Help! Engine shudder at 4k RPM

M

mar4k

New Member
My 3.4l 2002 (200k miles) Tacoma's timing belt went out on the highway between Idaho and Utah. I got the belt replaced but ever since then the engine shudders right at 4k RPM. It only happens every once in a while (when I shoot a gap on the freeway) so I've let it go a while.

Right when I get to 4k I can feel the whole motor shake and lose power. I have to back off the gas or it keeps shuddering. The guy at O'Reilly says that no codes come up relative to this and that if it were the cam position sensor there would be a code.

Some background. This is a really beat up truck (so I'm selling it soon) that I regret buying even though I love tacomas and it's my second one. I've had all sorts of issues with emissions, I've had to replace sensors etc. because the previous owner didn't change the oil. (It burns oil so I'm assuming that's what happened.

I recently didn't pass emissions and they said one of my cats was destroyed. I think it was the first one. I think they replaced the second one, as I can see the shiny metal halfway down my truck. Maybe it's the broken-up cat that's blocking exhaust and causing the shudder?

I did have the engine light come on but it was P0301, misfire on cylinder 1. I recently had a tune up but they didn't replace the spark plug cables/wires so I'm going to buy wires and see if that fixes the misfire issue. I think it's unrelated to the 4k RPM shudder.

I really could use your help as I'm trying to sell the truck. Thanks so much!
 
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Oh man if the timing belt actually broke all kinds of issues can happen. Everything runs into each other, causing bent valves. Other things like cylinder head or camshaft damage, and possibly piston and cylinder wall damage can also happen but not as likely unless you are going freeway speeds when it happens. If you didn't replace all the bent valves they won't be seating right and causing the "misfire"
Did a shop do all the work? If so I'd take it to them they may have not done something right.
I would also do a compression test and leakdown test those can tell a lot.
 
OR17TRD said:
Oh man if the timing belt actually broke all kinds of issues can happen. Everything runs into each other, causing bent valves. Other things like cylinder head or camshaft damage, and possibly piston and cylinder wall damage can also happen but not as likely unless you are going freeway speeds when it happens. If you didn't replace all the bent valves they won't be seating right and causing the "misfire"
Did a shop do all the work? If so I'd take it to them they may have not done something right.
I would also do a compression test and leakdown test those can tell a lot.
Click to expand...

Agree with OR17TRD.
 
1st gen tacos are nondisruptive, if the timing belt goes out they don't grenade! That doesn't necessarily mean go ahead and run 'er til it goes. Just means typically you're not totally up a creek... if it's got high mileage it could be the counter balancer, 1st gen tacos and 3rd gen 4runners in the 6 cyl platforms can/eventually have those go bad, usually they'll warn you if you pay attention. If it's a 4 banger she's probably just really tired.
 
Although a non interference engine can get bent valves if...if the carbon buildup decreases the clearances between them and the piston. Especially at freeway speeds. Higher mileage engines could have that buildup. I'm sure it is a rare thing but... just thinking.
 
4k rpm! I have never pushed my Yota that high, and I have a supercharger. At 3500 that thing is whistling dixie. I get too nervous about old gaskets lol.
 
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