Misfire at higher boost

[HawkesTSI96]

I have recently did a compression test on my motor ( Okay numbers 150-160 through all cylinders.) before compression test running 18 psi on engine no problem. after compression test I plug everything back in. while driving at higher boost it misfires and pops really bad. not like a fuel cutt but just misfires. prior to compression test and problem have replaced spark plugs and spark plug wires. i have double and tripple checked everything spark plugs are gapped at .032 and have been gapped at that while running 18 psi with no problem. when i turn down the boost to 12psi and have minimal to no problem i have still experianced it at lower booost. I have tried adjusting it up every psi and seems to start at 15psi. I have read to reduce spark plug gap to maybe help at higher psi, but i have not tried that yet. im jsut confused on why it would all of the sudden having a probelm at higher psi. I have not checked for a boost leak. or at least havent done a boost leak test. recently have replaced injectors as well. I am Going crazy I have been searching for information on this topic but have had no luck with what would cause this. and it was absolutely perfect before compression test. boost fine on 18 psi. also for some reason my wideband o2 sensor went bad right after this had happened not saying anyting related but strange. any advice or info on the subject would be much aprreciated. ( I am running a evo 16g turbo, walbro 190 fuel pump.)

 

[99ECLIPSEGSXDSM]

What type of plug do you have? NGK BPR7ES for higher boost numbers

 

[HawkesTSI96]

I think they are the NGKs but dont remember anything after that. but like i said doesn't really match up to why it boosted fine for a year before i did the compression test until now. ugh ugh ugh!

 

[4everboosted]

If you say it doesn't sound like fuel cut, more of like a misfire, and it started right after you did a compression test, check your timing, who knows maybe when you were turning your motor over during the test you knocked it off a tooth. Other than that try a boost leak test. But if it happened directly after a compression test I would say something didn't get put back right.

 

[HawkesTSI96]

i wouldnt imagine the timing off just beacuse it boosts just fine at lower boost..! but yeah I double and tripple checked everything i had done. which was just spark pluges taken out and the spark plug wires. I did diconnect the ecu, but I have swapped ecu's thinking i might have a bad one but both are doing it. Ill try the boost leak. this is just the worst.. ha thanks for all the input. any other suggestions would be much appreciated.

 

[4everboosted]

i wouldnt imagine the timing off just beacuse it boosts just fine at lower boost..! but yeah I double and tripple checked everything i had done. which was just spark pluges taken out and the spark plug wires. I did diconnect the ecu, but I have swapped ecu's thinking i might have a bad one but both are doing it. Ill try the boost leak. this is just the worst.. ha thanks for all the input. any other suggestions would be much appreciated.

You double checked everything you had done? In order to do a compression test you have to turn the motor over. It is not impossible for you to have knocked something off a tooth. You say it pops and misfires, that is almost always a timing issue. I'm not telling you what to do but if it were me I would check that all my timing marks line up, for all the longer it takes to do so. Might be the problem, might not, but why not rule it out?

 

[HawkesTSI96]

I will absolutley check timing i was just eyeing it the other day and seemed good but did not line them up ill try that and check if that helps. im also going to do a boost leak test as soon as i can! thanks

 

[Roberti 2G]

It's most likely your plugs/gap they should be gapped at .028 if not even closer. NGK BPR7ES like said earlier for higher then stock boost levels.

 

[HawkesTSI96]

Yeah i took that info and have gapped plugs down to .030 just to try it out i will gap even lower soon!

 

[HawkesTSI96]

still having issue. more relative information. I have replaced Knock sensor, and mpi relay and hasn't made any difference. purchased EcmLink. v3 full. new wideband has been ordered old innovate sensor went bad.... I have replaced almost everything i could think of and is still having problem. problem is only under load at around 4k rpms. and happens on and off. but mostly does it. feels like it just sputters and misfires. just replaced 2g cam sensor. on the cam gear (96).. any more info would be much appreciated.

 

[HawkesTSI96]

sorry more relative info. this is happening on new rebuilt engine. only running 8 -12 psi and still is spitting and stuttering.

 

[inthemidst]

Do you still have the stock blow off valve

 

[97 eclenger]

Cogged injector or fuel filter? If there's not enough fuel, it'll cause a misfire. just a thought

 

[HawkesTSI96]

have 1g crushed bov. ran great before with same bov. i haven't serviced.fuel filter sense I've had the car but id does have a rewired wally 255. and replaced injectors. not too long ago. maybe ill try that again.

 

[jery1234]

Since you have a ecm link why don't you pot a log of the problem .

 

[riceless90]

try to install a different set of plug wires. just because they are new doesn't mean they are good. I have bought new ones ( especially aftermarket ones) and they were bad.

 

[TalonSpeed]

What is your setup? Stock motor? 4000k it breaks up? I am thinking either spark blow out (Regap to .018) or lean misfire at the onset of boost (wideband log required). Running a maf? if so do a boost leak test.

 

[TalonSway]

check your base timing, if you have a 95 and have a inverted CAS this could be the problem, if you have a 1g CAS then adjust it to make sure its at 5* BTDC. Improper adjustments will cause high rpm break up. I went through this problem with my inverted CAS and had to switch to a 1g CAS that i could adjust. Solved my problem of high rpm break up. Just something else you can look into if you are still having this problem.

 

[Teezy]

I had a misfire issue very similar to yours and I cleaned my spark plugs and the inside of my coil pack, which had some crap inside of it. I tested it out today and it actually fixed my issue! I''m using NGK Bpr6es gapped at .028.

 

[HawkesTSI96]

I'm going to replace to spark plugs all together soon. and with the CAS. I have a 96 so its on the cam gear. just recently got new wideband will take a log and post it if possible. thanks for all the info. I'm going to try a few more things.

 

[HawkesTSI96]

More relative info. just rebuilt engine and maybe has 3000 miles on it.

 

[TalonSway]

i bet its your inverted CAS. Switch to a 1g style and you will be golden!

 

[HawkesTSI96]

thought about it. decided just to get a new 2g CAS.. still does it. same thing is happening to another car here. in a 2g with 6bolt swap with 1g cas.. i don't believe that is it. but will try some other stuff. and post results. it might even be better to go with 1g cas. but before i do so ill check some other stuff.

 

[TalonSway]

ever figure out the problem?

 

[HawkesTSI96]

nope put new 6bolt 2.4l engine in. ran great for a while and now I'm having another similar misfire feel. but now its only in 1st and 2nd and usually when i try to launch.. I now have link and have done a bunch of logs but can't see any difference between a good log and a bad. so I'm still trying.... It comes and goes just like before. its really weird i have too many logs now unfortunately and did label them effectively.. so now I'm deleting them all and going to try and get some new ones. and see if i can see whats happening.