1994 Toyota 4x4 with Stutter Off Idle

Don't put away wet...

I am not a Toyota expert, but most injection systems have similarities! Since the truck is pre 1996 the computer has no memory so you cannot check it's history and since you are not experiencing a check engine light I suggest you start with things that are not monitored by the computer! First of all I suggest you check the compression as an old out of spec squeezer will cause all sorts of problems to surface. Check fuel pressure and also the effect of applying vacuum to the fuel pressure regulator. Pressure should drop when vac is applied! I would also suggest you check the operation and resistance values as you sweep the TPS from one extreme to the other. The TPS when moved sends a signal to the computer which in turn tells all injectors to give one extra shot of fuel which acts like the old accelerator pump on a carb.. Hopefully these tests will shed some light on your problems!!!

You need to identify whether is is running rich or lean at the moment the problem exists;

If it sets over night and starts in the morning with no problems than it maybe a fuel pressure regulator or fuel filter. Check to see if the fuel pressure regulator has an internal leak. It will cause a warm engine to run rich. Clogged fuel filter or worn fuel pump will cause rough idle intermittent fuel flow, loss of power at high speed.

If it isn't running rich when warming up then the problem is with a vacuum sensor. perhaps EGR or mass air flow sensor. In most cases if the mass air flow sensor has failed the engine will run lean.

If it runs rich and rough idles, when operating temperature is met, the EGR is stuck or vacuum leak present on gas tank fuel canister or vacuum line is cracked.

These are a few other things to check out over the week end.

Regards,

Tim

The most common failure is the egr modulator, check the small vacuum ports on the throttle body on top they are marked P,R,Q make sure they are not clogged up, clean them out with a small wire and some spray cleaner, if you have a vacuum gauge check for vacuum at these ports with the engine between 1400-1800 rpm, the vacuum should be steady, this is a two stage system so one port will get vacuum at a lower speed the other port will get vacuum at higher rpm.
The temp sensor is located on the egr valve housing, it is almost never the cause.