No Power...rough Idle & Loud Exhaust Spuddering

[RandySC400]

PLEASE HELP ME OUT... I HAVE A 1993 LS400 AND YESTERDAY OUT OF NOWHERE MY CAR STARTED SPUTTERING AND I HAVE LOSS OF POWER! I HAVE NO CHECK ENGINE LIGHT ON AND I RAN THE CODES AND NOTHING SHOWED UP... I REPLACED MY SPARK PLUG WIRES AND STILL NO FIX! I THEN REPLACED ALL MY PLUGS AND THEY WERE ALL BURNT AND I HAD REPLACED THEM MAYBE 6 MONTHS AGO! LATELY MY CAR HAS BEEN RUNNING RICH...THE SMELL OF GAS IS STRONG AND AT THE TAILPIPES VERY STRONG. ALSO MY EXHAUST HAS BEEN SOUNDING ALITTLE LOUD BUY MY FEET AREA AND I JUST REPLACED BOTH DOUGHNUT GASKETS AND NOW THEY SOUND BLOWNOUT! I HAD REPLACED MY STARTER MAYBE 2 MONTHS AGO AND I HAVE THOUGHT THAT MY CARS IDLE WAS A LITTLE OFF AND THAT IT WAS RUNNING RICH.... SO I FEEL IT COULD BE A FEW THINGS WRONG WITH IT BUT I DONT WANT TO START REPLACING HIGH DOLLAR PARTS IF NOT NEEDED....SO I NEED YOU GUYS TO HELP ME OUT HERE AND GIVE ME SOME ADVICE....IT COULD BE MY 02 SENSORS...BUT HOW CAN I CHECK THEM TO SEE IF THEY ARE BAD? MY CHECK ENGINE LIGHT IS NOT ON... MY CATS ARE NEW SO I WILL BE *BLEEP*ED IF THEY ARE PLUGGED...COULD THEY BE? COILPACKS...IS THERE A WAY TO TEST THEM? LAST OF MY IDEAS ARE THE INJECTORS...HOW DO I CHECK TO SEE IF THEY ARE BAD OR MALFUNCTIONING... PLEASE HELP ME GUYS!!! I NEED MY CAR BACK ON THE ROAD ASAP!! THANKS FOR ANY HELP YOU CAN GIVE ME

[curiousB]

Well you need to narrow it down to fuel or ignition. I would try to examine ignition first. There are some posts about shorted distributor (Arcing to engine block) wires leaving four cylinders without spark. That would cause very rough engine and dump fuel into exhaust, probably burning and or backfiring there. I would see if you have that problem first.

Then there is quite a few posts about crankshaft position sensor but I suspect that would throw a code into the ECU error log. Maybe read through those to see if anything is suspicious.

I believe faulty O2 sensors will throw a code in the ECU so if you don’t see that I wouldn’t go rush out and put in new O2 sensors just yet. Anyway your car runs in “open loop” mode when first started up cold as the O2 sensors need to warm up before they start controlling (then system goes into closed loop mode).

If the roughness is just while idling it could just be a simple throttle body and IACV valve cleaning is required. Lots of threads on this. This wouldn’t explain roughness at higher speeds though.

I’d also clean the MAF sensor as if is giving false air flow readings the fuel injection will be very messed up.

Most of these things are easy enough to DIY if you’re game. No guarantees but you have to start eliminating possibilities.

[SRK]

About the only part that doesn't throw a code is an ignition coil. Test the primary resistance of each, or if you have one, use an old school timing light to confirm high voltage at each secondary terminal wire.

[Quack11]

PLEASE HELP ME OUT... I HAVE A 1993 LS400 AND YESTERDAY OUT OF NOWHERE MY CAR STARTED SPUTTERING AND I HAVE LOSS OF POWER! I HAVE NO CHECK ENGINE LIGHT ON AND I RAN THE CODES AND NOTHING SHOWED UP... I REPLACED MY SPARK PLUG WIRES AND STILL NO FIX! I THEN REPLACED ALL MY PLUGS AND THEY WERE ALL BURNT AND I HAD REPLACED THEM MAYBE 6 MONTHS AGO! LATELY MY CAR HAS BEEN RUNNING RICH...THE SMELL OF GAS IS STRONG AND AT THE TAILPIPES VERY STRONG. ALSO MY EXHAUST HAS BEEN SOUNDING ALITTLE LOUD BUY MY FEET AREA AND I JUST REPLACED BOTH DOUGHNUT GASKETS AND NOW THEY SOUND BLOWNOUT! I HAD REPLACED MY STARTER MAYBE 2 MONTHS AGO AND I HAVE THOUGHT THAT MY CARS IDLE WAS A LITTLE OFF AND THAT IT WAS RUNNING RICH.... SO I FEEL IT COULD BE A FEW THINGS WRONG WITH IT BUT I DONT WANT TO START REPLACING HIGH DOLLAR PARTS IF NOT NEEDED....SO I NEED YOU GUYS TO HELP ME OUT HERE AND GIVE ME SOME ADVICE....IT COULD BE MY 02 SENSORS...BUT HOW CAN I CHECK THEM TO SEE IF THEY ARE BAD? MY CHECK ENGINE LIGHT IS NOT ON... MY CATS ARE NEW SO I WILL BE *BLEEP*ED IF THEY ARE PLUGGED...COULD THEY BE? COILPACKS...IS THERE A WAY TO TEST THEM? LAST OF MY IDEAS ARE THE INJECTORS...HOW DO I CHECK TO SEE IF THEY ARE BAD OR MALFUNCTIONING... PLEASE HELP ME GUYS!!! I NEED MY CAR BACK ON THE ROAD ASAP!! THANKS FOR ANY HELP YOU CAN GIVE ME

This seem to be a very common problem with the LS400 and i'm experiencing the same. I've done everything this site has recommended and the car have not moved an inch in the last two weeks. It will start at the first turn of the key and run for a few minutes before the erratic idle problem. If anyone has other ideas or solution, please post to the site.

[curiousB]

What steps have you done?

If you fire up cold will it run ok when moving and not idling?

[RandySC400]

thanks guys im going to do the MAF and check the coils...i gave the car a full tune up like 5 or 6 months ago...thats why i was so surprized when my plugs were totally shot...also my car is just not rough at idle but also when its in drive...i can barely get over 10 mph! it running so bad!...Would a TPS through a code or would a bad TPS be the cause??? i had simular problems with my SC400 and my cats were glowing red!...thats been parked and another whole project i have!! anyway thanks for the advice and i will let you all know how it goes...hopefully it will be a quick easy and inexpensive fix! thanks again

[RandySC400]

one more thing...i dont know if it has anything to do with it or not...but about 2 hours before my car loss power i had cleaned the motor at the car wash and while washing it it stalled...then it took about 20 minutes to start up again...it ran rough for a bit then it ran fine for about 2 hours.... maybe water shorted something out?? thanks...

[dpellet]

I would focus on you coils, check drivers side first. Not much clearance there. But symptoms for a bad coil are there.

[dpellet]

With your exhaust. Have you replaced your motor mounts or know if they were done? If not this happened to me recently. Your engine under load (kickdown engaged) puts out torque and it will twist slightly, weak exhaust connections (Flanged exhausts are terrible) can be opened creating a louder than normal exhaust tone. For me as soon as I would let off the kickdown the motor would sound normal but under load it was loud.

Once I did the mounts, both were broken everything was back to normal.

[curiousB]

one more thing...i dont know if it has anything to do with it or not...but about 2 hours before my car loss power i had cleaned the motor at the car wash and while washing it it stalled...then it took about 20 minutes to start up again...it ran rough for a bit then it ran fine for about 2 hours.... maybe water shorted something out?? thanks...

Pretty key info. I would open up distributors and dry them out. My guess is moisture has given electrical system a problem. Get it dried out and it should recover fine.

[RandySC400]

thank you guys i will let you all know tommorow!! thanks!

[nc211]

one more thing...i dont know if it has anything to do with it or not...but about 2 hours before my car loss power i had cleaned the motor at the car wash and while washing it it stalled...then it took about 20 minutes to start up again...it ran rough for a bit then it ran fine for about 2 hours.... maybe water shorted something out?? thanks...

Uh...yeah...that might be the problem... ;)

Chances are your caps are wet...

you might want to check to see if your airfilter isn't a mushy mess of paper too "that, would be bad".

[VBdenny]

I would never spray water on my engine at a car wash. That is why you have the problem. There are many sensors and electronics connections that you got wet. I think our Carolina friend hit it correctly, water in the distributor. Sometimes just spraying some WD-40 around helps with that. Use a leaf blower and make sure all the water is out as it can be trapped in some areas. I might add that there are also natural opening that would allow water to get under the intake manifold and perhaps swamp the starter. Drying everything out is the key.

[eatingupblacktop]

one more thing...i dont know if it has anything to do with it or not...but about 2 hours before my car loss power i had cleaned the motor at the car wash and while washing it it stalled...then it took about 20 minutes to start up again...it ran rough for a bit then it ran fine for about 2 hours.... maybe water shorted something out?? thanks...

Here's a perfect example of a wild goose chase! I would STRONGLY advise any newbies to include all relevant information when posting a prob. Older members have learned to avoid chasing their tails by describing their issues in detail. Even with the best of intentions, those of us offering solutions can only go by how much info is attached to the OP's prob.

At bare minimum, included should be:

• What year is your car?
  
• Is it stock or have you done any mods?
  
• What does the car do that's abnormal?
  
• When does this happen?
  
• Under what circumstances does it happen?
  
• How long have you had this prob?
  
• Have you had this prob before?
  
• If so what was the solution at that time?
  
• Are there any other probs with the car?
  
• What is the general condition of the car?
  
• What's the recent history of this car? - ie - service, parts changes, previous probs
  
• Have you had any qualified assessments?
  
• What remedies have you already tried and what was the result?
  

I'm sure my fellow members have other suggestions as to what info they'd like to see when trying to assess any prob, but at least starting with a list like this one, the OP will get some relevant advice sooner than later. There's nothing more frustrating when trying to determine someone's prob through their description on the forum alone and without seeing the car or experiencing the actual prob, than to get additional relevant information, piece by piece.

In this case, as NC, curious, and VB have suggested, dry out your electricals and you're likely to be on your way again.

PS - Maybe the mods should consider creating a sticky on "HOW TO POST YOUR PROBLEM" primer. It would surely save everyone a lot of time spinning their wheels chasing bad leads or dead ends.

[Quack11]

PLEASE HELP ME OUT... I HAVE A 1993 LS400 AND YESTERDAY OUT OF NOWHERE MY CAR STARTED SPUTTERING AND I HAVE LOSS OF POWER! I HAVE NO CHECK ENGINE LIGHT ON AND I RAN THE CODES AND NOTHING SHOWED UP... I REPLACED MY SPARK PLUG WIRES AND STILL NO FIX! I THEN REPLACED ALL MY PLUGS AND THEY WERE ALL BURNT AND I HAD REPLACED THEM MAYBE 6 MONTHS AGO! LATELY MY CAR HAS BEEN RUNNING RICH...THE SMELL OF GAS IS STRONG AND AT THE TAILPIPES VERY STRONG. ALSO MY EXHAUST HAS BEEN SOUNDING ALITTLE LOUD BUY MY FEET AREA AND I JUST REPLACED BOTH DOUGHNUT GASKETS AND NOW THEY SOUND BLOWNOUT! I HAD REPLACED MY STARTER MAYBE 2 MONTHS AGO AND I HAVE THOUGHT THAT MY CARS IDLE WAS A LITTLE OFF AND THAT IT WAS RUNNING RICH.... SO I FEEL IT COULD BE A FEW THINGS WRONG WITH IT BUT I DONT WANT TO START REPLACING HIGH DOLLAR PARTS IF NOT NEEDED....SO I NEED YOU GUYS TO HELP ME OUT HERE AND GIVE ME SOME ADVICE....IT COULD BE MY 02 SENSORS...BUT HOW CAN I CHECK THEM TO SEE IF THEY ARE BAD? MY CHECK ENGINE LIGHT IS NOT ON... MY CATS ARE NEW SO I WILL BE *BLEEP*ED IF THEY ARE PLUGGED...COULD THEY BE? COILPACKS...IS THERE A WAY TO TEST THEM? LAST OF MY IDEAS ARE THE INJECTORS...HOW DO I CHECK TO SEE IF THEY ARE BAD OR MALFUNCTIONING... PLEASE HELP ME GUYS!!! I NEED MY CAR BACK ON THE ROAD ASAP!! THANKS FOR ANY HELP YOU CAN GIVE ME

This seem to be an issue with many LS400 and there are plenty different guidance and trouble shooting steps to solve it, I'm having the same problem with mine and still no resolution. Some of the steps i've done includes; removing the fuel pump and checking the output pressure, changing the fuel and air filter, checking the wire harness in the trunk for chafing, cleaning the MAF sensor, cleaning the throttle body/ butterfly, checking all air hoses for leak and cracks, removed and cleaned the IACV, reset the ECU (Clear the memory) check the TPS for proper operation, check the distributor, cap, wires, plugs, etc for serviceability, check fuel pressure regulator, EGR valve and all other sensor and part I came in contact with. After cleaning the IACV the car ran fine for 20 miles and the the ghost re-appeared. It's been parked since July 7th and have not moved an inch mostly because I am not home to continue further trouble shooting. My son starts it daily and he said it will idle great from a cold start for 10-11 minutes and the it shuts off. It will restart fine and will idle for anywhere between 30 seconds and 5 minutes and then shuts down. The car will start up on the very first crank but will not stay idle for long. If he tries to drive it, it will run fine and then the erratic idle starts. The only thing I did not check is the exhaust system so that will be one of the items to check. Most thread points to the IACV which cost over $1100.00 at most places, a fix I think is too expensive for the year vehicle. I got a used one today from the junk yard, will clean and install it when I get back to the East coast and let the forum know if it fix the problem. Good luck and keep us posted.

[curiousB]

This seem to be an issue with many ....... install it when I get back to the East coast and let the forum know if it fix the problem. Good luck and keep us posted.

Well its not clear if you have an idling problem or an engine running problem. If you can start it and get it going can to get onto a straight highway and go 15 miles and then return without it stalling (ie running at steady speed non idle for extended period of time)? If it's an ignition problem that occurs as engine warms up it would seem you'd have troubles at all speeds. If it is just IACV or dirty throttle body then it will just be an idle pproblem. If its just idle then if you use you foot to keep idle rpm to say 1000-1200 can you stop it from stalling? If so then try new IACV. There is test procedure to check the wiring of the coils in the IACV which you should do b4 spending $$$. Maybe one of the coils is fried. Are you sure its clean? Is the valve freely moving or is it binding some?

[curiousB]

This seem to be an issue with many ....... install it when I get back to the East coast and let the forum know if it fix the problem. Good luck and keep us posted.

Well its not clear if you have an idling problem or an engine running problem. If you can start it and get it going can to get onto a straight highway and go 15 miles and then return without it stalling (ie running at steady speed non idle for extended period of time)? If it's an ignition problem that occurs as engine warms up it would seem you'd have troubles at all speeds. If it is just IACV or dirty throttle body then it will just be an idle pproblem. If its just idle then if you use you foot to keep idle rpm to say 1000-1200 can you stop it from stalling? If so then try new IACV. There is test procedure to check the wiring of the coils in the IACV which you should do b4 spending $$$. Maybe one of the coils is fried. Are you sure its clean? Is the valve freely moving or is it binding some?

[Quack11]

The car will run fine upon initial start up at both high and low speed but starts to act up once it is warm, normally idle fine for the first 10-11 minutes. IACV check good when B1, B2, S1 - S4 was grounded, the audible click on shut down is also present. When the terminals were grounded the "open/close" travel was very limited so I took the valve apart. It was corroded from the electrical grease used during assembly, the grease was broken down and became hardened to the shaft which in turn restrict its full travel. Upon re-installation the can ran great for 20 miles and idle for 43 minutes without any problem. At high speed the car will starts to jerk/hesitate but it will continue until lower speed is reached or a complete stop. Putting it in N and staying on the gas pedal does not prevent it from cutting off but it will start back up on the very first turn of the key. I'll be installing the new/used IACV this weekend so if there is any other checks anyone can think of, please let me know. This is a 91 LS400 with 134K, it is well maintained, no maintenance was done to it prior to this happening, the ECU did not have any stored codes and the engine still sound like new. Thanks CuriousB for the assistance, let me know what else I can try over the course of this coming weekend.

[SRK]

From your description it's not the IAC valve. That's an output device. Sounds like an input problem. My guess is crankshaft position sensor, but you have no code. Whatever it's a big input, not an individual cylinder thing. So it's not plugs, or wires, or even coils. Could even be the wiring harness from the CPS.

Different from the original poster's problem.

[lexfourcam]

my car would cut off, after it had been running a while and then the next day it would run fine, then after i had driven it a while it would die and id have to keep my foot on the gas pedal. turns out it was my fusebox, and one of the relays for the fuel pump, check ALL the electrical stuff.

[Quack11]

From your description it's not the IAC valve. That's an output device. Sounds like an input problem. My guess is crankshaft position sensor, but you have no code. Whatever it's a big input, not an individual cylinder thing. So it's not plugs, or wires, or even coils. Could even be the wiring harness from the CPS.

Different from the original poster's problem.

I will take a look at that circuit and sensor to see if there are any problems I can identify. There is another post regarding this same issue and the poster said his fuel relay gets very hot. I've noticed the same with mine but I am not sure if this ties into the problem. Thanks for the input and hope this will soon be a happy ending.

[curiousB]

From your description it's not the IAC valve. That's an output device. Sounds like an input problem. My guess is crankshaft position sensor, but you have no code. Whatever it's a big input, not an individual cylinder thing. So it's not plugs, or wires, or even coils. Could even be the wiring harness from the CPS.

Different from the original poster's problem.

I agree. IACV has no influence at higher throttle positions. I think you need to find out why the car doesn't ride well at higher speeds. If you still have an idle problem once that is resolved maybe more work with the IACV is advised. Until then I'd chase the big issue first.

These cars are famous for issues with one bank of distributors going intermittent. That is an output device but it is not detected by the ECU so if it fails they'd be no code in the ECU error log.

Are you sure there are no codes in the ECU giving further clues? As SRK points to input device there is a good chance that would throw a code.

[lexfourcam]

yea that sounds about like what my car was doing. there was a short in it, and when the car got really hot the relay shorted out from all the heat. i kno sounds crazy but thats what happened to me. sounds to me though you might have another problem besides the relay though.

[RandySC400]

ok im back...i checked the dist. caps and they were both fine... i had replaced them maybe 3 months ago. i cleaned my MAF....and still nothing!! as for asking wat i've done on my vehicle in the past few months was new caps & rotors wires plugs i have a injen cold air intake on it i just cleaned my filter so its not dirty...new exhaust cats back...new starter and fan bracket new belts new water pump new timing belt...im going to check my coils next and see if they are the problem.. i appreciate ALL the advice you guys are helping me with...so thanks again and i will post my results

[Quack11]

From your description it's not the IAC valve. That's an output device. Sounds like an input problem. My guess is crankshaft position sensor, but you have no code. Whatever it's a big input, not an individual cylinder thing. So it's not plugs, or wires, or even coils. Could even be the wiring harness from the CPS.

Different from the original poster's problem.

I agree. IACV has no influence at higher throttle positions. I think you need to find out why the car doesn't ride well at higher speeds. If you still have an idle problem once that is resolved maybe more work with the IACV is advised. Until then I'd chase the big issue first.

These cars are famous for issues with one bank of distributors going intermittent. That is an output device but it is not detected by the ECU so if it fails they'd be no code in the ECU error log.

Are you sure there are no codes in the ECU giving further clues? As SRK points to input device there is a good chance that would throw a code.

There are no codes in the error log, I will be scanning the ECU for errors again this weekend with an OBD I scanner to see if something was over looked. Which bank normally have problems and what are the trouble signs displayed? My guess is that there will be cracks, chafing or broken connection in these close tolerance areas. Thanks for your help.