Hello Guys,
I am the 2nd owner of a beautiful 2003 Jag s type 4.0. I bought the car from a used car dealer that purchases from auction and I don't have service records. The car has near 110k miles on it and I want to keep it on the road for years to come. One problem I have is the first 20 min after start up the rpm..spike up and down at idle then goes away after the engine warms up. Is this coils? Or is a timing chain more likely an issue? I replaced plugs...all fluids ..thermostate and housing...ac condenser. Any suggestions for a jag at this mileage?
I appreciate any help. 2003 S type 4.0

 

That sounds like a sensor to me. Do you have a code reader? You can purchase an inexpensive Elm 327 online for next to nothing.
BTW, I'm not sure when they started using metal cam chain tensioners, but the plastic ones should be changed around 100K miles (ask me how I know) -

 

Jaguar only made the 4.0 from 2000-2002.
2003 MY is the 4.2 liter engine. Check your VIN.

See attached .pdf for MY ID.

bob

 

Your right I checked the vin it's a 4.2. No I don't have a code reader but I should get one. Any budget friendly suggestions appreciated. I definatly rather spend some money now to save the engine. I do have 110k miles

 

Ordered the elm...your right.. next to nothing. I will check the codes when it arrives. Greatly appreciated guys

 

Welcome Shane and congrats on your very nice looking car . . . not only the 4.2L V8 but the superb ZF 6HP26 trans . . . great combination. OK, tools?

• Second priority, ELM327, you have ordered. Cheap as chips and terrific value as your "go to" diagnostic tool;

• Third priority, Smart Charger or Battery Tender, as per "Battery 101" listed in my sig. Check the write up for why absolute top notch battery performance is a critical issue on these cars;

• First priority, aha, will cost you nothing more than time and patience. Download all the resources like JTIS, TSBs, wiring diagrams both here on Stickys and Gus' JagRepair.com, although some really well heeled members lash out a few hard earned pounds, drachmas, euros, or in my case AU$9.95 (2 coffees) to have all the 1,000s of pages on a handy CD.

Best wishes for you and your S-Type,

Ken

 

Usually you can hear timing chain (called chain slap) at startup if it is stretched. You can also look for signs of chain slap on various surfaces around chain passage. Not sure on your engine, but generally you can see it with just valve cover off. Typically, replacing chain and guides is a very expensive job, so make sure you need it first. Also, I'd first replace chain tensiometer to see if this addresses chain slack.

To summarize - it is probably not chain, if it is chain you should make sure tensiometer working, if you end up needing a new chain make sure to also look at the chain guides, as broken guide can cause perfectly good chain to jump.

 

Thanks Ken and sinf!
I have already been digging through the repair site..Thanks for that tip Ken. I don't hear a chain slap so hopefully isn't my timing belt Sinf. I just have RPM spike 1k-3k while it's cold. The elm I ordered should be in soon to help with more info. Maybe it's just a vacume leak or something minor. I want to keep my jag on the road and going to retire my current daily soon and let the Jag become my new daily if I can sort out the issues.

 

If it's the newer car (VIN after M45254) the surging may be the known torque converter issue.

elm327 should let you look at such as pending & actual codes plus fuel trims.

 

No timing chain problems with the 4.2L so I would look to the TQ causing the RPM changes.

Have you serviced the ZF yet? Did you replace the sealing sleeve as well? Did you get the fluid level correct?
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This engine does not have a timing belt (it's a chain) nor is there a known issue with chain slap or tensioners.

Tell us more about the 'RPM spike'.

 

@Mikey I had some high-mileage BMW with original chain, but all of them were in-line I6. Chain passage is much simpler that way. With V8 engines chain is just a lot more finicky to last lifetime of the engine. Plus, S types are now old enough to start experiencing tensiometer failures.

I don't think chain slack is OP's problem, but you shouldn't outright dismiss it as a possible problem.

 

It's got to be about the last thing to suspect (and may be the first ever, especially at such low mileage for that engine).