Stutter, but only in one gear???

[mikey-t]

Hi all as you can imagine I have driven the car loads since I got it yesterday but today I noticed a fault that hasn\'t happened on the test drive and has happened 2 or 3 times now.

The car pulls well in all gears right through to redline but today ONLY in 4th it would pull strong, hesitate quite obviously at 5k revs and then continue.
This only happens in 4th at 5k

I can only think that when we pulled a plug to compression test it something happened then but why only in one gear at a certain rev point?? Could it be map.
I spoke to the seller and he recommends replacing the plugs as that\'s usually the first point to check but what else could it be? As I say its only in 4th at 5k revs.

It\'s Lewis\'s old car specced at street ported, non sequential with mild air mods exhaust mods and bigger fuel pump oh and running apexi gear for monitoring.

Any help is appreciated with me being so new to this

[mikey-t]

Anyone? Don\'t want to have it happen if its damaging the engine, can get a video if that helps

[Grant Monkhouse]

, does it do it when you accelerate gently or when you are hammering it?

My car used to do it, needed the map tweaking, too much fuel at a certain point as the engine had bedded in the seals a bit more.

Try the plugs first. Also how\'s the oil? Won\'t have anything to do with it but might be worth renewing the oil

[mikey-t]

Oil is full and fairly fresh only just started loosing its colour. It may be the map now its fully bedded in! Will have to try find someone local to map it again. I wouldn\'t say it\'s just when hammering it its at any pace but always at 5k in 4th which made me think map.

Also it has quite a noisy exhaust I know you can get db reducing baffles but would that affect it enough to knock the map out? I read somewhere that because its just a tube with holes in the gasses can still flow freely its just the resonance it takes out but that don\'t seem right to me especially on such a sensitive engine!

[samoht]

Since Carl knows the car, I\'d try and contact him and see if he can suggest any likely issues.

I was going to suggest the turbo changeover, but yours is running parallel twins so that shouldn\'t be an issue I guess.

[Grant Monkhouse]

I would take it to the tuner that knows the car. And previously mapped the car, was it Carl? If so he will sort you out and give it a check over whilst your at it. It is worth the trip IMO.

[Grant Monkhouse]

Have you sniffed the oil? If its starting to smell like petrol, change it. Change the plugs first though. Should be the cheapest option:)

[mikey-t]

The engine was built by Carl but I think the map and mods were done elsewhere, I was going to service it as a fresh start for me anyway just don\'t want to break anything, I know it is just a engine but everything is different and that makes me paranoid.

Did someone mention a guy who maps in Redditch? Pretty sure I saw that on this forum somewhere.

Also best place to buy proper plugs and mineral oil all my local outlets just stare blankly at me

[wolfie1]

You want 10w40 MINERAL oil only, dont put anything else in even if your local motor factors say that what they say is the right stuff, people have no idea when it comes to rotarys, depending what spec your car is at would depend on plugs you need, if your still running the twins BUR9EQP is the plugs your after. Your not running premix? (Putting 2 stroke oil in with your fuel) cause if you were there is other grades of oil you can use

Ebay is good for these items and prob the cheapest too

[mikey-t]

You got me sniffing everything now! Oil does have a tang to it, when I downshift I sometimes smell clutch ( I put that down to poor technique I am a truck driver)  and the exhaust smells of petrol which is not a surprise the amount these cars drink. All in all time for a good service and map

[mikey-t]

Think I have it cracked now! I went out onto my private very long very straight drag strip and set my boost gauge to record as its hard to see everything that\'s going on at the same time, turns out the turbo is boosting to its imposed limit which I believe is just over 1 bar the car is at around 5K it stutters the boost drops down to .7 or .8 and then continues. Why it does this or how I don\'t know. Seems like what you would get with a sequential but this has been non sequential for a while. Curiouser and curiouser. Needless to say she is still getting her service and map.
I have been looking at the mineral oil sold by mazda rotary parts. If it is as good as they say its worth a punt I just hope they do 1l sizes for top ups or that could get very expensive very quick

[wolfie1]

I usually just use this stuff,  best to change your oil every 2000 miles http://www.ebay.co.uk/itm/Carlube-10W-40-Mineral-10-W-40-Car-Motor-Engine-Oil-5Liter-XPL050-/260998288580?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item3cc4b5d4c4

I have noticed that when on the dyno and my car is let off throttle there is a lot of smoke when the oil is old, but when new dont get any. But hey you get what you think is best

[JayDee]

Sounds like ignition break up, did you drive it in 4th hard on your test drive.I would say whip the plugs out, they will tell you how your car is running, you could post pics up on here someone will be able to guide you if they look like the car is not running to rich. I personally would get new plugs.


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Think I have it cracked now! I went out onto my private very long very straight drag strip and set my boost gauge to record as its hard to see everything that\'s going on at the same time, turns out the turbo is boosting to its imposed limit which I believe is just over 1 bar the car is at around 5K it stutters the boost drops down to .7 or .8 and then continues. Why it does this or how I don\'t know. Seems like what you would get with a sequential but this has been non sequential for a while. Curiouser and curiouser. Needless to say she is still getting her service and map.
I have been looking at the mineral oil sold by mazda rotary parts. If it is as good as they say its worth a punt I just hope they do 1l sizes for top ups or that could get very expensive very quick

[mikey-t]

It smells like it might be, back end smells heavily of fuel. Cheers for all the help guys its appreciated