Greetings all,

I have a problem with my 1988 4Runner with the 3VZ-FE engine. I understand that it is difficult to diagnose a problem remotely, but I am rather desperate.

The engine was rebuilt by a professional mechanic, a friend or mine, and installed. After some issues with timing, the engine now starts on the first attempts and runs without any hesitation or change in rpms or sound. The problem is that it has no power. I live in the mountains, and once I start driving up a hill, estimated as 12 – 15%, I had to downshift all the way to the first gear, and even then, the car has a difficulty to make it on the top.

What I know:

1. The compression on all the cylinders is within specs;

2. The fuel pump is slightly above the specified pressure;

3. The injectors work, verified by looking with a camera into the cylinders;

4. The timing is correct;

5. New spark plugs.

Any ideas would be appreciated. Also, if anyone knows a good mechanic knowledgeable about these cars in the Escondido, Temecula area, I can rent a trailer and deliver it there.

Kindest regards,

M

 

You are right that it can be hard to diagnose remotely, but here are few things that come to mind to check:
Plugged exhaust- easily checked with vacuum gauge, which would be a good test to run, anyway
Clogged air filter or other intake restriction (frozen or blocked AFM? Could also check AFM with multimeter)
Make sure the throttle is opening all the way in case someone did not install the cable correctly
Clogged fuel filter or other fuel restriction
Check for vacuum leaks or vacuum lines routed incorrectly
If you just checked the base timing, make sure it is advancing properly, or check anything that could be retarding the timing too much during load, like the TPS or knock sensor.
Make sure the timing belt is installed and tensioner working properly. Years ago I worked on a Camry that was doing the same thing as your truck and it was an improperly installed belt tensioner spring (which is a different setup than the 3VZE). I think the belt was just loose enough to alter the timing, but not slip a tooth.

 

Hi @the_supernerd ,

thank you for the reply.

I forgot to mention that the fuel filter is new and since the injectors were checked as mentioned, I do not believe that the fuel delivery is a problem. The opening of the throttle was checked when installing the cable.

I will definitely research how to diagnose the other potential issues that you mentioned, (i) the plugged exhaust , (ii) the frozen or blocked AFM, and (iii) the vacuum hoses, however should you know a practical reference re (i) and (ii) I would greatly appreciate it.

I was also wondering whether the O2 Sensor could not be a culprit.

Kindest regards,

M

 

It sounds like the fuel system is probably fine based on what you said. I would think if it was severely deficient in flow then it would throw a check engine light code for lean mixture.

Here is a thorough video on checking plugged exhaust:
You should just be able to put your finger in the AFM above the air filter and make sure it moves smoothly. For the electrical part, here is a thread that might get you started: https://www.yotatech.com/forums/f116...adings-299184/

The o2 sensor is worth checking. I feel like that significant of a power loss without other symptoms puts it lower on the list, but it is certainly possible. Does the exhaust smell overly rich, or any pinging/misfiring when going uphill?

 

Hi @the_supernerd ,

thank you very much again for your reply.

The fact that there is no pinging/misfiring is the strange part. The engine sounds alike, just with a loss or power and RPM. No smell, and there do not seem to be any leaks in the injectors, verified by spraying carburetor cleaner which did not result in change of RPM.

I will start with the tests you recommended, once I finish working for a living.

Kindest regards,

M