Urgent advice needed on rough running/misfire! (1 Viewer)
- Thread starter Eharmz
- Start date
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Yea, installed the other 5 coils in my LC and it’s still idling rough intermittently. Ran like new for like 15 minutes then back to random rough idle. Going back to the mechanic on Monday! Might start looking for a newer vehicle!
These are likely bad coils. Coils get hot when operating. OEM coils use quality windings. Cheap coils use junk windings. Junk windings when too hot (failing) can increase resistance and produce a weak spark.
What plugs did you put in? Why did you replace all of the coils? Did you keep the OEM coils?
Is the coolant sensor an OEM component?
- Thread starter
- #24
**UPDATE**
So I was finally able to replace all of my coils (OEM) and the problem still persists. Currently the coils and the coolant temp sensor have been replaced as well as the started (about 5k ago) and the trouble starting while hot still persists. While I replaced the coils I pulled the plugs and they look good (replaced them about 12k ago with densos). I will go ahead and replace the fuel filter tomorrow because its due anyway but I am stumped as to why it starts right up while cold but struggles, but ultimately starts, while warmed up. I don't want to just chuck parts at this so any further help will be much appreciated.
So I was finally able to replace all of my coils (OEM) and the problem still persists. Currently the coils and the coolant temp sensor have been replaced as well as the started (about 5k ago) and the trouble starting while hot still persists. While I replaced the coils I pulled the plugs and they look good (replaced them about 12k ago with densos). I will go ahead and replace the fuel filter tomorrow because its due anyway but I am stumped as to why it starts right up while cold but struggles, but ultimately starts, while warmed up. I don't want to just chuck parts at this so any further help will be much appreciated.
Can you describe more about the hard start symptoms? Cranking strong? Is it firing at all?
JunkCrzr89
Competent Ignoramoose
Are the misfire codes gone and your CEL is off? I think you can now safely rule out spark as an issue. That leaves two other potential sources of the problem: fuel or air. I'd start checking the following in order: 1) vacuum lines, including PCV and VSV Scored 2007 Unicorn. The holy grail of 100 series. ; 2) intake manifold gaskets; and 3) fuel injectors. At your mileage, any one of these, or even all of them, could be the culprit. Wouldn't be a bad idea to do a compression test either.
What were the codes that you were getting before? Were any of them "lean" codes? As multiple other people previously noted, if you post the codes, that will help us help you...
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- Thread starter
- #27
The only code I have gotten was a few weeks ago and it was cyl 6 misfire which went away with a coil pack replacement. I have a code reader and there is nothing currently. Cold start is easy and immediate but its the warm start that needs two or three cranks but eventually fires and runs strong. After the coolant temp sensor and all 8 coils replaced didn't do anything my next thought was injectors. The only thing that stumps me is why would a leaky injector start immediately after sitting overnight and not shortly after it has been running? I am no mechanic and as frustrating as this is, it is a good learning experience and I appreciate all of the input. I am also putting MAF and o2 sensor into the culprits...anyone agree with that?
JunkCrzr89
Competent Ignoramoose
9 times out of 10, this is a symptom of a) battery going bad, b) corroded/poor cable connections at battery terminals or starter, or c) starter going bad. You said you replaced the starter 15k miles ago - was that a new Denso starter, rebuilt/reman starter, or box auto store starter? Have you had your battery voltage checked when cold and warm?
gregnash
Anal Retentive Analyst
Don't know if this will help or not but something I noticed last night. I have been playing with the Techstream Software while borrowing a buddies laptop. One of the "Active Tests" that is in there is an injector test that you do once the vehicle is warm, engine off but IGN in the ON position and truck in P. I did the injector test briefly and then went to start the truck afterwards and she did not want to kick over and grab. Almost like a flooded carb in my 60. Couple of cranks later she fired right up, ran rough for a moment then was fine. My assumption is that the test actually fires the injectors while running, thus dumping fuel into the cylinder. This overly rich mixture doesn't allow the truck to actually start until the "rich" mixture is cleared. Similar to your leaking injector right after hot.
With it sitting overnight and the cold start immediately in the morning, the gas has more than likely evaporated at that time so the mixture is close enough to a normal start mixture that she just fires up. After the truck is warm, you are attempting to start with the mixture being out of whack and acting like a "flooded" cylinder(s).
Just replaced the coils in mine. Problem solved.
1
job.
1
job.
Also, I bought this thing a couple years ago. Plug and play. It's paid for itself a half dozen times already. There's about a gazillion of them out there.
JunkCrzr89
Competent Ignoramoose
He’s already replaced all coils and plugs with new OEM ones.Just replaced the coils in mine. Problem solved.
1
Ahhh. I just re-read it. Yes.
Injector do behave a little different when hot. FIS does a cold and hot test during testing, cleaning and rebuilding. But seems for your issue to be injectors leak down it would be after sitting for some time, like when cold. Long crank to start when cold is a sign of excessive injector leak down.
Since your issue is after warm up. It's something comes into play after warm up. First thought that comes to mind is open loop vs closed loop. Here's my limited understanding. When cold (pre engine at operating temp), ECM is in open loop mode. The fuel injectors pump/pulse at a high rate to get lots of fuel into cylinder. Once engine at operating temp, ECM takes over control of fuel injectors metering (reducing amount of fuel typically) the pulse to achieve target fuel/air mixture.
A few test that come to mind.
1st, make sure "water temp" is ~187 F after warm up. Running too cool or hot is a coolant system issue (most often), or a fuel mixture issue or both.
2nd, Pinch off fuel return line, Edited: Pinching could damage line! while idling after warm up. (This may help trouble shoot low fuel pressure) See if RPM goes up.. If so, this indicates a fuel pressure issue. Most times a fuel pump or filter issue or both.
We're seeing more and more fuel pump issues, which cam be hard to detected.
I'll add, It's a rabbit hole we go down using non OEM parts. I'm okay using Denso coils and plugs, rather than Toyota Denso.
You noted Advance Auto temp sensor. What brand coils, did you install. They for sure react differently when hot, if China junk. Advance Auto seems to have legitimate parts, in that not bootlegs from China claiming to be legit. But they have may sources at varying price points, not all good.
Sometimes it's process of elimination. Hope that helps.
Since your issue is after warm up. It's something comes into play after warm up. First thought that comes to mind is open loop vs closed loop. Here's my limited understanding. When cold (pre engine at operating temp), ECM is in open loop mode. The fuel injectors pump/pulse at a high rate to get lots of fuel into cylinder. Once engine at operating temp, ECM takes over control of fuel injectors metering (reducing amount of fuel typically) the pulse to achieve target fuel/air mixture.
A few test that come to mind.
1st, make sure "water temp" is ~187 F after warm up. Running too cool or hot is a coolant system issue (most often), or a fuel mixture issue or both.
2nd, Pinch off fuel return line, Edited: Pinching could damage line! while idling after warm up. (This may help trouble shoot low fuel pressure) See if RPM goes up.. If so, this indicates a fuel pressure issue. Most times a fuel pump or filter issue or both.
We're seeing more and more fuel pump issues, which cam be hard to detected.
I'll add, It's a rabbit hole we go down using non OEM parts. I'm okay using Denso coils and plugs, rather than Toyota Denso.
You noted Advance Auto temp sensor. What brand coils, did you install. They for sure react differently when hot, if China junk. Advance Auto seems to have legitimate parts, in that not bootlegs from China claiming to be legit. But they have may sources at varying price points, not all good.
Sometimes it's process of elimination. Hope that helps.
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I had a cylinder 1 misfire in my 01 LC. Gave rough acceleration but seemed to clear up after warm but still persisted. Replaced the plugs and still had misfire. Moved coil pack to other cylinder and still gave misfire on 1. I dont always buy top tier gas so put in some fuel injector cleaner and drove a tank but problem did not improve. Had to be injector
Took it in to replace fuel injector and so far seems to have been the issue. No more misfire.
Took it in to replace fuel injector and so far seems to have been the issue. No more misfire.
My 2000 LC with 220K is having the exactly same problem as yours; it runs good for 15 minutes, and then rough idle at a stoplight while in D with foot on the brake. RPM is around 600 and stable. If I put the gear into N, the vibration is gone and its RPM is 700. I don't have any CEL codes or engine light yet. Have you solved out this issue?
"D" vibration is often sign a tune-up (w/spark plugs and all vacuum leaks corrected) needed. Key to a good tune: Disconnect negative post of battery first thing, do not reconnect until after MAF sensor cleaned and reconnected.
It can also be a sign of misfire(S). Which is most associated with weak/bad coils.
The 100 series uses an electrical booster motor for the brake assist, not vacuum. Common misconception!
Brakes ...... Overdue write-up.
First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...
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Try cleaning your MAF sensor
