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Misfire or bucking when I hit boost?

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98TsiAWD

DSM Wiseman
2,864
8
May 19, 2002
94 3000GT VR-4, North_Dakota
My car acts like it misses whenever it hits boost. I have tested all my pluh wires and plugs with an ohm meter and checked the gap, set at .028

Today I did a boost leak test, I had 2 fitting for my boost gauge that were leaking, I fixed them and now its all good and sealed, no leaks.

However I still have this problem....

My next guess would be injectors and/or coil?
How do I test those?
I am not getting any codes in the computer other than P141 which is because my second o2 sensor heater isnt grounded.
 
BTW, it only does it if the car is FULLY warmed up. If its even partially warmed up it wont do it. So I was thinking intake manny gasket or exhaust manny cracked? Are those possiblities, since it only happens after its warmed up real good.

There are 3 hairline cracks in the top of my exhaust manny, I plan to weld those when I pull it off next week to swap the 14b on.
 
You may want to check the vacuum line running to the wastegate actuator. I persanally had a problem with that line. It was leaking at the connection and whenever I stepped on the gas thus applying vacuum to that line it would leak. My wastegate would open so my turbo could spool and then it would close suddenly when the line leaked causing my car to buck and sputter. Easy to fix but a pain in the but when youa are driving.
 
Originally posted by TalonTSi16G
You may want to check the vacuum line running to the wastegate actuator. I persanally had a problem with that line. It was leaking at the connection and whenever I stepped on the gas thus applying vacuum to that line it would leak. My wastegate would open so my turbo could spool and then it would close suddenly when the line leaked causing my car to buck and sputter. Easy to fix but a pain in the but when youa are driving.

alright I will check that, that may be it, but why only when the car is fully warm, does rubber expand from heat? I dotn know the properties of rubber.
 
When the car gets warm the rubber lines do become soft and pliable. Since the astegate acuator vacuum line is near the turbo it will become very warm most likely sooner than others.
 
When the engine compartment, including intercooler, gets hot after running for a while AND the external air is hot, intake air density drops dramatically. The reduced air density does not support combustion very well. When the outside air temperature increases at this time of the year, I turn my manual boost controller down all the way - so max boost is only 9 lbs. The car certain doesn't have the power I'm use to, but it stops that annoying hesitation and bucking at WOT. Try this and see if the problem goes away. One other possibility, is that your knock sensor is telling the ECU to retard the timing - but when that happens, the engine cuts out completely - until you get your foot off the gas pedal. If you want to run full boost during the hot weather, you will need to upgrade your intercooler. There are kits you can buy that sense the hi temp and spray (or drip) water down the front of the intercooler to help cool the air flowing thru it. I don't know how well they work, but I've been thinking about buying one. If you get around to doing it before I do, let me know how it works.
 
Originally posted by eb4i
When the engine compartment, including intercooler, gets hot after running for a while AND the external air is hot, intake air density drops dramatically. The reduced air density does not support combustion very well. When the outside air temperature increases at this time of the year, I turn my manual boost controller down all the way - so max boost is only 9 lbs. The car certain doesn't have the power I'm use to, but it stops that annoying hesitation and bucking at WOT. Try this and see if the problem goes away. One other possibility, is that your knock sensor is telling the ECU to retard the timing - but when that happens, the engine cuts out completely - until you get your foot off the gas pedal. If you want to run full boost during the hot weather, you will need to upgrade your intercooler. There are kits you can buy that sense the hi temp and spray (or drip) water down the front of the intercooler to help cool the air flowing thru it. I don't know how well they work, but I've been thinking about buying one. If you get around to doing it before I do, let me know how it works.

But I have a hahn intercooler and the scantool shows an intake temp of 78 degrees at wot after its all good and warmed up, that is good isnt it?
 
Originally posted by TalonTSi16G
When the car gets warm the rubber lines do become soft and pliable. Since the astegate acuator vacuum line is near the turbo it will become very warm most likely sooner than others.

I replaced the vacuum hose on the MBC, it still bucks, so that is not it.
Any other ideas?
 
The intake temp at WOT is good. I still think that you should try turning down the max boost to see what happens. You could also fill up with race-gas and see how it runs. Both of these ideas will tell you if it is a problem with the air-fuel mixture. If your intercooler is working well, it very well could be the knock sensor. You could try unscrewing it or disconnecting the plug (it may cause a check engine light - but that won't hurt anything).
 
I just swapped my stock plug wires on, I foudn them in the closet. And guess what runs fine now. Guess Ill have to order some new plug wires.

I found a crack under the little rubber boot on the bottom of one of the wires, didnt see it before when I tested them and inspected for arc-holes.

Something so simple caused such a headache :mad:
 
interesting, that maybe my problem, I just installed my new accels and thats happening to me. I swap back the stock wires and it works fine.
hmm, I'm not goin to blame the wires yet cause i havent checked my plugs yet.
so I'll be back
 
i was having the same exact problem and i changed my plugs and wires and it runs awesome, crazy that thats all it was
 
Agreed- especially for the cost, I'd go ahead and replace the plugs at least, and take a look at those wires running in the dark. I don't know of any test that'll spot a bum spark plug, and the ones for ignition wires don't clue you on the insulation very well, either.
 
im having the same problem... its fine when im not making any boost, but when i hit even 1psi, my car sputters and bucks, and makes a terrible whirring noise. It all happened in a span of 15mins. At first, I wouldnt exceed 10psi and i have a greddy profec b spec 2 set at 14psi on high. After I took it home and checked all my vac. lines, i took it back out and the sputtering happened. this sound like the same problem?
 
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