Hi,
Just recently got my fourrunner back up and running in October, when the weather was still decent. Now that the temps are going below 30 degrees the truck runs horrible when i start it up. After about 15 minutes and it is warm and I shut it off and then start it again, it is fine. It does this every morning now. Yesterday it was actually alot warmer than normal in the morning, i fired it up and it ran like a champ. Is there something that might be bad on the motor, some kind of sensor for when its cold... Never had this happen before. Thanks. Lisa

 

Not sure which engine you have. Could be one of several things, cold start injector adds fuel when cold, mainly when starting and it has a sensor that controls it. Then there is the aux. air valve that adds air to the cold idle to speed it up and make the engine warm up faster. Then there is the coolant temp. sensor for the ECU that tells it how cold or warm the engine is. A Factory Service Manual has testing procedures for those plus a troubleshooting guide.

 

It is a 1993 fourrunner and it has a 3.0 V6 with approximately 280,000 miles on it. Came out of an 88 fourrunner I used to have, it did not do this when it was in that truck I know, very odd.. Its been running up at start just fine up until this colder morning weather. Thanks

 

Might be something was not connected right in the swap, or it may be that there are some minor ECU and component differences between the '88 donor and the '93. I know the earlier engines had more things that had automatic controls while on the later models, the ECU turned more things on and off directly. Probably best to go through the cold start items on the engine and assume they are bad until you can prove to yourself that they work by testing them.

I used to have a VW with fuel injection and it would start hard and run rough when it first started getting cold every winter. Once the lower temps bottomed out mid-winter, it would start and run just fine. I figured there must be some sort of bi-metal switch someplace that was dirty or something and it took a low enough temperature for it to finally work itself clean and start working properly. Then it was fine for the rest of the winter and the next year until the temps started dropping again.

 

The 88 3vze has different sensors than the 89-95. The injectors are different also. I swaped an 88 3vze donor into my 94 and had to replace all the electronics with the old ones from the 94 3vze. Down to the distributor, injectors, temp sensors..etc. I am assuning you had to do the same since the sensor conectors would not even connect to the harness. They had different pigtails. I would bet that you have an issue with your temp sensor. It could be wiring or the sensor itself.

Check out this page for more info on the cold start time switch.
http://personal.utulsa.edu/~nathan-b...ne/97colds.pdf

 

I also have had the same problem with the cold starts with my 89' 3vze. A buddy of mine with the same engine, 89' 3vze, also has the same problem, and both of us have the original engine. My 3vze has 225,000km and my buddies has like 320,000km.

The engine starts up hard and then has a major hesitation when cold, but as soon as it's up to temperature it's perfectly normal. It's like the engine doesn't realize how hard your actually pushing on the pedal and then jerks a few seconds later.. Could it be a problem with the valuetrain when the temperature is so low? Another thing I was thinking was that it's an injector issue or throttlebody issue. I don't think it's the cold temp sensor or cold start injector because it still idle's high when started up in the cold and idle's like normal, which would indicate that both of those are still working. But the cold injector time switch is definitely something I'm going to take a look at.

 

If you guys have searched up, down left and right for the problem, im willing to bet it's circuit I15 wires going lame. Shielded wire can go bad after so long. Look at my thread, search for "3vze ignition nightmare" and try my solution. I was having the exact same type of cold no start/crappy run problem until I happened across my fix.