2004. Spark plug change.lost gas milage
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 379
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From: Florida
2004. Spark plug change.lost gas milage
I changed my plugs a week ago and i was getting 25+ highway 16-18 city on old plugs. Now under 22 highway 14-16 city . Makes no sense to me. 94k on car. The old plugs were not bad at all.
Lexus Test Driver
Joined: Apr 2015
Posts: 1,085
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From: Texas
Did you verify that all the plugs had the proper gap? While they should be pre-gapped, and you shouldn't gap them, it's still important to verify that they have the proper gap. And did you use OEM plugs? And did you make sure that all the coils were on properly?
Pole Position
Joined: Mar 2011
Posts: 2,188
Likes: 729
From: Texas
First thing that come to mind is that the LS430 still "remembers" how the old spark plugs performed, and now with new and different plugs, the whole performance dynamic is suffering a mismatch - have you tried disconnecting the battery to reset the ECM and start again from factory default settings?
Otherwise, maybe one of your cylinder is not firing. See attached procedures to troubleshoot ignition problems.
Otherwise, maybe one of your cylinder is not firing. See attached procedures to troubleshoot ignition problems.
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 379
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From: Florida
I took the battery out to change the plugs.So yes every thing was reset. The next warm day i think i will put the old ones back and see what happens Should be tomorrow.Run a week then will repost results.
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Pole Position
Joined: Mar 2011
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From: Texas
Remember, the LS430 is constantly learning to optimize performance. It may take a bit of time for it to return to the optimized settings for your driving style.
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Lead Lap
Joined: Jul 2005
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From: CA
A week's worth of driving and you know that your MPGs have dropped from 25 / 16-18 to 22 / 14-16?? I question the validity of that data. I'd suggest giving it more time and measure your MPG carefully over the next 3 or 4 or 10 or 20 tanks.
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 379
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From: Florida
The car ran perfect with the old plugs . I just thought i would replace them at 94k miles. I know if it is not broken don't fix it. I have only had the car for 6 weeks and fixed a few things.I have had 3 outher 430 so i know something about these cars. 2- 2001 2003ul now a 2004 sport. Preffered the non sport. They road smoother less bumpy.
Advanced
Joined: Nov 2015
Posts: 675
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From: Texas
Three observations:
1) I left the two tubes off of the air breather and it definitely affect that performance of the car.
2) I've actually bent the end of the spark plug when inserting it in the engine once. I would pull all the new spark plugs and verify gap. Also use a torque wrench, set at 14 ft-lbs, and make sure each spark plug is seated uniformly.
3) Also check each electrical plug to the Coil on plugs to make sure it is seated tightly.
1) I left the two tubes off of the air breather and it definitely affect that performance of the car.
2) I've actually bent the end of the spark plug when inserting it in the engine once. I would pull all the new spark plugs and verify gap. Also use a torque wrench, set at 14 ft-lbs, and make sure each spark plug is seated uniformly.
3) Also check each electrical plug to the Coil on plugs to make sure it is seated tightly.
Driver
Joined: Jan 2008
Posts: 126
Likes: 2
From: GA
I paid a repair shop to replace mine simply because I do not like screwing a metal based plug into an aluminum block and having to use multiple socket extensions to perform the task. Cost me some $235 for OEM plugs but this is one project that I cower from performing.
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 379
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From: Florida
the MAF sensor looked brand new.There was not 1 speck of dirt on it and the wire was still silver and I did clean throttle body did not really need it tho. Even tho the carfax showed no service there has been a good amount of work done because of new parts and how clean every thing is under the hood;
Thread Starter
Intermediate
Joined: Oct 2009
Posts: 379
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From: Florida
So i went back with a torque wrench and tighten then about a full turn or more to 14 ft pounds. Maybe that will help. I travel the same route everyday. Same traffic, same stop signs, same lights,. I reset tank MPG and i am down 2 MPG every trip. Will see if tightening the plugs will make a difference
Last edited by lexman52; Dec 24, 2015 at 09:04 AM.