OK guys, I have been working hard at getting this 88 comanche i bought last month running right. I have gotten a lot fixed, and still have some to go. I am trying to get a bad miss fixed that I just cant seem to run down. 88 auto, I6. It has about 111k original miles (per title, it could have been run with speedo unhooked). I have cleaned throttle body, checked and fixed vacum leaks, put in new 746 injectors, new tps, new iac. The previous owner put in new plugs, wires, and dist cap (prolly chasing the same problem). I pulled plugs and checked gap, checked spark on each. Coloration seemed to be eaqual on each.
When the engine idles it has a shake to it, like a miss. And when the truck is running and lugging in 3rd or 4th gear, it has a horrible shake, the whole truck shakes like one or two cylinders are not running.
BTW, it does have a bit of an exhaust leak. This miss seems too bad to blame on an exhaust leak, but who knows. I was hoing to fix the miss before I spent the time and money to fix the ex leak. I was figuring an new ex mainifold and O2 sensor when I do fix it.
So what should I try next? I hate to dive into ex mainifold and get that done and it still be running horrible.
Thanks!
(maybe it just needs a novak 5.3 conversion!! HEHEHE!)

 

Was it doing it before inj. replacement? If not you have a bad inj. somewhere.
If so you could have no inj. pulse at inj. harness.. check with node light, or you can unplug the inj(s) one by one if it gets worse that's a good one, no change bad one. Leave the ones that show no change unplugged so you do not forget them and check with node or circuit tester.
Also have you verified fuel pressure at 31#, if not do so, fuel filter?
Have you done or read any of Cruisers Renix tips?
C-101 connector believe you have one, may need cleaned.
Exhaust mani get one from a pull your part, have it repaired if need be "WAY" cheaper than a new one, less you are going performance.

 

NewKindOfClown, cruiser54, Dflinstone, are the renix masters, this link is a must
https://www.cherokeeforum.com/f51/cruiser54s-mostly-renix-tips-153657/

 

highmileage, yes it was doing it before the injector swap. That is one reason I did the injector swap was to see if it would fix this problem. It idles a lot better now, but still not perfect. And it didn't help the miss/vibration under load at all. Yes, I have read all of cruiser's tips.
Could a bad reading to the o2 sensor from the leak cause this? I wouldn't think the leak is bad enough yet to get a false reading to the o2, and I also thought that it would only adjust mixture, not cause a dead miss.
What really throws me off is how uniform all of the plugs look. It looks like they are all getting the same amount of fuel burn. Yes, all injectors are getting fire. I checked that before and after replacement.
I am just stumped. I have seen enough to understand y they dumped Renault. I think they were stupid for using them to start with. Musta been $$$$. I miss my CJ258 with motorcraft carb. lol

 

Don't forget
Dflinstone

 

My 88 had a seeking idle with a bad o2 sensor, short time at 800rpm short time at 500rpm. Dflinstone with his 90 had the same problem. Have you adjusted your tps per cruisers instructions? Do all his tips. It will save you a headache I promise. Clean iac? Check fuel filter and pressure at the rail for fun.
Goodluck

 

Agreed^. There is a "dynamic" compression test. I would first pull each plug wire loose from the cap and set them back 1/2 in. Now start it and go around one at a time lifting the wire off the cap. You will be able to hear (and maybe feel) it sparking. The idea is the more the rpm's drop, the more that cylinder was doing. With that you can find which cyls are the problem. I might check for a crisp blue spark, especially the suspect plugs.

Our CPS test only takes a couple of minutes. I recommend ruling that trickster out. Three minutes well spent. Likewise allot of threads end with grounds ending up being the problem. (a buzzing fuel pump relay the other day!)The sensor ground test is a minimum must.

If my 90 had a C-101 I would eliminate it, or at least have cleaned it. (your injector wires go through there)

I've got to mention...the book is WRONG! #1 is at 5:00 as viewed from the side, (153624 clockwise).

 

READ the tips? That doesn't do any good unless you also PERFORM the tips.

 

^^^^^ This

 

That's like putting the vacuum cleaner in a room that needs vacuuming and hoping you'll come back to a clean room......

 

Hey alabender, don't let Cruser put you off. This is a pretty friendly forum, with just a few grumpy old farts. And WELCOME (Btw). I sort of like your problem...there is something screwy going on there. Besides following Cruisers tips, (grounds, C-101, and ICU contacts), are on my mind, A "niod liight" will tell you if the injector's are getting power. Up to there it's all stuff to do anytime. Fuel pressure tester is free, (in the end) at auto zone here. The signal from the CPS works in pairs, 120* apart. (the cam sensor in the dizzy is not it, it will run fine with that unplugged). The <$5 digital meter from Harbor Freight actually will work OK, at least for a while.

 

I'm working on a new revision for my tips.

You print them out. Put them in order from top to bottom so #1 is on the first page.

Insert the pages into a plastic sleeve like you get at Staples.

After dark, place the sleeve face down so the first page is facing your valve cover.

Shut the hood slowly so as to not displace the sleeve.

By sunrise when you open your hood, ALL the Tips will be done.

.

 

LOL. Thanks dflinstone. Cruiser can give me a hard time all he wants, he already helped me chase down a trans shifting problem. I have gone through and done several ground checks. I will do the running comp test. I have checked/cleaned the 101 and no difference. I have not done a CPS test yet either. Those two will be next.
Cruiser, the post u did on indexing the dist I do not completely understand per the instructions. What would be the need for this and what does it correct exactly? I follow it until you take it out and put it in a vice and start cutting on it, then im kinda lost as to exactly what your deing and why. Im sure its something simple, but I just don't follow.
Cruiser, I followed your directions and left the papers under the hood all weekend! I think it gained about 25 hp, but still misses.
I will not have a chance to mess with it for a few days, but I will post what I find for future references.
I was thinking about pulling the head and doing little porting and adding a cam (this is a project truck), but the more I mess with this renix stuff the more I am thinking 5.3 at some point in the future. I have had some mid 90s Cherokee HOs and loved them. If I could get it to purr and be reliable it would save $$ on a swap.
Thanks guys

 

What don't you understand about the indexing?

IF it is off, then you pull the dizzy, cut the ears off of it so it can be turned when reinstalled.

 

He neglected to check with me before he posted that. He's suggesting you cut an OLD cap, to actually see if the rotor is aligned with the electrode. He has modified his CPS to run more advance. You can put the CPS in a vice, and smack it to move it's sensor forward. Now with our "static" computer controlled advance, the game changes. (hence the carnage of the tab). The spark needs to leave the rotor, at O*, or even after TDC, then still make the trip, maybe well over 20* advanced. It's only mildly complicated. Because Renix has a knock sensor (you test by tapping on it, and listening to the engine). Renix will retard the spark if it "pre-detonates" , or "pings", so you can just "bang" it more advanced, and let the ECU figure it out. Max advance is always the goal. I'm busy enough now, but some day I'll do all that and see if I can get up toward 25 MPG with premium. (got her to 22 ish, highway, with almost 280K, on 87 octane). (Don't forget 20* on the damper pulley is only 10* on the dizzy, turning 1/2 speed).

Please test your CPS. Minimum .35 AC volts from it, unplugged. 200 Ohm's plus/minus 75, but the ACV is what the ECU sees. Also that dynamic compression I mentioned might be helpful. I'd need to dig a bit to see which pairs are 120* apart.

If someone with a DRB-II scanner want's to share their timing curve, I'm all ears.