very bad backfiring with black smoke

[RCJP]

hi to all,
(JZ 1998 4.0 L6)
I recently was able to fix astalling problem, but to find it i did a lot of stuff that did not help.
One was I took out the CAT converter, and the O2 sensor that was attached to it now i'm wondering if this is causing this problem ideas?

all though my back fireing also happens when the car is cold and i try to rev it. my RPM will reamain at les 1k and i can here small back fire some times in front (on the intake or manifold area) and other on the tail pipe.

I have not goten the codes yet (next step).

also i wont to check the MAP and TPS to begin

Any other Ideas are welcome


thank you ..

 

[Jester32]

Well you need 02 sensor whether you have a cat or not. The o2 after the cat is for monitoring cat efficiency so you have to plug it in but leave it out of the exhaust stream. The one before must be in place as it controls the air fuel mixture. If there is only one sensor then it must be in the exhaust stream.

 

[Jester32]

Pull your plugs and check the condition. Check plug wires etc.

 

[RCJP]

Pull your plugs and check the condition. Check plug wires etc.

Another symptom, a can't go from full stop press the gas to much or i will stall, it has to be smood .....
thanks for the repply i will check my plugs i get back..

 

[Jester32]

Your first post said you removed an u2 sensor. Did it get re installed?

 

[RCJP]

Your first post said you removed an u2 sensor. Did it get re installed?

no i did not reinstall the down stream O2, i do have the upstream in place

 

[Jester32]

Ok. Install the downstream. Just tie strap it in place. Leave it out of the exhaust. All the down stream needs to see is a constant value. The upstream is the one that switches and adjusts fuel trim etc.

 

[RCJP]

OK, I changed the plugs and cales, checked the TPS, and MAP all good. the plugs and cables were in bad shape, what I do think is bad is the Upstreaam O2 sensor I'm geting a 1.4V read-out in cold conditions accroding to the manuel it shoud be between .2 and .9Volts.

It is same read our i'm getting from the harness that does not have the O2 connected ...

i'll replace it and get back

 

[RCJP]

OK, I changed the plugs and cales, checked the TPS, and MAP all good. the plugs and cables were in bad shape, what I do think is bad is the Upstreaam O2 sensor I'm geting a 1.4V read-out in cold conditions accroding to the manuel it shoud be between .2 and .9Volts.

It is same read our i'm getting from the harness that does not have the O2 connected ...

i'll replace it and get back

Hi just got the new O2 sensor. installed it but i have the same issue.:???:

took it for a drive and it stalled and back fired from the intake when i accelarated. got it to turn on again but it stalled as soon as i put it in Drive.
got it going again. and when up a very small hill and again it stalled. :???:

seems to stall when "load" is demanded.

in the garage i keep seeing the bakfiring in the Intake whe i rave-and-let go of the gas had a volt meeter connected to the O2 output. when the backfire happens the voltage goes to 0.1~0.4 .

HElp

 

[Jester32]

Check fuel pressure. Sounds like it's leaning out under load.

 

[Mikey4x4]

I think it's a vacuum leak ck manifold gasket and all lines may be bad gap on spark plugs

 

[RCJP]

ok so I started the swap game ....and i'm loosing

just changed the IAC motor and the MAP sensor still the same problem also cleaned the Intake it was full of thick sut. it runs alot better but i still have the problem of getting explosions on the intake...

what is the best way for checking leaks in the manifold? with out going to a shop

also I just got a hand on a good scan tool is the INNOVA 3130 it can read live values from a lot of sensors and also fuel trim i'm going to see if i can find a pattern or something wiht this tool...any tips

thankyou for the ideas

 

[Jester32]

Long term fuel trims should be within 5 to 10 percent. Short term should be no more then 25 % check fuel pressure. Make sure it's in spec. Make sure all plug wires are where they should be. Check for any dtcs etc.

 

[MudderChuck]

I read somewhere that the rear O2 sensor makes sure there is enough extra oxygen for the newer type catalysts to function properly. It has to have some sort of trim affect on the fuel to air ratio. It may be mor eimportant than people think. I've seen the wires for the rear O2 sensor short on the exhaust pipe and cause all sorts of grief.

I'd read my plugs and try to see exactly what is happening. What color were your plugs?

Just off the top of my head, but it kind of sounds like you may have a short in the CPS circuit. The sync sensor is on the same circuit in many models. I'm not sure if the O2 sensors use the same 5 volt power supply.

Pretty easy to test for a short, find the 5 volt feed for the CPS and back pin it, test for volts to ground. If it has a partial short to ground the volts will be way low, like 3 volts maybe

 

[RCJP]

hi to all installed the downstream O2 sensor, and after that lost a lot of power special uphill can get above 20mph unless i floor it . so i decided to disconnected hoping i would go back to wear I was...but no luck the only way I can go uphill at decent speed is if I disconnect the TPS, and even with the obvious erratic acceleration, i get up the hil faster and my commute has a lot of hills. So I changed the the TPS but problem remains....

Another thing when the TPS is disconected the backfire form the intake is reduce very significantly

IDEAS??/?