- My model of MX-5 is: __ NC1 Sport
- I’m based near: __ Colchester
- I’m looking for technical help or recommendations on: __ Throttle hesitance when on a straight, caused by DSC?
Hi all,
On straights I have found the throttle to hesitate when I put my foot down. This is from low revs & low speed, to high revs and high speed. The car will lift around 500 RPM or so and then drop 300 RPM or so before then setting off. It’s happening on straights as much as in corners. It’s especially frequent when the car is up to temp.
Interestingly, I have tested turning off the DSC and found the problem goes away. As this is a new issue, I imagine that the DSC may be malfunctioning. Is that even possible!?
Any ideas on why the car may have suddenly decided to do this would be very welcome!
Thanks
Andy
Any ODB codes being flagged up ?
Are you using cheapest petrol?
If so try a few tankfuls of V-Power to clean out the clag.
My low mileage Niseko was very unhappy at low revs and balancing the clutch when I picked it up from the dealer, but its symptoms were exactly what my old Vextra-b had before I fed it V-Power.
In both cases the engine was then cured of all hesitations and reluctance.
Hi guys,
I only use 98/99 RON petrols. No OBD codes showing up.
I have a bottle of cataclean ready though, so will.give that a go too.
Andy
Could be a spurious reading from a wheel speed sensor giving the impression that a wheel is slipping so the PCM will reduce power.
If you can monitor individual wheel speeds, do this and see if they are all the same.
Ok so the plot thickens,
Wheel speeds all the same thanks Robbie. Car went into Vincent and the TCS/steering wheel position is all fine. Still no codes showing.
However, I think I may have found the issue.
I had a nice long journey home on the M6/A14/M11 last night.
To begin with the car was super hot, having done some traffic in and around Birmingham in 30 degree heat.
I had a nice long run and then slowed for 10 miles of contraflow (with no worker in sight ofc), then sped up again. I had the issue all through the first half of the drive. After the 40mph works though, it settled right down!
Below is some data from my OBD tracker. I’ve used throttle position to show the progress of the journey, then a couple of shots of other readings in comparison.
As you can see, the car was moving off much better in the second half of the journey, relative to throttle position.
Comparing MAF flow and power from MAF, before and after the “dip” notice the final throttle peak in the 2nd half and the first throttle peak in the first half.
This is probably the conclusive one. Air intake temps producing very strange readings in the first half of the trip.
Essentially I think it’s my direnza intake sat next to a boiling hot ally coolant tank that is messing with the MAF. The brief slow down allowed some heat to dissipate from the engine bay. Photo of my set up below.
Anyone care to hazard an opinion for me please?
Thanks
Andy
I haven’t experienced that issue and I’m running an almost identical setup as you with the Direnza intake and alloy header tank, the only difference being I wrapped the outside of the metal box thingy that goes around the filter in heat reflective tape and did the same thing with the metal tube that the MAF sensor mounts into.
I’m assuming you’ve done basic stuff like checking the plugs are OK and making sure the MAF sensor is clean etc?
Did the issue only start after you changed the intake? If so if you have the stock airbox I’d be tempted to bung it back on and see if the problem goes away or if it stays the same.
I’d say you’ve found the issue with your open cone-type air intake in hotter weather, which is next to other hot engine components as you’ve pointed out = heatsoak.
Swap back to the OEM airbox would be my advice 
Ignoring heat soak for 1 moment.
The top of the direnza box looks to have rubber/foam padding on it. Does the Direnza box fit flush against the lower side of the bonnet ? If yes , its a ‘sealed box’ much like the OE & would indicate the majority of air flow entering the cone filter was from the front of the vehicle as usual. If not , its not really helping much to keep heat away from the filter.
Thanks guys,
Yes the basics have been checked. And no, the box is not flush to the bonnet.
I’ll wrap it in heat protective tape and try and get a thicker seal for the box. After checking the stock airbox stops the issue of course.
Andy
I only did the outside of the box because I didn’t see any point in putting it on the inside, I don’t know if it makes any real difference but (to my eyes) it looks better and let’s be honest 99% of the stuff we do to our cars is mostly to alter the way it looks.
I’m interested to see if you can find anything thicker to put around the top of the box so it seals against the underside of the bonnet. If it does then I’ll most likely pick some up and make the same modification myself and possibly add a Fresh Air Duct like this one so the box gets a mild Ram Air effect while the car’s moving.
You are clearly on exactly the same journey as me with this thing. I was looking at the cobalt version on Moss.
Now I know that exists and is considerably cheaper than the one on rev 9’s site I’m looking at it too 
Cobalt air intake , and possibly cap the filter box ?
Approx £60 online for intake.
Heat reflective tape as you mentioned works at treat.
I lined the intake box of my 911 years ago , ran some tests and found the inside of filter box was 28c cooler after a hard run.
That’s interesting. ‘Lined’ as in, put the tape inside the airbox or on the outside?
Yeah sorry I should have been more specific.
The outside of box and all related pipe work etc.
Used heavy duty aluminium type tape that we used in oil industry.
…about £75 a roll if bought but can’t remember the manufacturer.
Done some work on it. Will report back.
That looks great mate, let’s hope that makes a difference in your NC and even if it doesn’t it still looks cool.
A case of your hot air intake reducing performance.
Agree, needs top enclosed also.
