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imzjustplayin
 
Sign of weak sparK?

I've got an LS400 that is running like shit, it basically misfires all across the RPM range, high and low load, sometimes it really makes the car vibrate, sometimes it's imperceptible, cold or warm, it runs like crap. I've been slowly getting it to run better but still can't get it running optimally and so in the various experiments I've tried with this car, I've found that running Regular vs the requirement of premium gasoline actually helps a bit. I found I was able to climb my steep hill in 2nd gear which is quite an accomplishment considering that just a week ago, I had to floor it in first gear and make sure it didn't upshift because if it did, going into second gear would find the car losing speed quite quickly, only to shift back into first gear.

There is something I'm obviously not telling you and it's that I've run Redline SI-1 fuel system cleaner in my car right before adding the regular gasoline. But with that aside, is it possible that with a weak spark ignition system, that premium and regular are the difference between horrible performance and somewhat ok performance?

Oops, just forgot another important point, when climbing the hill last week, it was much hotter like 80-90F than it was tonight which was only 52F, maybe that was the reason.. Hmm, I guess I'll have to try climbing it again when it warms up tomorrow.
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Last edited by imzjustplayin; 05-20-2009 at 11:37 PM..
Old 05-20-2009, 11:27 PM imzjustplayin is offline  
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wwilliam54
 
have you tried changing the sparkplugs
also check you fuel pressure



get a sparkplug
rest it on some metal in the engine bay, away from belts and stuff
pick a wire to hook it up to
crank it up a few times
the spark should be blueish white, with maybe a hint of yellow
if its really really orange you definatly have a weak spark
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Old 05-20-2009, 11:47 PM wwilliam54 is offline  
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imzjustplayin
 
Quote:
Originally Posted by wwilliam54 View Post
have you tried changing the sparkplugs
also check you fuel pressure



get a sparkplug
rest it on some metal in the engine bay, away from belts and stuff
pick a wire to hook it up to
crank it up a few times
the spark should be blueish white, with maybe a hint of yellow
if its really really orange you definatly have a weak spark
Isn't that what a multimeter/ohm meter is for?? I don't think it's a fuel pressure issue and the reason why I haven't tested the spark plugs or injectors with a multimeter is because I don't have the tools necessary to remove all the goddamn covers. If this was a civic, it'd be easy as pie to get to all the necessary parts to test them, all bunch of fucking nonsense if you ask me..
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Old 05-20-2009, 11:54 PM imzjustplayin is offline  
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wwilliam54
 
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Originally Posted by imzjustplayin View Post
Isn't that what a multimeter/ohm meter is for?? I don't think it's a fuel pressure issue and the reason why I haven't tested the spark plugs or injectors with a multimeter is because I don't have the tools necessary to remove all the goddamn covers. If this was a civic, it'd be easy as pie to get to all the necessary parts to test them, all bunch of fucking nonsense if you ask me..

Yes you could use a multimeter to test the coils.
Look in a haynes manual to find out what the resistance should be

I just do it with a plug personally.
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Old 05-21-2009, 12:24 AM wwilliam54 is offline  
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[H]ard|On
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Are there any codes?

I wouldn't suspect weak spark right away but more like a failing fuel pump.

Check fuel pressure, tape the guage down to the window and drive with it if you have to, that's what this sounds like to me - or clogged cats or something... that car has coil over plug ignition and an overall system failure like you're describing has to be more centralm like a crank angle sensor or something

Also do not ever add any more cleaner to anywhere... more often that not it destroys injectors and causes more probs that it will fix. If you have a failing injector, some caustic shit isn't going to help.
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Old 05-21-2009, 12:29 AM [H]ard|On is offline  
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SmashingPumpkins
 
failing fuel pump, clogged cat/exhaust system, clogged intake, bad/clogged injectors, bad plugs, etc

could be one of a million things tbh
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Old 05-21-2009, 03:34 PM SmashingPumpkins is offline  
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yoda634
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i worked on an ls400 a while back with that EXACT set of symptoms...check your tps.

edit: it actually ended up being the tps circuit in the ecu, but i'd look at the tps first
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Old 05-21-2009, 08:27 PM yoda634 is offline  
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imzjustplayin
 
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Originally Posted by yoda634 View Post
i worked on an ls400 a while back with that EXACT set of symptoms...check your tps.

edit: it actually ended up being the tps circuit in the ecu, but i'd look at the tps first
Why would it be the TPS? You can rev the engine from within the engine bay, are you saying that if you can rev it from the engine bay and it's smooth but rev it with the accelerator and it's bad, that it is the TPS?

What else can you tell me about the issues you had with your TPS sensor? Like how you revved the engine with the accelerator while in park or something..

I should also let you know that for awhile, I had a check engine code saying lean malfunction, and through an "italian tuneup", turning off the car and back on again, the code went away... Again running ever so slightly better, but well for all I know, I could've messed up the O2 sensors into thinking it's not lean anymore..
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Last edited by imzjustplayin; 05-21-2009 at 11:33 PM..
Old 05-21-2009, 11:23 PM imzjustplayin is offline  
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KpaBap
 
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Definitely sounds like failing coils to me, which fixed my car right up, but at the same time, I had the same symptoms from a clogged catalytic converter as well...

Since you mention that regular gas makes it run a bit better, I'd lean towards the issue being ignition related - lower octane is easier to ignite.
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Old 05-21-2009, 11:30 PM KpaBap is offline  
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[H]ard|On
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You can test your TPS with a DVm and some paperclips. Looks up what voltage it is supposed to produce and turn it through it's full range.

Have you checked your fuel pressure? I just can't believe that all the coils would die at once.
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Old 05-22-2009, 12:29 AM [H]ard|On is offline  
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imzjustplayin
 
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Originally Posted by [H]ard|On View Post
You can test your TPS with a DVm and some paperclips. Looks up what voltage it is supposed to produce and turn it through it's full range.

Have you checked your fuel pressure? I just can't believe that all the coils would die at once.

Well one of the coils could be bad, by the way, this car does NOT have COP, or anything resembling that, so whom ever said that, shame on you! This car has two coils, one for each bank of cylinders. Oh and I changed the fuel filter, old one was a little clogged but not too bad, so I don't think it's a fuel pressure issue though you could argue that it is the fuel pressure regulator I suppose.
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The answer to 1984 is 1776.
Calling an illegal alien an undocumented immigrant is like calling a drug dealer an unlicensed pharmicist.
Is hindsight 20/20 for someone who is legally blind?
Old 05-22-2009, 01:46 AM imzjustplayin is offline  
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[H]ard|On
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Quote:
Originally Posted by imzjustplayin View Post
Well one of the coils could be bad, by the way, this car does NOT have COP, or anything resembling that, so whom ever said that, shame on you! This car has two coils, one for each bank of cylinders. Oh and I changed the fuel filter, old one was a little clogged but not too bad, so I don't think it's a fuel pressure issue though you could argue that it is the fuel pressure regulator I suppose.

So you haven't checked the fuel pressure... you're still at step one.

As for coils if there's only two you can OHM them out with a DVM as step #2 after you check fuel pressure.
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Old 05-22-2009, 02:01 PM [H]ard|On is offline  
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