1998 Morgan Plus 8 with 3.9 Rover engine (hotwire fuel injection)
I have a query on behalf of a friend.
He has owned the above vehicle for just over 2 years and on a regular basis experiences an issue with the engine speed not returning to idle speed when the car is slowing down. While the car is still moving, the engine speed can be kept up to 1600 rpm until the car becomes stationary. Also, if the car is put into neutral and continues to free wheel, the engine speed can stay up until the car stops moving. It is then that the engine speed returns to idle (approx 700rpm).
We are aware that the car has a motion sensor which possibly has an influence over the engine revs and it could be this which is keeping the engine revs up longer than is required.
Has anyone got any suggestions as to how this could be cured? I seem to remember a similar issue with 4/4s being debated in Miscellany a while ago.
Best regards
Tim
V8 Idle Issues
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Phil Egginton
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Re: V8 Idle Issues
Hi Tim
My red monster also suffered something simmilar I recall. I think we ended up changing the hot wire thingy but I'm sure Chas will recall.
The 4/4 issue is different and more a 'by design' by Ford and was to help stop transmission shunt on reps Mondeos's (I think).
Cheers
My red monster also suffered something simmilar I recall. I think we ended up changing the hot wire thingy but I'm sure Chas will recall.
The 4/4 issue is different and more a 'by design' by Ford and was to help stop transmission shunt on reps Mondeos's (I think).
Cheers
Phil Egginton
"Think very carefully… because if you ever start, you will never be able to leave it alone" — Donald Campbell CBE
"Think very carefully… because if you ever start, you will never be able to leave it alone" — Donald Campbell CBE
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Jim Mountain
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Re: V8 Idle Issues
Hi Tim
Sounds like a fault with the stepper motor (Idle regulation valve), take it out and give it a clean up with a bit of brake cleaner, plus you may be able to reinitalize it, by switching the ing. on and off in a certian sequence, but i'm sure someone with more experance of Rover V8's will be able tell you more.
Merry Christmas to you and Jane
Sounds like a fault with the stepper motor (Idle regulation valve), take it out and give it a clean up with a bit of brake cleaner, plus you may be able to reinitalize it, by switching the ing. on and off in a certian sequence, but i'm sure someone with more experance of Rover V8's will be able tell you more.
Merry Christmas to you and Jane
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chas windridge
- Tech Comm
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Re: V8 Idle Issues
Hi Tim
A common problem with Lucas 14 cux hotwire system and a pain in the neck! - as not all cars with this problem seem to respond to the same tweaks.
If it always returns pretty quickly to normal idle when stationary then the idle control stepper motor is probably OK, the plenum air bypass adjuster (allen screw) is set about right and there are no induction air leaks(check). The problem is often the road speed sensor which "tells" the ECU the car is still moving ( it's a Range Rover thing !!) and although you've lifted off the throttle, the ECU keeps the idle control Stepper motor open too much until it gets the message the cars' stopped !
The road speed sensor is in the speedometer cable under the dash - on earlier cars follow cable back from speedo and you should find it,on later electronic speedo cars it's near the bulkhead from memory, it has a yellow and green wire to a connector plug. Unfortunately if you just disconnect it, most cars will stall when you come to a halt although the "over-revving" is cured !! Some don't so problem solved ! Then try a new roadspeed sensor which often works with some cars. Sometimes though, it just seems to be the particular ECU which is the problem and John at JED often sorts them out tweaking the control chip.
A common problem with Lucas 14 cux hotwire system and a pain in the neck! - as not all cars with this problem seem to respond to the same tweaks.
If it always returns pretty quickly to normal idle when stationary then the idle control stepper motor is probably OK, the plenum air bypass adjuster (allen screw) is set about right and there are no induction air leaks(check). The problem is often the road speed sensor which "tells" the ECU the car is still moving ( it's a Range Rover thing !!) and although you've lifted off the throttle, the ECU keeps the idle control Stepper motor open too much until it gets the message the cars' stopped !
The road speed sensor is in the speedometer cable under the dash - on earlier cars follow cable back from speedo and you should find it,on later electronic speedo cars it's near the bulkhead from memory, it has a yellow and green wire to a connector plug. Unfortunately if you just disconnect it, most cars will stall when you come to a halt although the "over-revving" is cured !! Some don't so problem solved ! Then try a new roadspeed sensor which often works with some cars. Sometimes though, it just seems to be the particular ECU which is the problem and John at JED often sorts them out tweaking the control chip.
Chas
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Lorne Goldman
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Re: V8 Idle Issues
Hi Tim,
There are a few things that could cause the same issue.
!. I would start off by following Chas's advice above. Your symptoms are not exactly the classic speedo transducer (that is the correct term for the thingie)..but close enough. Often it is simply a matter of a bad earth. Inevitably the MMC earth becomes compromised and simply tightening its fastening will do the trick. Here is an image of the transducer.
2. Check your throttle components and cables for chafing. Have some watch it when you use the throttle to see if something is obstructing its free movement.
3. I would also consider the stepper motor..(right side of the plenum). They get very dirty over time and should be cleaned if not replaced. If you do clean or replace it, use a new washer and a bit of loctite on the threads.
4. I would check the throttle potentiometer (left side of the plenum). This item tells the ECU where the the throttle is and is set at idle. I have seen some of them go weird.
For these last two, 3 and43, you need a multimeter and instructions. You can find the later off the GoMoG Plus 8 page http://www.gomog.com/allmorgan/plus8.html under EFI SPECIFIC there is a link entitled "3.9/4.6 Injection System (Checking Procedure for the)". If you need any specific help or more pics and instructions..they are available for you.
Lorne
There are a few things that could cause the same issue.
!. I would start off by following Chas's advice above. Your symptoms are not exactly the classic speedo transducer (that is the correct term for the thingie)..but close enough. Often it is simply a matter of a bad earth. Inevitably the MMC earth becomes compromised and simply tightening its fastening will do the trick. Here is an image of the transducer.
2. Check your throttle components and cables for chafing. Have some watch it when you use the throttle to see if something is obstructing its free movement.
3. I would also consider the stepper motor..(right side of the plenum). They get very dirty over time and should be cleaned if not replaced. If you do clean or replace it, use a new washer and a bit of loctite on the threads.
4. I would check the throttle potentiometer (left side of the plenum). This item tells the ECU where the the throttle is and is set at idle. I have seen some of them go weird.
For these last two, 3 and43, you need a multimeter and instructions. You can find the later off the GoMoG Plus 8 page http://www.gomog.com/allmorgan/plus8.html under EFI SPECIFIC there is a link entitled "3.9/4.6 Injection System (Checking Procedure for the)". If you need any specific help or more pics and instructions..they are available for you.
Lorne