running rich.

[rainman]

'95 xj, 4.6l, comp 68-232 cam, 702 injectors @49psi
hello,
It is currently running rich, warm idle is 14.3 afr(wideband), & 22"Hg. After sitting for 3 weeks.
Last month it was running fine would warm idle at 14.6-14.7 afr, was always rich at WOT but that is another story.

I thought it was the Map sensor, cause it was reading low ( 1.2V ) at warm idle FSM says 1.5-2.0 V is correct, however, 3 different units all read the same thing. TPS is new.
With my scanner I can see the narrow band OXy sensor voltage swinging from low to rich constantly.
this is my question, I know a badly spraying injector can cause an increase in fuel consumption as the pcm throws in more fuel in an effort to get the narrow band to give a correct reading, cause the normal amount of fuel is not burning correctly. will this extra fuel cause a wideband (reading before the cat) to show rich. I'm thinking yes i mean it makes sense but is is not something I know. Does anybody else know?

Any other suggestions, I read the FSM to see the inputs the PCM uses to calculate injector duty cycle for warm idle, Engine coolant sensor is good, TPS is new and good, Intake manifold temp is good, map is good as well, oxy sensor "looks " ok, it swings rich to lean.
any other ideas?
Its not a instrumentation problem with the wide band, exhaust smells rich and MPG is $hit.

I need the car for the next 2 days, so don't want to pull injectors, see that "yes they spray shit" then put them back, just to pull them in 2 days and get them cleaned. if/when injectors are spraying well and it is still a problem i suppose it is replacing the narrowband oxy sensor, it is a NGK, 7 years 20,000 miles (tops) old, it *should* be fine.
Any suggestions?

[Cheromaniac]

702 injectors @49psi

Are you sure you have the 702 injectors and not the 703's? The 702's flow only 21.0lb/hr at 49psi whereas the 703's flow 24.1lb/hr @ 49psi.
With the 702's I'd expect your engine to be running lean. However yours is doing the opposite and the MAP sensor reading is low, so I suspect that you have a vacuum leak somewhere.

[rainman]

yep typo 703 injectors.
hmm vac leak you say. i will have a look. Ta.

[rainman]

so looked for a vac leak.
used carb cleaner to spray around the manifold at idle to see if the revs picked up. nothing.
built a smoke unit to smoke the manifold -no smoke coming out of the manifold.
Vac is 22"hg @ warm idle. I'm thinking there is not a vac leak.
Injectors flowed the same and had good pattern.
had to order a new trany mount from rock auto. so bundled it with a new NGK oxy sensor. Should be here next week.
Any other ideas? suggestions?

[jsawduste]

have you verified it`s going into closed loop ?

[Cheromaniac]

Vac is 22"hg @ warm idle. I'm thinking there is not a vac leak.
Injectors flowed the same and had good pattern.
had to order a new trany mount from rock auto. so bundled it with a new NGK oxy sensor. Should be here next week.
Any other ideas? suggestions?

You've definitely ruled out a vacuum leak. O2 sensor would be my next suspect so hope that works.
The MAP sensor definitely ISN'T at fault as a reading of 1.2v would be normal at 22" Hg vacuum (i.e. 8" Hg MAP).

[rainman]

yes its is going closed loop, the oxy voltage is bouncing high then low consistently, it is hunting around its value of 14.2, its working its just not hunting around 14.7afr.

[Cheromaniac]

yes its is going closed loop, the oxy voltage is bouncing high then low consistently, it is hunting around its value of 14.2, its working its just not hunting around 14.7afr.

That's normal behavior for a narrow band O2 sensor A:F ratio gauge at hot idle.
When the ECU goes into closed loop how does your gauge read under hard acceleration, steady cruise, and deceleration?

[rainman]

so dropped the fuel pressure from 49 psi @wot to 43psi. @ reset the PCM.
behaves the same, injectors are open for a little bit longer. at idle that is it. still looking for 14.2-3 14.3 at idle.
14.1-14.2 at gentle acceleration, goes lean during deceleration and was only 12.3 at WOT. previously much richer 11.8. ( all afr numbers from wide band )
obviously its still learning. we will see, new narrow band oxy sensor should be here next week.