1997 4.0 XJ behaves like running out of fuel

[vaco]

Hi!
I am new here and quite new to XJ (I have it for 1/2 year now). My XJ is 4.0 1997, I have an issue with it that I cannot solve.
Symptoms: sometimes it behaves like it was running out of fuel, firstly it loses power, RPMs are getting lower, then engine stalls and gets alive again in about 1 second cycles, then cycles are getting longer. It almost never happens right after starting the engine, usually it shows up after 5-15 minutes of driving. First I thought that it happens only while engine is hot but it also happens on cold engine. Other thing I noticed: when I drive very gently (max. 2000 RPM, mostly up to 1500 RPM) everything is ok, I can drive for 10 km (not tested for longer distances) without any problems, stronger (not really strong, I would call it a bit stronger than normal) acceleration brings the issue back, sometimes after first such acceleration, sometimes after few of them. Almost always when I stop the car issue disappears unless I try to rev it. When I turn off the engine for few minutes I can drive it normally again for some time.

What I checked/replaced and some other info:
- it is not real lack of fuel, fuel gauge works, issue shows after refueling
- IAC is replaced
- throttle was cleaned
- CPS is replaced
- fuel pressure was tested and was ok also while the issue appeared
- there is no problem with staring the engine, it starts smoothly when it is cold and hot

There is other minor issue with my XJ that it has since I got it, maybe that can be a clue to solve the main problem: on idle I can see short (like tapping acceleration pedal), small (the gauge barely moves) and irregular changes in RPMs, they get more often when the engine is hot.

Other thing that may have caused the problem: few days before the problem started I took XJ for an ultra-light off-road, it was actually mostly driving unpaved roads, not real off-road, but it was really hot day, that plus driving slowly must have caused really high temperatures under the hood. After that my XJ was driving normally for two or three days before it started misbehaving.

Last thing: that probably has no connection with the problem, but I noticed that when I took off fuel cap before refuelling just before the issue appeared there was some water in it (at least I think it was water, I smelled it and it did not smell as strong as fuel), it was not a lot, like quarter of teaspoon.

I will be grateful for any clues.
Thank you!

 

[vaco]

I forgot to write that "Check engine" did not light up, I could not read any errors with ELM327.

 

[Black_Black]

Have you replaced the fuel filter?

 

[vaco]

I assumed that fuel pressure test that showed slightly above 30 PSI (also while the issue occurred) tells that there is no issue with fuel pump, filter and fuel lines. Am I wrong?

 

[RCP Phx]

That fuel pressure is low for a '97!

 

[vaco]

I am sorry, it was 3 bars, that is ~43 PSI. I do not use PSI often, I thought I remember how to convert bars to PSI, but I do not. Sorry again.

 

[Black_Black]

I would still replace the pump and filter with your symptoms. It's more likely the cause than the stuff you've replaced so far I think. Genuine bosch only they last around 200k

 

[vaco]

Ok, thank you, I will try that and let you know whether it fixed the issue.

 

[vaco]

I assume the pump you meant is Bosch 67658, but it seems that it is not available, is there any other make that you can recommend?
I searched for 4874173AB and the only pump I found is Airtex E7154 (pump itself, without filter and some other stuff).

 

[Black_Black]

I've tried airtex and Carter pumps they were both junk. I think one did 10k and another did 40k miles. It's definitely worth sourcing a bosch

 

[vaco]

Ok, I found and ordered Bosch pump without the "enclosure" (P/N 69316), I will get in till the end of month, I will report whether it helped.

 

[Anak]

Make sure you also replace the filter. An old, clogged filter can be the death of a new fuel pump.

 

[vaco]

I ordered the filter too. Do you recommend flushing the fuel system? I will clean the tank beacuse I will have to remove it anyway, but what about the rest of the system?

 

[RCP Phx]

It wouldn't hurt to run the pump before connecting it up to the injector log just to flush the line!

 

[Anak]

What you find in the tank should tell you whether or not you need to flush it, and with a plastic tank I would not expect things to be particularly bad.

I have a steel tank I am trying to clean up--it is a rusty mess inside. I doubt you will find anything like that.

 

[75SV1]

I might look at the distributor. See if the shaft wiggles any. The spec is .001. On one of my '98s, it was way worse. Also, there is a sensor in there too. Its also the CPK sensor. They are not cheap. Almost better to by a rebuilt distributor with a new one.

 

[vaco]

I might look at the distributor. See if the shaft wiggles any. The spec is .001. On one of my '98s, it was way worse. Also, there is a sensor in there too. Its also the CPK sensor. They are not cheap. Almost better to by a rebuilt distributor with a new one.

I also thought about electric problems, however I think (and of course I might be wrong as I have almost zero experience and only know more or less how theoretically engine works) that the fact that issue appears after stronger acceleration and does not go back right after it, it needs some time, suggests that most probably:
- using more fuel for a moment causes that there is lack of it for some time after it
- something similar with air
- there is problem with one of exhaust elements, like clogged catalytic converter, that works ok when it needs to let out small amount of fumes, but when there is more fumes then it cannot "process" it



I will describe step by step how the problem occurs, could you please tell me whether your situation was similar?
- I start the engine, it works ok
- I drive gently (up to 1500 RPMs, rarely up to 2000), it works ok, I can drive like that for at least 15 minutes (I did not check longer distances)
- I accelerate slightly more intensively, in the beginning (for few seconds) it works ok, at some moment the problem occurs, RPMs are getting lower, at some point engine starts to stall, it breaks in about 1 second intervals, then intervals are getting shorter
- now if I will stop this process early by stopping the car and shifting to neutral (probably shifting to neutral is not necessary) then engine "recovers" almost instantly, if I force it to drive as long as it is possible then it cannot "recover" it works like it would get fuel in intervals, I have to turn the engine off, wait some time, like 30 seconds or minute, after that usually it works fine, sometimes it needs a bit more time (I think the longer I force it to run when it chokes the longer I have to wait)
- now I can repeat whole process

 

[Black_Black]

You should definitely check the distributor and rotor condition, coil connections all that stuff. Check your ballast resistor if you have one, go ahead and bypass it and see if that makes a difference.

I wouldn't worry about the cat, I think it's only a problem when the ceramic matrix breaks and causes a physical obstruction. My original cat was spotless when I replaced it and my jeep even ran rich for some years.

Yes I had the same issues. It was always fuel.

 

[vaco]

Distributor cap and rotor have been replaced, that did not change anything.
I unplugged almost everything I could and checked visually for corrosion, cleaned if I it was corroded and plugged back.
All XJs I've seen on YouTube had the resistor on the driver side just under the hood, there is no such thing in my XJ, so if that's the only place it could be then no, I do not have one.

 

[vaco]

It was a mechanic who checked the fuel pressure, now I ordered pressure gauge kit, I will do some more tests, the effect is much stronger now, requires less load to show up, so maybe it will detect something.