I've been scratching my head for awhile on why my car has been acting up.

It's and evo9 with simple bolt on's such as....toxic fab exhaust mani, pte5858, injectors and running on aem with map sensor. Basically everything to support a vband pte5858. The long block is completely untouched! I am running two maps one for pump and one for VPms109.

So, how the car is acting on start up it'll usually sound like a "Subaru" to put it easy sounds really deep and almost like its missing. And when its acting up under load it'll start missing as well. NOTE when it first started acting up it was on pump fuel and it idled fine but when getting on it the car started to miss in boost, so all I did at the time was change plugs and it was fixed for say 200 miles.

Then I realized its obviously a different problem. So, I went ahead and I
drained my pump fuel and put the ms109 in with the ms109 map. Also at the same time I changed spark plugs (again), changed coil packs (OEM), pulled the fuel pump to check it all over (walbro400). When I changed all that, the car ran fine for 100 miles with the ms109 so I drained that thinking I fixed the problem somehow and went on to putting the pump fuel and map back on. NOTE on ms109 when coming to a stop it would sometimes act like it got flooded imo and die. But it would fire right back up when starting it. Also possible thats in the tune just thought id note it.

So, when I changed fuels back to pump. I figured I better take it for a test drive since the next day I was going on a cruise. Well the test drive went good! Drove for about 15 miles and hit boost to make sure no missing etc, parked it for the night. Got up the next day went to fire it up same BS sounding like **** at idle and failing on its face bad under loaded. So, I changed plugs and it fixed the idling like crap but under a load it would fail on its face like cutting out but i could manage to somehow get it to drive "decent" feathering the throttle at a certain rpm mid range.

Sorry for the novel just trying to be descriptive! I do have new OEM cam sensors I can install if you guys think it can be the problem. I haven't checked the timing but figured its not that cause it acts up randomly!? Thanks for any help! And it pulls vacuum fine and fuel pressure is good.

 

Sounds more like coil pack is bad, it can't produce a strong enough spark to fire plugs at boost and likely just functions on and off at idle. Now you are sure you plugs are gapped properly and arent gas soaked etc?

 

But I've changed coil packs when I swapped to ms109 and changed plugs, which it ran just fine then. And I have same coil packs on that worked then.

Ya the plugs every time coming out look good. running the br8eix's gapped to 24. I had the car tuned end of April with all the mods couldn't of been happier with the car! The past month is when this issue has came up.

I've thought about ordering aftermarket coil packs but since the car was tuned and drove on OEM ones for two months they should hold up just fine in theory.

Coils are what seems to make sense that would cause the problem but since they were swapped out with new oem ones idk what to think. Also, I just had to move it from shop to shop and its "jumpy" first getting on the gas pedal slightly. Like ludges quickly if that makes sense. But when I give it slightly more throttle it clears out. And im talking car is moving very slowly is all the throttle im giving it

 

Came up with an idea while at gym lol...It ran fine when I had ms109 in it after changing plugs and coil packs then when going to pump went down hill again. SO idea, is that its something ignition wise and that maybe the ms109 with the better octane and being oxygenated was able to keep up with the weak spark. So was going to try to change spark plug wires this time. I have a cheap set from oriellys coming in two days from now. Figured id try a cheap set first. Anymore im willing to just keep trying things and throwing money at it just have no ideas what it could be!!!

 

Well update.... I cleared the ecu and reloaded the fuel pump map back on and car ran fine for the 15 miles I drove it. So I thought it was all fixed and go to drive it three days later same old ****. Has a weak idle like bad spark almost so hardly running and when i go to rev it up it revs up slower than it should.

My question is. Is there anything that can act up randomly that this would be....? PS I tried reloading the map back on the aem ems and it didn't fix it this last time