Rough idle on some cold starts

[thegipper]

It was relatively consistent but it all depended on how long it had been sitting for.

Check your coolant level in the reservoir after the truck is full warmed up and take note of where it is (mark a line on a piece of tape). Then keep an eye on it for the next few days/weeks. It should stay pretty much exactly where it was. If you notice it slowly going down, you can investigate further.

 

[AntleredRuin]

If you can run a gauge to the interior where you can watch while driving, the FP test should be pretty conclusive.

IIRC, you need to be around 43.5 PSI constantly, whether idling or at WOT, hot or cold startup, etc. That's the purpose of the FPR; it uses it's vacuum driven check valve to appropriately adjust the pressure regardless of airflow.

If the pressure flaps around, you probably have a bad FPR. If it's constantly low, you probably have a bad fuel pump or clogged filter or injector. If it starts low but raises when the idle smooths out, you probably have a leak somewhere (like the injector).

This is the adapter you would need.

It allows you to hook up pretty much any standard fuel pressure gauge to the fuel rail on Toyota's/Honda's and I'm sure some other companies use this setup also.

That adapter would have been a godsend for me a few months ago. I might get one now, just in case.

 

[Anthrax]

Replaced pcv valve and havent had the issue since. Could that have been the problem or maybe its just a coincidence it's not doing it after I replaced that part. Wont hold my breath.

 

[Anthrax]

Well I finally got around to testing fuel pressure to get to bottom of my problem. I ordered connecter and rented brand new fuel pressure tester from autozone. I think something was wrong or I didnt do it right but I cant figure out what was wrong. After turning key to on I didnt get a fuel pressure reading. After starting my car it started at 0 and went up very slowly. If that was real doesnt seem like car would be running and starting right? Dont really know where I could have messed up testing it tho. Seems pretty self explanatory.

 

[FunBobby]

Mine had a rough idle on cold start, that turned into a long start, that turned into a miss; it was the fuel injectors, details can be seen in my build thread.

 

[Anthrax]

Mine had a rough idle on cold start, that turned into a long start, that turned into a miss; it was the fuel injectors, details can be seen in my build thread.

That's what I'm leaning towards. The PO replaced 2 of the injectors but I dont know what his symptoms were. Any way to narrow it down to which injectors are going bad?

 

[FunBobby]

That's what I'm leaning towards. The PO replaced 2 of the injectors but I dont know what his symptoms were. Any way to narrow it down to which injectors are going bad?

You should be able to see which cylinder is running lean by comparing the spark plugs, it was obvious on mine

 

[96 ToyRunner]

Mine was a new reman injector that was wet after setting over night got it replaced and it did it a few days later and it was a gas fouled spark plugs after getting that change it’s been running good this past 2 weeks