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Look for person or shop knowledgeable with Renix issues

D

DRMB Crash

NAXJA Forum User
Location
California
Hey guys I'm new but at my wits end. I got a new (to me) xj it's an 89 and it idles fine but back fires and pops like crazy at any Ron over 1k. It has an after market onboard system and everything's looks to be reading ok except it's rich at idle. Enters closed loop sometimes sometimes it stays in open loop. The guy I bought it from have up on it after replacing what looks like ever sensor on it. TPS, CPS, MAP, MAT, 02, and Coolant temp. So if no one has had a fix for this I can include the numbers from the onboard system. Or anyone knows a shop or person around Sacramento I'd just like to get this thing running before spring. Thx guys
 
Blondejon will probably have an answer for you but it is probably the TPS. They can be bad from the factory and it sounds like an issue I was having with my 88 for a bit.

Im taking a guess here but try unplugging the TPS while running to see if it does anything different. And you can also try adjusting the TPS to see if it runs any better.
 
Yea I've tried 2 different new TPS and it doesn't seem to make a difference and that's with them adjusted to 18* was told between 15 and 20 so set it to 18. The funny thing is is runs better with the MAT unplugged you can drive it but it has a bad random miss with it unplugged. With all the sensor plugged in it won't go above 1k-2k depending on how much of a pain it feels like being. I'll post all the different numbers later tonight. It has some kind of aftermarket Renix monitoring system installed pretty cool.
 
My leading suspects would be incorrect spark plug wiring, bad coil, distributor indexing, or a badly indexed cam. Once I actually had a CPS cause a similar problem (weird).
 
New correct tapped plugs at .035? New wires. Now the dist could be clocked wrong and coil could be bad. But the timing shows around 15 tbd on the monitoring system I believe I'll. Heck after work. But it did come with another random dist in the rear. The cam never been messed with from what I was told but maybe it jumped a tooth?
 
I'd start with the cheap stuff. Also, I believe it's unlikely the dist jumped a tooth, but definitely check that it's indexed correctly since it has been replaced.

verify grounds are good and shiny, check the vacuum lines, inspect wiring harnesses and plug connections for wear and corrosion.

Don't assume that this step has been done by the previous owner, seems like they spent a lot of money chasing this problem.

It's time consuming and expensive to overlook a basic inspection.

There's a lot of information on the forum regarding these types of diagnoses, check out the OEM and modified tech forums here those guys are gonna be the ones to ask
 
Last edited:
Ok I'll deff check that out I originally came here because I'm in Sacramento and if anyone knew a shop or local guy I'd really appreciate the help.
 
These are the readings from the Renix onboard data system

MAP. 7.6
VAC. 8.8
WATER TEMP. D. 210* m. 150*
AIR TEMP. 53*
RPM. 700
VLT. 14.0v
O2 SENSOR VLT. 0.72v
EX STATUS. Rich
VHT. 14.0v
LOOP STATUS. Open
EGR. Off
TPS. 16*
TH POSITION. Closed
TIMING ADVANCE. 15btd




WOT goes to red line. But if you try to hold a specific RPM it back fires and misses.

After warming up dash guard shows 230 system shows 170.

Goes WOT very easy after warming up. Still has trouble holding an RPM other then WOT.
 
in the water temp reading the "D is for dash gauge" and "M is for the onboard system meter" even after heating up and the dash showing it getting hot at 230 240ish (the electric cooling fan is missing so it gets warm at idle and after the WOT snaps) the renix system reader shows only 170.
 
Check all your vacuum connections. If you have a vacuum leak the MAP will tell the ECM to dump way too much fuel. Are those the original injectors?
 
DRMB Crash said:
These are the readings from the Renix onboard data system

MAP. 7.6
VAC. 8.8
WATER TEMP. D. 210* m. 150*
AIR TEMP. 53*
RPM. 700
VLT. 14.0v
O2 SENSOR VLT. 0.72v
EX STATUS. Rich
VHT. 14.0v
LOOP STATUS. Open
EGR. Off
TPS. 16*
TH POSITION. Closed
TIMING ADVANCE. 15btd




WOT goes to red line. But if you try to hold a specific RPM it back fires and misses.

After warming up dash guard shows 230 system shows 170.

Goes WOT very easy after warming up. Still has trouble holding an RPM other then WOT.
Click to expand...

Looking at those numbers, your O2 sensor is trying to lean out the motor but is pegged out. Leads me to think there is a problem with your injectors.
 
Test then replace as needed all sensors. My
Money is on dizzy indexing, intake exhaust vacuum leaks , bad tps,
Cps, o2.
A bad coolant sensor will screw
Things up. Clean your grounds before you do anythig.
 
I bet dizzy is off or cam sensor is bad??? Timing chain didnt jump ? No leaks ?
 
No leaks. Most sensors are new. The things that's weird is if you mat it to the floor it's rev to red line strong and fast no misses. But if you try to hold it at any RPM it backfires and pops like it has antilag on a turbo setup
 
Grounds on a renix are key. Although the few I’ve owned never had a grounding issue, it is a common problem. Misfiring throughout the rpm range?

What spark plugs are being used?
Anything but a copper plug(champions preferred) are a big no no
Especially in the renix
 
Nice glad to hear ! I had a feeling it was the dizzy indexing
 
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