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Francesco
October 2nd, 2017, 18:44
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

cruiser54
October 3rd, 2017, 06:43
Have you ever visited my website?
www.cruiser54.com

Do tips 1 through 5 first.

Did you adjust your new TPS?

What brand O2 sensor did you use?

burntkat
October 3rd, 2017, 07:51
Shouldn't this be in OEM Tech?

Francesco
October 3rd, 2017, 07:55
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

Francesco
October 4th, 2017, 18:47
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

old_man
October 4th, 2017, 20:02
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.

Rob Mayercik
October 4th, 2017, 20:09
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.

cruiser54
October 4th, 2017, 20:40
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.

burntkat
October 5th, 2017, 09:46
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.

cruiser54
October 5th, 2017, 15:30
Yup. 87s didn't even have a resistor.

Rob Mayercik
October 6th, 2017, 13:38
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.

lawagoneer
October 6th, 2017, 17:11
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.

cruiser54
October 6th, 2017, 21:24
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.

Francesco
October 7th, 2017, 10:14
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.

Wayne Sihler
October 7th, 2017, 10:46
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.

Francesco
October 7th, 2017, 10:53
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.

cruiser54
October 7th, 2017, 13:16
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.

Francesco
October 7th, 2017, 13:54
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.

cruiser54
October 7th, 2017, 14:09
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.

Hard to say. Maybe not now, but keep that on your radar screen.

Francesco
October 8th, 2017, 10:17
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.

burntkat
October 9th, 2017, 07:58
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.

What is this MAP upgrade??

Francesco
October 9th, 2017, 07:59
Basically you remove the rubber plug from the throttle body, tap it, and use a brass fitting for a better seal.

cruiser54
October 9th, 2017, 08:21
What is this MAP upgrade??

http://cruiser54.com/?p=280

Green XJ Jeep
October 9th, 2017, 11:11
http://cruiser54.com/?p=280

In my opinion that should be closer to the top ten

Francesco
October 9th, 2017, 17:27
In my opinion that should be closer to the top ten

Well, you can only have so many in the top ten.....ten to be exact

Green XJ Jeep
October 9th, 2017, 18:48
Well, you can only have so many in the top ten.....ten to be exact

I did say closer 31 seems a little far down the list

cruiser54
October 9th, 2017, 21:45
I did say closer 31 seems a little far down the list

The first 5 are prioritized. The rest came along in a willy nilly manor.

Francesco
October 9th, 2017, 23:40
I kid, Green Jeep. I agree this one is pretty important. Will update tomorrow with results, hopefully this fixes it.

Francesco
October 10th, 2017, 14:36
Well, I've done the fix, and SO FAR, it seems like a success. My throttle delay is gone, as well as my weird idle issue, bringing up an OLD weird idle issue, but I can live with that one. Here's some quick pics:

First, I disconnected the air box hose, and removed the throttle body, which were a T45 and a T30 I believe.

https://i.imgur.com/h6T0pn8l.jpg
First the top hose

https://i.imgur.com/kGolUCSl.jpg
Then the bottom

The throttle body comes off after this, just remember to disconnect the two sensors, and pry off the throttle cable, a flathead works great for this, and to install just a simple set of vice grips works fine.
After that, I mounted the TB in the vise, gently as to not scratch it, and slowly tapped the MAP sensor hole, i went about 2 turns at a time until it was pretty close to seating. For reference, I used a NPT 1/8-27 tap.

https://i.imgur.com/5BK7qQUl.jpg

Then, since I had no Permatex #2 like Cruiser suggested, I just used copper gasket maker, should be OK I suppose, would probably seal on its own anyways. Then I threaded it in and tightened it down.

https://i.imgur.com/vapa7Vkl.jpg

Took the time to clean the throttle body again, as well as the intake surface it mounts to. Installation was the reverse, and from what I read, torque is about 15 ft lbs, so I just snugged them up, my torque wrench does not read accurately that low.

The only issues I ran into were I believe the elbows were slightly too small, and difficult to fit on, but they're definitely not going to leak air, on the upside.

https://i.imgur.com/7vxFb14l.jpg
Fully installed

https://i.imgur.com/u31hWHZl.jpg
Old cable

I hope this helps somebody else, and thank you again cruiser!

burntkat
October 10th, 2017, 16:27
Good work. FYI, though in a perfect world a NPT isn't supposed to require sealant, it's never a bad idea to use some. I just use RTV, the stuff you used is even better. Teflon tape can work but it's always a crapshoot in my experience.

Green XJ Jeep
October 10th, 2017, 19:25
Nice write up

cruiser54
October 11th, 2017, 06:28
Nice job!!