Help Me Pass MOT (Emissions / Handbrake)

[Strudul]

EDIT: RoverGauge screenshots and logs added at start of page 2
'

94 400HC Chimaera. Just got the outriggers done, body back on, sent for MOT, but it's failed on:

• Parking brake efficiency less than 50% of required value
• Exhaust carbon monoxide content after 2nd fast idle exceeds default limits
• Exhaust lambda reading after 2nd fast idle outside specified limits
• Exhaust carbon monoxide content at idle exceeds default limits
• Brake hose excessively deteriorated Offside Rear

The brake hose is just a simple replacement job, but the other 2 are a bit daunting.


Handbrake (EDIT: Think it's now fixed by simply tightening the adjuster)
It's always been crap, but after reinstalling it since replacing the outriggers (body lift) it's not adjusted as tight as it was (5 clicks now), but the tester said that shouldn't cause the problem and it's more likely something seized (cable or mechanism).

The performance was pretty symmetrical and rear brakes were fine, which presumably rules out pistons.

Any hints on common issues or where to look?


Emissions

• CO was around 2.8 I think, but was supposed to be <0.3 at fast idle
• Not gone craxy with getting it super hot, but was up to temp, and tried running it at >4k rpm but results were worse (CO of >4)
• Pre-cats are deleted (but don't think this should cause any issues)
• Main cat is in and looks ok from what I could see (?)
• Spark plugs were all black, but cleaned them up now
• Air filter (Pipercross foam) was a bit dusty, but given it a clean and it's now drying
• Tune resister is 3.9k ohms (confirmed with multimeter on the blue connector and ECU pins 5 & 27)
• "Cable tie misfire test" seemed to indicate no misfires (melted when held on each header pipe shortly after startup), but not sure it's the most accurate test
• MAF voltage, red/blk and grn/blu wires, ignition on - spikes to 5V for a split second, immediately drops to 0.93V, quickly to 0.5V over the next few seconds, slowly dropping to 0.34V over 10 seconds or so
• MAF voltage, red/blk and grn/blue wires, engine running - Over the space of about 20 seconds from starting, it's initially 1.92V, climbs to 1.98V, then settles down to 1.88V
• MAF (adjuster) voltage, red/blk and blue/red wires, ignition on - Goes up / down when turning the screw. Was at 1.6V, I've set it to 1.8V now as that's apparently the default?
• O/S lambda voltage (wht+blk wire) - mostly sits between -0.5V and -0.6V, jumps to between 0 and -0.4 briefly
• N/S lambda voltage (wht+blk wire) - mostly sits at around 0.04V, jumping to between -0.4 and -1V briefly

Thoughts:

• MAF test taken from blitzracing here
• Lambda test taken from blitzracing here
• Borrow a rovergauge cable to check it's actually running the correct map?
• MAF is faulty? Overshoot and long time to reach 0.34V?
• Why are lambda voltage values negative? Pos probe was to white wire, neg probe to black
• N/S Lambda is faulty?

Any help would be greatly appreciated.

Cheers

Edited by Strudul on Monday 2nd November 23:30

Edited by Strudul on Tuesday 3rd November 23:01

Edited by Strudul on Wednesday 4th November 17:26

[Steve_D]

Rovergauge will fill in so many of the gaps. Could be so many things.
Throttle position
Coolant temperature
Fuel temperature
Etc

Rovergauge. One of the best tools we use.

Steve

[Strudul]

Steve_D said:

Rovergauge will fill in so many of the gaps. Could be so many things.
Throttle position
Coolant temperature
Fuel temperature
Etc

Rovergauge. One of the best tools we use.

Steve

Would be the first thing I did if I had the cable, but just been tied up with so many other bits I kept putting off sorting one out, so the voltmeter is the best I could muster up at short notice unfortunately.

[phillpot]

Handbrake: stripped and rebuilt the calipers on my Griff (same calipers) made a world of difference. Like yours, footbrake was fine but all the handbrake mechanism inside them seizes up.

Reconditioned calipers are available if you don't fancy doing yours.

[QBee]

Those plugs look pretty sooty.
I have found my car runs a lot cleaner on NGK BPR6EIX plugs, but any 6 rated plugs will be better than the TVR standard 7s, which are well known for fouling.

[blitzracing]

I'd say the MAF is faulty if it takes time to stabilise. Chech out the waveforms and testing here.

http://www.g33.co.uk/pages/technical-fuel-injectio...

You have the lambda out put wrong. White is earth, black output, red 12v. If the probes are working and the mixture rich you should see over 1 volt on warm engine, but check you have the heater supply on the red.


The co trim has no effect on the white map.

[Welshbeef]

What fuel do you use? 95/97/99 Ron

Have you considered the Wynns fuel additive that will help.

How much are you driving it? Does it go on long trips to go through hot cold hot cold cycles.

How old is the fuel in the tank? If a low user might be a better bet to only fill to 1/3rd ish to keep the fuel fresher.

Plug doesn’t look good

[Jon100p]

Handbrake

Have you checked that the spring-loaded lever on the callipers is returned fully to its stop by the spring when the handbrake is released?
If the lever doesn't return fully then the internal automatic adjustment mechanism in the calliper can't work properly (to compensate for pad wear) and the handbrake gradually loses efficiency.

There are typically two possible reasons why they don't return to the stops. One, the spring may have lost some of its tension and the lever has got a little stiffer over the years. And /or, over tightened handbrake cable adjustment so that the cable prevents the levers from returning fully home.

If you find that the levers are off their stops; return them fully with the handbrake off using a screwdriver or similar for a bit of leverage (adjusting the handbrake cable to get enough slack if necessary) and give the foot brake several pumps before applying the handbrake again. This should get the callipers to take up any slack in the internal mechanism and may be good enough to get through the MOT.

[Strudul]

QBee said:

Those plugs look pretty sooty.
I have found my car runs a lot cleaner on NGK BPR6EIX plugs, but any 6 rated plugs will be better than the TVR standard 7s, which are well known for fouling.

Someone mentioned this to me, and I appear to be on 7s, so will look to changed once I've found out what's making it rich in the first place.

[Strudul]

blitzracing said:

I'd say the MAF is faulty if it takes time to stabilise. Chech out the waveforms and testing here.

http://www.g33.co.uk/pages/technical-fuel-injectio...

You have the lambda out put wrong. White is earth, black output, red 12v. If the probes are working and the mixture rich you should see over 1 volt on warm engine, but check you have the heater supply on the red.


The co trim has no effect on the white map.

Yeh, excessive stabilisation time on the MAF and voltage is 0.2V higher than expected at idle.

-Of course white is earth...
-So the readings were accurate, just omit the minus sign.
-Engine was warm, but will check the heater supply.
-Based on the voltages, would you say one or both sides are faulty? They are acting differently, so assuming at least one must be bad? Or do I need to fix the MAF before I do anything else?

[Strudul]

Welshbeef said:

What fuel do you use? 95/97/99 Ron

Have you considered the Wynns fuel additive that will help.

How much are you driving it? Does it go on long trips to go through hot cold hot cold cycles.

How old is the fuel in the tank? If a low user might be a better bet to only fill to 1/3rd ish to keep the fuel fresher.

Plug doesn’t look good

99 super.

Was considering additive as last resort, but assuming it won't be enough alone.

Recently did 100+ mile trip on the motorway, but been sat in the garage getting outriggers replaced for last 2 weeks.

Fuel was fresh, had to top up the morning of MOT.

Plugs are cleaned up now.

[NDA]

Strudul said:

• Parking brake efficiency less than 50% of required value

I have a car I've owned from new, that's rarely driven and always fails on this... very annoying. But on talking to the MOT chap he said next time I take it for an MOT drive for a mile or so with the handbrake on by one click and it will then pass.

[QBee]

NDA said:

Strudul said:

• Parking brake efficiency less than 50% of required value

I have a car I've owned from new, that's rarely driven and always fails on this... very annoying. But on talking to the MOT chap he said next time I take it for an MOT drive for a mile or so with the handbrake on by one click and it will then pass.

I found mine passed if I volunteered to sit in the car and operate things for the tester.
Obviously before COVID.
But they are borderline at best.

[Hedgehopper]

Handbrake...

Some say that applying the footbrake first to bring the pads up to the disc then applying the handbrake helps.
Also, handbrake works best when cable is not over-adjusted...about 4 clicks to full on works for me.

[Riff Raff]

Hedgehopper said:

Handbrake...

Some say that applying the footbrake first to bring the pads up to the disc then applying the handbrake helps.
Also, handbrake works best when cable is not over-adjusted...about 4 clicks to full on works for me.

On mine the foot on brake technique is the only thing that will cause the handbrake to hold on even the slightest of inclines. (And even then it's a two hand pull on the lever).

Edited by Riff Raff on Tuesday 3rd November 11:22

[QBee]

Riff Raff said:

Hedgehopper said:

Handbrake...

Some say that applying the footbrake first to bring the pads up to the disc then applying the handbrake helps.
Also, handbrake works best when cable is not over-adjusted...about 4 clicks to full on works for me.

On mine the foot on brake technique is the only thing that will cause the handbrake to hold on even the slightest of inclines. (And even then it's a two hand pull on the lever).

Edited by Riff Raff on Tuesday 3rd November 11:22

Mine is better adjusted - Mat Smith had a good go at it about three years ago.
But I agree, the foot on brake pedal works for me too.
However, I believe that an MOT tester has to test it on its own as an emergency brake, in case you suffer hydraulic brake failure.

A working handbrake saved my entire family, including me, from a serious, possibly fatal, acccident back when I were a lad, when the brakes on our Austin Cooper S failed on a short steep hill between two main roads running at 90 degrees to us. Only my father's quick reactions grabbing the handbrake saved us from sailing out into the path of an HGV.

[Steve_D]

Open a new thread for finding a MAF.
There are plenty on here who have gone aftermarket ECU and have a MAF sitting on a shelf somewhere.

Steve

[Classic Chim]

QBee said:

Mine is better adjusted - Mat Smith had a good go at it about three years ago.
But I agree, the foot on brake pedal works for me too.
However, I believe that an MOT tester has to test it on its own as an emergency brake, in case you suffer hydraulic brake failure.

A working handbrake saved my entire family, including me, from a serious, possibly fatal, acccident back when I were a lad, when the brakes on our Austin Cooper S failed on a short steep hill between two main roads running at 90 degrees to us. Only my father's quick reactions grabbing the handbrake saved us from sailing out into the path of an HGV.

As my father drove us about in cars without seat belts for many years I remember him regularly shooting his arm across to stop us all flying forward whenever he had to hit the brakes, like an automatic reaction he couldn’t get out of. I somehow felt safe though

[TV8]

How long have you had the car? I find it’s easier to fix a car that has been fine as usually it’s one thing that makes it run rough. If the car is new to you, it could have lots of things changed tweaked etc.

[Strudul]

Handbrake might be sorted now. Everything seemed free so just tightened the adjuster and now at 3 clicks it seems to hold and 4th click is nice and tight.

Edited by Strudul on Wednesday 4th November 20:48