91 V6 tunning problems

[Aussie4Runner]

91 V6 tuning problems

Hi

I am new to the forum. I live Australia and own a 91 V6 Ltd.

The problems started with a missing/surging problem. I have taken it to four different mechanics including Toyota. None of them were able to fix the problem.

They all started by saying the plug leads need replacing, which had been done and didn't fix the problem. Toyota followed this by wanting to replace to whole engine. The last mechanic put it on a dyno and said it was running too lean. He corrected this by tweaking the airflow meter. This certainly helped, but I felt that it was only masking the real problem. The problem continued to get worse until it was completely gutless up to 3000 rpm, then it would suddenly take off.

With 350000km on the clock I decided to rebuild the engine. Unfortunately the same problem is still there. So much for Toyota's idea!

It idle's smoothly and pulls fine above 3000 rpm.

Anyone out there with any ideas? I really like my 4Runner and don't want to get rid of it.

Regards Andrew

 

[turbosol93]

if it's running lean i would check for any air leaks...if there is a vacumm line that looks questionable i would replace it...as far as it doing the same thing after an engine rebuild then it would seem like an efi problem...

 

[Aussie4Runner]

Have found that all contacts on the oxygen sensor are open circuit. I assume that it is not supposed to be like this and have ordered a new one. Hope this is the only problem.

 

[Aussie4Runner]

Oxygen sensor

Replaced the oxygen sensor (not cheap!). Runs a little better, but still not great.

I noticed in another post that someone said a newly rebuilt engine will improve with time. I suppose this makes sense, as the engine runs in, it should increase compression.