Boost Leak Maybe?...Real Bad Shake

[SchmeelDeal]

After finally getting my car back from a four month rebuild from hell (rebuild, then it crankwalked, so I got a Jasper 6-Bolt), it seems to shake real bad when the "Stock boost gauge" reaches a certain point. It doesn't matter what gear I am in, just when the boost gauge reaches midways between 7 and 14, the needle raise about 1/8" more and the whole damn cars shakes unitl I let off the throttle. The car idles fine. Plugs are gapped right and the wires are brand new. I plan on doing a boost leak test. Does this sound like a boost leak? What else can I add to my list of things to check?

 

[Boosted4]

you pretty much just explained it yourself. it has something to do with when the boost guage goes between 7 and 14 ... although i recommend an aftermarket guage ... autozone carries em now for about 60$ i think, would really be worth looking into. anyway seems like the first thing i would check, that and maybe your coil pack

Good Luck

Brandon
91 Laser RS-T

 

[SchmeelDeal]

(Sorry, its pretty long, but did I alot of trouble shooting today)

Did a boost leak test as per the vfaq, and immediately discovered a real bad leak in between the throttle body and intake manifold. After inspection, found that two of the bolts holding on the throttle body were finger loose. Took apart the throttle body and cleaned it, as per plymouthlaser.com, and put it back together. There was a slice in another little line coming out near the intake and going into the "actuator" below the turbo. Fixed that. Okay now no more boost leaks.

But then I noticed that the vacuum lines for the purge valve cannister (below where the battery is) were just looped back into each other . Found a bunch screwed up vacuum connections too. Vacuum line by the fuel pressure solenoid and the purge control valve were all jacked up. One of the egr valves vacuum lines was looped back into itself and split with a "T" connector. So I just refered to a combination of the vacuum diagrams from the Factory, Haynes, and Chilton manuals, and completely traced them all down and made sure everything was where they were supposed to be.

Tried the car out and it still no change as far as the "extreme shake" under boost. Car pulled like a mofo except when the boost hit around 12, it would shake. Although sometimes it would shake right at 7 psi, but I am using a stock boost meter, so there is no way to judge.

Now I began to get curious about the CEL. The rebuild shop "told" me neither they nor Mitsubishi could read a code from it. Said it was blank. Its funny, how I followed the directions in the Haynes manual with a voltemeter and got two errors codes: 21, and 31.
21 says faulty engine coolant temperature sensor, and 31 is for the knock sensor.

Okay, so I checked out the coolant sensor according to the Haynes manual. Did the voltage test on the connector and it check out okay, 4.6 volts. Did the Ohm resistance test on the sensor itself, both at base, and operating temperature, and the they checked out ok. Next I cleaned the connecters with contact cleaners and coated them with dialectic grease, hoping that it was just a bad corroded connection.

Started the car back up, still got that shake, CEL still on. So, I cleared the code and ran the car for like two minutes and the CEL came back. Sames two codes again, 21 and 31.
So, tommorrow I will get a new engine coolant temperature sensor. As far as 31 goes, the knock sensor + wiring harness was replaced (by the idiot shop) after new engine was dropped in because of the code 31. It didnt fix the code, so I am guessing that there is a fault in the circuit somwhere. I will try to take it out and torque it ~4 ft lbs like the specs say and wire brushing the threads out (because the engine block is new and painted) to see if that helps.


Okay, and even after all this, I have come across yet another problem (just gotta love DSMs). When testing the coolant temperature sensor, I had the car off and the key on, like the book said. I noticed an "arcing" sound coming from around the throttle body. Turns out its the ISC. Okay so I unhook the ISC wiring harness, and the throttle position sensore starts making the same arcing sound. Then I unhook the TPS wiring harness, and hook the ISC harness back up and it doesn't make the noise. So I'm wondering maybe this is a bad TPS. Could a messed up TPS tell the ECU a bogus throttle position, which could then make the ISC go apeshit? Just wondering. I dont know if the ISC is directily related or connnected to the TPS . Could the TPS becausing the shake?


I think that is just about it for now...Any insight or words of widsom or advice? Anyone?

-James

EDIT: Just wanted to add that one of the coil packs was replaced right before the rebuild. I guess it is possible that the other one is bad, but the missing in the engine is sorta selective and just doesn't seem the same as the miss I had when the first coil pack went bad.

 

[SchmeelDeal]

Since doing the above, now my cruise control does not work. Wonder if it has anything to do with the TPS?

 

[doodie]

What kind of plugs are you using? Have you taken them out to check if they're fouled up or not? You should have went with the cheaper solution and changed out the sparks with some NGK BPR6ES before you did all that. It just might be it.

 

[SchmeelDeal]

Plugs are NGK BPR6ES's gapped at 0.28. Wires are Magnecore 8.5mm. Both brand new. I put tried swapping out the plugs with the old Bosch ones that I had and there was no change so I checked the gap on the NGK's and put them back in.

 

[SchmeelDeal]

Replaced the coolant temperature sensor today (the one that goes to the ecu) and that took care of the CEL code 21. However, this didn't help out with the jerking and misfiring.

I still have a CEL code 31 for the knock. The rebuild shop told me that they had replaced the knock sensor, but I decided to take it off and retorque to to make sure it wasn't over torqued (pain in the ass to get to). Once I got it off I noted the part number on the knock sensor and hand tightened it, then snugged it about 1/2 turn. Got the battery and everything back in, and the CEL code 31 came back.

So I figured, I would just replaced the knock sensor. I looked up the part number in CAPS and found it to be MD141510 for 1g AWD Turbo DSMs. But the part number of the knock sensore in my car was MD300670. Looked it up and it turned out to be for a 2g AWD Turbo.

So they replaced my knock sensor with one for a 2g. Wonder if this could be the culprit for the crappy running and misfiring? Gotta wait til Monday when I can pick up the right one from Mitsu.

 

[SchmeelDeal]

Put in the right knock sensor today. No more CEL. Drove the car for like 20 minutes, being real heavy on the gas and everything seem A'okay.

...problems resolved....I hope...

 

[89_laser_32]

If you don't mind, whenever you figure out your problems...will u pm me about what you did to fix them? cuz i'm going through the same crap. Thanks

 

[azkikr10]

im probably wrong but i thought 2gs didn't have a knock sensor.

 

[Nayr747]

I have heard of the "bucking" happening because of a bad TPS. You should test that and make sure it's working correctly: http://www.plymouthlaser.com/tps.htm