Xj dies at idle

[Ryn89xj]

89 xj
HO stroker swap
Running Rich (black plugs)
Won't idle very long
17 miles on it

I have read every post I could find on this issue. I've done all of cruisers tips and tested and retested sensors. All vacuum lines are new. I cannot get this thing to run right. It starts easy just dies after it gets warm. Dies at a stop sign unless im in Nuetral with foot on the gas. It seems like tuning a Renix isn't a thing so I don't know what my next step should be. Any help would be greatly appreciated and I'm beyond frustrated at this point.

 

[Ryn89xj]

Can a cam thats to big cause this?

 

[Anak]

A vacuum gauge might help answer that question.

I know nothing about Renix except that it is not at all like H.O. (or pretty much any other OBD system). From my understanding you can't just plug in a scanner and see what the sensors are reading. But perhaps you can get raw data with a multimeter.

I think it is "Nick in Time" (or something like that) who makes a device for interfacing with the Renix system. Might be worth looking into.

 

[Ryn89xj]

He does and I believe he has another batch getting ready to sell.

 

[mewz99]

The only time my Renix has run rich is when the O2 sensor, heater, or relay was bad. It switches into open loop which runs rich and stays there. If you have a leak or crack in the exhaust manifold, that could cause it too (fresh air being added would cause the O2 sensor to read lean, resulting in rich condition no matter what you did)

The dying at idle unless you open the throttle sounds like not enough air for the amount of fuel getting dumped in at idle. Try just opening the idle adjustment screw (if you still have it on your TB) or even the butterfly adjustment screw.

What RPM does it idle at?

 

[Ryn89xj]

Exhaust is new, aswell as the 02 sensor (second one NTK). I swapped the 02 heater relay with a known working one. When it does idle it idles at about 500. I adjusted the butterfly screw to no avail so I put it back to closed

 

[Anak]

I have to wonder how it is that the butterfly adjustment makes no difference.

IAC controlling the RPM? Is 500 RPM the correct idle? Seems low to me, but again, I don't have any experience with Renix.

 

[Ryn89xj]

Idk, my thoughts were since I can keep my foot on the gas and it'll idle fine, I could mimic that butterfly position with the screw. It just didn't work. IAC is new.

 

[Anak]

Trying to look for info/ideas, came across this thread: Comanche Club, Idle Problem

Bummer is the lack of a solution posted. Still may have some suggestions for areas to pursue.

At any rate, it doesn't sound like an entirely unique problem, and it does appear that 500 RPM is lower than it should be.

 

[mewz99]

Exhaust is new, aswell as the 02 sensor (second one NTK)

Check the wiring? If it's routed wrong, might have melted on the pipe and be grounding out. Or maybe the wiring to the relay - is that a fusible link? You could check voltage on pin 9 of the 15 pin diagnostic connector, that's the O2 heater relay output.

I have to wonder how it is that the butterfly adjustment makes no difference.

Yeah, that's bizarre. No difference between that and stepping on the gas a touch.

Is 500 RPM the correct idle? Seems low to me

The greybeard at my local dealership told me their rule back in the day was "500-900 is acceptable, never over 1000". 500 is about the minimum that my Renix will actually idle...below that it almost dies and even at 500 the alternator doesn't produce 12v.

 

[Ryn89xj]

It questioned my results on the butterfly screw so I shimmed between the buttery and screw ever so slightly. Got the rpms upto 1000 and it stuttered and died anyways.

Checked the wiring and nothing is melted or burned. I didn't tear into the whole harness.

At the #9 pin I'm getting 14.9 volts.

 

[mewz99]

What’s your fuel setup? Stock pump and FPR? Stock injectors or oversized?

 

[Ryn89xj]

Stock pump, FPR is stock off a 95 I believe. I switched to that rail. The injectors are off a 96 I wrecked.

 

[Ryn89xj]

I questioned the injectors and best I can tell they are about 17# off the 39 psi pump. That tells me they aren't big enough but the plugs seem fouled like it's to much fuel.

 

[letank]

first thought, crankshaft position sensor, easy to test -I had it happened on the YJ with renix-

Otherwise EGR

Time to pull that vacuum gauge.

Renix is challenging, all you need is a voltmeter and test leads

 

[Ryn89xj]

Deleted the egr. It has the 99 intake on a 95 head I think. Its the 7120. The vacuum lines are all new. I built this motor from an 89 block. As in applicable machine work to block and head, New bearings, New Crank, New pistons, New cam, New lifters etc.. Everything is new and everything thing seems to test ok. All grounds were refreshed as I went and all plugs were unplugged and cleaned.

 

[Ryn89xj]

I checked ohms through the ground pins on the ecu connectors and the negative battery terminal. 5.5 on all except the knock sensor ground pin. It showed nothing. From what I'm reading, the knock sensor isn't that important?

 

[Ryn89xj]

So I went to check for vacuum leaks with smoke and I pulled the vacuum line from the brake booster to blow the smoke in. It started with me standing outside the jeep then Idled fantastic. Alittle high maybe at 1500 but it didn't waiver from there. It idled for probably 20 minutes got upto full operating temp. I even reved it several times and it went right back to 1500. This is a huge for me. It did die though as soon as I replaced the tube to the brake booster.

 

[Ryn89xj]

Changed the check valve on the booster and it didn't help. It still died when I reinstalled the vacuum hose.

 

[letank]

dang, I thought that the check valve would have solved your issue.

time to check the booster.... not expert on booster but this can help, most brake system are similar, check the post for picts

95 Vacuum Booster Brake Help

www.wranglerforum.com

MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neutral.
(3) Pump brake pedal until all vacuum reserve in booster is depleted.
(4) Press and hold brake pedal under light foot pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away, master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Release brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
MASTER CYLINDER/POWER BOOSTER TEST
(1) Start engine and check booster vacuum hose connections. Hissing noise indicates vacuum leak.
Correct any vacuum leak before proceeding.
(2) Stop engine and shift transmission into Neutral.
(3) Pump brake pedal until all vacuum reserve in booster is depleted.
(4) Press and hold brake pedal under light foot pressure.
(a) If pedal holds firm, proceed to step (5).
(b) If pedal does not hold firm and falls away, master cylinder is faulty due to internal leakage.
Overhaul or replace cylinder.
(5) Start engine and note pedal action.
(a) If pedal falls away slightly under light foot pressure then holds firm, proceed to step (6).
(b) If no pedal action is discernible, or hard pedal is noted, power booster or vacuum check valve is
faulty. Install known good check valve and repeat steps (2) through (5).
(6) Rebuild booster vacuum reserve as follows: Release brake pedal. Increase engine speed to 1500
rpm, close throttle and immediately turn off ignition.
POWER BOOSTER CHECK VALVE TEST
(1) Disconnect vacuum hose from check valve.
(2) Remove check valve and seal from booster (Fig.
1).
(3) Hand operated vacuum pump can be used for
test (Fig. 2).
(4) Apply 15-20 inches vacuum at large end of
check valve (Fig. 1).