Cutting out and intermitant power loss?

[Jon Brown]

Car seems to be cutting out when stopped at junctions, sometimes it just dies and other times it sputters and then dies. I was hoping this would be sorted when i changed the cam but still seems to be an issue.

Also, sometimes when driving the car hesitates as if its bogging down or over/under fueling other times it goes really well.

I assume these are probably linked as they seem to happen on the same journeys. I want to say stepper motor but this has been cleaned not that long ago and i can usually here it whiring when i turn the car off.

Would the ignition amp cause these problems?

Help would be greatly appreciated especially as im supposed to drive to Wales on Saturday

[Malcster]

Might sound weird, but mine did this when it was low on coolant.
It just wouldn't idle.
Might be worth checking the expansion tank is half full?

[Excitedoldgeezer]

I have a similar problem, when I put it on the rolling road recently the guy suggested the following:

air filter clean?
air filter intake by plenum clean?
Fuel pump connections corroded
Fuel pump knackered

basically the engine is cutting out because it is being starved of something air or fuel? his opinion anyway. Planning on doing my suspension refurb after the summer and will clean up the fuel pump area then, the filter and intake are clean. Will change all fuel and ignition relays as well. All ignition components have been changed recently and work well, so not an ignition related fault. Will keep yu posted.

On a brighter note, sailed through the mot requiring only a new steering rack seal ;-)

Enjoying the sunshine
Steve

[Jon Brown]

Interesting comments, having just changed the camshaft and a few other bits I would have thought the coolant level would be correct but i will double check this evening.

As for the below

air filter clean? - Only a year old but no doubt needs a clean, especially baring in mind its location.

air filter intake by plenum clean? - When we changed the cam everything was cleaned with break cleaner

Fuel pump connections corroded - One of the cables to the fuel pump has recently started to fall off, so i have replaced the spade connector and the actual connection looked clean.

Fuel pump knackered - A possibility

Anyother sugguestions welcome, Im convinced that the two must be linked. Although i am having the diagnostics run tonight. Hopefully that will shed some light on the matter

[macdeb]

Air leak on induction? easy done.

[gavgavgav]

Another suspect could be the ignition module, it's a difficult one to diagnose without replacing as the faults are intermittent and often heat related.

For me a new module fixed the random dieing at idle.

[peaktorque]

Mine used to cut out at junctions etc randomly. I cleaned the stepper motor, but it made no difference. I've since adjusted the base rate (once I'd un-seized the adjustment screw) and now it never cuts out. Although one issue that has arisen since doing this is that the idle does seem to 'get stuck' a 1000 rpm for a duration on occasions, but will drop back down after a while.

I still think the issue with mine is the SM but since the BR has been set up it can't possibly idle any lower than ~ 800 rpm, but can if the SM gets stuck open idle higher.

The other issue described sounds like a fuelling issue, but unlikely to be linked to the SM.

[ChimpofDarkness]

Jon Brown said:

Car seems to be cutting out when stopped at junctions, sometimes it just dies and other times it sputters and then dies

Ok so I had this and traced it to a bad connection at the back of the speedo.

Sounds odd right?

Well the ECU needs a speed signal, and in the case of a Chimaera the path from speed signal generation to ECU is thus:

SOURCE: Speed sensing pick up at the diff

DELIVERED TO: The Speedo Head

FROM THERE TO: The iffy TVR speed signal converter box under the dash

AND FINALLY TO: The ECU

The ECU needs a speed signal to reinstate fuel as you approach a junction, otherwise the car would stall.

Because TVR used a different speedo to Range Rover they needed to design a box of electronics to convert the signal from the TVR speedo into something the ECU would recognise.

The thing is, like most things electrical designed in-house by TVR, the speed signal converter box is not the most reliable thing in the world.

You may find like I did it's just a bad connection, the best advice I can give you is start at the back and check everything in the chain.

If the speedo is not working it's likely to be the speed sensor at the diff or a speedo failure.

If the speedo works fine (like mine did) it's the output signal wiring from the speedo to the TVR speed signal converter box that lives under the dash.

Or it could be there is a fault with the TVR speed signal converter box itself.

I believe this little box of tricks to be the source of many odd Chimaera running issues that are often misdiagnosed as a stepper motor fault.

Interestingly it seems after a lot of testing & development by Steve Heath of his "ECU Mate" he has come to the same conclusion.

So much so that I believe Steve is developing a more reliable replacement for the TVR speed signal converter box.

At the end of the day all the above is just another thing to check, it's almost impossible to reliably diagnose an issue like yours over the internet.

Good luck with finding your fault, Dave.

[Alexdaredevilz]

Fixed my cutting out with a simple adjustment on the tps but took me a week to find it

[ChimpofDarkness]

Alexdaredevilz said:

Fixed my cutting out with a simple adjustment on the tps but took me a week to find it

Excellent point Alex, probably the best place to start to be fair.

[Alexdaredevilz]

It felt as if it were miss firing or running out of fuel, I think what was happening as I go on/off the throttle it was 'out of range' making the already stupid Ecu confused

[Jon Brown]

Excellent responses, much appreciated.

Any idea where the tps is located?

[Alexdaredevilz]

Just on the side of the throttle body (Throttle Position Sensor)

Throttle Potentiometer

The potentiometer (or Throttle Position Sensor – TPS) can only be adjusted after the throttle body has been set correctly as specified by Land Rover. Using a digital Voltmeter put the negative probe into the Red/Black wire (engine side of throttle potentiometer plug), and the positive into the Red wire. The throttle potentiometer wires have only two colour codes according to age. The change occurred with the “Serpentine” engine around 1994, as follows:

EFi Loom Early TPS Serpentine TPS
5 Volt Supply Yellow Yellow Brown
Signal Red Red Green
Ground Red/Black Green Blue


Leave the potentiometer connected. Start the engine and check that the voltage reading is 0.32 – 0.34 Volts.

Incorrect Voltages produce the following symptoms. If it is less than 0.28 Volts, the system will not adjust the idle speed. The idle speed will probably be very low, and the vehicle may tend to stall (note that this is not the only cause of stalling). If the Voltage exceeds 0.38 then the system will not recognise that the throttle is in the idle position, and the idle speed stays at 1100 to 1200 RPM despite setting the Base Idle speed correctly.

If the reading is incorrect then slacken the mounting screws, rotate the potentiometer to achieve the correct reading, and then retighten. Note that some potentiometers do not have slots for the mounting screws, and in this case the mounting holes may need to be elongated to allow adjustment.

Check that the voltage rises smoothly as the throttle is opened. It may be easier to stop the engine before performing this test, but do remember to leave the ignition on when reading the meter. If there is any wear in the potentiometer then it will show up around the low throttle (just off idle) position, since this area gets the most use.

Incidentally, the 5.0 Volt feed on the Yellow wire is derived directly from the ECU internal 5.0 Volt rail, and should be very stable and accurate. If there is a significant deviation then this is a clue to an internal ECU fault, or a major wiring fault.

[ChimpofDarkness]

Jon Brown said:

Excellent responses, much appreciated.

Any idea where the tps is located?

The Throttle Position Sensor is located on the throttle body.



It is secured by two small screws, loosen the screws to adjust.

You may find you need to slightly elongate the holes in the TPS to gain sufficient adjustment.

Adjusting to the correct position is best done using a multimeter, you want the following readings on your meter:

.085 - .545v with the throttle fully closed & 4.2- 4.9v with the throttle fully open.

You are also looking for a smooth swing on the meter indicating there are no breaks in the tacking or dirt that may cause a sudden interruption in your meter readings.

Take the opportunity to confirm the throttle butterfly itself opens and closes fully too.

[ChimpofDarkness]

On the back of my speed signal post above this make for interesting reading:

http://www.geocities.ws/pbtn6/injspec.htm

Read the topic titled "What's a Road Speed Sensor For?"

Also apparently you can check your road speed signal is getting all the way to the ECU by disconnecting the
ECU plug and checking the voltage at pin 6 with the ignition on.

Find a reliable earth & roll the car forward slowly with the live meter probe on pin 6.

Your meter should show either a fluctuating voltage from 0 - 12V or from 0.5 - 5V depending on the type of sensor fitted.

Edited by ChimpofDarkness on Thursday 7th June 18:30

[Jon Brown]

Thanks for these, my lamba sensor wiring was not making a connection. although this is now fixed (last night) it hasn't made any difference but should help overall.

I shall investigate next week and let you know the outcome.

[simonej]

Probably of no help to you but when mine had the same symptoms as you it was one of the battery post clamps that was slightly loose. Tightened it up and problem solved. As I say, probably not what you've got but it's another thing you can tick off the list.