Need help with friends 1991 4Runner V6 engine issue

A friend of mine has a 91 4Runner V6 (with about 190K miles) that has a couple of issues that the mechanic working on it has not been able to solve.

Before taking the car to the shop it was running rough (and surging) and smelled of gas. The check engine light would come on intermittently and my friend took it to a local (non-toyota shop) to get it looked at.

The mechanic said he could see gas coming from one of the fuel injectors and replaced the leaking injector with a rebuilt one. The mechanic has been unable to get it to run right. Apparently, when the engine is cold, it runs smoothly, but starts running rough when it heats up. He has replaced the first rebuilt injector with a second rebuilt one and the issue still persists.

My thought was that OEM injectors should have been used.

Does anyone have any suggestions as to what might be causing this problem and possible solutions?

 

when were the spark plugs, and coils last replaced?

i'd also consider cleaning the MAF, and inspecting the emissions system-- sometimes the return circuit will stop working which can result in surging as well

 

I will check and see if he knows the last time the plugs and coils were changed. Cleaning the MAF is also a good idea.
Thanks, I will pass on the info.

 

It's a 3.slow V6.
Surely they checked for a blown head gasket, right???

 

I would have thought that they would but I will find out today.

 

I had an old Mazda pickup that would do that. It was a bad thermostat.

 

3.blows dont have a maf. The have a afm that use a flap to gauge airflow and aren’t serviceable.

It’s probably the ECT.

No one knows how to work on these motors anymore so good luck. I would never recommend anyone that isn’t comfortable with a wrench and a multimeter to own one as it will drive you crazy. Pre odbii efi troubleshooting is a real art that most techs don’t have

these motors made me a lot of money back in the 90s, and again in the 2010s tearing them out and dropping in 3.4s.