Misfire/Hesitation under slight load at highway cruising speeds

Hey there,

I’m having a problem with my 2008 Speed 3. When I’m travelling along the highway with cruise control on and I go on a slight incline, the engine begins to burble/misfire after that slight load is introduced. It doesn’t seem to do it under full boost conditions. Only just at low rpms under medium load.

Details on car
148000kms
Corksport Turbo Back Exhaust with Catalytic Converter Delete
Cobb Access Port with Custom Stage 2 Stratified 91 octane Tune
Cobb Intake
Autotech Fuel Pump
Cobb Motor Mount
NGK ILTR6A-8G .032”

 

Bump

 

From the looks of it, you have an ots tune of some sort. I would suggest getting a pro tune. If I’m wrong about that then start by closing up the gap on your spark plugs to .028 or desired gap from tuner.

 

Plug gap is too big. clean MAF, logs to see if O2 Sensor is meh.

 

Ok I will try new plugs with a smaller gap to start. And yes it’s an OTS stage 2 tune. Do you mean just cleaning the maf with some contact cleaner?

 

There's is a specific MAF cleaner, spray it into to the sensors (removed form car) you'll be able to the wires getting cleaner and let it dry out it back in.

Your original post said stratified 91 octane tune and you made mention of the OTS stage 2 which one are you using? Or is it a stratified OTS tune? Reason folks are dialed into that is because Cobb maps are notoriously poop and can cause issues.

also what do you consider "low rpm"?

 

Okay I will get a specific map cleaner and pull it out and clean it.

Sorry I’m new to the accessport and mazdaspeed 3 platform so I’m not really too sure. It has a couple of maps loaded onto the AP, and I think the one it says at the moment is Stratified OTS Stage 2 91 octane?

around 2000-3000 rpm in 6 gear coasting along the highway

 

okay so you're on the stratified OTS tune, not the cobb one thats good, Lex put some good effort into those and they run better than stock or cobb ones.

I can tell you from personal experience that the cars don't like the load below 2500, but that shouldn't cause your issue. Hopefully with the MAF cleaned and fresh plugs appropriately gapped it resolves your issue. Like raider said take a data log of when it happens and post the CSV file so that it can get looked over.

 

Oh okay cool. When I get to the car I will double check for sure. It doesn’t seem to do it straight away. Only after driving for about an hour or so. And once it starts it does it on the highway with the slightest bit of load as you go up a hill.

I will also say that I live in the Canadian Rockies at an elevation of about 4200 ft. Would that causing my vehicle to run richer than usual? When it does start to misfire I will be sure to datalog and post.

 

So I checked what tune it was and it says

REV1 STRATIFIED 91 STG 2 FT MAZ V3.00

 

You don't need another set of plugs you can just regap the ones you have

 

I just read from Cobb’s map notes that they reccommend the ITV22’s for when running more boost? Is that not necessary? How long between changes do these direct injection engines need before changing plugs?

 

Stage colder plugs start to be recommended when running more power. To my knowledge that's generally part of the tune, as in not just swapping heat ranges
@Easter Bunny can set the record straight on that though.

NGK >denso so their colder plugs would be NGK 6510. Personally I'd be more concerned about the stratified map notes matching it rather than Cobb's

 

ahhh shoot, I’ve already ordered the Denso’s. Should I go back to one of the Cobb tunes preloaded onto the accessport when I install the new plugs?

 

Plug heat range should be based on the primary use of the car. If it is a DD then stock would be fine unless you had really stupid power.

Weekend toy or primarily track use start running colder plugs

If you have colder plugs in a DD they will run cold, duh, and foul more quickly


I would never run any of the Cobb tunes

 

So why is it that Cobb specifically recommends running a colder plug when increasing boost levels?

What would you reccommend I do to try and get the car running right? It seems to only do it after a while of driving, not straight away. How long of an interval would you leave between changing plugs? These ones havent been changed I think for about 10000 miles or so. I’m not entirely sure though because I only just bought the car

 

Sorry I forgot the interval on plugs in my last post 20k miles is recommended for the speed the biggest thing is keeping that gap at .026-.028" that's where I'd start to get your car running better and a MAF clean, could clean your throttle body as well (another cleaner for that).

As for Cobb I don't know their rational

 

I would check the gap on the plugs you have already and see if it helps. It's free to do so just do it. The plugs supposedly last 100 k miles. I have been changing mine at 50 k but honestly they look good when I pull them out. As long as the center electrode isn't worn down and the porcelain isn't cracked they are fine

 

So I cleaned the MAF with actual MAF cleaner, and gapped the ITV22 plugs to .028” and so far so good. Haven’t seen any issues yet, but I’ve only driven it for about half hour or so since, and the problem was only occurring after 1 hour++ driving. So will report back after a longer drive

 

Ok so I’ve had a chance to properly drive the car now, and the issue is still there. It’s still getting a hesitation/burbly misfire.

any thoughts on what to try now?