I've got a rough running V6 that throws codes (25 and 51). Code 25 indicates that the engine is running too lean. I think code 51 is a switch issue with the A/C or the throttle position sensor (TPS). The TPS checks out ok at idle and wide open, but I didn't check out the steps with a feeler gauge. The air flow meter (AFM) checks out good too. I didn't check out the injectors, the fuel pressure or the oxygen sensor. I am noticing that it has what I believe is low vacuum at the PCV port on the manifold (15"). That got me checking the compression to make sure the rings weren't bad. So far I checked out the passenger side cylinders and got good readings (175, 165, 175). What am I missing? -- Matt

 

I'm gonna swap the O2 sensor for one that is in a good running '89 4runner next. Both vehicles are '89.

 

Make sure that the main intake hoses are not cracked, split, or missing. Mine split underneath right at the throttle body and caused a rough idle, hesitation, and running lean.

 

I'm just getting started so it sure couldn't hurt to give the intake hoses a second look. Thanks.

 

So I still want to hear what a good manifold vacuum reading should be for the 3VZE. I'm reading 15". I'm not absolutely sure about the accuracy of the gauge but it feels and acts like a low vac situation. I'm thinking a healthy engine should have mid-20"s. -- Matt