have you read my posts?

the 5-7 ohms resistance check only confirms the condition of the heating element of the o2 sensor, the signal can only be checked by an oscilloscope with engine running.

waveforms as below:



have you confirmed that you don't have an intermittent vacuum leak - some leaks pop up when cold and others when hot - and some don't care about the temperature
have you confirmed that your injectors are good?

you can just disconnect the o2 for your diagnosis, it would only run a little rich. Disconnect the o2 in the morning before start up - you'll most probably figure out if it was the o2 acting up or not.
bad IAC will not cause surging or power loss - it may indeed cause an oscillating idle

have you checked the TPS and MAP wiring as I mentioned?
TPS can be adjusted using the method the member @cruiser mentioned.

the surge you talk about can also be because of a bad FPR - you can test the fuel system by connecting a gauge and driving to see realtime data. If under acceleration fuel pressure falls a lot, say below 30 psi- it may be be bad regulator or a very very clogged fuel filter.

pinch the return line using a plier or whatever is handy - with the fuel pressure gauge connected - and see the change in fuel pressure - it should jump upto around 55-60 psi - do not keep the return line pinched for any more than 3 to 4 seconds.

EDIT: check the CMP connections as well..

 

I forget your year. Filling out your info really IS nice. Since I told you to adjust your TPS I'm guessing its 87-90.

The 02 sensor does nothing while it is cold in open loop. I don't think it would ever cause the engine to not respond to pressing the gas pedal. The throttle position sensor might though.

 

My Jeep Cherokee Laredo is a 1989.
Yes!~I have read every post and still down the list.
I changed the fuel pump and gas filter last year.
Replaced the cap, rotor, spark plugs, and spark plug wires.
I have cleaned the IAC and throttle body.
Inspected and cleaned a lot of the connections.
Replaced the ground cable to the battery and put on the new body ground.
Looked at every vacuum line and replaced a few.
Pulled all the injectors and put new O rings on all of them.
Check the (PSI) fuel at the rail and its great, but not when driving it in the am.
Checked the vacuum line to the MAP sensor pulled it off and the engine ran ruff.
Ran the engine and pulled the TPS and the engine died.
Took the two screw hold the MAP sensor on and inspected all the wiring
The last morning I drove it the engine ran great, but after 5 minutes it had little or no response to the gas peddle. It even seemed to race a little and engine continued to idle.
I drove the Jeep yesterday afternoon at least 50 miles...no troubles.
Climbed the divide here and dropped it down to 4 gear and punched it and just passes like 3 truck - great response.
One thing I know the engine is running so rich it is giving me a headache and the plugs are black. Plan on changing the gas filter, O2 sensor, and looking at the TPS next.


Thanks!~John...we will figure this out.


PS. Every once in a while I hear some kind of noise coming from the rear.
Can't really determine what it is.
It is only once in a while and like a solenoid type click.

 

Ok!~what about engine codes.
Looks like the 89 4.0L fuel injected has a the deal that flashes the engine light?
Turning the ignitions key 3x on and 2x off will tell the code if you count the flashes?
Does a OBD 1 or 2 work on ours...I lost my Chilton's book?
Just a thought because my friend has the Craftsman set of engine code readers.
Still plan on using the old multi-meter and testing everything.
I printed Cruiser's list and we are going to work some more on it Sunday.
Does the CPS have a boot or grommet that keep the sensor clean & dry...mine don't ?
John

 

No codes no matter what you do. Do the Tips.

 

Like said, no, no memory or stored codes for 87-90 Renix system Jeeps. Feel free to post up how it's going checking the TPS, we will be glad to help!

 

Well I still haven't got to the TPS. I cleaned the whole coil and ICU last night.
Had about a pound of sludge on it. Wanted it to be clean and dry so I used the old hair dryer. I don't know how to read the volt meter and lost the instructions and my Chilton's book. But I printed Cruisers tips, the whole 9 pages on sensor diagnostics (Eric Giordano), and what ever (www.lungh.com/tech_Articles/Engine/Cam_ Position_Sensor_Sync_Pulse_St...) is. I have a new Sun multi-meter.
Don't know why I can't get a reading on the TPS cranking the engine with the plug taken a part and red wire in the A and black wire in the B...you do connect the meter to the sensor side of the lead? There are to many positions for the volts on my meter.
John
Which one do I put it on?
I am about ready to just go buy a new CPS from Napa and say the hell with it.
John

 

Messed up... meant CPS check with volt meter while cranking the engine...
John

 

set the multimeter to 200v AC or whatever the lowest AC scale is available, a 1V or 2V would be best.. since you'd be measuring the voltage less than 1volts anyway

yes you connect the meter to the sensor side

and crank the engine

you should not have any less then 0.35v while cranking

 

AC volts....................

 

I don't mean to come off "too big for my britches" (I did learn most of what I know about Renix from Cruiser), but! Sorry, you need to get on a somewhat deeper page with that TPS. Getten your "feet wet" with that digital meter checking your CPS AC output voltage, directly from the unplugged CPS is great start. I always take a second to check the CPS.

Adjusting the TPS is only more difficult because you need to leave it plugged in, and back probe, the wire, with a pin or paperclip or something jammed in there.

 

Yes AC volts. .

Sorry for the brain fart moment

 

Well I did go to Napa and got a new CPS and installed it.
The new sensor was in there wrong and I heard something scrapping the flywheel.
I took the CPS out (getting good at this now) and it was the plastic piece that fits into the bell housing of the trans.
Removed it and placed it back it flush and installed the CPS again.
No troubles this morning when I drove the Cherokee to work today and was early.
I am not sure this was the problem for sure, but an friend of mine told me always check something that has been worked on lately.
The trans and clutch was the only thing worked on, which meant taking off the CPS.
The wires burned up and I replace them on the CPS and my popping noise in the exhaust was gone and so I figured I had fixed my problem. It still ran rough in the morning.
When I installed the new CPS I routed it better and used zip ties to keep it away from the exhaust. Another thing I did was used some of that split plastic tubing over the wires.
Cruiser I am still working on the other renix tips (TPS) trying to figure out how come my exhaust is so strong smelling in the vehicle and why the spark plugs are so black.
I have visited some of the other posts and found out more about multi-meters.


So far-so good!
Thanks!~Everyone!!!

 

Great job. Pay close attention to the following:

 

Thanks!~Cruiser, I checked the vacuum line to the MAP sensor and it was good, no restrictions, took it off and inspected it, no cracks ect., blew threw it and it is clear. Started the engine and pulled the vacuum line and the engine started to run rough. Then plugged it back in and the engine ran smooth again. No more hesitation and it starts faster in the am.


So what else could be making this Jeep run so rich and the spark plugs be so black? The air filter is clean and dry.


My friends old Wrangler is the same way with about 165,000 miles.


Thanks!~John


A friend of mine said I should run Marvel Mystery oil threw the gas tank.