Running rough (1 Viewer)

[woodstock]

Good morning folks! My 2000 LC for the past couple of weeks as it’s gotten cooler has begun dying when I start it up. It will idle normally for about 5 seconds and then cut off. When I restart it will run very rough like it’s missing and die again unless I rev it and let it get it out of its system, so to speak. The rest of the day it will run and act normally. I have not noticed any significant drop in fuel economy either. No CEL either.

I have cleaned the throttle body well, replaced the air filter, and cleaned the MAF sensor. I‘ve got a new fuel filter ordered and is on its way.

Am I checking off everything that I’m supposed to? Thoughts, please?

Thanks!!!

 

[Trunk Monkey]

Sounds like coil pack on it's way out (you can check for pending codes) or possibly fuel pump going.

 

[woodstock]

Sounds like coil pack on it's way out (you can check for pending codes) or possibly fuel pump going.

Do you think that my inexpensive OBDii scanner find that potential coil pack issue or will I need that diagnosed with a higher end diagnostic tool?

 

[jsloden]

If it's not throwing a CEL then it's probably not going to find a code. A couple of years ago mine would have a stumble at about half throttle or more. If felt like the trans was on it's way out. It never threw a CEL. I took all of my coils out and realized one of them had a crack down the side of it. It had been arcing inside the spark plug tube.

 

[Trunk Monkey]

A cheap OBD reader will pick up a pending code (and is good to have regardless for the $20 they cost).

 

[NE Snowman]

I had a bad coil this summer, only missed on heavy load. No check engine light but i did have pending codes when I scanned it with my cheapo WiFi scanner.

Three codes, random miss, and 2 cyls with misses. Was one coil setting both off when I moved it. Replaced them all because of age and mileage.

 

[woodstock]

Does that track for you guys that it only does it on start up? Cool weather possibly contributing to it?

 

[jsloden]

Not exactly, mine would do it all of the time.

 

[NE Snowman]

Nope not cold related, mine was barely noticeable under load, seemed shaky and weak. Idled and started fine and if I didn’t stomp on it it, it would get up to speed normally.

Fwiw I replaced spark plugs a month before and noticed I had a non oem coil and a few starting to get cracks in the side. I sent it for about another month till my misfire started.

Cold is odd, I know a lot see the fuel pump dying under high temps after driving for awhile and stall out.

 

[woodstock]

Quick update here… no codes showing or even pending codes for that matter. When I start it up in the morning and it does what it has been doing I will have the ODB plugged in and ready.

The fuel filter was delayed in transit, of course, so I haven’t changed it out yet.

I need positive vibes please, guys. lol

 

[2001LC]

Looking at air and fuel, was good thinking.

But typically a fuel starve issue, is long crank to start. Mostly associated with fuel injector leak down. OR Crank no start at times, then start other times. Often associated with fuel pump failing. Neither have much to do with cold days.

Toyota fuel filters can get somewhat clogged, but handle it well. They don't tend to be cause of rough start. With these, will see fuel trims run a little lean.

Sometimes we've multiple issue going on. Making sure engine is well tuned. Which includes no vacuum leaks, including your PCV grommet. Using only Toyota purchased parts or parts from known good sources is key. Many bootleg or sub par parts in the market.

Typically a weak coil, acts the worst when hot. But I've seen symptoms similar to yours, with a bad coil. Replacing an aftermarket coil, that some INDY shop installed. Solved that issue of rough cold start and cold idle.

A weak coil will show up as a misfire, typically underload. But this takes tech stream to see. There is a glitch in tech steam that hide these misfires. Which there is a work around for. We had issue, where we'd see a misfire in tech stream for one moment on a cylinder, that would vanish. So the bad coil eluded us for a while. As thought was, the monetary seeing a misfire, was the glitch's. The opposite was true.

Had another with cold engine near stall, that ran fine warm-up or warm days. It had an aftermarket MAF sensor (no CEL or DTC confirm or pending). Unfortunately, the condition went on for many years and killed a CAT. Fact is I've been finding more and more with no CEL. That replacing MAF sensor, we'll see fuel trim improve. They just seem to get weak.

 

[woodstock]

Alrighty… so I replaced the MAF yesterday and things seem to be working normally now! I guess that the cleaning I did on the old one just couldn’t fix a bad MAF.

Still planning on replacing the fuel filter whenever it decides to arrive.