Loss of power, Sluggish and revs are dipping when braking?

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Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Fri Jul 17, 2015 11:26 pm

Hi Everyone,

I am posting to see if anyone has had the same problem? Currently i use my mx5 daily but recently i have noticed when i approach a junction and brake the revs seem to dip to 500rpm, The car almost stalls but it seems to catch its self. Recently i have noticed a loss of power and it feels sluggish, Doesn't accelerate and rev as freely as it should.

Full Service and MOT - June 2015
New Airfilter
Spark Plugs NGK
Carb Cleaner
Oil Change
Oil Filter
New Brake Pads
Brake Fluid Change

Any help or comments would be appreciated as i am at the end of my tether.

Thanks :wink:
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Sat Jul 18, 2015 12:13 am

Lift the passenger side carpet.

That means do not feel the top of the carpet.

Remove the kick plates under the door and on top of the sill, lift the carpet.

Is there water there and has the ECU which is where the passengers feet would be, wet?

Post your results.
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Sun Jul 19, 2015 5:34 pm

drumtochty wrote:Lift the passenger side carpet.

That means do not feel the top of the carpet.

Remove the kick plates under the door and on top of the sill, lift the carpet.

Is there water there and has the ECU which is where the passengers feet would be, wet?

Post your results.


Hi drumtochty,

Just so you know underneath the carpet is completely dry and so is the ecu, everything seems to be ok! Don't know what else it could be.

Thanks
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Sun Jul 19, 2015 6:16 pm

You need to check for fault codes.

Buy this from Autolink or make one up yourself from Maplin kit.

http://www.autolinkmx5.com/diagnostic-f ... 6665-p.asp
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Sun Jul 19, 2015 6:33 pm

I have bought one a few months ago! No fault codes at all, that's why it's so strange :?
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Sun Jul 19, 2015 7:07 pm

Go over setting the base idle, clean the idle control valve, do a compression test.

Check the temperature of each brake disc after a run is one a lot hotter than the rest.
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Sun Jul 19, 2015 7:28 pm

If possible get a set of HT leads off a "good car" and see if that sorts your car.

The sockets that the plug leads go into on the coil packs are both sockets and the end of the leads that go in there clean and shiney
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Tue Jul 21, 2015 5:51 pm

drumtochty wrote:If possible get a set of HT leads off a "good car" and see if that sorts your car.

The sockets that the plug leads go into on the coil packs are both sockets and the end of the leads that go in there clean and shiney


I have checked the HT leads they seem perfectly fine they have been changed not to long ago. Both ends of the Ht leads and sockets are spotless nothing wrong with them? Cleaned the air intake box out and sprayed carb cleaner in the intake, haven't done a compression test as I don't know how to? Would need to get a mechanic to do that, diagnostics are fine not any faults? Took the car for a drive and the brake discs are warm all the way round with no cold spots :? i have had new brake pads and callipers all round then bled the system completely with Dot3
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby OldSpice » Tue Jul 21, 2015 6:27 pm

Just wondering if the fuel filter has ever been changed..perhaps in a time past you ran it nearly dry and sludge got sucked in.
Also, perhaps the "base idle" is suspect.
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Tue Jul 21, 2015 6:39 pm

As Old Spice has mentioned and more work here.

From what you say, we assume the spark plugs, plug leads and brake callipers are all good.

Therefore you need to do a few other things that you did not pick up from the last few messages but if you are not good with spanners, as you say get a trusted mechanic to do the jobs.

A compression test checks the health of each of the four cylinders and gives you a figure for each one of the four cylinders.
The minimum pressure is 146 psi
The maximum pressure is 209 psi
The difference between the lowest and the highest reading should be 28 psi

Setting the base idle go here and print out the instructions and give them to you mechanic.
http://www.miata.net/garage/KnowYourCar/S7_Idle.html

Clean the Idle Speed Control Valve, link here again print out and give to your mechanic.
http://www.miata.net/garage/isc.html
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Wed Jul 22, 2015 2:09 pm

OldSpice wrote:Just wondering if the fuel filter has ever been changed..perhaps in a time past you ran it nearly dry and sludge got sucked in.
Also, perhaps the "base idle" is suspect.


Hi oldspice,

The fuel filter was changed last week, I forgot to mention that in my first post. The only time the revs drop is when I brake and it's close to the car stopping. As for the throttle body that is completely spotless! The only things I haven't changed are HT leads, everything else has been done because the car was lying for a while
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby OldSpice » Wed Jul 22, 2015 3:09 pm

Well,
Since clearly the brakes are not connected electronically to the fuel/electrical system, for me it only leaves something bizarre going on when current is applied to the brake lights...or ABS if you have it. I'm beginning to sniff an earthing issue somewhere.
Apart from the brake warning light circuits...mmm.... :roll: Zee plot it thickens yes?
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Wed Jul 22, 2015 3:55 pm

OldSpice wrote:Well,
Since clearly the brakes are not connected electronically to the fuel/electrical system, for me it only leaves something bizarre going on when current is applied to the brake lights...or ABS if you have it. I'm beginning to sniff an earthing issue somewhere.
Apart from the brake warning light circuits...mmm.... :roll: Zee plot it thickens yes?


I honestly don't know what it could be, so say I'm driving along and the lights change to red? I press the brake the car slows down and then when the revs reach 1,000 rpm it goes way past the 850rpm which it idles at and goes to say 500rpm and then nearly stalls but catches it self and goes back to idle? So I thought maybe the vacuum between the servo and the brake system? Maybe I'm wrong :? The car is a mk2 with no ABS
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Wed Jul 22, 2015 5:29 pm

This is exactly what happens to my car.

http://mx5cartalk.com/forum/viewtopic.php?f=76&t=60434
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby OldSpice » Wed Jul 22, 2015 5:36 pm

Out of that little lot, the binding throttle cable & resetting base idle are my favourites.
Sometimes cars are like our wummin. They exasperate, deceive, trick us, like new bits & things, and cost a bomb to maintain. :lol:
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby drumtochty » Wed Jul 22, 2015 5:48 pm

SC91

I have advised you to go through the Base idle setting procedure as have the posters on the forums linked too.

Can you please advise if you or your mechanic have gone through the procedure for setting the base idle as in the procedure not any other way.
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Re: Loss of power, Sluggish and revs are dipping when braking?

Postby SC91 » Wed Jul 22, 2015 9:15 pm

drumtochty wrote:SC91

I have advised you to go through the Base idle setting procedure as have the posters on the forums linked too.

Can you please advise if you or your mechanic have gone through the procedure for setting the base idle as in the procedure not any other way.


My apologies Eddie, I noticed that as I scrolled up the thread, thanks for the help and advice! Really appreciate :D my friend who's a mechanic will reset it for me. I will make sure he does the correct procedures and does it correctly. Will post on this again when he has done it and fingers crossed it will be the end of it!

(oldspice) I could have not said it any better my self! They do exactly that and my little 5 is the exact same takes every penny I have for its self :lol: so tempremental, I wish someone who stayed near me (Glasgow) would come and have a go in my 5 to see how they think it compares to their own.

Thanks Eddie & Oldspice!
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