youforia

About 1 out of 4 or 5 starts, when I crank the key and starter kicks in, there is a shudder coming from the engine and a slight hesitation before the engine starts. The "shudder" as best I can explain it vibrates the car a bit (originating from the engine compartment) and makes a hesitating uh-uh-uh sound. The sound is low frequency and if I were to replicate it I might grab a rubber mallet and bang on a solid piece of metal several times to imitate it.

For a bit of recent work history on the car, I have recently had the (1) crankshaft position sensor harness repaired (a critter ate through a part of the harness) and (2) had the timing belt and water pump replaced. When I took the car back to the place that fixed items 1 and 2 to mention the shudder, they could not replicate it and could find nothing wrong. The car has about 120K miles on it. Thanks for any help and/or advice!

youforia

Any help here laides/gents? I've read that shuddering while moving has been fixed by flushing and refilling the transmission fluid... think that could help at all? Thanks!

Tammy

Could be something as simple as a poor ground connection, at the battery and/or at the other end of the wire, where it bolts to the body. I believe that's under the battery. Inspect and clean wire end with baking soda and water. Adding a large star washer at the body helps the connection. Don't forget the postive battery connections for loose or corrosive connections.
There additional ground wires that attach to the fenders, one pair on each side. But they come into play mostly with the fuel and vacuum system.

Shuddering at start, the only driving force is the starter motor. And it's intermittant. This is why I lean towards the electrical connection. It is least costly. Your transmission, as you suggested, should not be in play, as it's in park when your starting.
And , of course, it could very well be the starter motor itself about to fail. It has solenoid contacts that burn and cause a poor postitive supply to the motor. And then there are the motor brushes that also wear out, also meaning a remanufactured starter motor assy.

cip

When this occurs how long does it last? I've had it happen that when I start the car, the RPM's are so low the computer tries to compensate for not giving it a 'full' start and hesitates but the engine catches (about 1.5 -3 seconds) and then runs fine. This usually only happens when cold, where I don't let icrank long enough. Let me know if this fits your situation

Also, how are your engine mounts??

youforia

Thanks for the information, Tammy/cip.

Tammy, I will check my electrical connection and see what that does. I'll also see if I can diagnose my starter and see how it's performing.

cip, when the shuddering occurs, it's quick -- about a second or two. It seems to happen a little more frequently in the cold, but will also occur after garaging it all night and after starting the car when it has recently been run. I'll try and crank the engine longer and see if that has any effect as well. I'll check out the motor mounts.

Tammy

Oops ... Yes , check the mounts; both on the engine and transmission.

youforia

Even when I leave the key engaged in the starting position, the shuddering still occurs. I didn't have a chance to look at the mounts yet (they look hard to get to), but did try and shake the engine and it seemed solid. I don't think the starter is the cause... the shuddering occurs as the engine is starting and almost after the starter is done doing it's job. I might try and rig up a camera or audio recorder to see if I can record the shuddering as it occurs and then post it up. Stay tuned.

PureDrifter

iTrader: (10)

wheen it shudders do the revs drop at all? if so then theres a small chance it could be the idle speed control valve.

youforia

I'll watch the tachometer to see if the RPM's drop when the shuddering occurs... I'm also in the process of trying to videotape it in the act -- tried it this morning, but it didn't shudder... will try again later.


WB

Tammy

Have someone punch the throttle while checking movement at the mounts. A cracked mount will be notable as gaps appear in the rubber between the metal plates. The mount may not be broken clear through, just partically. Recommend using a good flashlight while checking for movement.

idsrvit

youforia...sorry for hijacking your post...but I couldnt find a way to pm Tammy.

Tammy...I notice your name all over this forum, and you definatly know your stuff. I have an emissions question I am hoping you can help me with.

I realize this is a Lexus forum...but help with this issue would be very much appreciated.

My husband has a 2001 Ford F150 with a 5.46 V8. His mechanic cannot get it to clear two of the error codes to enable him to get an emissions sticker. The error codes are for the evap system and the catalytic converter. The mechanic says that the truck does not have a problem because it tests fine, and the check engine light is NOT coming on. My husband replaced the battery in Oct of 05 and according to the owners manual, changing a battery will cause the on-board dianostics system to reset to a "not ready for test" He has followed the driving procedure for readiness for testing and retested the truck, but the error codes still won't clear.

Do you or anyone have any other suggestions...or things to try to fix this? In order to not continue to hijack youforia's post...can you please PM me @ idsrvit or email imtwaite@aol.com
Thanks in advance.
Trace

youforia

Tried videotaping the shudder, but it really didn't jiggle the engine or anything, so there wasn't anything to see. When I watch the tachometer for RPM's when starting, the RPM's do not drop when the car shudders. Just cleaned my battery contacts so I'll watch to see if there is any change.