aroundincircles

So.... I bought it, and it didn't have brakes and so I drove it home very slowly (using the parking brake to slow it down). I don't remember this being an issue when i bought it, but I also didn't go over 35mph, all I did in the engine bay before I tried to drive it was:
1) replaced the oil filter adapter 0 rings
2) replaced the spark plugs and wires
3) replaced the vacuum lines because they literally had like plumbing pieces zip tied into place, so I put on a brand new renix vacuum line harness.
4) replaced the fuel injectors with 4 hole injectors
5) replaced the motor mounts
6) freshened up the ground points.
7) replaced the NSS (had no backup lights)


But then I waited like 6mo to get a lift kit, I had two on order for months, and finally got one shipped, so it sat that whole time since the suspension was collapsed, and the rear was sitting on the bump stops, so I couldn't drive it anyways. installed the lift kit and was so excited to drive it only to find that it wouldn't...
since then I've (in order that I remember not in order of what I did):
1) fuel pump,
2) fuel filter
3) fuel injectors (3x) including stock style ones
4) all the sensors (CPS, Map, knock, etc)
5) spark plugs and wires (plugs twice, wires just once)
6) new distributor that I clocked
7) refreshed my grounds again
8)disconnected the tail pipe before the cat to make sure the cat wasn't plugged
9) removed the head, and had rebuilt, since I realized I had a leaking head gasket in all of this, and replaced the head gasket.
10) replaced the ECM
I've done a tone of other work that is unrelated, like changing out the transmission fluid/pan gasket, oil pan gasket, rear main seal, new seats, new head liner, new head unit, new tires, new brakes, new axle shafts, new ujoints everywhere, etc. I have $10k+ in the jeep at this point in parts, not including my labor.

Took it to a shop where it sat for nearly 3 months, where they worked on it in their "spare time" and the only conclusion they have is that it's not getting enough fuel, if they put a rag in the throttle body to hold it open, they could pour fuel in, and it would rev up. I need to check this myself, but I had a few spare parts I had ordered previous, figured I would just swap them on. I don't know why, if it is true, adding more fuel fixes it. that would mean my injectors are not getting enough fuel, but when I check my fuel pressure on the rail, it's just fine, within renix spec, and the 4 holes should be putting in plenty of fuel, or I have a massive vacuum leak somewhere causing far more air to get in than expected, but at WOT, that shouldn't matter as much since it's trying to get as much air as can fit on the cylinders anyways right? and it runs just fine at idle (usually where you see more issues with a vacuum leak)

Somebody has suggested I check timing. I honestly have no idea how to do that. I've never done it before. I've tried to get somebody I know who does to swing by, but they haven't had time. I am also open to all other suggestions. I'm not a mechanic, and I don't have fancy oscilloscopes and stuff. Part of me is kinda done with it. just thinking about it annoys the crap out of me.

dmoe69

Were you ever able to figure out your problem? I went back and looked at all of your REM videos. It seems like there were not consistent indications from a few sensors on a few of the videos. Perhaps you were replacing components in between videos. I had a similar problem to you, but from a different cause than your REM is showing. I remember thinking the problem could be 1 of 50,000 things and it seemed futile to guess anymore. Then, with the help from this forum and the REM I was able to narrow it down and correct the problem. As suddenly as a light switch is flicked it ran. That was back in July, I've put over 2600 miles on it without it missing a beat. If you have any energy left, I would like to help if you still need it.

aroundincircles

Nope, never got it figured out. To be fair, it super went on the back burner. I was dealing with custody of a niece, a dying father in law, and a crazy work schedule. Custody is settled, father in law is buried, and got a small promotion so I'm less in the trenches, so I can focus back on it. I actually just moved it from the side of the house where it was out of the way to the driveway on Saturday so I can look at it. I have family in town this week and next, but hoping to dig into it right at the start of the new year. What was your smoking gun? I was going to check timing next. I've never done that before on any vehicle.

aroundincircles

I went back and looked at your thread here:
https://www.cherokeeforum.com/f2/won...262616/index2/

Looks like your issue was with your fuel tank, was it just old gas, or did you have settlement in the tank blocking the pickup?
did you check your fuel pressure? I've replaced my fuel pump and my fuel filter twice. When I swapped out fuel filters I didn't notice any gunk come out of new replacement, even the original looked OK. I also have fuel pressure that is just fine at the rail.

dmoe69

My “smoking gun” was a very high short term fuel trim (ST). >128 the ECM is receiving input that the engine is running lean. The ECM on mine would drive the ST to 256 and beyond based on sensor input. Above 256 the ECM essentially passes out - and the engine did exactly what your does at about the same RPM. I had old gas/water/sludge in my fuel tank that ruined the brand-new Bosch injectors. Once that was all cleaned up it has run perfectly for several months.
From your REM videos, yours seems to consistently have low ST, meaning the ECM is receiving input that the engine is running very rich. There is no “pass out” point on low ST, but it is possible that the ECM essentially stops giving the engine enough fuel to rev any higher. This may explain why your mechanic said it would rev if he poured gas directly into the throttle body.
When you are ready, I would like to compare REM readings from your engine running in park or neutral with mine. I am most interested in ST, O2, TPS, IAC, ignition advance, and MAP/vacuum, but if you are willing to record/exchange some video, we can decide which sensors to combine at that time.

Your engine runs well to a point. I don’t know if I would tear into the timing cover quite yet.

aroundincircles

Sure, I am leaning towards a fuel deliver problem for sure, but with a new fuel pump, new filter and new injectors, I just don't know what it would be. I can record a new video probably tomorrow night, and throw it up here (and on my YT channel). Go through each of those for sure.

dmoe69

I’ve never posted a video, can I post one directly to the forum? ST is one of the indications that the REM displays that is coming out of the ECM. It is a result of collective input going into the computer. It is the ECMs response to bring the fuel mixture back to the base fuel curve. In other words, with bad data the ECM can starve an engine that is already running lean or flood an engine that is already running rich.
In my case the injectors were partially clogged and the ECM was trying to provide more fuel, but it couldn’t provide enough – so the engine starved and started that rev limited shaking at about 2500 RPM. It is possible that your ECM is being provided input that compels the ECM to believe the engine is running too rich, even though it isn’t. Its response to the input is to reduce fuel injector pulse width (mS on the REM) and starve your already starving engine. The end result would be the same symptom as mine, rev limited.
I’m hopeful that it will be helpful to compare the sensor input of my REM and yours, rule out which sensors seem to be operating normally, and then concentrate troubleshooting on the one(s), if any, that are suspect. Or at least then look at the processes in the engine that provide input to the sensor(s).

aroundincircles

Let me know if you need more information:


If you have a gmail account, you can upload to youtube for free.

dmoe69

Understanding its Christmas eve, this can obviously wait for a few days. I have made a few short videos, one was from start up to closed loop. For some reason it stopped recording halfway through. Conditions won't allow me to re-take that for several hours. Of all the videos I took, I think this is going to be one of the most telling comparisons. The RENIX 4.0 should be in closed loop except for the first moments at start up when cold and at wide open throttle. When the ECM reverts to open loop the ST and O2 indications stop cycling. I'd like to see your REM display with these indications.

You Tube

aroundincircles

I will have to get that video for you probably tomorrow or Monday, but in previous videos I made months and months ago, my engine stayed in closed loop and unless I'm trying to rev it up over 2000 RPM the o2 sensor swings as it should. but I will double check that this week.

This is the old video I was talking about:

dmoe69

I hadn’t seen that video, it was before the original case melted off. If it’s not too much trouble, I would like to see the RPM, open/closed loop, ST, and O2 to see if one of those indications could be causing open loop or open loop could be causing those indications to stop cycling. That being said, in that older video, it does seem to rev limit without the O2 sensor pausing. Open loop on its own isn’t what would be causing your problem, but I don’t think it possible to have the fault your having without the ECM going into open loop. It would be good to understand why it does that.
Also in that video the yellow light did flash. If you haven’t looked that up yet, that’s flagging a fault. The fault will show next to the offending indication with an asterisk. Perhaps you can reproduce that and find which one(s) are showing fault. The online REM website also instructs how to pull the saved faults. RENIX doesn’t “save codes” so you have to check for them before you turn the engine off.
A couple questions: Are you certain the fuel injector wiring is connected correctly, do you have the wiring colors for the fuel injectors? In the 30th post of this thread you have a picture of 6 spark plugs. Are those what are in the engine right now? If not, what spark plugs do you have in the engine? And at risk of getting blasted by the forum for this question, do you have a timing light?

aroundincircles

spark plugs are
NGK 7090 G-Power Platinum Spark Plugs BKR5EGP

I used this diagram for the wiring and it all looks correct:


and no, I do not have a timing light.

dmoe69

Good video, I think we’re on the right track. Can you look at the video between 13 and 20 seconds. Does the RPMs start jumping around and up to 2000ish RPM before you rev it up or is the audio off?

The spark plugs you are using, they are an interesting choice. They don’t appear in the application table for NGK plugs for the 4.0L. I’m not big on understanding heat ranges and all that, but, the insulator and the distance between the end of the threads and the electrodes is very short. I would think the electrodes would be about half an inch up inside the spark plug bore. Summit racing says that could create a need for additional ignition advance. I’m including the table and a photo I borrowed from a Cruiser54 post of plugs, of those, the NGK ZFR5N are what Cruiser54 recommends and work great in my rig.

If you had a timing light, or have access to one, what you would see if you were to use it is a flash about once a second at your idle. If you were pointing it at the timing scale the timing mark would be at about 14 degrees before TDC. As the engine RPMs increase up to just short of where you are “rev limited” the flashing would increase uniformly to about 3 times a second and the timing mark would disappear out of sight near 40 degrees before TDC. Here is where I start theorizing based on what my engine did. At the point your engine goes “rev limited” the flash would go from uniform to complete chaos with no discernable pattern and you would see the timing mark jumping around at random. That is the point where the ECM “passes out” or maybe has “a seizure” fits better. This is an indication that sensor input to the computer remained out of “spec” beyond the ability of the ECM to correct. The most common reasons appear to be too rich and too lean.

And I have a few more questions:

You said in the post sometime back you were planning to replace the O2 sensor, did that happen or is that the O2 sensor that was in the engine when you bought it?

No need to video it, but when you rev the engine up to its “limiter”, does the A/F by chance peg low at 13 or high at 16?

The Forum should have lots to add about this stuff now.

dmoe69

Disregard the question about RPM at 13 seconds. It was on my end. It cleaned up after I rebooted.

doublechaz

The ST should be 128. If I remember correctly 30 means the ECU thinks you are rich and is deleting a LOT of fuel which would lead to failing to rev. If your ST is 200 it means the ECU thinks you are lean and is adding a lot of fuel. This could also lead to breaking up and bucking enough to prevent revving. Your ST should not move very far away from 128 in any driving condition. I could have the lean and rich sides reversed, but either way it should be near 128. Before I took mine down for rod bearings it gave ST between 100 and 150 no matter how I beat and abused the throttle and load.