Whats wrong with my Renix.

[Ecomike]

I've already checked the TPS with an analog volt meter and its within spec and works smoothly.

You might want to check fuel pressure while it is running. Many have reported multiple new fuel pump failures. Also check the dizzy for wear in the shaft/bearing. O2 sensor? Lastly check the sensors, live, while running with the analog multimeter.

 

[DansGreyMj]

You might want to check fuel pressure while it is running. Many have reported multiple new fuel pump failures. Also check the dizzy for wear in the shaft/bearing. O2 sensor? Lastly check the sensors, live, while running with the analog multimeter.

Fuel pressure is right where it should be, i was thinking of putting the old injectors in to see what happened, but they got replaced because half of them leaked. Should i try it anyway?

 

[Ecomike]

I doubt it is the injectors. Sounds like a huge fuel pressure surge, or electrical problem.

 

[Ecomike]

My thought would be that your injectors are too large. Pull the plugs, take a picture and post it up.

My thinking is that if the injectors were to large the problem would be at idle, not during increased fuel demand. Am I missing something?

 

[5-90]

My MJ did the same thing.....I replaced the Manifold Air Temp sensor, added an extra ground from the battery to the front sheetmetal, and cleaned all the other grounds really well. Don't know which one fixed it, but now it works fine........

Given the way RENIX is built, I'm inclined to think it's a combination of cleaning up the grounds and improving the ground for the chassis.

OEM, the chassis grounds through the engine block, which is silly (and one area where AMC screwed up.) That's why I offer the additional chassis ground as an option on my RENIX kits - and I've gotten a lot of good reports from the field on it.

I do also suggest that the contact area around the firewall ground strap be cleaned down to bare metal and a corrosion inhibitor (you can find something in your hardware store's electrical section, I like Gardner-Bender Ox-Gard, myself...) on assembly. Clean the lugs as required with a wire brush or some very fine (320-grit or finer) sandpaper. The objective isn't to remove material, just remove crud.

@OP - this is probably what I'd do next. You're saying you've verified operation of the TPS (did you use an analogue meter, or a digital? You can backprobe and check voltage KOEO or KOER, or remove the connexion and check resistance KOEO.) This sounds for all the world like my 88 did when it developed a "flat spot" around 2300-2600rpm, and replace the TPS nailed it.

I've been kicking this around, and it seems as though you've gotten all of the other likely suspects.

The reason RENIX benefits from an improved ground return is simple - the ECU is mounted inside the cabin, and the ground reference plane is the chassis sheetmetal. If the ground starts to get stupid on you (at the firewall strap or at the engine connexion,) your sensor signals will start to be corrupted by the floating ground. Adding a ground directly from the battery to the chassis (treat as for the firewall ground strap, above) helps to prevent this as an issue.

 

[Ecomike]

KOEO or KOER?

 

[magimerlin]

KOEO or KOER?

key on engine off

key on engine running

 

[magimerlin]

when did this problem start. was it progressive or did it just"happen over night"?
in your vid it sounds more like something is hitting something. Is it just popping loud our is it really sound like something is hitting, in person? I know you replaced all that stuff and it happens only at a select rpm range but is fine before and after that range correct? just want to make sure I understand a few things.

Have you done anything with the map sensor at all or your knock sensor.

here is a link that has helped me out more times then not on Renix sensors...
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

 

[8Mud]

Most of the 2K misses I've seen are from a lean burn condition. Various causes, O2 sensor seems likely, but tends to act up more under load (while driving and mildly accelerating) at around 2K. And when it does act up the top RPM's tend to drop off.
I'd check the easy stuff first, like looking in the engine bay when it's dark outside, you may see high voltage to ground that way and be able to trace down where the leak is.
I've never had exactly what you seem to be experiencing, a 2K miss with the Jeep parked and not driving it.
Some easy things to check might be spark plug cable ohms. High ohms in the cables can cause the spark to break down at higher RPM's.
Like Mike said their may be an excess of resistance in the CPS wiring, though I've found CPS troubles to often be noticeable at lower RPM's.
Is it possible you crossed up the injector plugs? It will run if you cross a couple up, but likely not well.

 

[DansGreyMj]

I can rule out the injectors, threw in a stock set and still the same problem. I'm going to try and check some of the other thing you guys suggested. Keep your fingers crossed.

 

[RedJeep2.0]

That just happen to my buddys jeep.
Take your cat and muffler off.
Your cat melted and is stoping the air flow.

At an idle out your hand at the end of the of the pipe and feel how much air is not coming out!!

 

[DansGreyMj]

I was actually just wondering if it could be the cat, i'll have to try it in the morning so i'll be sure its cool.

I did clean the ground though and added a 4ga amp wire from the batery neg to the inner fender and there was no improvement.

 

[DansGreyMj]

Theres actually a ton of air coming out of the exhaust, it has gotten harder for me to duplicate the symptoms revving it up in my driveway but it still does in when I am out on the highway.

 

[Mike CZJ]

i have the same problem right now...

 

[DansGreyMj]

I found some bad wire connections at the ecu
First off the CPS wires are held on with butt connectors, and there is an extra set of vio/wht & wht/blk wires going to the ecu.

Then there is this black and yellow wire that i can't find on the haynes diagram

Then there is the fact that this isn't the original ecu

Does anybody know where these extra wires connect to? Could they be for an auto considering mine is a five speed? The blck/yellow wire has some solder on the end of it but i cannot find a corresponding wire.

 

[DansGreyMj]

i have the same problem right now...

Hopefully we can get this figured out quickly.

 

[Ecomike]

The cat internals can break loose, and when they do they sometimes make a rattling sound, that comes and goes. It can also periodically rattle into just the right location to block the exhaust, then a bumb in the road can knock it loose again. In other words it can randomly block the exhaust cause an intermittent problem.

 

[Ecomike]

Hopefully we can get this figured out quickly.

PM me an email address.

 

[DansGreyMj]

I just pulled of some wire looms under the hood to reveal more hacked wiring. The wierd thing is that the jeep drove great and never gave me any trouble and now all this crap shows up.

 

[Mike CZJ]

its not the cat on my Jeep... not running a cat.