High, rough idle and shuddering at constant speed? Help please!

willandrews · Post by **willandrews** » Sat Nov 26, 2011 2:07 am

Hi all, I just bought my 2003 Vibe GT in August. When I bought the car, the idle was normal around 1000rpm after warming up. Now, the idle is around 2200 regardless of temperature, and it fluctuates a small amount. The engine sounds rather rough all the time, and when driving at a constant speed, the car will shudder back and forth rather violently. I have noticed about a 20% decrease in fuel economy. The IAC motor has been replaced, as well as the throttle position sensor and spark plugs. I'm currently attempting to reset the ECU to see if the car will try to relearn idle. I took it to my local GM dealer and they couldn't figure anything out. Any input, help, or suggestions would be greatly appreciated as I'm totally lost. Thanks!

willandrews · Post by **willandrews** » Sat Nov 26, 2011 2:10 am

Hi all, I just bought my 2003 Vibe GT in August. When I bought the car, the idle was normal around 1000rpm after warming up. Now, the idle is around 2200 regardless of temperature, and it fluctuates a small amount. The engine sounds rather rough all the time, and when driving at a constant speed, the car will shudder back and forth rather violently. I have noticed about a 20% decrease in fuel economy. The IAC motor has been replaced, as well as the throttle position sensor and spark plugs. I'm currently attempting to reset the ECU to see if the car will try to relearn idle. I took it to my local GM dealer and they couldn't figure anything out. Any input, help, or suggestions would be greatly appreciated as I'm totally lost. Thanks!

star_deceiver · Post by **star_deceiver** » Sat Nov 26, 2011 7:39 am

Stuff to do:Is the check engine light on? If so, what codes. Clean the MAF sensorSpark plugs gapped correctlyNew air filterGo through the standard maintenance items first. As for the shudder, how old are the tires. Prpoer pressure, ect but it sounds like you need a wheel alignment.

DraziWDragon · Post by **DraziWDragon** » Sun Dec 11, 2011 3:04 pm

i have the exact same problem. its a misfire in the ignition.I replaced ignition coils, plugs, and all the trimmings.Only thing i didnt do yet, was diagnose the ecu.In detail....when cruising in any gear as to where the rpms are between 1000 and 2000.i release the throttle and press the clutch, it stays at that idle rpm. only when i rev it a little bit, does the rpms return to normal idle levels.you can reset the engine light by disconnecting the battery for 15 minutes, but the light will come back on if the car hits lift in 3rd gear. when accellerating from a dead stop, the car will hesitate/buck, while passing the 1000-2000rpm range. higher than that, and it runs fine.i reset my light every so often before a road trip, then make it come back on and goto autozone for a quick diag.Currently, it states I have a misfire in cylinder #2 and #4. Before i replaced the plugs and coils, It was only misfiring #4.I'm strapped for money, so an Insight on this matter, would greatly be appreciated.

2ZZGE · Post by **2ZZGE** » Mon Dec 12, 2011 1:58 pm

are you have check engine code?

DraziWDragon · Post by **DraziWDragon** » Mon Feb 06, 2012 3:14 am

DraziWDragon · Post by **DraziWDragon** » Thu May 17, 2012 7:18 pm

2ZZGE wrote:are you have check engine code?

Yes, only comes up as "misfire in cylinder #4" even dealer said the same thing as autozone.
I was pissed at dealer for charging me for info I alread know, and had gotten for free at autoxone. so they charged me for half an hour instead of an hour

well, after much testing and redlining, ive come up with a few conclusions.
UPDATE 7-13-2012
1: cam position sensor (Replaced)
2: crank position sensor (Replaced)
3: ECU is bad.??????? Removed ecu, needs to be tested.
Ignition Wires may have a short in it. need to meter test wiring.
4: Maybe fuel pump cant keep up with the fuel consumption anymore? (Works Perfectly)
5: Had 1 bad coil on the misfire cylinder, replaced and still isnt firing.
maybe O2 Sensor now?

funny thing is, ive tested all my injectors and cleaned the fuel lines. and still get "under 2000 rpm" bucking, and misfires over 6000rpms.
I use techron injector cleaner, and the low rpm bucking, doesnt happen. but the high idle still does. and so does the high rpm misfires. trips the same #4 cylinder code.
As the weather is getting warmer, the misfire happens more often, and the bucking happens just after ONE refuel, if i dont add a bottle of cleaner to it.
So at a tank of gas, PLUS $7 for the bottle, its pretty damn expensive.

Ive swapped positions of the injectors to see if that cylinder will trip a code, but its always #4, which is why i think it could be the fuel pump just not being able to keep up anymore.

so in short, change the crank & cam position sensors, the fuel pump, and swap injectors. then drive your car like you stole it.
If it trips a code, replace fuel pump and all should be good.
Retail price for all that is around $600. so ebay and junk yard them. ask for the doner car's milage before you buy, make sure its under 100k.

DraziWDragon · Post by **DraziWDragon** » Sat Jul 21, 2012 5:34 am

So being without my car for 2 months,
i finally started stripping the engine down to the cams.
And upon looking into the cam area, i noticed my cylinder #4
Valve rod, was frikkin snapped off. And the spring was barely
Touching the rocker.
I have 137,000 miles on my car, and my valves look like new still.
No sludge or deposits. There was a little bit of oil in the intake
manifold, but i cleaned everything out like new. All sensors have
been replaced/cleaned/tested. Fuses have been checked.
Ocv was cleaned.
NOW, my question is. Is there a way to remove my cams without
Taking off the timing cover? Or am i stuck with the headache
of that job too?