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Author Topic: XJ in Limp Mode??  (Read 3829 times)

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JonL

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XJ in Limp Mode??
« on: March 01, 2021, 11:52:32 AM »

Hi
For years now my XJ (1998 2.5TD) has been low on power - as ashamed as I am, I've just lived with it.....  :icon_sad:
I've not really given any thought to what the issue could be.... in fact, to be honest I never really considered it an issue, until a local garage did some suspension work and took it our for a test drive after and said it's lacking boost - but essentially the Jeep is still very driveable just lacks any form of acceleration but once up to speed runs fine. So anyway, I thought I'd look into this but not sure where to start. Could it be in limp mode and how can I tell? It revs fine - in the low gears I can get up to around 3500 rpm quite easily - and also in the higher gears it can get there but it takes quite a while.
There is no engine check light that comes one - apart from when I first turn on the ignition but it goes out straight away..... I've read that I can run the ODB diags by turning on and off the ignition several times and looking for a code..... but I see nothing. I understand that the engine check light should flash the code but it doesn't flash at all - so does that mean there are not stored error codes or should it flash at least to let me know I've correctly got into diagnostic mode?

I suspect this is turbo related and can see quite a bit of oil on and around the turbo but wanted to see if there are some other areas I can look to localise the issue before jumping into the world of turbo troubleshooting.

thanks in advance.
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daggie

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Re: XJ in Limp Mode??
« Reply #1 on: March 01, 2021, 05:03:10 PM »

the sensor on number 1 injector is the usual suspect :icon_winkle:
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JonL

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Re: XJ in Limp Mode??
« Reply #2 on: March 01, 2021, 06:40:39 PM »

Great many thanks. So will that result in the jeep going into limp mode but doesn’t cause the engine check light to illuminate or register any error codes?
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JamesH

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Re: XJ in Limp Mode??
« Reply #3 on: March 01, 2021, 08:22:28 PM »

My old XJ (4.0) used to run so badly it would stall and that never triggered the engine light so I wouldn’t use the light as a guide to much.

I think there’s a way to test the no.1 injector, maybe resistance, to see if it is faulty. Have a Google search or wait for someone who knows what they are talking about.

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JonL

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Re: XJ in Limp Mode??
« Reply #4 on: March 02, 2021, 08:40:41 AM »

Thanks James
I'll have to find the way to test the sensor - I read that it needs a resistance reading of 94ohms so hopefully not too difficult to test.

I'm not entirely convinced the Jeep is in limp mode at all - it has no acceleration but I thought that limp mode would restrict the revs to 2000 and I can get above that in all gears - plus no engine check light (I accept your thoughts on this not being an accurate diagnostic).

I rechecked the ODB code as I think I was using the wrong process before - I wasn't holding down the trip reset button before. Now when I do it I get the dial and gauge check which all looks fine and dandy. And when this completes the digital display just reverts back to the odometer reading - it doesn't then go to show any error codes.

BUT - I did notice that if I hold down the trip reset and then turn on the ignition (only once off and on) it shows '2.3' on the digital display - is this an engine code? looking it up it might be
"23 Incoming air temperature sensor may be bad"....... not sure

thanks again
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XJ Fan

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Re: XJ in Limp Mode??
« Reply #5 on: March 02, 2021, 09:30:18 AM »

I agree that it doesn't sound like limp-home-mode, due to the unrestricted RPMs. Number 1 injector could be at fault, and usually shows itself as an unwillingness to rev beyond 2000 RPM; it's simple to test, and a replacement injector can usually be found for £100 - £200; please note that number1 injector is different to every other injector you have, so you can't just buy a cheaper one and sling it in.
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bgbazz

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Re: XJ in Limp Mode??
« Reply #6 on: March 02, 2021, 04:00:14 PM »

A quick question for you...does yours have an intercooler? I might be barking up the wrong tree, so I won't say any more until I hear your answer.
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The Smiths

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Re: XJ in Limp Mode??
« Reply #7 on: March 02, 2021, 09:07:15 PM »

A quick question for you...does yours have an intercooler? I might be barking up the wrong tree, so I won't say any more until I hear your answer.

all of them should have an intercooler.


Have you changed fuel filter?
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bgbazz

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Re: XJ in Limp Mode??
« Reply #8 on: March 03, 2021, 07:21:09 AM »

Thanks...I wasn't too sure about that, but given that he mentioned the oil around the turbo, I would be looking at the air intake system, particularly the intercooler. I've had a situation where oil has been pushed up into the matrix of the cooler and partially blocking it...resulting in poor performance. I removed the whole thing and gave it all a good clean with petrol...it was quite amazing to see how much black, gunky stuff came out. After putting it all back together, the performance was very much improved, but I knew it would happen again, so I removed the turbo and had the seals replaced...all sweet thereafter.

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JonL

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Re: XJ in Limp Mode??
« Reply #9 on: March 03, 2021, 08:01:05 AM »

Thanks bgbazz - I think i'll start in that area too - it seems sensible to at least check and clean the pipes, flush out the intercooler and check for leaks etc. On other cars I've had the pipes can become sponge and can collapse a little which causes blockages too. I hoping its not too much of a big job to get the turbo off and check it over for stiff bearings and replacement seals.

The fuel, air and oil filters have all been changed recently to rule these out.

So at the weekend, I'll check the resistance of the No1 Injector sensor (as that looks easy to do) and probably make a start at looking at the turbo and intercooler.

I'm working on the basis that the Jeep isn't in limp mode as I can see no evidence of this outside the poor acceleration - but even that doesn't fit into the 'limp mode' cirteria as I can get above 2000 rpm.

thanks for the advice and thoughts so far - keep it coming  :icon_winkle:
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XJ Fan

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Re: XJ in Limp Mode??
« Reply #10 on: March 03, 2021, 08:43:46 AM »

Good luck - I would pop over and have a look with you, but probably best not to with the situation as it is, plus you are a bit far away   :icon_sad:
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Jonny Jeep

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Re: XJ in Limp Mode??
« Reply #11 on: March 03, 2021, 09:27:20 AM »

Pressing the odometer reset button when turning on the ignition just puts the cluster into the actuator test mode, which can be used to check gauges and cluster controlled lamps are working OK. XJs, similar to TJs, probably don't show trouble codes with the on-off-on-off-on key trick on 98-00 model years. So for those years you'd need a code reader.

Could 2.3 be the trip distance since it was last reset/battery disconnected?
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bgbazz

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Re: XJ in Limp Mode??
« Reply #12 on: March 03, 2021, 01:01:46 PM »

While you are in the air supply area, check the MAF, a dirty or malfunctioning one of those can cause some funny performance.

 :icon_winkle:
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JonL

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Re: XJ in Limp Mode??
« Reply #13 on: March 06, 2021, 09:18:30 AM »

Hi All
So I've just checked the resistance of injector 1 and am getting an open circuit.
I just want to make sure I'm doing this correctly - #1 injector is at the front of the engine correct? There is a thin(ish) black cable form this injector to runs towards the baulk head where there is a connector. When I open this connector I see two male spades on the 'injector' side of the connector and I'm placing my ohmmeter across these two spades - so measuring the resistance back towards the injector?
I was hoping for about 90 Ohms but not getting anything (open circuit) - my ohmmeter works fine and I get a closed circuit when touching the two probes together fine.

Is there any mileage (forgive the pun) in temporarily putting a 100 Ohm resister across the female side of the connector to simulate a good injector sensor and testing for better acceleration? - I think I've read that others have tried this.

many thanks 
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Dave69

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Re: XJ in Limp Mode??
« Reply #14 on: March 06, 2021, 01:06:17 PM »



i added a resitor to the circuit to bring the reading in tolerance, worked for me but the wires are not solder friendly and need a tinning process for the solder to adhere to.

my injector had been service by local injector specialist and was atomizing fine but the sensing circuit was at fault.

i did see an article on the tinternet where a guy took apart the injector to look at fix the simple sensing circuit (sorry cant find the article)
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JonL

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Re: XJ in Limp Mode??
« Reply #15 on: March 06, 2021, 02:39:21 PM »

ok - thanks Dave
Yeah - my plan was to simply put a 100 Ohm resistor across the female side of the connector (leaving the connector unplugged) so it looks like 100 Ohm to the ECU. Probably not worth it then.
I think this is the article you're talking about  http://www.ausjeepoffroad.com/forum/showthread.php?s=6003165bc3cc2281ddc20999d6f214fb&t=154680&page=2

He says it was easy but looks difficult to me....!

And it also looks expensive to buy new - plus unlikely to find a good second hand one...... I expect I'll just live with it as i have done for the last 5 years. Unless anyone knows of one for sale or a suitable (cheap) aftermarket option???

thanks
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Dave69

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Re: XJ in Limp Mode??
« Reply #16 on: March 07, 2021, 04:32:24 PM »



yep thats the article, taking the injector apart is the easy bit and removing the connector. the hard part is the winding of the coil, with the copper wire being brittle due to heat cycling. a rewire can be done but depends if you want to put the effort in.

i assume the sensor reads a pressure pulse signal to the pcm during operation, i did wonder if the system could be confused and operated without the firing pulse but never looked that far when i owned a vm
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The Smiths

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Re: XJ in Limp Mode??
« Reply #17 on: March 08, 2021, 12:47:13 AM »

The resistor mod normally only works on prefacelift
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JonL

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Re: XJ in Limp Mode??
« Reply #18 on: March 08, 2021, 07:43:45 AM »

Many thanks for all the help.
So I've decided not to do anything about this immediately - ie I'm not going o rush out and buy a new one for upwards of £350..... but I will keep an eye out for second hand ones, but they do seem a bit like hens teeth.
But I have a couple of further questions that may help me please.

Is this Injector used in other models or do I need to make sure I get one from an XJ? eg would one from perhaps a WJ be the same?

Secondly - Is the only difference between the #1 injector and the other three just the sensor?
My reason for asking is that my #1 injector is open circuit and therefore the senor isn't working - could I replace this with a standard injector (without the sensor), so the car remains useable, and then perhaps attempt a repair on the sensor as detailed here - http://www.ausjeepoffroad.com/forum/showthread.php?s=6003165bc3cc2281ddc20999d6f214fb&t=154680&page=2
I might give that a go if actually I've nothing to lose other than the price of a second hand (non-sensor) injector.

thanks
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XJ Fan

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Re: XJ in Limp Mode??
« Reply #19 on: March 08, 2021, 09:06:41 AM »

I was/am in the same boat as you, in that I'm not sure if my acceleration is "just the way it is". or if there is emoting at fault (I assume the former). I bought a known-working second hand number1, and had that fitted (with a slight rewiring) when she went to the garage a couple of years back. I've decided to just live with it, as it can be an expensive rabbit-hole to go down, and it may not even fix anything!

I'm pretty sure (although I'm sure to be corrected if I'm wrong) that the injectors are interchangeable for the VM engines, so the 2.5 and 3.1 TD lumps from XJ, ZJ, and early WJ should all be the same; although that does' make them any easier to find!
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JonL

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Re: XJ in Limp Mode??
« Reply #20 on: March 08, 2021, 05:44:37 PM »

Thanks - yeah, I'm think the same.... I didn't want to jump straight in and buy a new one only to find no difference - especially as mine doesn't 'seem' be be in limp mode (I don't get any error codes) and I can climb above 2000rpm. But my #1 injector is testing open circuit so that would indicate an issue.

Did your #1 injector also test faulty?
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XJ Fan

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Re: XJ in Limp Mode??
« Reply #21 on: March 09, 2021, 08:57:44 AM »

Did your #1 injector also test faulty?

To be honest, I didn't test it, I stumbled across a "known working" number 1 on ebay, and snagged it as it was a good price.
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JonL

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Re: XJ in Limp Mode??
« Reply #22 on: April 10, 2021, 11:06:39 AM »

Hi all
Just revisiting this one as I've managed to get hold of a new #1 injector and may as well give it a try - not sure it'll be the root cause of my lack of power but worth a go now I've managed to get hold of one.

Is this something that an 'average' mechanic can do? I've never fitted an injector before and not entirely sure what all the pipes do. I know there's a tool for this which I don't have but have been told that removing the rocker cover and using a swan-neck spanner is an acceptable alternative - I have a 28mm swan-neck so this would be my approach - Is that doable??

If so  - is the following correct:
Disconnect battery
Remove rocker cover - I have a replacement gasket
remove the two fuel hoses from each side of the injector and clamp the hoses - there look like they just pull off.....is much fuel likely to come from either of these?
remove the metal centre fuel pipe - I assume this is the main fuel supply.... is this pressurised at all?
Unplug the sensor cable and pass it through the 28mm spanner
loosen the injector - I assume normal thread direction - and remove entirely
screw in the the new injector hand tight
pass the senor cable through the 28mm ring to allow a tighten using the spanner - I guess there is a torque setting for this but I'm unlikely to be able to accurately gauge that - is that a problem.... is it ok to be nearly accurate  :icon_biggrin:
reconnect all the fuel lines - is there anything that needs to be bled?
reconnect the sensor
add the new rocker cover gasket - using sealant to get a good seal - and bolt back the rocker cover
reconnect the battery
start the car??

Anything that I've missed, should be careful of or simply not try and leave it to a professional......

thanks as always
Jon
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XJ Fan

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Re: XJ in Limp Mode??
« Reply #23 on: April 12, 2021, 08:30:15 AM »

If so  - is the following correct:
Disconnect battery
Remove rocker cover - I have a replacement gasket
remove the two fuel hoses from each side of the injector and clamp the hoses - there look like they just pull off.....is much fuel likely to come from either of these?
remove the metal centre fuel pipe - I assume this is the main fuel supply.... is this pressurised at all?
Unplug the sensor cable and pass it through the 28mm spanner
loosen the injector - I assume normal thread direction - and remove entirely
screw in the the new injector hand tight
pass the senor cable through the 28mm ring to allow a tighten using the spanner - I guess there is a torque setting for this but I'm unlikely to be able to accurately gauge that - is that a problem.... is it ok to be nearly accurate  :icon_biggrin:
reconnect all the fuel lines - is there anything that needs to be bled?
reconnect the sensor
add the new rocker cover gasket - using sealant to get a good seal - and bolt back the rocker cover
reconnect the battery
start the car??

Anything that I've missed, should be careful of or simply not try and leave it to a professional......

thanks as always
Jon

I've not done the job, but it sounds a logical approach to take. I even bought the special injector socket thing; I picked it up at Helfrauds for not too much. I'd have some cloth or towels to mop up any spilled fuel, and I would take pictures of everything before, during, and after, so you have reference points if you forget how something was before removal. Other than that, take your time, have a cup of tea, and enjoy the learning :)

I'm pretty sure The Smiths would have done this, and I've always found them approachable with questions, etc.
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