:1 AFR. If you goodle the two terms you will find a more detailed explanation. The FSM also covers this.

[Tuffy]

Ok all,
It's been a while, but I was finally able to get a wide band O2 sensor on my Jeep. I am running 15-15.2:1 Air/Fuel ratio, this stayed constant at all speeds, idle through wide open throttle, it never really changed much. We also "whistled" the motor to get the exact compression ratio, which turns out to be 9.5:1. The 258 was bored .30 over, so I was told that should make the motor around 260 cu. inch. What are your thoughts? Will replacing the injectors get me to where I need to be to stop the pinging? If injectors, what size/flow do I need to purchase, and where is a good place to obtain them from? I am ok with needing to run super unleaded fuel, as this is a toy, not a daily driver, I only put about 2-3K miles on it a year at the most.

I really appreciate the help all have given, it is certainly a learning experience with this stuff!

Thanks

[Tuffy]

All,

I spoke with an individual that sells fuel injectors. Explained what is going on and gave all the info I have about the motor and the pinging. The individual felt I am definitely running way too lean. He states with todays fuel containing ethanol and alcohol, that we actually need to be running around 13.9:1 AFR. He states that since I am using 18 year old injectors from the junk yard that I am not even close to running the correct flow of fuel. He also recommended the same injector as Silver XJ, which is going to flow around 26 lbs at 49 psi with a 4 hole spray. He states this should really work well with the specs of my motor. He felt my 9.5:1 compression ratio was actually right on provided I use premium fuel. The injectors are new Bosch with EV1 connector. The new injectors will be similar to the 0-280-155-703, only a brand new injector with a different number. I could have gotten rebuilt injectors, but seeing as how everything else is brand new on this motor I decided to go with new injectors. The place states they will exchange the injectors if I find I need even larger injectors, but the man felt these should be right on for what I need. Hope this all works out ok. I just want to be able to drive my jeep and enjoy the new motor without severe pinging.

Thanks again, I will report back when I get the new injectors installed next week.

[SilverXJ]

Ok all,
It's been a while, but I was finally able to get a wide band O2 sensor on my Jeep. I am running 15-15.2:1 Air/Fuel ratio, this stayed constant at all speeds, idle through wide open throttle, it never really changed much.

That is pretty lean especially for WOT, which is puzzling. You should see it change some what and go richer under WOT. But, junk yard injectors are never a good idea.

[renogeno]

If your pressure regulator is on the rail you should put an adjustable regulator on and maybe a MAP sensor adjuster. Lots of ways to fine tune if injectors aren't exactly right. You can try here:http://www.strokedjeep.com/regulator.html, or Hesco or Goggle it!

[Tuffy]

Per the earlier part of my thread, it is a single line fuel setup, no pressure regulator at the rail. I have been told by individuals that make adjustable MAP sensors that they only come into play at or near WOT? So really an adjustable MAP sensor is not going to help much.

I will give the new injectors a shot and see what happens. I am starting to also question whether or not my engine computer is working as it should?

[SilverXJ]

The MAP sensor adjuster will only work in WOT (open loop), with the exception of changing timing. Being that you are showing lean in closed loop there is either a problem with the injectors or your O2 sensors.

[Tuffy]

SilverXJ,

Thanks, I am hoping the injectors take care of the problem as my O2 sensor is a new Bosch so that should be good. The injectors are 18 years old, they sat all last winter as the motor was torn apart, not to mention they were junk yard obtained. Looking forward to seeing if the new injectors make the difference, should certainly help with the added amount of fuel the motor will be getting.

[CobraMarty]

With 15:1 AFR, why isn't the ecu adding fuel via the short and long term trim tables to bring it back to 14.7? Need more run time?

[SilverXJ]

I'd take a closer look at that O2 sensor. Before you turn the key and the sensor is ready, what is it showing?