Homerlasvegas

So here I am. I posted on my other post "New 1990 XJ Owner, Replace ENgine?" but getting no response.. so . I will go with a new post.

1st this is what I have done.
1) replaced Freeze Plugs
2) replaced Head gasket
3) replaced Water Pump
4) replaced badly broken exhaust manifold
5) replaced Injectors with rebuile 746.
6) cleaned dipstick ground
7) Tested Grounds
8) refreshed connections
9) Refreshed Coil connections
10) New Champion Copper PLus 9yc plugs gapped
11) New cap and rotor (Autozone)
12) New TPS Sensor (Autozone)
13) New O2 Sensor (NTK)
14) New CTS (BWD - Advance auto)
15) new vaccuum lines (dorman)
16) checked Fuel pressure (31 when running, 31 at key on. bleeds down if not started)
17) Refreshed ECU connection
18) cleaned Throttle body
19) cleaned IAC
20) Changed the Oil
21) Radiator Flush
22) New to me Rubicon Express 3.5" lift in rear with shocks
23) New Air Filter
24) New Powersteering pump.. (need to put on)
25) Drove it. . . . .
26) hmmm trying to think.. what else .
27) Retightening manifold bolts
28) New head lights
29) New Fog Lights

To come: Replace front springs, shocks, Stabilzer bar and bracket, have most of the part for the steering as well.

BIG PROBLEM.. Will not pass smog. got a:
Idle Speed CO 5.46% (must be less than 1.2%)
High Speed CO 7.07% (Must less than 1.2%)
Idle SPeed HC 382 parts Per million (must be lower than 220)

After I replaced the TPS and 02. it looked good.. for a couple of days. Then it went bad. My 02 was jumping up and down like a happy Kangroo. 4.8 ... 0.2 4.8 ... 0.2 Got the REM captures to show it. but now.. on start up it starts at 4.8 bleeds down to 2.6 or so then goes into the 3.0 and settles. I have a few vids to show what it does according to REM.

Really want to get this thing resolved.. Your help is appreaciated. Please watch both attached vids to see if you can help me determine what to do next..

OH on the Ground test. They all Ohm to Near 0 accept for the ground from the Trans side of the TPS .. it is 0.797. Any idea where this ground is?? is this a clue???

Watch the Vid's for the readings.



13)

Homerlasvegas

OH.. I took out the IAC the other night cleaned it up again.. put it back in.. when I had it out.. I ran my finger in side and it came out very Black.. "sooty" . is that normal???

I can fix about anything if I know what is wrong. However, my diagnostic skills .... well they aren't so good..

-H

awg

How does the engine seem to you...does it go well in all aspects, idle smooth etc ?

Does it have any apparent running issues ?

I would grab a few vital OEM sensors out of a wreck...like entire throttle body with sensors, and front O2 sensor, probably distributor

Do direct transplants

Otherwise you will probably need an oscilliscope, and advanced diagnostic skills

Homerlasvegas

LOL.. where do I find a 1990 4.0L ????? I have not seen any in Las Vegas. This is a Renix...

-H

Homerlasvegas

OMG.. I just checked .. and just on 2/10/2021.. my local pic a part yard.. Stood and 86, 88, 89. Does anyone know what engine parts would swap directely??

-H

awg

I thought that you would have wreckers in a place as large as that

If not, most wreckers usually have access to a database that has info on where one may be located

otherwise off a list like this, Craigs list etc etc

I did not think a '90 would be so uncommon in USA ?

In my experience of owning many much older vehicles, in order to keep them on the road, it is essential to have a stash of certain spare parts, and develop good diagnostic & mechanical skills

The alternative is take the vehicle to a skilled diagnostic technician

Homerlasvegas

If you notice the long list of things done.. I've done a ton already. I believe it is one last small thing .. or perhaps ONE HUGE thing.. Again.. Remember this is a 1990 4.0L.. these are not the same as the 91 to 01 4.0L. (different brains RENIX (Renault Bendix))...

Plus attached are the videos of the diagnostics. I'm trying to see if anyone can help me from the posted info determine where to go.. Does anyone know where the grond for the Trans side of the TPS is?

It runs ok. Honestly, if it were not for SMOG and the Renix Engine Monitor(REM) telling me that there is a problem.. I'd probably be driving it like a happy clam. However, It does not pass smog and the REM tells me the 02 sensor is not giving the correct responses and it is running in OPEN LOOP.



-H

ijeeep

The 86 might yield some non electronics parts for you but you can cross it off the list of sensor donors because 87 was the first year of both the 4.0 and EFI in the XJ.

4.3L XJ

Get yourself some new O2 sensors and you had better plan on a catalytic converter too. Both are needed to reduce carbon emissions

robsjeep

How is your intake manifold vacuum? test it with a gage. If you read my recent posts about my 1990 Renix, how it would not go into open loop, you will find how a failed egr valve caused my intake manifold vacuum to be to high. Under poor vacuum the ecu will not allow the renix to go into open loop. manifold leaks can be detected by a vacuum gage test. also the ecu requires high enough temperature to go into open loop control. so make sure your coolant temp sensor is working and ohm meter can be used to check the temp sensor.

have you checked these yet?

Homerlasvegas

I have replaced the 02 sensor. This engine only takes one. Imediately after replacing the 02 sensor .. it appeared to work. I replaced it with the Cruiser/Nickintime recommended NTK.

The readings bounced like a happy clam.. for a bit..

-H

Homerlasvegas

I just changed my CTS. Before the new CTS i was getting a 185 ish temp. Now post CTS replacement.. I am getting 195 to 205 temp.

Check my video link, I believe the Vacuum is good. According to Cruiser.. in a previous thread he thought my Vaccum was good.

Does anyone else use the REM?

lawsoncl

TPS ground on the trans connector I think goes to the TCM. It won't cause emissions problems though.

Homerlasvegas

According to Nick IN time... the REM creator..

MAP at idle < 15 HG MIne around 11
Map at Full throttle ~ 15 - 30 Mine no trans engaged.. goes weird . drops(8.9).. if trans engaged.. goes up 22 at 2500 RPM

VAC at idle > 15 Mine 15+
Vac at full throttle ~ 0-15 .. mine no trans engaged goes weird goes up(20.).. if trans engaged drops

Intake air temp checked .. read at what the resistance readings said it should (don't recal the actual reading)

Idles around 650.

I unplugged the IAC and nothing changed... Does anyone know how a bad IAC effects things??

-H

doublechaz

Your vacuum and MAP readings are normal for what you are doing. I would like to get a solid look at your short and long term fuel trims and a smell of your exhaust.

I think there was a bit in the video that showed that the REM reports the ECU thinks you are lean. You would not smog with high CO and high HC if you were lean. Through the net is not easy, but this is my theory. This happened to me once on a different platform.

I was getting sluggish O2 readings and reduced power and much reduced mileage. The exhaust smelled worse than normal.
I put in a new O2 as it had been 50k+ miles since the last. No improvement.

Then I put on my thinking cap. At that time it didn't fit very well as I was fairly new to doing all my own work. After a good deal of study on the theory of operation of gasoline internal combustion engines and EFI I figured it out.

I had a very small exhaust leak where the manifold joins to the head. It sounded like a valve tick. I knew that it was there the whole time, but I was thinking I would kill the big problem first and then polish things.
What actually happened was that exhaust would puff out of the leak on the exhaust stroke for that runner making the sound. Then after the puff it would draw in a little fresh air into the exhaust. When this reached the O2 and was measured as significant O2 in the exhaust the ECU decided MORE FUEL! But the more fuel can never really eliminate the O2 in the exhaust because you aren't getting combustion in there. Result was running very rich. Enough to reduce power. Much HC and CO in the exhaust.

I fixed the exhaust leak and after about 50 miles for it to relearn all the fuel trims it was back to normal.

In total there seems to be a lot similar from my old situation to your current one. Exhaust leaks that can do this can also be small enough to be quite difficult to detect. In the worst case adapting a vacuum leak smoke machine to your exhaust to search for the problem may be needed.

Also, as someone else pointed out, an EGR leak can cause significant problems. I don't think that is a perfect fit for your symptoms, but I've been wrong before so you could try blocking it off completely just for testing.

Finally, it looked like in the video that your tach was pointing at zero while you were idling. If that isn't a camera perspective thing, I would continue to chase grounds and the C101 connector if you have it until the tach is resolved. If you have subtle electrical problems then it's possible for some or even every sensor reading to be a lie. And you know what they say about computers: "Garbage in, Garbage out."