Engine shake and spiking RPMs

Tiny
WILSON27
  • MEMBER
  • 1998 SATURN SL2
  • 1.9L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 234,000 MILES
So my car sounds horrible the engine shakes enough to rattle the exhaust. I've only had two codes one is a cylinder 3 misfire p0303 and a knock sensor code p0327(pretty sure that's the right code number). When I hit the brakes the rpm jump up then slowly go back down same when I put it in park or neutral. I've replaced the plugs, wires, tested the ign coil and ignition control module both tested good. Replaced the fuel injector on cylinder 3 runs better(more acceleration) but still jumps rpms and still shakes. The previous owner told me he had a vacuum leak test done and ensured me there were no vacuum leaks and the hoses look good. Ran seafoam through it today and its again much better on acceleration but still the same problems. Mount looks OK although I didn't check the one underneath yet. Replaced the knock sensor and the wires all look Ok same with the connector. Any ideas?
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Sunday, March 6th, 2016 AT 4:15 PM

13 Replies

Tiny
WILSON27
  • MEMBER
Oh not to mention on occasion the check engine light flashes, yes I know it means its unsafe to drive but I have a baby and its my only car so I have no choice if I need formula or something of that nature.
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Sunday, March 6th, 2016 AT 4:32 PM
Tiny
HMAC300
  • EXPERT
Check resistance in coil and spark plug wire if you have it then check compression. After that check fuel pressure with a gauge auto parts rent it.
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Sunday, March 6th, 2016 AT 5:10 PM
Tiny
HMAC300
  • EXPERT
Oops forgot cyl#3
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Sunday, March 6th, 2016 AT 5:10 PM
Tiny
WILSON27
  • MEMBER
Well the wires are new and if I pull the wire off there is def spark. I've already checked the coil and the coil runs two cylinders so I have only 2 coils for all 4 cylinders so I'm thinking if the coil was bad that would also set the other cylinder off. I have a compression tester but haven't done the test yet bc if it has something to do with fuel delivery you would think that would not only effect cylinder 3 but all of them. If I do the compression test I'm sure cylinder 3 would be lower then the rest if it was fuel so what else would that tell me other then if the seals are bad?
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Monday, March 7th, 2016 AT 8:13 AM
Tiny
HMAC300
  • EXPERT
Well the best thing here is to have it scaned for codes by a pro so he can freeze frame It to check other sensors to see if they are ok. I t may be one of them or an injector causing the problem. Do that before you dump any more money in it
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Monday, March 7th, 2016 AT 9:28 AM
Tiny
WILSON27
  • MEMBER
Any other sensor would throw a code, tps, iac were changed and the fuel injector was already replaced. Knock sensor was replaced wires, plugs, throttle body clean. The only thing I can't think is dirty valves from the fuel injector dumping fuel in before it was changed bc the plug had carbon on it so I'm assuming the valves are about the same. Seems to be running better after the seafoam treatment. Anything else I could check idk if its relevent but the lights on the dash flicker so maybe not enough voltage getting to the fuel pump. Is that possible?
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Monday, March 7th, 2016 AT 10:17 AM
Tiny
WILSON27
  • MEMBER
Oh another thing one of the pullys is squeeking if its the idler pulley can that cause these symptoms?
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Monday, March 7th, 2016 AT 10:28 AM
Tiny
HMAC300
  • EXPERT
A pulley squeaking won't cause your problem however belt and tensioners should be replaced every 60,000 mi. And the reason I told you to have it freeze framed is the sensor may not be totally bad but weak and causing your miss/shake etc. Check coil reistance for the same cylinder
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Monday, March 7th, 2016 AT 12:15 PM
Tiny
WILSON27
  • MEMBER
Most sensors would cause multiple misfire though. And the idler pulley has a bearing in it if that bearing goes bad that would cause it to sqeek which since its a bad bearing couldn't it lock up sometimes? Idk if the tensioner was ever replaced I bought the car recently. I bought it for cheap bc I'm broke that's why I'm on this forum. Not to be told that I should take it to a mechanic. There is no reason why I can't get the live data off a scan tool from Autozone I use to work there so they have no problem with me using it myself but there should be resistance tests I can do at home and maybe get an idea of which sensors I should be checking
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Monday, March 7th, 2016 AT 2:20 PM
Tiny
HMAC300
  • EXPERT
Guess you know everything then I've replied to what you should do so have at it
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Monday, March 7th, 2016 AT 3:52 PM
Tiny
WILSON27
  • MEMBER
Aren't you suppose to tell me at least which sensors should be looked at? Some expert pretty sad when a girl knows as much about shit as you do with your 40+ years experience. Thanks for nothing
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Sunday, March 20th, 2016 AT 6:06 PM
Tiny
WILSON27
  • MEMBER
Could've at least told me what other possibility it could be like internal engine damage or whatever all u said was could be a sensor. And if its not? You don't know right? You watch me take it to a mechanic and they say all the sensors are good bet money on it
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Sunday, March 20th, 2016 AT 6:08 PM
Tiny
HMAC300
  • EXPERT
What is fuel pressure? And compression? You freeze frame it to see if a sensor is out of whack, may not set a code but voltage is screwed up so it causes amisfire. Auto parts rent fp gauge, get back with the results if you don't do the basics as far as scanning for codes and checking fuel pressure you are going in blind and coming out the same way.
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Sunday, March 20th, 2016 AT 8:26 PM

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