I swapped out my injectors to BOSCH 746's. (used but cleaned & flow matched) I have a pretty ruff idle & hic up even at advanced RPM"s. I'm running a can of BG44K through her now & after almost the full tank the sputter is lingering. No better.
All other components have been replaced (IAC, TPS, MAP, CTS, O2, CPS, plugs & plug wires, dizzy cap, rotor, ignition coil, ICM.
I cleaned & moved the IAT to the air box. I have tested all of the sensors per multimeter & all are well within specs & adjusted properly. Throttle body has been spit shined with a new Felpro gasket.
I have a new BOSCH fuel pump & FUEL PRESSURE regulator (NAPA).
All connections have been re-freshed per Cruiser's "PINK". I have cleaned & up-graded all grounds & terminals.
This morning I tested the FP. When key switches to ON I get 31 right away. I hear the pump. I have 31 & 39 respectively at IDLE.
When I shut down My pressure rises about 5 psi. After 30 minutes it's still reading 31+ psi. Hasn't dropped at all. After 1 hour it's reading 25 psi.

I'm not so sure this pressure reading staying this high for this length of time is normal?

I'm wondering if I may have a Fuel Pressure regulator problem causing a weird fuel delivery while running causing the popping & skipping? Fuel filter is brand new btw.
I'm going to by-pass the ballast resistor with a permanent jumper. I've heard a gimpy BR may cause some issues even while running but I don't know if that's true?

I'm also getting a HOT CAT. & my new Champion coppers (.35 gap) are showing a warm & lean condition.

Ideas?

 

 

The cat is suppose to get hot, that's how you know it's working. (The catalytic element causes any unburnt fuel to burn). (fuel mix right against metal, and in the gap above the piston rings might not burn in the cylinder).

Boy, how irritating, after what you have been through! I might check the CPS output, that only takes two minutes. Then the TPS adjustment? I guess you did that but maybe double check it? Idk there.

It sounds like your fuel pressure is OK. The 280 155 746 HAD been an experiment, but myself and at least a couple others are doing fine with them.
You DID get "155 746" I hope. I don't even know if there is a "150 746".

Being your pressure seems OK, gotta doubt it's the resistor. Still though it's easy enough to bypass it at least to diagnose.

Since you have done about everything I'm at a loss. In my experience a restricted exhaust shows up as a lack of power. Still the vacuum test seems easy enough. I can't say from experience how well it works. Once on an old "K" car, when I loosened the header pipe to manifold bolts, (making a leak), it was hands down night and day, ran great. (clogged cat)

 

Yea but My cat is getting CHERRY RED HOT. It's melted my undercoat. Plugs are showing a lean look too.
My CPS is spot on with voltage. My TPS is adjusted perfectly.
As for the injectors I just don't know. They aren't leaking inside or out. I may have a sticky one or 2 that's why I'm running the BG44K through there.

I can't find a vacuum leak. All my hoses are new from front to back. MAP hose is new.

Another mystery.

I got 6 new injectors in the mail today from PrecicionInjectors as a replacement for the set I took out. I may swap & just see what happens???

thanks DFlint.......

 

I just opened the "new" injectors. Made by BOSCH for Ford. Metal body 4 hole.
Numbers are 280 150 939. Those numbers ring a bell DFlint ?

I may try em when I get a chance to swap out.......

 

CRUISER’S VACUUM TEST FOR EXHAUST RESTRICTION

Your vacuum gauge should come with an instruction booklet outlining the procedure. Hook the vacuum gauge up to a source on the intake manifold. Start the engine and note the vacuum reading. Usually 17 to 21 inches of vacuum. Throttle the engine up to 2,000 to 2,500 RPM for 20 seconds or so and the vacuum reading should stabilize to the same reading you got at idle. Let the throttle snap shut. The vacuum reading should shoot up about 5 inches of vacuum higher for a second and then come quickly down to the original reading. If the vacuum reading stays high and comes down slowly with jerky needle movements, you have an exhaust restriction.

 

10 4 thanks I'll check it tonight........

 

Those look great, I guess. They are 19#. Their resistance is about 2 ohms lower, 14 instead of 16. I really don't know that that matters. Maybe a tad more current will go through the ECU, but I'm not sure.

The red cat may well mean too much fuel out the pipe, A miss? PLEASE, Check your wires on the cap one more time. #1 at 5:00 viewed from the side. (the book is wrong there). Then clockwise, 153624. That could explain both the missing and the red cat.

Back on the 746. The 150 is a significantly higher flow rate injector...maybe enough to overheat the cat. Just putten that out there, it's not hard to be one number off. 280-155-746 would be correct.

 

19# Bosch 746 Injectors - SET OF 6- SONIC CLEANED,REBUILT, FLOWED - 0280155746

Yep..that's them. I'll check my wires again but I wasn't drinkin when I well you know what I mean........

 

Did you ever resolve this issue? I am struggling with the same symptoms. After some research I came across something saying it is necessary to change your fuel rail and regulator to a 91 + when you upgrade to the 746’s. Can anyone give me some insight on this?

 

totally false.

 

I’m stumped. I’m having the same scenario. I was really hoping this would be the golden ticket to resolving the stumbling.

 

Have you visited www.cruiser54.com and done the first five tips yet?
What year is your Cherokee?

 

I have done 1345 but I have not messed with the icm. I will go over the five tomorrow. (4 since I have a 1990). Thank you for all you do, I am constantly coming across your post and appreciate you for doing them. I am struggling with brain damage after getting hit on the freeway riding my motorcycle home from work. My xj is my only “release” and I want her running right.

 

For what it's worth, my Renix sits happily right at 40PSI all the time with some mild variation based on throttle input, and I have no problems whatsoever. Yes, I have backup-tested the gauge, the reading is correct. I used to have lots of throttle input issues and would pop and sputter with the old factory one-hole injectors, but I replaced all with the tried-and-tested Volvo 5-holers and have only had a few problems since, all of which were unrelated to the injectors. I didn't replace my fuel rail either, the 746's worked fine without a change, they were 100% plug-and-play. (I even get a consistent 20mpg on the highway, which is nice.)

Though, um... I should mention that since I was poor, when I had to replace the destroyed exhaust, I couldn't afford a new cat and the old one actually was plugged up. An arrangement was made that allowed me to have a vehicle and drive it every day.

The things you've replaced and tested on the jeep seems to suggest you shouldn't still be having the problems you are. My only possible question is about timing and plug order. If you maybe fudged the order, that could explain some of this.

Edit: It's a shame that RENIX-style AMC diagnosing tools are so hard to come by. Wasn't somebody making them nowadays for people?

Edit 2: https://nickintimedesign.com/product...ne-monitor-ii/ Found it. A bit spendy, but at the end of the day it's something you can use again should the need arise.