Diesel Turbo 2.5L Diagnostic Manual & "Sagging"

Hi, got a 2.5TD manual RHD export cherokee sport 98 which is "sagging/missing" up hills on the highway (air con switched off or on). Basically we have checked just about everything we can think of( cylinder pressure test/injector tests/injector pump tests etc). Got the 1998 2.0/4.0/5.2L/5.9L SFI powertrain diagnostic procedures manual which does not relate to the diesel version.
Anyone know the part number of the correct MSA/PCM diagnostic procedures manual? Note that it is not listed on the USA Tech Authority site and Daimler Crysler/Jeep USA refer me to our local agents who do not have the manual and do not release/sell it to the public and probably have never seen it. Had this sag/miss for 12 months now and its starting to really crack me (thats putting it mildly)! The dealer has spent a lot of my money replaceing parts so far. cheers A

Hi

think it might be a ZJ/ZG 2.5L Diesel powertrain diagnostic procedures manual. Anyone heard of this? I need a part number or a better description please.

Hi,

i do have a diagnostics manual from the 2,5 TD engine from VM. I think this should be your engine.

Send me your mail via PM and i try to send you the manual i have. Hope this is the one you want.

But don't really think that they know all problems. They are sometimes miles away from a solution.

Maybe you can desribe the "sagging/missing". As the 2,5 TD is not too powerful - maybe it is normal?
And be careful and don't niggle the engine. It has a problem with the cylinder heads which are cracking very easily !!!

greetings from austria
Rainer

Hi,

Thanks for reply, I have sent a PM. WRT the sagging/missing, its mostly at constant acceleration up an incline (does not have to be steep) at around 2000rpm with the aircon and all auxilliaries switched off to conserve power. Had the vehicle for 4 years now and this is a new problem (1 year old).
Description: Each miss does not make a noise, the revs drop slightly during it, the vehicle slows down, the vehicle fires correctly again and picks up revs and speed. Sometimes there is only one miss, sometimes there are a number strung together. The misses do not cause the vehicle to jerk (this happened when the dealer destroyed my No 1 cylinder indicator 2 years ago) but rather it is a gentle miss.
WRT the cylinder heads - you are spot on - I am on my second set for the last 40000km (really liked the idea of the front bumper drill holes). It seems that the 98 also only came out with the one fan or one mechanism (noisy fan has never kicked in and cannot find one in engine) and not the two fan or two mechanism like on my friends newer version which kicks in the noisy fan under heavy loading/high temp conditions. This means that on the 98, there is more heat - my head (no4) closest to the bulkhead went 1st.
regards andrew
(africa)

to the problem .. i will ask a friend .. really don't know what this could be ...

my TD is a 98 and i have 2 fans . the one which is connected via Visco and an electrical in front of the other ... this setup should be in from 97 (here in europe it's mostly the case).
the electrical runs when the A/C is switched on (cyclic).

Hi

Thanks for trying on the problem.

WRT the fans, can you see the electrical fan through the back of the cowl in front of the viscious one on your vehicle?
My friends more recent 2.5TD has a slightly different cowl to mine and his definetly runs when the A/C is switched on. cheers A.

my friend also don'T know what it could be .... he meant he would need more infos ... but remote diagnostic is difficult ..

yes i an see the electric fan .. but you have to look carfully ...

Hi

Just a big space in front of my viscious fan and no connector wires lead into the space that I can see. Looks like there is a bottom bracket at back of radiator with two rectangular slots about 10cm apart in this. No support for it from the top. I remember my friends cowl had a metal strap/pin thing that sits in the middle of the top of the cowl. I guess this to be about opposite the bottom rectangular slots. Would be great if I could find a scrapped vehicle ala spare parts - will have to keep hunting. I will check on his as to where the wiring leads from as I probably do have this wiring loom. Whilst checking last night, found RHS engine mounting rubber broken on one holder- that will take care of my belief of a slowly failing monroe front shock. cheers A.

Hi amac,

i got a mail from Bertie who had a similar problem like you (he read this here but couldn't reply.
He wrote:

My XJ developed a stutter (feels like 2 misfires in quick succession) that
would happen around 1750 rpm. It would happen suddenly and thereafter be
quite normal again. This sometimes happened at constant speed or when
accelerating normal or hard, thus no consistency, but usually under normal
acceleration. When it originally began, it happened about once a day. Soon
it tapered off to about once a week and sometimes even longer. I thought it
could the throttle position sensor (TPS)that needed to be cleaned/replaced
(and this might still be his problem) but it is real difficult to take that
thing out on a RHD model. To make a long story short, a few months later I
suddenly discovered a pool of 'oil' underneath the engine and closer
inspection revealed that it is coming out from between the head and the block.
I took it to a local Jeep mechanic who has experience with diesel Jeep
engines and he identified it as water leaking out, looking like oil because of
the anti-freeze. After taking the heads off it turned out that all the 'welsh
plugs' had rusted and that water was seeping through. One only needed to put
slight finger pressure on these plugs to pop the rusted portion out which
would have caused major water leaks and probable engine failure soon. OK, so
new 'welsh plugs' were inserted. This was about two months ago and the
stutter has not happened again. I still do not know how to link the stutter
to the water leak (and if that was the problem) but to be on the safe side I
think AMAC must make sure that he does not have a similar problem as it
potentially could turn into something serious.

Like AMAC, I am also from South Africa (Pretoria) so he can contact me if he
needs more information.

Best regards,
Bertie Kemp.

Hi Woodstock

Thanks a lot for the info from Bertie. The accelerator pedal sensor is definitely on the list (pushed higher up the order now) and I will look at it once the EGR is properly blocked off. Seeing that pipe go off from the EGR housing to a vacuum/pressure unit which is connected to the turbo also makes me want to check if it is partially blocked as there is a lot of gumf around there.

WRT the coolant, been thinking about this and my thoughts are that it should have no effect on Bertie's performance (other than overheat and unless he has a slight head gasket leak that needed the water pressure to remain sealed - highly unluckly [high pressure]- my head crack pushed air into the water but my performance was still good). I think when they replaced the welsh plugs they had to remove some part (like the EGR hopefully! - SAfricans are extremely optermistic wrt rugby and vehicles) and when replacing they renewed the gasket which fixed his problem.

His welsh plug corrosion is good advice and I will check them - thanks.
Will be away for a week from now. regards amac

I have never owned the XJ turbo deisel but have experience with other deisels so take this advice as a friendly suggestion. A stuttering like that in a deisel engine while going up hill might indicate a fuel pressure problem. Put your fuel gauge on and check it (although it might give correct pressure at idle but not enough under higher use). Could be the pump or the bypass.

Hi

Thanks HossHoffer. The pump was pulled apart and some parts replaced but it had no effect. The bypass valve has not been changed. The diesel specialist did put a gauge on the inline but I do not know if he had it in the cabin whilst driving - probably not. The bypass valve is quite expensive! The bypass valve also had a little bit of fine bright metal along with a bit of dirt in it when I pulled it apart - the diesel specialist said it should have had more metal flakes in it for it to be worn. Maybe a very good idea to swop out with another vehicle. Also if you had the gauge in your cabin, then if the bypass operated, it would give a dip in the pressure - definitly tell you its not on the turbo side but on the fuel side. Thanks for the advice. regards amac.