t3banshee

1991 toyota pickup 3.0v6 automatic trans 4x4

Idles about 400-600 rpm. So it varies.

Aadjust idle screw and nothin happens.

Truck runs lil rough bout 1000rpm to 2000rpm. 2000 and above it runs great! Has good power.

Ideas?

Thanks

4runnertank89

Have you checked your TPS (Throttle Positioning Sensor)? If it isn't adjusted right or not functioning correctly it will most definitely cause a problem like yours. Also check for vacuum leaks going towards the intake.

TNRabbit

Check for diagnostic codes FIRST.

Gamefreakgc

x2. Sound like a bad TPS, they don't always throw a check engine light when they go bad. See link on how to test it with a multimeter (ohmmeter): http://personal.utulsa.edu/~nathan-b...93throttle.pdf.

Check vacuum leaks by spraying carb cleaner on all vacuum hoses on a COLD engine while it's running. Any change in idleing, up or down, means you have a leak. This could be why it runs rough.

Also, if the engine shakes violently side to side at all in low RPMs (sub 1500) or if you have low compression in one or more cylinders you may need a valve adjustment. Just finished mine and it runs as smooth as silk. Don't take my word for it though, took me 23 hours (along with PCV valve fix, injector cleaning, hose replacements, etc.), it's no easy task. It's recommended every 90,000 miles on a 3VZ-E. Fix easy things first, then work your way up if the problem isn't fixed.

t3banshee

i will look in to those ideas!

thanks!

Co_94_PU

iTrader: (-1)

Best to go thru the whole intake system, FSM mfi system.

Start with cleaning the air box of loose dirt and trash, and make sure there isn't anything stuck in the intake tube that feeds the box. Clean or replace the air filter.

Test the AFM, make sure it has a nice smooth reading on VS-E2 thru the full range, no dead spots. Make sure the plug ends are clean and fully seated.

Test the TPS, again a nice smooth reading on VTA-E2. Clean and fully seated plug.

Verify the throttle opener isn't stuck, and the throttle plate isn't obstructed.

.. and on and on..


My moneys on the air box/filter is full of crap, and after a cleaning the idle screw will start working .

t3banshee

Had a lil bit of time today to look at the truck. I did notice the intake boot was cracked at the throttle body so i taped if for the time being since no wrecking yard is open today near me. I'll find a new one in the next week.

as well as buy a feeler gauge to test the TPS.

Air box was clean from when i installed a k&n air filter when i bought the truck. the filter was nasty. The previous owner said transmission was junk. well i changed the fluid and filter after flushing it and its good to go! haha

Thanks for the help and will let ya know what i figure out.

t3banshee

well i started the truck up to pull it in the garage and the check engine light came on. codes were for o2 sensor which is new and air flow meter which makes sense because i could not get my multimeter to read anything on it.

anyhow i also did compression test and found that 1,2,3,4, and 6 were between 165-175 psi. however cylinder 5 (passenger side rear cylinder next to firewall) read about 25 psi.

guess its time for leakdown test.

ideas

Gamefreakgc

Was it a code 25? I just resolved that issue. #3 had low compression because the exhaust valve wasn't fully closing, allowing unburnt oxygen into the exhaust. Valve adjustment did the trick.

The fact that it's #5 makes me think it might be something else. I've heard of the backside of the engine overheating due to the crossover pipe and burning out cylinder 5. Do the leak down test and let us know where you are hearing the air escape from: coolant, oil (crankcase), throttle body, or out the exhaust tip. You want throttle body or exhaust, that's the easiest since it means a intake or exhaust valve that needs to be adjusted (can also mean cylinder head need to be pulled and machined...). Coolant usually means blown headgasket and crankcase usually means it's about time to retire the engine.