Really bad shudder

[jetblack]

I've a '03 MSP that anywhere from jerks violently to shudders just a little, to no jerking or shuddering at all sometimes. It's always between 2500 and 3100 RPM, but sometimes only between 2900 and 3100 or so. It's not the WGA, it's not a vaccuum leak (had both tested at a shop), and no Check engine light comes on. It has to be fuel cut, but I have no idea what is going on with this thing. Really aggravating to not be able to drive it properly. Help!

 

[yudkib]

how much boost, and is it only at WOT?

 

[ucMP3]

Is that RPM range when the VICS engages? I'm thinking that or it's when the EGR closes.

 

[KrayzieFox]

Sounds like a worn clutch

 

[MassJDM]

im kinda having the same problem but mine happens in all different gears and at different times... it used to just have a dead spot but then i did a tune up and a timing belt water pump and now it has like a hesitation which i think is fuel cut... but idk...

 

[SpeedAdiction20]

I have similar issues, but since i have a wideband I know it is fuel cut, it use to be a bad EGR valve and then possibly bad or old coilpacks, but replaced both and it is still running rich, I am in the process of replacing my smic/hardpipe kit with a fmic kit and relocating my MAF sensor to hopefully help it a little, and tune the car afterwords, but it would be helpful to know what mods you have and if you have an O2 sensor, what it is reading

 

[MassJDM]

my car is all stock except for i took out the resonator.. i have stock heat range plugs and there new and so are the wires.. so u think its fuel cut, or fuel too rich?? big difference..

 

[SpeedAdiction20]

well the shuttering would be from fuel cut, if it doesn't do a full fuel cut like at the lower rpms, it's just "kinda fuel cutting" if that makes any sense, I think what I experience are miss fires from running so rich and it just boggs the engine so much, but fuel cut is pretty much the same thing, the car runs so damn rich, the injectors can't keep up at some point and as a safety precaution, the car kinda seizes the engine for a split second to prevent the car from running without any fuel being injected, at least that is how I see it

 

[MassJDM]

yeah thats what i used to have like the engine just shuts off for a split second then comes back to life but now i have a different weird problem where the car like shudders or has a loss of power through the whole time im getting boost around 2500 is where it starts then it shakes till around 3500 or 4k and then hang on cuz it pulls hard!! like it has awesome power after that and it used to but now after my tune up i can barely get the tires to break loose and the car just seems dead..

 

[yudkib]

if ive learned anything about these cars, its impossible to diagnose anything without a wideband and a boost gauge... EGR, coils, plugs, MAF, leaky BPV or vac leak... theres a bajillion things.

 

[MassJDM]

i know its not plugs or coils... i do have a egr code and have had it for a while but dont think its that but idk.,.. and bpv well idk about that either.. sooo idk what it could be just wanted to get an idea..

 

[SpeedAdiction20]

+1 for what Yudkib said, but for the time being, clean out the EGR valve, really good, because that can cause the car to run crappy, might not be the only thing, but it isn't good, especially since you have an egr code..

 

[ucMP3]

OP- What plugs do you use?

 

[MassJDM]

the egr isnt the problem but i put a boost gauge on it to see if the wastegate was leaking and its holding steady 5psi in 2nd gear... and it still shudders. soo im buying a coil and a fuel pump to see what happens then and ill repost the results..

 

[MassJDM]

and im running stock heat range plugs but there ngk coppers..

 

[SpeedAdiction20]

well I was just saying that the egr valve will cause a lot of problems, when mine was bad it was causing it to run really lean and idle really badly, and overall just drive worse.. its a good thing to clean and fix

 

[MassJDM]

well like you said the egr is only affecting the idle... i bought a coil and pout it in and tada it was fixed... lol so i though i am a mechanic and have a scan tool and so i drove the car and it was good for the first run then when i went home it shuddered again and prior to replacing the coil it had a 301 code replaced the coil and it changed to a 304 which the new coil was on. so i changed the coil with the other one and drove again... it shuddered again and i checked the code and it was a 302 which is where the new coil was so i went back and got a new coil and it will be in tomorrow so i will see what happens...

 

[SpeedAdiction20]

ya I was only saying that the egr valve for some reason made me run leaner overall even in boost and stuff, but it was really really dirty, but bad coils are no good.. and bad/rich tune

 

[jetblack]

I've got a boost gauge, and it's saying that that side of it is fine. 6 psi at WOT, and 20 vacuum at idle. I've got an aftermarket exhaust with a generic cat, but it did this before when it was straight-piped with a different muffler so that can't be it.

It doesn't matter which gear I'm in, it does it in all of them at the same range. Also, after driving for a while, it eventually smooths out and the range of RPM that it jerks at get smaller and smaller until it only has a slight twitch every now and then at 3000-3100. It's like the car has to warm up or something.

It's hard to say what all the mods are, but from what I can see it's just the exhaust, a boost gauge, and a cold air intake. It has to be fuel cut, I can't think of anything else. I remember reading something about a dealer flash of something that pertains to fuel delivery. Is that relevant to this?

EDIT: Oh, and I don't know what spark plugs I have to be honest. I've only had the car for a month. It only jerks when the throttle is being pushed. It seems to be related to whether there is boost or not.

 

[SpeedAdiction20]

ya with the cai and the fact that you said it has to be warmed up makes it seem most likely like fuel cut, if it gets worse when it's colder out like at night (depending on where you live) then that is even more evidence that it is fuel cut, the tune on these cars are just really bad, I really suggest saving up for an ssafc, look on Protegegarage.com for it, it is worth the money big time, and don't get the dealership reflash, just tune the car, because once you reflash it, as far as I know you might not be able to go back, but really even if you can, your better off just tuning it correctly with the ssafc because all the reflash does it retard the timing instead of correcting the fuel maps

I think with these cars, since the stock air box and everything is in the engine bay, and with the stock hood, the engine bay area is really really hot, so it is sucking in really hot air, the car is tuned for that hot air, so with a cai, the difference in air temp and air being read from the MAF sensor I think throws it off enough to cause fuel cut when it's not really hot outside.. at least that is what I think