2000 100LC Stalling Out (1 Viewer)

[cgunn18]

Hello all,

This is the first time that I've had to actually post here usually finding the information I need by some previous discussion. This weekend my car started to misfire and threw up the usual blinking check engine light and eventually the VSC TRAC and VSC OFF. Today I went through the coil packs and found the foul one, I replaced that, held the batter terminals together to reset and and boom all good. An hour later I came back to the truck to start it up and started for about 3 seconds and dead, tried 3 more times and the same result. I thought maybe it was a vacuum leak because in order to access the left side I had to take off the airbox--checked and no loose seals. I took the battery terminals off again held them together to reset and boom the car ran great. Drove it around for half an hour and parked it. After another hour so of it sitting I decided to check it again and the same stalling issue. What do y'all think could be the problem? Could the new coil pack be faulty--should I try putting in the old coil pack and see if it doesn't stall but misfires?

 

[Patassa]

Any codes? I had a mystery problem like this also recently, turned out to be the MAF sensor, and searching here was inconclusive also. Sometimes throwing parts at the problem is the solution.

And what do you mean by stalling, exactly? Is it dying at idle, or just rough idle?

 

[BB3551]

Blinking CEL and VSC lights are consistent with bad coil(s) in my experience. Might not hurt to move coils around and see if the codes move to the respective cylinder numbers. You may have more than one that's bad.

Make sure your terminals are tightly secured to the posts, and confirm that the posts are clean/free from corrosion.

How old are your plugs? How old is your fuel pump?

 

[DanTheBetterMan]

Hey guys, hoping to restart this thread because I'm having a very similar issue: I purchased the car (2000 LC100 w/ 4.7) about 6 weeks ago and was told a lot of parts were new (spark plugs, fuel filter, one coil, air filter, etc) and that the gas tanks (it's a VXR so it has 2 factory tanks) had been recently cleaned since the car supposedly sat for several years and they were dirty/rusty. Well, I took it on a shakedown trip a couple of weeks ago that involved going to warmer climates and up/down mountain roads, and that's when I started to experience stalling at idle. Before that I had noticed it was hard to start if I drove it somewhere, got it to temp, and let it sit for 30 minutes to an hour, but it was idling ok when on. On the way back from the shakedown, the idle was low, around 300-400 rpms and it'd stall if I didn't keep my foot on the gas, but ran fine if I kept the rpms above 700. When it'd stall it'd be hard to restart and would take 2-3 tries. The CEL came on (no flashing, just solid) but would turn off when it'd stall and not always come back on. I managed to get it back to the city and to the mechanic but he's struggling to figure out what's wrong. So far this is what has been done:

• replaced fuel filter because the one that was on it was extremely dirty even though it was supposed to be new
• injectors were cleaned/tested and appear to be working fine
• throttle body was cleaned
• coils were tested and all seem to be working well without any grounding on the housings
• plugs do not appear fouled though I'm told the ones that are on it may not be the OEM ones, they are Denso's K20R-U's
• Mechanic tells me the MAF appears to be working ok because the car stalls if the air filter housing is removed from the throttle body, not sure how accurate of a test this is since a lot of you on here seem to think a faulty MAF could cause similar issues... though I did have another mechanic before this hook up a scanner and review the readings, which seemed normal at the time
• Recently the starter was replaced
  • Reading through some of these threads I'm wondering if the mechanic may have somehow screwed up the intake gasket which is causing this?

Another thing to note is that during the shakedown, my synchro's failed and I had to have the transmission rebuilt in the town where I was. The transmission seems to work fine now though the speedometer/odometer seemed to have been left unplugged. Not sure if a wiring harness could have been left unplugged when this was being done that may have caused all of these issues.

Any suggestions on what may be going on? What could be checked next?

 

[DanTheBetterMan]

Posting an update in case anyone else has this problem in the future: the MAF was tested using a scanner and appeared to be ok, so we started by cleaning the throttle body instead; taking it down to the potentiometers and testing them along the way. The same was done for the throttle valve actuator. Not sure if all models are like this but mine works electro-mechanically, meaning the first ~70% of the throttle movement is read by the potentiometer connected to the morse cable, and then sent to the electric actuator to actually open up the valve. Once that 70% mark is reached, the rest of the valve movement is done by the cable. Everything was a bit dirty but tested fine. Once we put the throttle body back together and mounted it, the car would run but would still idle extremely low (300-400 RPM) and pressing the gas pedal would not make the engine rev up until you got to that 70% mark that was cable actuated. After lots of messing around we thought we'd try resetting the ECU with the throttle body fully opened (this is done on some motorcycles to recalibrate the potentiometers and actuators) - this fixed the unresponsive throttle issue but not the low idle. Eventually I came across this thread, which explains that some models use a variable resistor to set the idle mixture and after changing it a bit we were able to get the engine to idle closer to the 700-800 RPM mark.

I'm not 100% sure what caused the rough idle and stalling initially, or what fixed it, but at this point I think it may have been a combination of things: a plugged fuel filter, dirty malfunctioning injectors, dirty throttle body, and maybe a idle mixture resistor that got reset somehow when the transmission was being worked on. If you have any ideas as to what may have caused all this, I'd love to hear them!