4.0 V8 - Misfires only at low RPMs and other related symptoms
#21
Whilst the inlet manifold is removed, replace the return hose to the throttle body as they tend to fail at the large to small hose joint.
Check the brake servo hose as the seals can perish causing an air leak.
Another important item that hasn't been mentioned is the primary and secondary timing chains, guides and tensioners. If their replacement with the latest version is not documented in the vehicle history, remove the cam cover(s) to confirm the secondary tensioners are the metal bodied and not plastic bodied type. Failure of the secondary tensioners can potentially cause catastrophic engine damage if the secondary timing chain jumps more than two teeth.
Check the brake servo hose as the seals can perish causing an air leak.
Another important item that hasn't been mentioned is the primary and secondary timing chains, guides and tensioners. If their replacement with the latest version is not documented in the vehicle history, remove the cam cover(s) to confirm the secondary tensioners are the metal bodied and not plastic bodied type. Failure of the secondary tensioners can potentially cause catastrophic engine damage if the secondary timing chain jumps more than two teeth.
#22
One more thing to consider with the vacuum leaks you've discovered so far. Medium and large leaks can make smaller leaks undetectable until you get the big stuff fixed. This can be very frustrating as you may have to disassemble all sorts of stuff a second time for access, not to mention having to procure any additional parts.
A troubleshooting workaround is to temporarily block off the obvious leaks with heavy clay (edit: non-hardening) or similar. This makes the smaller leaks easier to detect, and hopefully will save you some aggravation.
Last edited by kr98664; 09-30-2020 at 09:14 AM.
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#23
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The_Portuguese (10-01-2020)
#24
Another possibility...
So, introductions done it's time to try and start getting the S-type running like new.
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
Any help would be appreciated!
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
- Constant (what seems to be) misfires at idle that are physically felt and heard inside and outside the car.
- Car shakes and shudders somewhat violently like it is going to stall and seems to lose power starting at around 80kmh/50mph until around 110kmh/70mph (I assume it's RPM related, not speed related since the violent shakes stop if I speed past or stay below the mentioned speed/RPM combination).
- Very strong gas smell as soon as I start the car that seems to remain even as the car is driven.
- Extremely excessive fuel consumption at low speed, low gear driving (Average of 48L/100km/5mpg, confirmed with the loss of around 40km/25mi of fuel autonomy in just a few minutes of city driving).
- Car does not show any codes and the engine light never came on.
- Using the OBDII reader what was mostly apparent was that the SPARKADV is all over the place at low RPMs/idling when the symptoms show, going from say, 15 to -3 to 14 to -5 and so on constantly. It, however, becomes stable when I take the car to high RPMs and keep it there.
- The OBDII reader also seems to show it's throwing fuel in excess to the cylinders.
- All the other values I took from the OBDII reader seem to be normal.
- The car seems and feels to act smoothly at high RPMs, either driving or with the car stationary in neutral.
- All the symptoms remain with the car in gear, reverse or neutral. As such, a transmission issue seems out of the question.
- Fuel consumption is within spec on the highway when the symptoms are not present.
- I cleaned the MAF and changed the spark plugs but it made no difference at all.
Any help would be appreciated!
I found my 05’ S-type 4.2 on my birthday, for a song. She was on her way to the junk yard, scrapped by 2nd owners who tried to service it at a BMW shop. Cosmetically perfect, mechanically questionable. Got her for half the cost of a new set of tires.
Mine behaved similarly when I bought it, needed a jump to start it, and I didn’t think it would make it the 5 miles in stop and go traffic to my indie Jag Shop without a tow.
If they aren’t maintained consistently, a vehicle if this age is likely to have vacuum leaks and I’ve dealt with two, plus an air flow sensor.
My initial underlying issue with the rough performance was a bad ignition coil (only $75 usd to replace)...but it’s well worth it to do all coils and plugs at the same time because if one fails, the rest will.
She purrs and glides smoothly after addressing those issues and gas mileage improved to just under 30 mpg.
I’ve spent $2000 usd total on this beauty.
These are such great cars when maintained well. I’ve now passed the 200k mile mark and still going strong.
Last edited by Susie Q; 10-01-2020 at 12:06 PM. Reason: Typo
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The_Portuguese (10-01-2020)
#25
I can't express enough my gratitude to all of you. Really.
Thank you so much as well for your encouraging words Susie Q, a beautiful specimen with a background to match. I hope you drive yours for 200k more miles.
At the moment, I am getting my hands into a smoke contraption that can get enough smoke with enough pressure so I can make sure all the leaks are found. I will update all of you as soon as I give it a try. It should only take a few days.
Thank you so much as well for your encouraging words Susie Q, a beautiful specimen with a background to match. I hope you drive yours for 200k more miles.
At the moment, I am getting my hands into a smoke contraption that can get enough smoke with enough pressure so I can make sure all the leaks are found. I will update all of you as soon as I give it a try. It should only take a few days.
#26
4.0 Misfire
So, introductions done it's time to try and start getting the S-type running like new.
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
Any help would be appreciated!
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
- Constant (what seems to be) misfires at idle that are physically felt and heard inside and outside the car.
- Car shakes and shudders somewhat violently like it is going to stall and seems to lose power starting at around 80kmh/50mph until around 110kmh/70mph (I assume it's RPM related, not speed related since the violent shakes stop if I speed past or stay below the mentioned speed/RPM combination).
- Very strong gas smell as soon as I start the car that seems to remain even as the car is driven.
- Extremely excessive fuel consumption at low speed, low gear driving (Average of 48L/100km/5mpg, confirmed with the loss of around 40km/25mi of fuel autonomy in just a few minutes of city driving).
- Car does not show any codes and the engine light never came on.
- Using the OBDII reader what was mostly apparent was that the SPARKADV is all over the place at low RPMs/idling when the symptoms show, going from say, 15 to -3 to 14 to -5 and so on constantly. It, however, becomes stable when I take the car to high RPMs and keep it there.
- The OBDII reader also seems to show it's throwing fuel in excess to the cylinders.
- All the other values I took from the OBDII reader seem to be normal.
- The car seems and feels to act smoothly at high RPMs, either driving or with the car stationary in neutral.
- All the symptoms remain with the car in gear, reverse or neutral. As such, a transmission issue seems out of the question.
- Fuel consumption is within spec on the highway when the symptoms are not present.
- I cleaned the MAF and changed the spark plugs but it made no difference at all.
Any help would be appreciated!
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Susie Q (10-01-2020)
#28
hello, my S Type Sport had the same problem, the long and short is; you’ll need to order those coil packs and check your fuel pressure at the rail. My Jaguar was very very happy after replacing all the coils and changing the spark plugs to triple platinum. A new fuel filter is a plus as well.
Were either of you getting any misfire codes (P0300-P0308) or anything else related? What's very unusual with this thread is he is experiencing the rough running but with no fault codes.
#29
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#30
Similar probs
I have a 2000 xjr with similar shaky at idle weird exhaust sounds etc but I have low compression could that just be the heads need to be rebuilt ? I don’t know what’s going on but I’d love some input I’ve changed plugs and sealed various vacuum leaks as it is and also rebuild the sc I checked the timing chain which is tight and not broken
#31
Here's the sequence of events for me:
It ran fine at higher speeds for a while. I was out of town so stopped by an auto parts store to have them get the codes. I notified my mechanic, to make sure it was OK to drive it back, and I did with no problem other than that check engine light. Then the misfires began and instrument panel message "restricted engine performance, " which threw more codes when checked again, and I was told to bring it in.
Portugese, if you're having misfires with no codes, are you getting any messages or lights on the instrument panel? If not, is it possible something electrical/ or fuse-wise might be interfering with that?
Last edited by Susie Q; 10-02-2020 at 02:08 PM.
#32
I did get codes
I did get codes like the one you showed and I have a few that don’t clear also I have the check engine and restricted performance lights on just a side note I took it to a jaguar “professional “ and he told me all of this was bc I had a lower but consistent compression in the engine all cylinders at 120 psi he told me I’d have to either spend $7k to “fix the problem” or junk the engine and put a brand new one in for $5k
#33
Big $$$$
I second NB Cat's post, and I'd never consider the expensive replacement suggestions without a second opinion from a reliable independent shop that's been working on Jags for a long time.
There are a lot of other issues that could cause a pressure change.
There are a lot of other issues that could cause a pressure change.
Last edited by Susie Q; 10-02-2020 at 02:38 PM. Reason: typo
#34
Another thought is China (Coil) Syndrome. When you replaced the spark plugs, did any of the coils look new? Any visible brand name on them? OEM coils (and equivalent) are quite robust and can last a long time. But perhaps the previous owner decided to replace the coils for reasons unknown. Maybe there was a problem. Maybe they got changed just because. However it happened, the $34 set of coils on eBay is no bargain. Many forum members have learned this the hard way. So if the coils look relatively shiny and new, that could be part of the problem..
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The_Portuguese (10-03-2020)
#35
Fuel is only good for a few months at best. As it ages, the more volatile elements evaporate. High octane fuel is the worst for this. You end up with low octane crap that does not burn well.
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The_Portuguese (10-03-2020)
#36
@kr98664
I did not check the fuel pressure on the injector rail, I did on the OBD scanner tho. It read 270kPa while the normal value would be 300kPa. That difference doesn't seem to be significative.
Regarding the coils, yes, I did notice something when changing the spark plugs. Two of the coils (and only two) were different from the other 6. These two did not bear any marking and are clearly aftermarket. But again, that is only two of them that were like that, the other 6 had markings on them (I believe they are the OEM ones).
And regarding the fuel, I did already went through a gas tank of brand new premium fuel. If that was a problem, it is gone now.
I am pretty certain the vacuum leaks are the issue, it fits all the symptoms.
I did not check the fuel pressure on the injector rail, I did on the OBD scanner tho. It read 270kPa while the normal value would be 300kPa. That difference doesn't seem to be significative.
Regarding the coils, yes, I did notice something when changing the spark plugs. Two of the coils (and only two) were different from the other 6. These two did not bear any marking and are clearly aftermarket. But again, that is only two of them that were like that, the other 6 had markings on them (I believe they are the OEM ones).
And regarding the fuel, I did already went through a gas tank of brand new premium fuel. If that was a problem, it is gone now.
I am pretty certain the vacuum leaks are the issue, it fits all the symptoms.
#37
Regarding the coils, yes, I did notice something when changing the spark plugs. Two of the coils (and only two) were different from the other 6. These two did not bear any marking and are clearly aftermarket. But again, that is only two of them that were like that, the other 6 had markings on them (I believe they are the OEM ones).
If those two coils look somewhat older, it's more likely they had been working fine. Shiny and new is more indicative of a potential problem that was never fully corrected.
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#38
Low rpm misfire and no code(s) shown
So, introductions done it's time to try and start getting the S-type running like new.
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
Any help would be appreciated!
The first, and as of now, only major issue (it appears it's all related) I am aware of consists of the following symptoms:
- Constant (what seems to be) misfires at idle that are physically felt and heard inside and outside the car.
- Car shakes and shudders somewhat violently like it is going to stall and seems to lose power starting at around 80kmh/50mph until around 110kmh/70mph (I assume it's RPM related, not speed related since the violent shakes stop if I speed past or stay below the mentioned speed/RPM combination).
- Very strong gas smell as soon as I start the car that seems to remain even as the car is driven.
- Extremely excessive fuel consumption at low speed, low gear driving (Average of 48L/100km/5mpg, confirmed with the loss of around 40km/25mi of fuel autonomy in just a few minutes of city driving).
- Car does not show any codes and the engine light never came on.
- Using the OBDII reader what was mostly apparent was that the SPARKADV is all over the place at low RPMs/idling when the symptoms show, going from say, 15 to -3 to 14 to -5 and so on constantly. It, however, becomes stable when I take the car to high RPMs and keep it there.
- The OBDII reader also seems to show it's throwing fuel in excess to the cylinders.
- All the other values I took from the OBDII reader seem to be normal.
- The car seems and feels to act smoothly at high RPMs, either driving or with the car stationary in neutral.
- All the symptoms remain with the car in gear, reverse or neutral. As such, a transmission issue seems out of the question.
- Fuel consumption is within spec on the highway when the symptoms are not present.
- I cleaned the MAF and changed the spark plugs but it made no difference at all.
Any help would be appreciated!
I had a similar problem with my 3.0 V6 which eventually showed a misfire dtc. I swapped the respective coil to another cylinder and the misfire followed it. Replaced the coil and it has been perfect to date.
Boa sorte!
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kr98664 (10-05-2020),
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