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questions about running rich

B

banniexj

NAXJA Forum User
Location
vancouver wa
Ok so I have 4.6 injectors in my stock 4.0 and I went to emissions and they said I was running rich. Is it the injectors that sends the signal to your fpr to send the right amount of fuel or does the fpr control the amout of fuel to the injectors. If I put stock fuel injectors back in would that make a difference or is my fpr bad??? Thanks
 
What is the condition of your exhaust manifold? Even the slightest of a crack will cause false readings in the o2 sensor Causing the computer to compensate fuel mixture.
 
Yeah and hows your air filter I pulled in some water wheeling al Hollistern hills OHV last year and made a mess of my air filter. I didnt replace it for a little bit as its not my DD. I recently relised my Jeep was running rich as a result.
 
Mnkyboy said:
Since he didn't say what year I'm gonna add that he has a 1990 Xj,so were talking Renix.
Click to expand...

Clean your throttle body with some throttle body cleaner (different than carb cleaner) make sure to clean your IAC and adjust your throttle position sensor.

I just did this to my 89 and it runs so much better now its ridiculous.
 
banniexj said:
Ok so I have 4.6 injectors in my stock 4.0 and I went to emissions and they said I was running rich. Is it the injectors that sends the signal to your fpr to send the right amount of fuel or does the fpr control the amout of fuel to the injectors. If I put stock fuel injectors back in would that make a difference or is my fpr bad??? Thanks
Click to expand...


To answer your question, The FPR just reduces the fuel pressure in high vacuum situations like idling and coasting and keeps fuel pressure at a predetermined amount the rest of the time. Purely a mechanical device.

The injectors are controlled by the ECU. The ECU controls those injectors based on input from engine sensors like TPS, MAT, O2, MAP, by varying the pulse width (amount of time) they are opened.

Clean your throttle body, Idle Air Controller mounted on the throttle body, and check/adjust your TPS for starters.
 
mojojojo said:
IAC ?
Click to expand...

Idle air controller. It's a solinoid on the front of your throttle body. There are some really good write ups on here about cleaning it and adjusting your throttle position sensor.
 
Great info. ref additional write ups... I know that search is your friend but i have a heck of a time sometimes just picking the right search terms then pouring through the results. If you know of a thread and would consider adding the link to your post that would be great. Not asking you to search for me though! I am not that lazy... Thanks again! Great info.

Now I guess I really need to get after the exhaust manifold leak that I have on my 1990 XJ. It has been there for a while and I have just been avoiding the pain of what seems to be an extensive replacement project plus motor mounts even though mine are still good , yes I will replace then too!
 
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