97 4.6L 30lb injectors?

[BlueCuda]

Hey Everyone,

I have a 97 XJ with a 4.6L budget stroker, 753901 cam, and LT1 24lb injectors.

I have had a lean condition on the plugs every since I built it(18K on it). The plugs are WHITE look like they have never been in a motor. Its not lean enough it trips a code or anything but I would like to remedy the problem. It runs good, lacks some on the low end but runs strong for a 4000lb+ jeep.

A friend of mine has a set of 30lb ford injectors I can try. Any feelings on this? Didn't know if it would make it to rich or not? They are easy enough to swap back and forth just wanted to make sure I wasn't crazy for trying them. It for sure needs more fuel at least according to the plugs. Can't bring myself to spend the money to dyno my trail rig with a wideband 02 .

 

[CanMan]

Id at least give them a try. Like you stated, it wont take long to swap them out. Gotta experiment to get the right combo.

 

[tealcherokee]

map adjuster.

 

[old_man]

Before you do that, spend a couple of bucks and have a tailpipe sniff done. That will tell you how lean, if any, you are really running. I failed rich on emissions and my plugs were nice and white. Some plugs simply don't read as well as they did with leaded gas.

I was running rich with my 4.7L and 23# injectors. What cam are you running?

 

[BlueCuda]

Before you do that, spend a couple of bucks and have a tailpipe sniff done. That will tell you how lean, if any, you are really running. I failed rich on emissions and my plugs were nice and white. Some plugs simply don't read as well as they did with leaded gas.

I was running rich with my 4.7L and 23# injectors. What cam are you running?

I THINK its the Crane 753901 but its been awhile. I guess the computer would do its best to get the correct AF anyways wouldn't it? Just been trying to figure out why this thing isn't so hot at the hit of the throttle. I will try and get those injectors swapped this weekend and report back. Gives me a reason to fix my broken axle joint and drive the thing lol.

 

[BlueCuda]

map adjuster.

97 model map adjust=check engine light. I like the fact it hasn't ever had a CEL on from the day I fired it up.

 

[Dr. Dyno]

map adjuster.

I agree that would be the best route. The 30lb injectors are way too big and you can almost guarantee the engine will run too rich.

 

[BlueCuda]

I agree that would be the best route. The 30lb injectors are way too big and you can almost guarantee the engine will run too rich.

Does an adjustable Map change the WOT mixture or just part throttle? My feeling is that when in closed loop the computer will just learn around the correction to the air fuel ratio. At least it will on an OBD II and when it figures out something is wrong it will throw a check engine light. Also at WOT the computer should go into Open loop and I am not sure it reads the Map sensor in open loop, I am almost certain it doesn't read the 02 at wide open. I wish we had someway to REALLY program these things .

 

[Dr. Dyno]

The MAP adjuster will only affect the A/F mixture when the computer is in open loop (warm-up, deceleration, acceleration at >70% throttle). When the computer is in closed loop (cruise, acceleration at <70% throttle), it reads the output from the O2 sensor and corrects any change that the MAP adjuster makes.
This works for both OBD I and OBD II, though the '00+ engine computers are particularly finicky and throw MIL codes when you alter sensor outputs.

 

[BlueCuda]

Hmm interesting, thanks for the info.

 

[CartsXJ]

The MAP adjuster will only affect the A/F mixture when the computer is in open loop (warm-up, deceleration, acceleration at >70% throttle). When the computer is in closed loop (cruise, acceleration at <70% throttle), it reads the output from the O2 sensor and corrects any change that the MAP adjuster makes.
This works for both OBD I and OBD II, though the '00+ engine computers are particularly finicky and throw MIL codes when you alter sensor outputs.

On this note, would it be possible to develop a voltage regulator to change the voltage coming from the O2 sensor? For close loop mods and then have the Adjustable MAP sensor to take over when the system goes to open loop.

 

[gradon]

hmm