Hello!

I have a 1999 4 Runner 5VZ-FE that I bought on craigslist a few weeks ago. Ever since I have owned it I have noticed that I have an engine light (O2 sensor/"too lean"). I also am noticing that for about 5 minutes after I start the vehicle on a cold start, I have greatly decreased power to wheels. It accelerates normal for the first 20% of throttle but thereafter it gets bogged down like a weedwhacker that too rich. This seems to resolve without any problems after a few minutes.

I just took a look at the spark plugs and they actually look good although there is only one ground on them. The air filter is clean. I am getting just over 20mpg as it is now.

I think the power to the wheels, whether in the first 5 minutes or not, isn't quite where it should be. It is shifting down to get up minor inclines at 60-70mph. Any other suggestions?

 

I'm trying to figure out my pops truck and The truck will turn over but doesn't fire out the #1 plug wire. I've put new coil in the internal distributer, had the ignighter replaced, and the EFI relay fuse, no blown fuses. Anybody got any ideas?? I've Been working and trying to figure this out for 3 days now. Starting to believe it the ECM but trying to avoid buying a 100$ part. Any inputs?

 

Motor can run pretty good if it's overly rich actually. Your truck is low on power after startup because it's very lean. You have unmetered air getting into your motor after the MAF. Check your intake tube, all the hoses and fittings. You should be able to hear an audible hissing sound too. You can buy a can of starting fluid and start spraying it around all the hoses and gaskets and see if the engine slows down or bogs when you hit it with the ether.

When the truck warms up, the o2 sensor is able to detect the extra air (closed loop) and make the ECU compensate, to a degree, thus is runs better.

IDK if the scan tool at Oreilly's is capable, but if you can get get access to a scanner that can read the STFT and LTFT (short term and long term fuel trims) they should be very high, like 20+, this would also be a dead giveaway that you have an air leak.

 

Check compression if you can. Might have bad/dirty fuel injectors or as Vasinvictor mentioned an air leak.

 

Not picking on you but if the motor runs fine otherwise I see no reason to do a compression test. It's a lot of extra work. If you had a total cylinder miss then yes.. In which case you'd have a rich code as there would be a lot of unburnt fuel in the exhaust. Also if injectors were dirty it would not run well after warmed up.

 

Dude, start your own new thread.
You completely hijacked the original guy's thread.