'91 Maxima SE 5 speed....

Coming home from work about 2 weeks ago I had a major brain fart while attempting to downshift from 5th to 4th while passing another car. I inadvertantly shifted into second at the same time I mashed the accelerator and let the clutch out. At that moment I heard a pop and grind of sorts from the engine area and immediately devloped a tap. The pop and grinding sound only lasted that initial moment but the tap stayed for aprox 3 miles. I thought I may have hurt a valve and slowly limped home. I pulled into the driveway and left the car idle. It was idling at nearly 2K but not tapping. I shut the car off and decided I would look at it more closely the following morning.

The next day it was a noticeably cold morning (more on this later). It took 2 short attempts cranking the engine to get it to start (it normally starts on the first try). I decided to drive it to work hoping it wouldn't grenade on me. The idle was still around 2K but I shifted into 1st and pulled down the drive and onto the highway. I almost immediately notice an increase in power over anything I've ever felt from this engine. It was at that point I came to the conclusion that I may have slipped the timing belt and advanced the timing? All was fine for a few days minus the high idle. Then the weather warmed up and all went to $hit power is now weak and it has a knock similar to being out of timing. Does my diagnosis sound in the ballpark????

I'm now at the point where I need to make a decision whether to take it to Nissan or tackle this issue on my own.

Any feedback regarding DIY repair or dealership repair is appreciated.

 

just replace the engine you proboly bent several valves and it would cost more to fix them then to just replace the engine which would proboly be around $500

 

If the valves were bent..wouldn't it still be tapping?

 

I seriously doubt you bent a valve yet.
but something is wrong, just not sure what

 

do a compression test and that will tell you if you bent any valves

 

A compression test wouldn't hurt, but I'm 99% sure you didnt' bend any valves. you would have near zero compression and the car would run VERY VERY poorly if you did... It wouldn't have ran well for that few minutes.

I bet the pop sound you heard was either the engine hitting the hood/strut brace or engine mounts bottoming out from the forces. it could have also been a backfire from fuel if the ECU saw the high RPM jump and tried to feed it gas while doing it.
could have also been something internal to the engine, but I doubt it.


sounds to me like you slipped the timing belt as well.
first thing to do is pull the timing covers off and check your cam timing against the crank.

might as well go ahead and replace the belt since you're in there. won't take but another 45 min to replace the belt and water pump since you're there, but you should immediately see if the timing belt has slipped. line the crank pulley up to the alignment point on the engine block and then check the cam position(s). if they're off, then you slipped the belt. replace it. If they're not off, then you may have other issues. verify again by spinnign the engine a couple times and make sure they're [not] lined up properly.. wouldn't hurt to change the belt anyway and fire it back up, but at this point it may be moot..