Newbie Renix Stroker Tuning Help Needed

[wolfehound428]

First post on the forum, although I have used a lot of the information here to build a 4.6 stroker for my daughter '89 XJ, Thank you for all the great information that has alllowed me to assemble the engine.

Here is what I built:
'89 Renix Block - decked .020
.030 Over Pistons 24 cc dish
258 rods
Renix Head, mild clean up
Stock intake
24 # injectors
68-201-4 Comp Cam
Bored TB - TPS set at 3.94 v - .830x of input 4.75v
Adjustable FPR - set at 40 #s
Adjustable MAP - set st 5.0v
Pace Setter Header
Borla CAT back exhaust
new battery cables and chassis grounds

This is the second engine in this XJ, we received this from my father in law for free for my daughter w/ a siezed engine. I took the easy way out the first time and put in a "good" used engine. It ran great w/ no issues for 500 miles then the bottom end gave out. No more easy way out and time for a rebuild and might as well stroke it if I have to buy a crankshaft any how.

The issue I am having now is the engine will idle at ~500 rpms and is way rich or idles low then dies. It appears the system is staying in open loop and will not read the O2 sensor to adjust the A/F ratio to allow it to idle. On initial cold start it idles fine for a few second at ~ 900-1000 then slow to 500 and is very rough, then back to 1000 and smooth, then back to 500 and rough, the back to 1000 and smooth the back to 500 and rough then loads up and dies. When warm it fights to idle at 500. Touch the throttle to bring up to 2500 rpm and it revs up nicely and cleans up from being rich smooths out with black soot flying out of teh tail pipe, although as soon as you let off to allow to return to idle it fights to idle then dies. Power is so- so. During the rough low idle I have unplugger the IAC w/ no change in idle, then unpluged the TPS with no change in idle. I have the service manual and have been following the diagnostics to check the sensors and have found all to be w/in spec. The O2 sensor reads 2.65v w/ key on engine off and quickly fall to .5v after start. I have checked all the ground connections. I am at wits end and would like to know where to look for solutions.

Thank you

Ron W

[yuppiexj]

It sounds like the MAP sensor is not connected to manifold vacuum.
Did you use the original plastic vacuum tube? It's probably cracked.
Sometimes a quick backfire will pop the Throttle body end out of place.
You will have similar symptoms and a slightly audible vacuum leak.

I proactively replace the map tube with Brake tubing of similar diameter using the OEM rubber ends.
Cheap permanent fix that will never get brittle and crack.

[wolfehound428]

Thank you for the suggestion. I have checked this line and it is sound w/o any leaks, although I will replace w/ the brake tubing as this sound like a permanent fix.

I have been working to sort this out w/ all the suggestion from this forum and the Renix Power forum.

OK, here is where I am today. Sorry at the beginning for the long post.
I have gone through all grounds and connectors. Took connectors apart and
checked for corrosion, did not find any bad, although just the exercise may have
helped, and reconnected. All ground were good. I did find a bare wire at the
output of the O2 heater relay, not broken or burnt, just bare. While I was
there I also cleaned all connections at the relays. During checking I also
checked for out put voltage to the O2 heater, found none. I checked the relay
and found it to wired incorrectly, not allowing voltage out to the O2 sensor.
Switched the wires and now have 12.5v at test connector 2-9 as per the manual.
All this gained a small increase in idle speed, no more complete shutoff, still
way rich and slow.
I changed the injectors back to the stock 20#s. It now idles better,
although still slow. So I started playing w/ the TPS and would get a slight
increase in speed although not consistent. Shut it off to hook up the fuel
pressure gauge and upon restart it idled at 2000rpm, progress, it is now doing
something different.
Shut it of again and restarted, back to low idle. Play w/ the TPS some more and
would get a slight change in idle speed to ~ 750rpm, Shutoff and restarted, back
to 2000RPM. Shut off and restart, back to slow. Replaced the TPS w/ one I had
in the garage, condition unknown, and found the same conditions.

It still is running ever so slightly rich at low idle, if I open the throttle
ever so slightly the idle increases to ~1000 and it cleans right up and smooths
out. With the 24's it would take 2000 rpm and 30+ seconds to clean up and never
really did fully clean up.

I drove it to work today, first time out of the garage for any distance, about
8-9 miles mostly high way, and the acceleration is excellent, about what was
expected for this combination. Above idle it is smooth and performs well. When I
pulled into the parking lot the idle was below 500 and it did stall before I
could catch it.

I pulled a plug last evening and the black soot was beginning to clean off,
still black w/ a white tip . I will go out at lunch today and pull a couple to
check for condition. I was hoping a little run time would help clean out all
the crud from before.

I feel better that the solution is close at hand.

Thank you for the help

Ron W

[yuppiexj]

This sounds very similar to a post on the RENIXPower yahoo group I mod.

[wolfehound428]

Yes, same person, same issue.
Hoping to catch different audiences.
Ron W

[bpranes]

Thank you for the suggestion. I have checked this line and it is sound w/o any leaks, although I will replace w/ the brake tubing as this sound like a permanent fix.

I have been working to sort this out w/ all the suggestion from this forum and the Renix Power forum.

OK, here is where I am today. Sorry at the beginning for the long post.
I have gone through all grounds and connectors. Took connectors apart and
checked for corrosion, did not find any bad, although just the exercise may have
helped, and reconnected. All ground were good. I did find a bare wire at the
output of the O2 heater relay, not broken or burnt, just bare. While I was
there I also cleaned all connections at the relays. During checking I also
checked for out put voltage to the O2 heater, found none. I checked the relay
and found it to wired incorrectly, not allowing voltage out to the O2 sensor.
Switched the wires and now have 12.5v at test connector 2-9 as per the manual.
All this gained a small increase in idle speed, no more complete shutoff, still
way rich and slow.
I changed the injectors back to the stock 20#s. It now idles better,
although still slow. So I started playing w/ the TPS and would get a slight
increase in speed although not consistent. Shut it off to hook up the fuel
pressure gauge and upon restart it idled at 2000rpm, progress, it is now doing
something different.
Shut it of again and restarted, back to low idle. Play w/ the TPS some more and
would get a slight change in idle speed to ~ 750rpm, Shutoff and restarted, back
to 2000RPM. Shut off and restart, back to slow. Replaced the TPS w/ one I had
in the garage, condition unknown, and found the same conditions.

It still is running ever so slightly rich at low idle, if I open the throttle
ever so slightly the idle increases to ~1000 and it cleans right up and smooths
out. With the 24's it would take 2000 rpm and 30+ seconds to clean up and never
really did fully clean up.

I drove it to work today, first time out of the garage for any distance, about
8-9 miles mostly high way, and the acceleration is excellent, about what was
expected for this combination. Above idle it is smooth and performs well. When I
pulled into the parking lot the idle was below 500 and it did stall before I
could catch it.

I pulled a plug last evening and the black soot was beginning to clean off,
still black w/ a white tip . I will go out at lunch today and pull a couple to
check for condition. I was hoping a little run time would help clean out all
the crud from before.

I feel better that the solution is close at hand.

Thank you for the help

Ron W

Did you figure out the issue? I have a similar Renix build I just finished with the same issue of running rich and idling. Still do not have O2 sensor though, bunghole in new exhaust just has a plug in it temporarily. Hoping for a good change once O2 installed.

[NickInTimeFilms]

Although I can't quite comment on your idle issues, I can tell you 24lb/hr injectors were way too much for my Renix Stroker as well. The stock poundage seems to work just fine, though I feel a 20lb/hr would be about perfect. I bought some 19.4lb/hr 0-280-155-712 Bosch Injectors which make a good EV6 4 Hole upgrade.

If you have a scan tool, check that your Short Term Fuel Trim is metering properly when it goes into closed loop. When mine had the 24lb/hr it would pull the trim to 0, then give up and go back to open loop.

Another helpful thing I learned is to disconnect the battery cables and touch them together to drain the ecu after a big change like injectors or fixing a vacuum leak. That way you clear any bad habits and it will re-learn properly. Good luck!