I just did my timing belt replacement and GSC S2 cams install, and car started to hesitate intermittently. Similar happened before this upgrade, l but not as consistently. It happens at wide open throttle and sometimes on highway cruising.
When it happens AFR leans out.
Changed the plugs, tried new spark plug cables and problem is still there. I did not tune it yet (stock evo9 tune) r but I don't think it should be misfiring or hesitate on highway. Timing belt is all aligned with marks... I need some ideas where to look. I am attaching log.. I have not replaced coils yet, but that is the next thing. I checked resistance of the secondary coils and it seems to be in specs. I have not checked primary coils as it requires 1.5v and little difficult to do.
Could cam angle sensor installed improperly to cause misfiring?
Any help and suggestion is welcome.
Mods: EVO9 - stock map, 3" exhaust, perrin, cams gsc s2,

 

Ya a lot of ppl accidentally install the cas upside-down during the reinstall. I've read a lot of threads where guys put it back in upside-down and it causes your exact issues.

 

I am 99% sure I have done this right. Followed evomoto steps, dowel pin up bigger vane on the right side down. But I will double check. Any other suggestions?
http://www.evomoto.com/article_image.../step_515.jpeg

 

If the issue isnt related to the install then its gotta reside on the tune. Has the car been tuned at all?

I swapped out my HKS 272's in favor of S2's this past weekend and the tune needed to be tweaked as my AFR's were going lean. Now my car didnt misfire or hesitate, but rather pulled cleanly through the powerband.

However, that probably had to do with the fact that it was fully dialed in prior on my other cams so while the S2's changed things, it wasnt a drastic change.

 

Car has never been tuned. When it leans out it goes above 17-18afr. Sounds to me either something with ignition or injectors are bad. I would not think tune is far off. I added 3" exhaust and intake.. and now cams. It could get little leaner but not to throw it all off. I might be wrong. I will try new coils next and then swap injectors. Is there way with evo scan to check trigger signal?

 

Wow, you really need to get it tuned. It should have been tuned after the intake and exhaust. Not only are you likely to blow the engine now, you were leaving a ton of power on the table before the cams. There may be other issues but it definitely needs to be tuned before you do any wot, imo.

My tune got thrown a good bit off just intalling s1 cams and it was already tuned for the previous mods.

 

I wanted to throw all these parts in and get it tuned. I just want to make sure car is healthy before I get it on dyno. Maybe tune will fix it. Again don't see reason why on highway cruising 65mph suddenly leans out 17-18 afr, I let the gas off and then on again and its fine for minute or two and then comes back..

 

Throwing all the parts in prior to a tune is fine. However do not get on it without proper tuning or else the engine will go kaboom. It may not happen the first time but I promise you it will eventually happen.

It sounds like the car may be misfiring as you mention it leaning out on the highway like that however personally knowing that misfires can be caused by improper tuning and knowing that your car isnt tuned I would spend your money on a tune rather than new injectors and coils.

But hey sounds like you know best so keep doing what your doing...

 

I assume you tune your car yourself? Thanks for the help.

 

Im actually sponsored by a good friend and former mod on here. So while I'm not personally operating the laptop, we are constantly changing my setup and tweaking the tune. I ask questions and am constantly learning. Thus, I'd venture a guess that I know more than the average joe about tuning from the past 7 years and probably 100 retunes.

What was happening during that log? Do you have your wideband wired into your ecu? Looks like you were basically cruising and got on it a little but then let off. Is that when you experienced the funky AFR's? Do you have a 3bar MAP sensor to log boost as well? Are you on the stock injectors and stock fuel pump as well?

Its just kinda hard to tell from the log you linked what we are looking at here.

 

I have wideband. It is not connected to laptop yet. I purchased PC cable that I lost and Im waiting to receive it this week. It is only 2nd and little of 3rd gear pull.
No 3bar sensor, but boost is stock, goes up to 20 and tappers down to 14psi.
Stock injectors and walbro 255. It also happens on highway 65mph without wot, and not all the time. When it happens on highway it leans out below 18afr and when gets better goes to 14.7. These are things that lead me to believe that tune is not problem but I will do it anyways soon. Wideband would read ~11afr at wot
and no knock.

 

I had experienced the exact same symptoms during an identical scenario. In my case the wires/boots were the culprit so i got purple magnacore wires/boots. try that, they were inexpensive.if that aint the fix you could put them back in the box and return them.

 

Not sure whether the misfires are happening for you going down the highway or not, but I just wanted to throw in the possibility that the misfires themselves are causing the lean condition your A/F gauge is showing. A misfire will push unburnt Oxygen into the exhaust, showing a lean condition, even though the mixture formation may actually be acceptable. Just a thought, FWIW.

 

That is what Im thinking. Im going to instal cop and try that. Looks like its good to upgradr anyways.

 

Did you do a leak down test while/before installing these cams and timing belt? Jw.....