Reniz 4.0 not running right and im stumped, kind of

(forgive the copy and paste from the other thread, but i dont wanna re type it all and it explains it the best i can haha)

im having trouble with the jeep running correctly. i bought it for 350 bucks from a guy who couldnt get it to run right. from the symptoms i figured it was just a grounds issue and wanted to capitalize on his inability to properly diagnose it. before it would only run with the gas pedal pressed in and it would run very rough. would barely idle if it did idle. after a full tune up and cleaning the iac and tps, and replacing the o2 and cps sensor it now will start on its own, and idle perfectly, for a minute. then it will randomly kill its self. sometimes it just bogs down where the rpm's barely register so it shakes like crazy and then i just shut it off. if i open the throttle too fast, and i mean any faster than a CH at a time, it will instantly die, yet when i do it slowly it will rev perfectly. but most times it will die if i just let off the throttle all the way. if i step it back down it will go back to idling. so ive been troubleshooting this thing on and off, and the haynes manual has helped some but nothing this specific. so ive gone from hardly starting and no idle to starts, idles great(before it shuts its self off) and kills its self when the throttle is opened. i also have not been able to check the fuel pressure cause i dont have a gauge and cant find one for an affordable price. i might just go to harbor freight in a little bit though. anyways. lastly, while its running, instead of opening the throttle a little at a time, if i go WOT immediately, sometimes it will stay running, but cough real bad for few seconds and then rev up and when the revs come back down and i try again, it will pop as if its coming from the intake. any help would be appreciated. i dont know the 4.0 real well, only from what ive researched and all my 4.0 buddies say.

thanks again

Is the vac hose to the MAP attached, in good shape?

It sounds like a vacuum issue to me. Whether it's the MAP, EGR or Fuel Press Regulator. Every RENIX I've seen worth $350 has had vacuum issues. Guys mess with the vacuum and then wonder why it runs like crap and won't smog.

I would check EVERY vacuum line, check for vacuum and repair/replace each one (including the HVAC and TC lines). Bulk vac line is cheap, then you can move on to the next system to find your Bogie.

ParadiseXJ has some good points.

Other things to consider:

Possibly a restricted exhaust.

Possibly a worn out distributor with side play in the shaft (a little up/down movement is Ok).

Bad fuel pressure.

Dirty fuel filter.

Throw a vacuum gauge on it and watch what happens when you slowly give it some throttle. Reading vacuum gauge: http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

ok. i got it running right. kind of. i found a $30 TPS at NAPA and changed it out. when she was running, it ran great. no more idle issues and would actually rev smoothly. i let it run for about 5 minutes and shut it off, then tried to restart it, and no bueno. i medded up the connector to the new CPS when i installed it(dont ask, it was messed up from the factory, i was tired, and messed it all to hell haha) so im gonna let it cool down, and see if it will restart. if it does, ill go ahead and reorder another one. if it doesnt, then ill go from there.

thanks to another thread on here, where someone mentioned that the TPS tells the computer to give more fuel to the motor, and as smart as i think i am, i didnt realize thats exactly what it does haha. so i replaced it and its all good.

now that i think of it, i probably could have replaced only that, and for $380 had this thing running right haha. but all that ive done was worth it for maintenance sake

Make sure the tps is installed correctly. Make sure the lever rotates when you open the throttle. I just fixed one yesterday that had the lever on the wrong side of the throttle arm. While you are at it, make sure you set the tps.

Make sure the CPS wire isn't against the header and melted.

i went back and it still hasnt started. maybe i havent left it long enough. if it starts tomorrow then ill go ahead and order it. if not, ill be pissed. i actually did not install it correctly the first time haha. then i went back and noticed the arm and made sure to make it attach properly, so it does move with the throttle now. when i did that, is when it started and ran beautifully. and now im at where it doesnt start at all. as the thread around me, cranks but doesnt start haha. ill check the wire on the cps tomorrow. but im pretty sure i just happened to pull on the wires earlier for some reason. i checked and it has spark, the fuel pump is working cause i hear it whine though i havent been able to check pressure. but i dont think thats it. im pretty sure its a sensor/electrical issue. we'll see.

oh and how do you set a tps?

91+ are not adjustable--what year is yours?

89 4.0 aw4 231 155k. one other thing i was thinking about. while i had it running, the last time it was running and the best it has ever ran since i got it, i did put it in reverse, then drive to see if it would die under load. it didnt which was good. and then i notices/remembered that it doesnt start, or even turn over in neutral. so im thinking the nss is an issue and maybe i just made it worse when i shifter it this last time? when i got it, it wouldnt start or crank in neutral. but would crank and fire in park. and now it only cranks in park and still nothing in neutral. yall think NSS might be an issue?

Can't hurt to clean it.

Don't forget retorquing the manifold screws - particularly the lower rear. They do tend to work loose, particularly where the same screw clamps down on both iron and aluminum, or where the screw gets hot (like the lower rear.)

Use a shorty socket with inbuilt universal joint - you can get them at Sears - and torque to 19-21 pound-feet. If it's been running with loose screws for a while, you may be in for a manifold gasket, as it would have burned through. A job just difficult enough to be irritating...

the nss is my next course of action if it doesnt start in the morning, or tomorrow night. depends on if i remember to try and start it in the morning. ill be sure to update though. gotta love cheap heaps and the work it takes to get em running haha. thankfully this is a project and i enjoy working on rigs.

If it cranks but doesn't start, it's not the NSS.

any ideas as to what else it might be?

ok quick update. i went back and started the jeep. took a little bit and a few tries of 4-5 seconds of turning over for it to finally pick up and start. then it would start almost immediately after when i had to restart it. it would die after a little bit. sometimes it is by its self, and some times it is after i rev it a few times and let it some back from, say 2500, to idle speed it will die. so NSS is out. but it still wont even crank in neutral. on to the more pressing. one thing it is doing, is popping out of the intake. what causes that? im told a lean running condition can do it, but i dont know how to determine that or what causes it, on these motors. i believe the random dieing and popping are related. it mainly pops if i rev at WOT a few times. not rev sky high, just going WOT for a split second. what other things can i check?

let me recap all ive done: new tps and installed correctly(not set by me but i dont know how to do that), new plugs, wires, rotor, cap, fuel filter, air filter, crankshaft position sensor. new battery also. fresh fuel in the tank. i cant think of anything else ive done.

i guess my main concern right now is the popping from the intake

Check your firing order on the distributor cap. 1-5-3-6-2-4, clockwise with #1 being at about 4 o'clock when viewing from the passenger side fender area.

ive checked multiple times and i replaced the wires the same as they were. i have a haynes and have tried to match them up, but the cap i got has no number 1 on it. im about 100% sure theyre right. cause when it decides to run right, it runs amazing. it just doesnt last. i ordered a new CPS since i might have damaged the one and it not working right when hot. ill have it around Wednesday. anything else i can do in the mean time?

Popping back through the intake means you are firing a cylinder with a valve OPEN.

As the timing is controlled by the ECU, possible causes are more like a sticking or carbonized valve or slop in the timing chain, or it might have jumped a tooth.

A damaged CPS/CKP crank sensor might not put the timing out far enough, as the high-altitude crank sensors have quite an offset to them.

I don't think if the distributor shaft was badly worn or the distributor off a couple of teeth it would give you other problems than popping out of the intake.

well i played with the grounds. getting the block to cable ground off was ridiculous. i had to separate the neg cable from the plastic thing it travels down to and feed it through a small space as i turned the entire bold out of the block cause the ground cables were corroded together so they wouldnt spin separately. it was not hard, but time consuming. probably took me 20 minutes to get it off. but i rewrapped the neg battery cable in a couple layers of electrical tape and then put a series of zip ties down the cable on the newly wrapped side so it wouldnt come undone. i will replace it soon. i also replaces the firewall to head cable with 4 gauge wire. that little strap was pathetic and looked like it wanted to break apart.

so heres where im at now. it wont start by its self. if i spray some choke cleaner in the intake tube, and then crank it over it fires right away and then idles at 2500 haha. it after about a minute it calmed down and idles just fine. i even backed it in and out of the garage just cause it hasnt moved since i got it in the garage two weeks ago haha. shut it off, and wouldnt refire, till i sprayed some more ccc(and i mean a half second spray is all) in the intake tube. i got a fuel pressure gauge and i screwed it on the fuel rail and cycled the key 3-4 times. it never got over like 10psi or so. i didnt start it with the thing on cause i didnt know if it was good for the gauge or not. any ideas as to what i should do now?