XJ40 ( XJ81 ) 1986 - 1994

Limp mode

 
  #1  
Old 05-31-2018, 07:20 AM
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Default Limp mode

I have a 1990 xj6 149,xxx miles. Starts up and runs fine, until I come to a stop sign or red light and have to slowdown. Once it hits or drops below 10 miles an hour it switches into limp mode. Please help.
 
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Old 06-01-2018, 01:26 PM
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Originally Posted by Justin Lemus-McGee View Post
I have a 1990 xj6 149,xxx miles. Starts up and runs fine, until I come to a stop sign or red light and have to slowdown. Once it hits or drops below 10 miles an hour it switches into limp mode. Please help.

Hi Justin,

Welcome to the Jaguar Forums! It's great to have you with us.

My first suggestion would be to check your transmission fluid. Low fluid has been associated with stalling when coming to a stop or slowing to make a turn. For an accurate check, the transmission fluid must be hot, so take the car for a good drive of 20 minutes or more.

Park on a level surface, and with the engine running, hand brake set, and foot on the brake pedal, move the gear selector lever through each position, pausing 3 seconds at each (Reverse, Neutral, Drive, 3, 2), the move the lever back to Park.

Open the hood, remove the transmission fluid dipstick and wipe it clean. Reinsert and withdraw it slowly to avoid flicking fluid all over the place. Read the fluid level on the end of the dipstick. It should be exactly at the HOT mark. If the reading is not clear due to streaks of fluid on the dipstick, wipe it clean and repeat until you get a clear reading of where the fluid line is on the dipstick.

The fluid should should have a good transparent red color and should not smell burned.

If the fluid is low, add a good Dexron III substitute like Mobil 1 ATF a few ounces at a time until the fluid is exactly at the HOT line and not over or under. Do not use Dexron VI because its viscosity is too low.

Please let us know if the transmission fluid level is good and we'll help you with further diagnosis.

Cheers,

Don
 
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Old 06-01-2018, 04:11 PM
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The TPS can also cause TCM faults. The TPS has two circuits, one for the engine and the other for the gearbox. (6 wires)


bob
 
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Old 06-01-2018, 05:41 PM
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I checked the transmission fluid and it was at a good level. What is the TPS and where is it located?
 
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Old 06-01-2018, 06:00 PM
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TPS is located below the throttle body (TB)
The TB needs to be removed to really be able to clean the TPS effectively.
1/4 drive with a universal joint, short extension and 10mm socket is the way to go.
Note! These bolts are tight. The TPS is red in colour for identification, it can get gummed up with blow by from the engine breather gunk seeping down through the TB spindle.
Once you have the TB off you can ease off the cover of the TPS and spray with brake cleaner.
While the TB is off the manifold it would pay to check the voltage is in the correct range, its a long time since I reset mine but someone will be able to advise what the value should be.
 
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Old 06-01-2018, 09:01 PM
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On our '93 a common cause of Limp Home Mode was oil contamination of the electrical connector for the TPS, which is mounted to a bracket on the intake manifold to the left of the Throtte Body. Cleaning both halves of the connector would usually clear LHM. However, our car never exhibited your symptoms of going into LHM specifically when slowing to 10 mph or less. But it would certainly be worth cleaning the TPS connector as an easy first step.

If that doesn't resolve the issue and you remove the TB to flush the inside of the TPS, drill two drain holes in the TPS case to reduce the accumulation of gunk in the future. Also clean the EGR and carbon canister purge valve port on the underside of the intake manifold. I have photos of all this work in the albums at the link in my signature.

Cheers,

Don
 

Last edited by Don B; 06-02-2018 at 08:37 PM.
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Old 06-02-2018, 01:58 PM
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This is all kind of confusing for me. I'm not a very experienced mechanic. I can see the TBS and I found the blue connector for it located to the left of the TB near the coolant reservoir. But the tb seems a little out of my experience to remove.
 
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Old 06-02-2018, 08:38 PM
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Originally Posted by Justin Lemus-McGee View Post
This is all kind of confusing for me. I'm not a very experienced mechanic. I can see the TBS and I found the blue connector for it located to the left of the TB near the coolant reservoir. But the tb seems a little out of my experience to remove.

Try cleaning the connector first. Zero-residue electronic cleaner is available at most auto parts stores. CRC is a popular brand.


Please keep us informed.



Cheers,


Don
 
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Old 06-03-2018, 08:10 AM
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Originally Posted by Don B View Post
Hi Justin,

Welcome to the Jaguar Forums! It's great to have you with us.

My first suggestion would be to check your transmission fluid. Low fluid has been associated with stalling when coming to a stop or slowing to make a turn. For an accurate check, the transmission fluid must be hot, so take the car for a good drive of 20 minutes or more.

Park on a level surface, and with the engine running, hand brake set, and foot on the brake pedal, move the gear selector lever through each position, pausing 3 seconds at each (Reverse, Neutral, Drive, 3, 2), the move the lever back to Park.

Open the hood, remove the transmission fluid dipstick and wipe it clean. Reinsert and withdraw it slowly to avoid flicking fluid all over the place. Read the fluid level on the end of the dipstick. It should be exactly at the HOT mark. If the reading is not clear due to streaks of fluid on the dipstick, wipe it clean and repeat until you get a clear reading of where the fluid line is on the dipstick.

The fluid should should have a good transparent red color and should not smell burned.

If the fluid is low, add a good Dexron III substitute like Mobil 1 ATF a few ounces at a time until the fluid is exactly at the HOT line and not over or under. Do not use Dexron VI because its viscosity is too low.

Please let us know if the transmission fluid level is good and we'll help you with further diagnosis.

Cheers,

Don
do I leave the transmission running when I check the fluid level?
 
  #10  
Old 06-03-2018, 01:14 PM
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Originally Posted by Justin Lemus-McGee View Post
do I leave the transmission running when I check the fluid level?

Yes, you leave the engine running for the entire process, and as I mentioned in Post #2, take a good long drive before checking the fluid to get it to full operating temperature.

Cheers,

Don
 
 
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