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Renix Issue

Francesco

NAXJA Forum User
Location
Ventura County
Hello all,
I'm stupmed. My renix 4.0 is running very funny. When it's cold I have around a half second delay in any gas pedal usage, and my idle bounces from 1k to almost stalling every second or two. If I give it a little gas, the rpms still bounce, just at a higher rpm(think leaving foot on the gas a bit) so its not just idle related. Here is a list of what I've done:
Checked:
Intake air temp
O2 sensor
Coolant temp
EGR and it's sensor
Replaced: (somewhat recently)
IAC
TPS
O2 sensor
Knock sensor
Fuel filter
So to recap, my idle bounces a lot when cold, and still does when warm, but a lot less. It has a delay in throttling up, more pronounced when cold. I also cleaned the throttle body about a year ago, so it had been a little bit but I wouldn't expect it to be gunked up yet. The engine runs well other than this, however it seems slower than it should be. Any suggestions? I will update this as I go , in hopes that this will be figured out.
Thanks
Francesco
 
Shouldn't this be in OEM Tech?
 
Maybe it should be in OEM Tech, I didn't even think about it, I apologize. And to Cruiser, I have been to your website, and I've done almost all of your suggestions.

Edit: to be more exact, I have:
cleaned grounds
1990 so no c101 connector
replaced coil recently and cleaned it
cleaned sensor grounds, and added 2 extra ground straps per your suggestions
tested egr via your method(engine almost stalls out when pulling back pin, and there is no vacuum at idle)
CPS timing advance mod
Volvo injector swap
 
Last edited:
Any suggestions? I have a new fuel pump ballast resistor coming in(mine is literally cracked in half, figured it's good to replace anyways), but I'm fresh out of ideas.
Thanks
 
Hook up a vacuum gauge and see what it is doing. Hook up a timing light and see what it is doing. These will tell you a lot about what is happening.
 
Don't know about the Renix, but on an H.O. like mine, the ballast resistor can be bypassed and eliminated - I believe all it does is knock down the voltage to the fuel pump slightly to reduce noise. When mine fell apart, I threw it away and spliced the two wires together.

If yours is cracked, maybe the connection through it is intermittent or weak. You could try jumping around the resistor temporarily and see if it changes how it runs.
 
Don't know about the Renix, but on an H.O. like mine, the ballast resistor can be bypassed and eliminated - I believe all it does is knock down the voltage to the fuel pump slightly to reduce noise. When mine fell apart, I threw it away and spliced the two wires together.

If yours is cracked, maybe the connection through it is intermittent or weak. You could try jumping around the resistor temporarily and see if it changes how it runs.

Yup. It's only there to reduce noise.
 
Don't know about the Renix, but on an H.O. like mine, the ballast resistor can be bypassed and eliminated - I believe all it does is knock down the voltage to the fuel pump slightly to reduce noise. When mine fell apart, I threw it away and spliced the two wires together.

If yours is cracked, maybe the connection through it is intermittent or weak. You could try jumping around the resistor temporarily and see if it changes how it runs.

Can confirm this works. I threw away mine in the 90, worked fine after.

Personally, I LIKE hearing my fuel pump during crank cycle.
 
Yup. 87s didn't even have a resistor.

Precisely - if memory serves, they first appeared under a TSB because people were complaining about "that strange humming noise from the back".

Mine's been gone so long I don't remember if I used to hear it priming prior to starting, but I don't recall any difference in noise once the engine was going.
 
How is your battery and charging system. Before I upgraded my system, alternator, battery, cables my Renix did all sorts of weird things with drivability and idle. Fully charged battery, properly functioning alternator, good cables, clamps and grounds and the idle and drivability weirdness went away. Everyone knows that a Renix is sensitive to grounds but they also like good clean power from the charging system.
 
How is your battery and charging system. Before I upgraded my system, alternator, battery, cables my Renix did all sorts of weird things with drivability and idle. Fully charged battery, properly functioning alternator, good cables, clamps and grounds and the idle and drivability weirdness went away. Everyone knows that a Renix is sensitive to grounds but they also like good clean power from the charging system.

Grounds are more important than the charging system.
 
Regardless, I have cleaned the ground at the block, the ground at the valve cover, added an extra ground from firewall to fuel rail, and from battery to core support area. I really don't think it's a grounding issue. I also have pulled the main harness plug, cleaned that, and filled with ox-gard equivalent.
 
Dont see anything about a MAP sensor or the related vac hoses.
Problem like this on the 87 was the rubber part on the TB had failed.
 
The hose is new, but I will try replacing the map with a spare I have(not tested unfortunately), and maybe doing Cruiser's map upgrade by tapping the TB today.
 
Regardless, I have cleaned the ground at the block, the ground at the valve cover, added an extra ground from firewall to fuel rail, and from battery to core support area. I really don't think it's a grounding issue. I also have pulled the main harness plug, cleaned that, and filled with ox-gard equivalent.

I'm not sure that's a good idea. Ox-gard is conductive.
 
I see. Should I pull and clean it? I did this quite a long timeago(6-7 months) and haven't had issues until like 2 weeks ago after my Jeep sat for 2 weeks.
 
Well I have parts coming on on Tuesday to do your MAP sensor line upgrade, since my line has been heat shrunk and repaired anyways, I figure it's worth it.
 
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