New to this forum, hoping you good people can point me in the right direction.
Having some issues with my 98 4runner sr5. 3.4 135k.
It stumbles badly when the engine is cold, truck will barely move. Runs better when warmed up, but still has a slight miss and slight hesitation. No codes.
Mileage is down around 12-13 from 17-18 mpg.
Timing belt changed at 100k.
New Plugs and wires.
Coolant Flush and t-stat change.
Fuel Filter changed and numerous bottles of techron run through the tank.
Air Filter, throttle body cleaned, maf cleaned.
Checked vacuum hoses visually and by spraying ether.
Nothing has made much of a difference.
Thanks in advance

Update*



Finally threw a code. Cylinder 2 and Cylinder 5 misfire. Changed the coil pack, wire and plugs on those cylinders. No joy, same code. Cleaned Idle Air valve and did seafoam treatment. Still no luck, same codes. I'm thinking about pulling the injectors and sending them out for cleaning and testing.


Anyone have additional thoughts?
Thanks.

 

What plugs and wires did you use? Hopefully, NGK or Denso.
How did the plugs look when you pulled them?
Have you cleaned the IAC valve in the throttle body?
What RPMs is it running at cold?
Using coolant or oil?

 

Denso wires and Denso K16TR11 plugs.
Plugs look perfect. I pulled them and rechecked the gaps.
I have not cleaned the IAC Valve yet.
Not using coolant or oil.
Rpm at cold start is around 5-600 rpm

 

I'm leaning towards the catalytic converters.

Edit: I missed the part about no codes but I have found in some instances that a P0420 doesn't always occur for catalyst system inefficiency .

 

btt update in op

 

Are you using any coolant? Pull the plugs again and see if they show anything.

Certainly could be the injectors are dirty or partially failed.

Also, a chance coolant is slightly seeping into those cylinders. Any white smoke out the exhaust after the engine is fully warmed up?

 

time to compression check

 

not using any coolant, no white smoke, plugs look fine.