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Toyota Service
Toyota Service, Toyota Expert
Category: Toyota
Satisfied Customers: 4944
Experience:  30+ Yrs of auto experience, Award Winning Svc. Manager; Just Answer Customer's Choice Award Winner
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My 2001 Tundra 3.4L V6 Auto Trans 2WD sometimes runs rough

Customer Question

My 2001 Tundra 3.4L V6 Auto Trans 2WD sometimes runs rough for about 10 to 20 seconds after a cold start in the morning. When it does it, it also has started bucking when I get above 50mph under load (up a slight incline). If it starts up without the rough idle, it doesn't seem to have the bucking problem and I can get up to 80mph without issue.
JA: Is the rough idle intermittent or consistent?
Customer: Random. Sometimes it doesn't do it at all other times it does and the engine light comes on.
JA: Are you fixing your Tundra yourself? What have you tried so far?
Customer: I've taken it to the dealership. They've replaced a broken sparkplug ($700) and rebuilt the heads because they were both cracked ($4,000). I've replaced the spark plug wires and replaced the center ignition coil.
JA: Anything else you want the mechanic to know before I connect you?
Customer: It's random and I've been unable to figure out any pattern. It seemed to happen more often on a low tank of gas. One time it was doing it at 1/2 tank and it stopped after I filled it up. I thought it must be the fuel pump but it's since done it on a full tank and has run fine other times on 1/4 tank.
Submitted: 10 months ago.
Category: Toyota
Expert:  Toyota Service replied 10 months ago.

Hello. welcome to Just Answer. Please allow me to assist you. Running rough after sitting all night can usually be attributed to leaking (dirty) fuel injectors. When the engine is shut off, you still have 30 PSI of fuel pressure on the (closed) injectors. If an injector is dirty, this allows the fuel pressure to push the fuel in the injector into the intake manifold. When you start it, the excess fuel fouls the spark plugs a bit; this usually clears up when the engine runs for a bit. Same thing on acceleration. If your injectors are dirty, they do not spray a cone shaped pattern of finely atomized fuel. In other words, you get drips. This causes a poor combustion issue. I would recommend, before you do anything else, that you get a can of a really wonder fuel injector cleaner (We use a great product called BG 44-K). Put this liquid in the tank and then drive it; running the fuel out as fast as possible (the cleaner loses potency if it sits for days). The BG 44K will clean the dirty injectors; we use this stuff all the time and recommend it very highly. You can find a dealer locator at the BG website: