Replaced the iat and the cts and fuel pressure was right there im thinking cps or o2 sensor like you mentioned that has not been replaced

 

Ya a previous owner had played with the distributer cap so we had to make sure it was were it was supposed to be.

The only thing i though i noticed is after cranking to adjust with the wires off after putting everything back on the cap and wires and trying to start it fired right up almost instantly i dident have to crank it hardly at all.

However after shutting it off and restarting it it was back to the same long cranking to start

And the tps doesnt appear to do much the jeep still runs the same as before with different tps old new junkyard. I get the same hesistation.

You can play with that sensor all day i even have several tps

 

OK...Steady at the Helm. It's not the knock sensor. Let's say the plugs looking clean is OK. It goes great when you floorboard it? Renix goes into open loop and ignores a bunch of sensors when you go past 70-80% throttle.
Mine did similar stuff that you mention when my wire gang to the lower sensors was shorting. If you don't know the history of your 02 sensor I might suggest you put an NTK, or OEM in there and check the 02 heater power, it's ground, and the CTS & Knock wires while you are there. I'm really reluctant to tell a poster to buy anything....just that that 02 is so crucial to mileage. Any of those wires down under there touching ground might do that.

I'm just not buyen a CPS issue.....If you got .4 ACV (about), from it, directly from the unplugged CPS, cranking with a good bat, it's working.

Long cranking to start? Yea, do check the CPS, BUT! Reinx always needs a few seconds. OK maybe even two...ECU needs to see 300 RPM for a second.

Try turning the key on, for a couple secs, off, and on like that a couple times, and see if that changes the crank time. If the check valve in the pump, an injector, or the FPR is bleeding off pressure it will need to crank longer to fire. (called the "poor mans prime").

And yes. a Napa #css890, or from Jeep on the CPS....if it's under .4, or .35. Also (hot) resistance is 225 ohms, plus/minus 75.

#1 is at 5o, (from the side) 153624 clockwise. Sounds like with all those you might have ruled out the TPS....? Fuel filter? But it will go like a raped ape if you floorboard it?

 

thanks df your info was pretty usefull . I took the firewall ground off and cleaned both ends even added a piece of 8 gauge wire going from the firewall to the neg battery. Dident appear to improve anything.

Also i replaced the cps with just a cheapo duralast the car might crank alil faster and the jeep might not be as doggy on acceleration but it will still die out more so in reverse if i just touch the gas it will stall i have to step on it to back out.

Also from what ppl say on here you dont get a reading from the o2 till its warmed up so the bouncing idle you would think couldent be from that keep in mind i have only 90 thousand miles on it

 

Check your fuel pressure while running. Mine would idle ok and then the pressure would drop or 0 really quick once you gave it a little gas. Couldn't get out of the driveway some days and then it would be ok for awhile. Turned out to be a bad fuel pump.

Don't disregard what Cruizer has told you. I had lots of intermittent problems that were ground issues at the dipstick and on the firewall.

I'm thining that if your jeep starts ok, the CPS is probably ok as well.

The TPS adjustment is pretty fine so you need to take the time to do that correctly. When you said " I can play with that sensor all day i even have several tps". I would buy at least one good one to be sure. I had a junkyard one that read fine on an ohm meter but didn't work well in the Jeep. My new one worked great after adjustment.

 

So it's idling more or less OK, but cycles. I think the 02 is doing that. But when you touch the throttle, even there in park it dogs/dies? Make real sure the little tube from the rubber plug on the inside of the TB, back and up to the map is free, not restricted. You can pull the connecter off the map with it idling and feel for vacuum, (it might die). The MAP sensing the drop in vacuum is what tells the ECU you hit the gas. I suppose you could blow through it.

It's always smart to listen to Cruiser. .80 from the TPS, not .84? Idk...might as well nail it correctly.

And you DID gap those plugs to .35, and the wires coming off the injector harness going down to the lower sensors seem OK, not chafing shorting, or melting on something....

Also that tranny kick-down cable. I set mine with just the slightest play, (a dime's width). There is a process for it to auto adjust...mine seems stuck or something. Anyway there is a button on the housing and it should not be taught. Idk. Thinking if yours was too tight maybe it could but a load on the motor before the engine get's fuel enough. Grasping there, I don't know if that's possible.

Just on GP, and to rule it out:

Vacuum leaks suck. I go around with short little shots of starting fluid, if you hit one the sound of the engine will change. Small little shots! You don't want that stuff to accumulate. It's a fire hazard, but It evaporates right away. Also with a tube, or a section of hose you can listen for it. Don't forget the lower O rings on the injectors need to seal as well. (uppers would leak fuel).
The manifold bolts have a habit of loosening, especially that rear one. On anything like that you never want to tighten only one. It can warp/bend, even crack things. If I found that any that where easy to reach where loose, I'd pull the air cleaner and tighten them all, starting in the middle and working out towards the ends. I go over about three times. It's a bear of a spot to get a torque wrench on them all. Just don't ape on it. If its firm and not turning, no point in going on to break it, a REAL *****. The rearmost bolt underneath takes a little doing, but it can be done with the right extension. For that very back one by the firewall I use way long extensions (18"), with a swivel at the socket. Anyway, that's a good thing to check on any old Jeep.

 

no i dont know about the injector wires. i put in the new crank position sensor. One guy sounds confused it starts slightly faster now that i replaced the cps i just put a new one in.

Also appears that when i hit the gas and let off the tac dont bounce down to almost 100 rpms and almost stall then shoot right back up.

When i hit the gas in park cold or hot driving around the tac would drop when i let off and level off.

Say i hit the pedal and the tach shoots up to 3000 rpm it will drop when i let off and the needle will stop at the rpm instead of bouncing real low then leveling off.

When i take off ill get a hesitation spuddering but now somehow the gas pedal seems more responsive so when i take off the jeep will come out of it faster seems like when i pressed the pedal before going up a it took off and dident slow way down going up it.

And to note that the cap looked clean inside shiny and brand new looking and the distrib was moving good looked oiled good.

I found a line that went to the map sensor from the tb that had a piece of rigged on fuel line holding it together in the middle i fixed that and it was air tight after.

Also i agree with cruiser but i have cleaned both grounds on the motor firewall and dipstick even added extra to em.

Also on the tps i have set the tps before have used 3 different ones the one that is on there now says standard electronics.

The original tps im pretty sure thats already been scrapped.

Keep in mind this tb is a junkyard one and had a sensor on it standard electronics i also have a brand new tps i bought last year.

My hesistation in park during takeoff, the up from idle then down idle dident magicly go away when i swapped out tps.

Keep in mind the tps that was on the junkyard tb prolly hadnt been moved in a long time if at all.

So are one of you to assume that none of the sensors where ever set correctly??? sounds crazy

And yes even though the plugs where pregapped we checked em all before we put em in.

Also dont know if this is normal but lately when i start the jeep even today with the new cps i notice the tac shoots up to 2500rpm then drops down around normal right after it fires

 

Do this simple test before anything else:

Cruiser’s Renix Sensor Ground Test
　
This sensor ground circuit affects the CTS, TPS, IAT, MAP, ECU and diagnostic connector grounds. It’s very important and not something to overlook in diagnosing your Renix Jeep as it is common for the harnesses to have poor crimps causing poor grounds. If any or all of the sensors do not have a good ground, the signal the ECU receives from these sensors is inaccurate.
Set your meter to measure Ohms. Be sure the key is in the OFF position. Using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS . The letters are embossed on the connector itself.
Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it runs parallel to the valve cover and also near the MAP sensor mounted on the firewall. If you have an 87 or 88 with the C101 connector mounted on the firewall above the brake booster, wiggle it, too.
You want to see as close to 0 ohms of resistance as possible. And when wiggling the harnesses/connectors the resistance value should stay low. If there is a variance in the values when wiggling the wires, you have a poor crimp/connection in the wiring harness or a poor ground at the engine dipstick tube stud. On 87 and 88 models, you could have a poor connection at the C101 connector as well.
Revised 06/12/2012

 

will look into that we were gonna rewire the sensor grounds neways. Also the car seems to run worse when it warms up. When cold it will take off

 

Above 80% throttle, (about floorboarded), it will go into "open loop", like when its below about 160*. Yea, double check the resistance on the sensor grounds, (I have less than a ohm), but if you get a chance, see if it goes like a rocket if you really gas it. Might be helpful, And fun!

 

How are you planning on upgrading the sensor ground circuit?

Worse when warm means it's using sensor input versus a preprogrammed setting when cold.

 

Same as I was thinking. "pre-programed" meaning default settings for open loop, which are over-ridden at full throttle. (Partly learned form Cruiser^).

About everything but the MAP, (and CPS), is ignored? Knock?

 

Run a direct ground right to the actual sensors right to the battery ground.

How would we check the o2 sensor???

 

What did you find in the sensor ground test?

 

Well, I gave it a swing. I got a piece of the ball. Right at the start is Mikes link where I got allot of info. > https://www.cherokeeforum.com/f2/ren...ce-rms-133153/

Really since it's so important for mileage, I might suggest just changing it if you don't know how old it is. Plus...my fluctuating (20-30 secs), idle smoothed out.