Renix Love Hate relationship

Hey guys -

Yes I searched but it seems that I suffer from a Renix nightmare. Everything and I mean everything has been checked or tested tightened or wiggled. Long story short it runs like crap at low RMP's off the line. Sometimes I can't even get avobe 1500 rpm without it kicking and bucking. A bonus feature is that I have toasted two computers. But it only happens occasionally and has been to jeep "specialists" for diagnosis and throws no codes. Even when it's happening. Renix guys please help......

Gunner

89 XJ
11" lift
38's 4:1 Klune V
4340 shafts in D30 detroit (haven't broke yet) Die trying included
8.8 rear welded
4.0 renix that I love and hate
Hydro assist

Possible timing issue. If everything electrical has been checked like you say... It could be a timing chain issue but, if these guru's have checked it like you say it couldn't be.

Are you sure it's not electrical?

Just a guess but, check ALL your grounds. Clean or replace every one you can find and find & do the same to the rest.

This is a common problem with my other habbit (2.3l turbo Fords) and you seem to be having a lot of the same symptoms.

To : Dirt

The timing was "supposed" to be in check after a new distrubutor.(with the advance/retard timing clicker they have) And it has been rumored that any oil in the the bottom of the distributor will fry the computer... So I'm told. Not real sure how it gets in there but there was a little.

To flyin.

I have not only checked and cleaned the grounds I have added a few. When the computer took a dive it was like someone unplugged the truck... Just dead all of a sudden.

SO my frustration only happens every once in a while. I am almost positive that it is electrical... I think.. It;s almost like one of the many sensors is having a fit somtimes. I only have 124K on the odo and its garaged. I am pulling my hair out. It's hard to crawl an obsticle and look cool while it's having a siezure.......

Gunner

The distributer has been changed? But your problem is intermittent?

Renix.. Stumbling at low RPM's, Try EGR.. look to see that the flying saucer looking thing by the exhaust manifold the little rod is moving all the way in and out. also check the vacumn to this. Then the C-101 connector, Its up on top of the Master Cylinder on the firewall. You will need a manual to find out which one it is, Clean it or what i did, make it a permanant connection... Its hard to diagnose over the internet, I know the system pretty well. Its not easy when things go south. Good Luck

Completely intermittent. Seriously I was in Moab heading towards potato salad hill and it would barley move. Sat there for a minute got out the electrical tester and got to everything I could and found nothing. Jiggeled this and that and after 10 min of this I got in and drove off like nothing happened. ... A little embarassing but I got down the road. But it didn't happen again until today in town at several stop lights... Got into the neighborhood and all seemed well.... Seems if there is no body to see it, that it doesn't happen... Kinda like a tree falling in the woods and no body was around to hear it.

XJING said:

Renix.. Stumbling at low RPM's, Try EGR.. look to see that the flying saucer looking thing by the exhaust manifold the little rod is moving all the way in and out. also check the vacumn to this. Then the C-101 connector, Its up on top of the Master Cylinder on the firewall. You will need a manual to find out which one it is, Clean it or what i did, make it a permanant connection... Its hard to diagnose over the internet, I know the system pretty well. Its not easy when things go south. Good Luck

Click to expand...

Oh wow! I'll bet he's right. You can also plug it off to check it.

Alright --- Then I have a really dumb question.... How do you check it --
The EGR is Parallel to the intake right??? I got my fingers in there and couldn't buge it. The "flying sauser thing" thats hooked to it how do I check that? Is it possible to bypass the whole thing... Sorry this is one thing I haven't messed with ( or should have) I bet there are threads on this.

Gunner

A couple things to look into and bear in mind...

RENIX won't "throw codes" - it's pre-OBD. The best you can do is get realtime data from the ECM. Most RENIX system diagnosis is done with a decent DMM anyhow...

I know you said "everything," but have you checked/replaced the TPS? Adjusted it? I had a wicked flat spot on my 88 right where I cruise, and it was the TPS.

EGR gasket isn't burned through, is it? That happens every now and again, and will give you a brutal vacuum leak. If you replace the gasket, a light coat of RTV Copper on both sides won't go amiss, and you should be able to replace those Torx bolts with either 5/16"-18 or 3/8"-16 hex heads, which makes them easier to get to next time. As I recall, the gasket and valve are both OEMR only. If the valve is half shot but the gasket is still sealing, you can disconnect the EGR solenoid (driver's side fenderwell) to turn it off entirely. Also, if you have a hand vacuum pump, there are a couple quick tests you can do:
A) With the engine OFF, attach the pump to the "flying saucer thingy" on the EGR valve (vacuum transducer. I'm not entirely sure what it does offhand) and pull about 15" of vacuum. Let it sit for about a minute, and see if it leaks down. If it does, repalce the valve. If that passes...
B) Release the vacuum, leave the pump connected, and start the engine. Let it idle, and pull a vacuum - the engine should stumble, and maybe even cut off (since you're leaning it out.) If that happens, the valve is working and the passage is clean, shift your attention elsewhere.

If you can detail what you've done so far - hopefully in order of your doing it, I can give you more ideas. I've got four RENIX rigs myself, and I think I'm fairly familiar with the system... Maybe we can come up with something that would work for you - but there's a starting point.

5-90

I have heard about you 5-90

Can I say a little flattered that you would respond to my problem...

You know your stuff. But with a 17 year old motor would I be ahead to just replace the old with the new??? I havent priced them but is it like putting new tires on a truck that doesn't run??

Gunner

Why not? I've got an 18-year-old engine with 250Kmiles on it, and it runs just fine. Most of what I've been replacing on it is original anyhow, and from reports I've been collecting, 200kmiles is "break-in" mileage for the RENIX engines. They used about the same high-nickel alloy for the castings as ChryCo did for the Hemi engines - too bad ChryCo downgraded the nickel content somewhat in 1991. Too bad ChryCo started lightening the block in 1991 for reasons of NVH (come on, people - it's a truck, not a damn Lincoln or a Caddy! If I want quiet and smooth, that's what I'll get. As it happens, I happen to like a little engine noise and vibration - reminds me I'm driving, and not riding my bicycle...)

RENIX ECM's are generally not prone to failure - to date, I've only heard of two that required replacing - and I've got one on the shelf here. Both suffered from fully cooked injector driver transistors. If you've still got the two you've "cooked," I'd be interested in getting those from you - I've got plans for the RENIX system, and some more guinea pigs wouldn't do any harm.

Anyhow, as long as the core electronics are in good shape, there's no reason that a sensor change (for a failing unit) wouldn't solve problems - I've done it.

And, frankly, I'll keep my RENIX rigs over ChryCo OBD any day - but I cut my teeth on 50's, 60's, and 70's muscle cars, and I'm used to doing troubleshooting with my noodle and a meter rather than codes anyhow.

5-90

(Oh - I should probably add that I'm flattered by your praise. I try to know what I'm working on, and I'd guess that my reputation in various technical circles comes from being right more often than I'm wrong. I won't say I'm always right - but I seem to be correct most of the time, and that's enough for me. I'm only human, after all...)

When my EGR vacuum solenoid started going out it would bog, stall, stumble, etc. The easy way to test if that is the problem is simply to unplug the outlet side of the vacuum line on it (it's on the drivers side fender area of the engine bay, right next to the airbox or your aftermarket intake) and either it makes an immediate difference, or you can test drive it to see.

When mine went bad I thought my timing chain had skipped a few teeth or something. Ran like crap until over 2000 rpms. It's still unplugged today .

Have you checked your wiring harness where it goes through the front grill and radiator support? That is the most common failure cause on older Renix rigs. The loom rubs and wears through, grounding one of several wires, including the yellow fuel pump power supply that goes to the resistor block on the driver's side inner fender.

99% of Renix issues arise from old/worm out wiring and connectors. The system itself is virtually bulletproof, brutally simple, and can accomadate a wide variety of fuel and engine mods.

Check your fuel pressure at the rail also. My 89 had a hard flat spot on acceleration. Checked everything electronically possible, and found nothing. I thought it was an electronic problem. Turned out I had 20 psi at the rail. The hose inside the fuel tank on the pump had slipped off about half way and was not supplying full pressure.
Just another thing to rule out.

Gunner, where are you located in Colorado. If you can get it here I can take a look at it for you.

I am actually down in Grand Juntion. It wouldn't be very easy to get it to Loveland. It's not running real great right now and I don't have a rig that would haul it on a trailer. I've got some tinkerig to do to it starting with the EGR, basically becasue that is the only original part still left that hasn't been replaced due to gremlin problems... If it isn't the problem (which is likely) then I'll run through the wiring again.. Unless of coarse you intend to pass through GJ for some reason in the future

If all else fails Google Megasquirt. At some point my renix will go byebye and be replaced with one controling fuel & spark and using a Ford EDIS system. No more dizzy, birng on the deep water.

If the cps is not the problem, intermittent problems can many times be traced to the C101 connector. It is the one mounted on the bracket above the brake booster. There is actually a service bulletin that has you cutting it out and wiring around it. I have done that on two vehicles now. I do it as a simple precaution. I'm and electrical engineer so the splicing is old hat for me. What I can't understand is your burning up computers. I have never seen a Renix go bad. My first reaction is that whoever said they were blown was looking for an easy buck.

I would unplug and reseat the C101 and bulkhead connectors as a starting point. I would most likely nuke the connector on the cps and wire it directly as well.

A friend of mine who runs a repair shop just had to replace the ECU in an 89. The ECU failed because the alternator went back and cooked it(high voltage). So there is one example of why they go out .