MayDay!! - Hard Accel Killed Idle

[AnotherOldJeepGuy]

[AnotherOldJeepGuy]

I just did soap test #2, I suds-ed up all along the top of the area where the manifolds connect and again saw no signs of any bubbles being blown, or soap being sucked in, and also no sign of RPM changes with the soap and then as I rinsed it off.  This is not too surprising since the water testing has already proven to not show anything, but it was another place to try the soap that was easy enough to get to.  Now I need to let it completely cool again and see if there are other places I can soap up and try again.  I am not loosing track that everything was great until the "maneuver incident" so although I cannot yet find any crack, a physical issue still seems more likely (at least to me) rather than some control that failed coincidentally at that same instant.

 

I have read over the distributor index posting at least 4 times at this point, and have not come to a sufficient understanding of that task to pursue it.  It may be beyond the extent of my mechanical grasp, time will tell.

[Gojira94]

REM is on the way via USPS, should be there Saturday. I also enclosed a new NTK sensor. It's one of the newer metal body design. I ended up not using it since I found a ceramic body NOS AC Delco 25176716 that gave me a perfect 6.2 ohms on the heater grid circuit. I measured the heater grid circuit resistance of the NTK and it's just a hair below spec at 4.8 ohms but I thought it might be useful for troubleshooting.

[AnotherOldJeepGuy]

On 6/3/2026 at 1:04 PM, Gojira94 said:

REM is on the way via USPS, should be there Saturday. I also enclosed a new NTK sensor. It's one of the newer metal body design. I ended up not using it since I found a ceramic body NOS AC Delco 25176716 that gave me a perfect 6.2 ohms on the heater grid circuit. I measured the heater grid circuit resistance of the NTK and it's just a hair below spec at 4.8 ohms but I thought it might be useful for troubleshooting.

Awesome, I'll be watching the mail!  Thanks again!

 

 

Edited June 6 by AnotherOldJeepGuy
6/5/26 - Captured Code Desc and Gauge Readouts Summary Pages for printing, and study!

[Gojira94]

https://nickintimedesign.com/rem-gauge-readouts/

 

We'll want to see MAP, VAC, ºFWT, VLT (system voltage while running), TPS at idle, vO2 / mVo, A/F, vHT, ST, LT, SYN, maybe a few more.

[AnotherOldJeepGuy]

OK, I got some info.  I am far from an expert at using this tool yet and I am trying to figure out the button driven menu system, but my first attempt I get the following:

 

REM installed, Key ON, engine not yet started.

CODES:

-REM CODES

--No REM Codes

-ECU CODES

--Injector 1 Open (this was not consistent, I later read instead I2 and I3 Open, but not I1)

According to the documentation on the website, "ECU does not detect Injector # wire has a ground path"

-TCU CODES

--No TCU Codes.

-ABS CODES

--Not Available.

 

Then with engine started.

CODES:

-REM CODES

--Loop Fault Lean

According to the documentation on the website,

Possibly faulty o2 sensor, weak fuel pressure, other fuel system imbalance.
– TIP: This code is more common during cold weather starts as the first Closed Loop attempt may fail due to the Cold Fuel Enrichment value still being too high. This code can be ignored if the 2nd closed loop attempt succeeds

-ECU CODES

--No Injector 12V** (This was consistent, but is to be ignored**)

--KO Tests Not Run

**According to the documentation on the website, if "No Injector 12V" is received along with "KO Tests Not Run" it can be ignored.

-TCU CODES

--No TCU Codes.

-ABS CODES

--Not Available.

 

Once I can get more familiar with the menu I'll try to grab the other items listed by @Gojira94.

 

 

 

[AnotherOldJeepGuy]

I collected everything I could find that lined up with the "REM Gauge Readouts Summary" with engine OFF before I got chased in by rain.  I got the reading through the menu  HOME->DIAG->READINGS and noted them in a copy of that list which I have attached here.  I got an error when I attached it, or at least a message, telling me that pdf was not supported?  I am guessing with no knowledge that the error means it calling be displayed in the thread, but I am assuming the attachment can be opened by anyone that can open a PDF.  Can someone confirm it can be opened so I know posting a PDF works or does not please?

 

Looks like there are other sub-menus but I don't have any REM for Dummys book to follow to know what other buttons I might need to push or in what order, so I am hoping this gets me where I need to do.  I'll update and repost with a version annotated with the same reading with the engine running after the rain.

REM Gauge Readouts Engine Off.pdf

[Ωhm]

PDF good by me. Must be signed in.

[AnotherOldJeepGuy]

Thanks for that confirmation, I figured but the warning was not clear!

[AnotherOldJeepGuy]

Rain Stopped so I collected the engine running dataset and added to PDF.  Note that since TSP was showing low I adjusted it to 17 before collecting the additional information.  My expertise doesn't let me identify good/bad but I don't see much that is obviously way out of line based on the REM documented expectations.  I guess I am most curious about the readings that kept moving around, because the movements coincide with the engine revving up and down during idle, and it didn't use to do that (IIRC).

REM Gauge Readouts Engine Off-On.pdf

[AnotherOldJeepGuy]

Continued with the soap bubble test.  This time I soaped up the connections at the Oxygen sensor and the pipe between the exhaust and intake manifolds.  And as much of the rest of the exhaust manifold I could get the soap sprayed on.  Still no bubbles.  I have probably gone as far as I can go with the soap bubble test, I don't think I can get to any other spots.  If there is a crack, it either can't blow a bubble or it's where I can't get to.

 

I studied the REM documentation a bit more and found that it says when the sensor is operating properly the reading should constantly swing between a high and low value, and mine is doing exactly that (1.7-4.8).  And it seems so unlikely to me that the  'maneuver incident" could have caused my relatively new sensor to go bad, but it is another test case I can try since @Gojira94 generously lent me a oxygen sensor for the test.  I did go back and check my Rock Auto order and the sensor I installed in Feb '25 was NTK 23553 Oxygen Sensor.

[Gojira94]

I agree that the O2 is working, which is good. The issue as I see it is that it should read very rich, given what's been observed with the plugs, if there is no leak at/ in the exhaust manifold. A (truly) rich condition being read as stoichiometric, more or less, says that the O2 is asking for more fuel to make itself happy because it sees a (false) lean condition. Short and long term fuel trims will almost certainly be very high as proof of that.

[AnotherOldJeepGuy]

Here is what I saw for those readings.  I am not expert enough to know if these meet the criteria of falsely reporting lean or not. or what would cause that to happen...  It is interesting that LT says the ECU is "using the Base Fuel Curve (I think that means Open Loop) while ST says it is not.  I have no idea what that means, but it seems like it can't be both.  I ran the engine for a while and watched the readings that indicates Closed, to see if they changed, I didn't see them ever change from reporting closed.

 

[Ωhm]

Injector Pulse Width (IPW) seem high (Engine Running at Idle 6.9) for factory stuff. Should see between 5.3mS & 5.8mS. I wonder if ECU INJ codes could be true. This would force the ECU to increase PW for the INJs that are working properly.

[Gojira94]

Base fuel curve is 128, a starting point that assumes everything is healthy. The STFT will be the first thing it tries to adjust. If STFT stays high or low long enough it will move to LTFT to 'accommodate' conditions that indicate a minor/ manageable issue with fuel/air ratio. I don't think you've had enough runtime since the last battery reset to effect any change in that yet.

 

There is a monitor in the REM that shows loop state - does it go into and out of closed or go into closed at all? Just re-read your pdf. So it is able to achieve closed loop in idle...

[Gojira94]

You might try setting to knock count and give it steady throttle open to about half - not slow, not fast blip. When it stumbles, see if you get knock. If an injector or two are cutting out or weak, those cylinders will momentarily go lean and misfire.

[Gojira94]

More low-hanging fruit - clean the heck out of the grounds at the oil dipstick brace mounting bolt (G105). That's where the injectors all get ground. All 6 injectors' grounds are spliced together and go to that ground point. It's also possible there's some wire chafing in the injector section of the harness along the driver's side of the valve cover.

[AnotherOldJeepGuy]

How are the injector numbers assigned?  Is it 1 through 6 from back to front, or front to back, or an assignment related to firing order?  Across the multiple readings I have gotten when I did see the INJ error, I saw I1 the first time, then I saw I2&I3 a couple times after that. 

 

I installed 1 new injector in Feb '25 to replace one that was leaking even after new o-rings.  2 others were replaced by a shop maybe a year earlier.  So I have 3 relatively new and 3 original as best I can recall all apparently working fine until my maneuver.  From back to front, if that numbering is 1 through 6, then I1, I2 and I4 would be where the original ones are, and the other 3 are new over the last 2-3 years.

 

If I knew how the numbers are assigned I could relate the failures to all old, or all new, or a mix.

[Ωhm]

27 minutes ago, AnotherOldJeepGuy said:

Is it 1 through 6 from back to front, or front to back

 

Front to Rear = 1 thru 6

[AnotherOldJeepGuy]

Gotcha.  So at locations 1-3 I have 1 old and 2 new injectors.  There is one thing unique with 1-3, the ones that have from time to time thrown the fault, they are probably the ones farthest from the ground lug based on how the wires are routed.  I'll try the knock test above then clean up that ground connection, and see what happens.  Probably be tomorrow morning cause here in Texas it's already too dang hot by about noon for me to do a lot of work out in my driveway!

[AnotherOldJeepGuy]

OK I finished my homework before the heat come back outside.  

 

Pulled 3 lugs at the block ground point, plus the primary ground cable.  The primary ground cable is relatively new and still looked clean, the other three were not terrible but for sure have been improved now.  I scuffed them clean with sandpaper, also the point of contact with the block.  Then gave them a bath of contact cleaner.  After the cleaner dried I put it back together.

I cycled about 6 times turning key to RUN and OFF, checking codes at each RUN position.  I saw I3 no ground detected the first time, then every time after that I saw "No Injector 12V” + “KO Tests Not Run”.  I did try wiggling the connection at I3 and the harness, that didn't change anything.  I never saw any complaints other that I3 during this limited test.

I started up and watched the Knock count, first letting it idle for a minute or so.  I did see it toggle to 1 and back to 0 occasionally at idle.  Then I bumped it up to around 2500 RPM, +/`100 I guess and I saw the knock counter report from mid-20 to mid-40.  According to the REM doc, 10-100 is normal at that RPM so based on that I assume my results are OK, and also I am assuming without any way to know otherwise, the knock sensor is reading correctly.

 

After this just for grins I disconnected the battery for about 30m for an ECU reset then repeated everything above after the ground cleaning.

After the ECU reset, switch between OFF and RUN (not starting) about 6 times.  Never saw the Injector ground open reported, but I did still see "No Injector 12V” + “KO Tests Not Run”.  Once I saw “KO Tests Not Run” by itself and once or twice I saw ECU report No Errors.  Then I started up and looked for knocks.  Results very similar although the knock count seemed to be a little lower hitting upper 30s.  But I realize this is a sampling of knock counts so I don't know that "a little less" means much especially since it is still in the range noted as normal by the REM docs.   

 

For future reference, how long is really needed for an ECU reset?  When I disconnect battery I have been disconnecting both cables and shorting them together help bleed off everything.

 

[Ωhm]

88 FSM Computer Relearn Procedures.pdf

[AnotherOldJeepGuy]

Thanks, I have been avoiding any time on the highway but it might be worth it to go do this at least once.  It doesn't really mention how long a battery disconnect might be to require this, so the assumption would be I guess that any amount of time counts.

[AnotherOldJeepGuy]

Remember the vacuum plug?  It is still there.  So I decided to see how much different the vacuum reading would be if I connected the hose back.  At idle it was ~17 (I captured it at 14.5-15.5 earlier with the plug in place).  This isn't much different so it seems to say that I don't have a vacuum leak in the lines supplied by this hose.

The REM doc says opening the throttle should lower the vacuum?  This seems backwards to me, I would expect the vacuum to increase.  Case in Point:  In the past, from time to time a crack would develop in the vac line that goes into the firewall and supplies vacuum to control cabin air flow, and when it started to develop a crack, the airflow would switch in part at least to the defrost, and at that point, increasing my engine RPM, the airflow would return to the cabin vents suggesting vacuum had been temporarily restored (increased) by the higher RPM.  So this sounds like more RPM increased vacuum rather than lowering it.  And also right now, part of my problem that resulted from "the maneuver"  is my power brakes are loosing assist, more-so at low RPM, that is to say increasing RPM restores brake assist at least some degree, which again suggests more throttle = more vacuum not less.  So I don't understand this at all!!

 

[Eagle_SX4]

53 minutes ago, AnotherOldJeepGuy said:

And also right now, part of my problem that resulted from "the maneuver"  is my power brakes are loosing assist, more-so at low RPM, that is to say increasing RPM restores brake assist at least some degree, which again suggests more throttle = more vacuum not less.

Make a plug for the brake booster port on the intake manifold like the other one you made and see if your engine runs better. It could be that the brake booster diaphragm ruptured and is causing a vacuum leak. 

 

Vacuum is more dependant on throttle position than RPM. An open throttle will have a lower vacuum on the manifold than a closed throttle at the same RPM. Example, driving up a hill at 2,500 RPM the throttle will be open and will result in a vacuum loss in the intake manifold. Driving down the same hill at 2,500 RPM the throttle will be closed while coasting, the manifold will see a lot more vacuum as the engine tries to pull air through every hole it can.