Holy goabs of torque batman!!!! And less pinging too!!!!
12-29-07, 03:08 AM
#46
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Have you replaced the ECU temp sensor ???
Thing is it's one of the service items [ not quite sure at what milage ] and it won't cost much , maybe just maybe the car is running crappy cos the ECU is telling it too , because the ECU is getting wrong info .
I know one guy who when he checked it actually running it was telling the ECU it was minus 31 degrees !!!
Now that is really gunna stuff things up , thing is it was still within parrameters so no fault code .
Another thing is have you had the injectors serviced ??
This is another of those things that people just forget to do , I think injectors are due for a tickle up at 140,000 K's , your injectors could be really ****ty ??
And one other thing , chuck a fuel pressure guage on it where it goes into the fuel rail and check that you have good fuel pressure when the car is actually running under load , at idle doesn't count .
It's a bit late now but when tracking down these sorts of problems you need to start with the most likely things and/or things that are cheap to do or easy to do [ like sensors ] and things that should be done anyway , this way you are either not out of pocket or out of pocket not much .
Things like MAF's and ECU's are known to be pretty reliable , as a note Japan Yahoo is the place to get ECU's and MAF's and such , the cars are not on the road over there anymore so that kind of stuff is cheap , you can pick up ECU's for about $25.00 and MAF's for about $100.00 .
Thing is it's one of the service items [ not quite sure at what milage ] and it won't cost much , maybe just maybe the car is running crappy cos the ECU is telling it too , because the ECU is getting wrong info .
I know one guy who when he checked it actually running it was telling the ECU it was minus 31 degrees !!!
Now that is really gunna stuff things up , thing is it was still within parrameters so no fault code .
Another thing is have you had the injectors serviced ??
This is another of those things that people just forget to do , I think injectors are due for a tickle up at 140,000 K's , your injectors could be really ****ty ??
And one other thing , chuck a fuel pressure guage on it where it goes into the fuel rail and check that you have good fuel pressure when the car is actually running under load , at idle doesn't count .
It's a bit late now but when tracking down these sorts of problems you need to start with the most likely things and/or things that are cheap to do or easy to do [ like sensors ] and things that should be done anyway , this way you are either not out of pocket or out of pocket not much .
Things like MAF's and ECU's are known to be pretty reliable , as a note Japan Yahoo is the place to get ECU's and MAF's and such , the cars are not on the road over there anymore so that kind of stuff is cheap , you can pick up ECU's for about $25.00 and MAF's for about $100.00 .
12-29-07, 08:00 AM
#47
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This specific issue of dead stop vs. rolling start acceleration seems to be pretty interesting. To me it points towards a drive train issue. Is the car shifting correctly? Does the ect button work at all? Is the car's acceleration lagging or are the engine's rpms lagging as well as acceleration? Ie: is the car's engine revving up as you would expect but it simply does not seem to have the power it should? If this is the case, do you have this problem only at low speeds or high speeds (ie passing power) as well?
Without going on endlessly, I would check over the transmission and torque converter to make sure that everything is putting the power down efficiently. I don't recall seeing you explaining how your engine itself is revving in relation to your acceleration, but if your engine revs correctly, a drive train issue may be the problem.
Good luck. You have replaced quite a few parts so far...
12-29-07, 09:00 PM
#49
Have you replaced the ECU temp sensor ???
Thing is it's one of the service items [ not quite sure at what milage ] and it won't cost much , maybe just maybe the car is running crappy cos the ECU is telling it too , because the ECU is getting wrong info .
I know one guy who when he checked it actually running it was telling the ECU it was minus 31 degrees !!!
Now that is really gunna stuff things up , thing is it was still within parrameters so no fault code .
Thing is it's one of the service items [ not quite sure at what milage ] and it won't cost much , maybe just maybe the car is running crappy cos the ECU is telling it too , because the ECU is getting wrong info .
I know one guy who when he checked it actually running it was telling the ECU it was minus 31 degrees !!!
Now that is really gunna stuff things up , thing is it was still within parrameters so no fault code .
I haven't done that, but I would assume low fuel pressure would be caused by a bad fuel pump? It's been running the same for a year and a half, so if the fuel pump was failing, it should've died by now.
12-29-07, 09:07 PM
#50
I just read over everything posted so far. Sorry you're having so much trouble.
This specific issue of dead stop vs. rolling start acceleration seems to be pretty interesting. To me it points towards a drive train issue. Is the car shifting correctly? Does the ect button work at all? Is the car's acceleration lagging or are the engine's rpms lagging as well as acceleration? Ie: is the car's engine revving up as you would expect but it simply does not seem to have the power it should? If this is the case, do you have this problem only at low speeds or high speeds (ie passing power) as well?
Without going on endlessly, I would check over the transmission and torque converter to make sure that everything is putting the power down efficiently. I don't recall seeing you explaining how your engine itself is revving in relation to your acceleration, but if your engine revs correctly, a drive train issue may be the problem.
Good luck. You have replaced quite a few parts so far...
This specific issue of dead stop vs. rolling start acceleration seems to be pretty interesting. To me it points towards a drive train issue. Is the car shifting correctly? Does the ect button work at all? Is the car's acceleration lagging or are the engine's rpms lagging as well as acceleration? Ie: is the car's engine revving up as you would expect but it simply does not seem to have the power it should? If this is the case, do you have this problem only at low speeds or high speeds (ie passing power) as well?
Without going on endlessly, I would check over the transmission and torque converter to make sure that everything is putting the power down efficiently. I don't recall seeing you explaining how your engine itself is revving in relation to your acceleration, but if your engine revs correctly, a drive train issue may be the problem.
Good luck. You have replaced quite a few parts so far...
12-30-07, 04:12 AM
#51
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Well it looks like you have covered most things , however the fuel pump is due and they can be intermitant and cause low fuel pressure one minute and be fine the next , this falls under the tittle " things that should be done any way !! "
So a new pump is in order [ not very expensive or difficult to do ] and get the injectors serviced and refit them with new "o" rings , make sure the place that does it flow tests them to check the spray pattern , again something that should be done anyway .
I would buy a spare set of injectors and have them done then just do a swop over , far more time efficient that way , I picked up a spare set of injectors for $50.00 .
Yes you should try and do an ECU swop over , doesn't take long [ about 20 min's ] and you can leave it sitting on the front seat while you try the other one , you should be able to get one from a wreckers for around $100.00 .
I have a spare one sitting on my shelf , actually two in fact as I already had a spare when I sourced the Mines ECU I run .
You really need to try and pin it down to either fuel or electrical , with a new pump and injectors done that will just about eliminate fuel , especially as you have already done the filter , a pressure test under load will also do the same .
If it was me I'd just do the injectors and fit a new pump as they are due anyway...Good -Luck !!
So a new pump is in order [ not very expensive or difficult to do ] and get the injectors serviced and refit them with new "o" rings , make sure the place that does it flow tests them to check the spray pattern , again something that should be done anyway .
I would buy a spare set of injectors and have them done then just do a swop over , far more time efficient that way , I picked up a spare set of injectors for $50.00 .
Yes you should try and do an ECU swop over , doesn't take long [ about 20 min's ] and you can leave it sitting on the front seat while you try the other one , you should be able to get one from a wreckers for around $100.00 .
I have a spare one sitting on my shelf , actually two in fact as I already had a spare when I sourced the Mines ECU I run .
You really need to try and pin it down to either fuel or electrical , with a new pump and injectors done that will just about eliminate fuel , especially as you have already done the filter , a pressure test under load will also do the same .
If it was me I'd just do the injectors and fit a new pump as they are due anyway...Good -Luck !!
01-01-08, 06:53 PM
#52
something electrical?
if all the mechanical parts are alright, then would it be something electrical?
maybe something as simple as poor/aged conducting wires connecting the sensors (a lot of sensors e.g. O2 sensors) in this modern fuel injected engine? this would lead to poor fuel-air ratio causing loss of power/economy...
sometimes with bad/non-OE O2 sensors, it won't cause the check engine light to go on...
there is a way to read what the O2 sensors are registering while the engine is running at some mechanics... that way, you'd know whether your loss of power is due to aged wires connecting the sensros and/or bad O2 sensors...
any leaks in your engine compartment noticed on the floor of your garage?
if yes, replace the appropriate seals.
maybe something as simple as poor/aged conducting wires connecting the sensors (a lot of sensors e.g. O2 sensors) in this modern fuel injected engine? this would lead to poor fuel-air ratio causing loss of power/economy...
sometimes with bad/non-OE O2 sensors, it won't cause the check engine light to go on...
there is a way to read what the O2 sensors are registering while the engine is running at some mechanics... that way, you'd know whether your loss of power is due to aged wires connecting the sensros and/or bad O2 sensors...
any leaks in your engine compartment noticed on the floor of your garage?
if yes, replace the appropriate seals.
01-02-08, 10:56 PM
#53
From the sound of your posts I can tell you are frustrated. Part of the issue is that you may not have the tools you need to really isolate the issue. The very next thing you might consider doing is investing in a $200 scanner. This will allow you to actually "see" the values and readings of all the engine sensors at which point you may compare those values to known good values from the shop manual. Also, you can watch the sensors shift values as you are driving and replicating the exact problem.
Having said that, you have described two major symptoms - power loss and spark "knock" under load. Knock is typically caused by the timing being advanced too far, a fundamental ignition problem (failed ignition wire), a faulty knock sensor or too little fuel. It is not likely that you have a failed ECU, and from your description, the engine sounds fine at idle and starts easily so it is probably not a mechanical issue with the engine itself. Most ECU's are programmed to detect major variances between O2 readings and MAF readings and will set a code if the two do not correlate. You did not describe a check engine light so I assume there is no code and therefore your MAF and O2 sensors are probably not the culprit (as you appear to have already determined at a cost of ~$1000).
If this were my vehicle I would do the following:
1. Hook up to scanner and monitor all sensors during test drive. Specifically try to replicate the knock issue and monitor timing advance and detected knock occurances. I would also look to ensure that the temp sensors (engine coolant and intake air -if there is one) are reading reasonable values. Hopefully something will stand out as not right on the scanner during this test and will point you in the right direction.
2. Check all around the engine for any loose, broken or disconnected wires.
3. Check the condition and age of the spark plug wires and replace if old or worn.
4. Pull all the spark plugs, one at at time, and inspect each for any unusual symptoms such as a lean condition in one or more cylinders. Replace as needed and note specific problem cylinders.
5. Check your oil for coolant and your coolant for oil - you want to be certain you don't have a leaking head gasket.
6. Check your exhaust gases for color and unusual odors.
7. Run Techron fuel injector cleaner through at least 2 entire tanks of gas to reduce the likelihood of clogged injectors being the problem. Track your fuel economy over these two tanks and see if you are getting better than expected or worse than expected fuel economy - this could be an indication of where the problem is. Better than expected fuel economy could indicate a lean fueling condition for example (too much air or too little fuel).
7. Replace the fuel filter if you have not yet done so - this could cause the symptoms you have described.
8. Test your fuel pressure at the fuel rail schraeder valve to see if it is in spec. If out of spec this could be caused by a clogged filter or faulty fuel pressure regulator. This test will also indicate a possible issue with a leaky fuel pump if that is the problem although I tend to doubt it as they usually fail catastrophically or simply work.
8. Leaky o-rings on the injectors are definitely not your problem - they will cause a slight lean condition and usually a slightly rough/fast idle as fresh air leaks into the intake past the injector. Under full throttle the amount of leaked air would not be sufficient to cause the major problems you are describing.
9. Also, sometimes the issue is easily overlooked yet obvious as an example, this problem could also easily be caused by a loose intake hose between the air cleaner box and the engine allowing a lot of air to enter the engine unmeasured by the MAF and possibly causing a major lean condition.
10. Double check all fluid levels especially engine oil and transmission fluid.
11. If you are going to replace parts, always replace the easy/cheap ones first!
If you are not up to doing your "homework" and getting a little dirty, you can either a) keep replacing parts or b) bring it to Lexus and allow them to run the full range of tests or c) bring it to a competent mechanic for the same.
Best of luck,
ABS
Having said that, you have described two major symptoms - power loss and spark "knock" under load. Knock is typically caused by the timing being advanced too far, a fundamental ignition problem (failed ignition wire), a faulty knock sensor or too little fuel. It is not likely that you have a failed ECU, and from your description, the engine sounds fine at idle and starts easily so it is probably not a mechanical issue with the engine itself. Most ECU's are programmed to detect major variances between O2 readings and MAF readings and will set a code if the two do not correlate. You did not describe a check engine light so I assume there is no code and therefore your MAF and O2 sensors are probably not the culprit (as you appear to have already determined at a cost of ~$1000).
If this were my vehicle I would do the following:
1. Hook up to scanner and monitor all sensors during test drive. Specifically try to replicate the knock issue and monitor timing advance and detected knock occurances. I would also look to ensure that the temp sensors (engine coolant and intake air -if there is one) are reading reasonable values. Hopefully something will stand out as not right on the scanner during this test and will point you in the right direction.
2. Check all around the engine for any loose, broken or disconnected wires.
3. Check the condition and age of the spark plug wires and replace if old or worn.
4. Pull all the spark plugs, one at at time, and inspect each for any unusual symptoms such as a lean condition in one or more cylinders. Replace as needed and note specific problem cylinders.
5. Check your oil for coolant and your coolant for oil - you want to be certain you don't have a leaking head gasket.
6. Check your exhaust gases for color and unusual odors.
7. Run Techron fuel injector cleaner through at least 2 entire tanks of gas to reduce the likelihood of clogged injectors being the problem. Track your fuel economy over these two tanks and see if you are getting better than expected or worse than expected fuel economy - this could be an indication of where the problem is. Better than expected fuel economy could indicate a lean fueling condition for example (too much air or too little fuel).
7. Replace the fuel filter if you have not yet done so - this could cause the symptoms you have described.
8. Test your fuel pressure at the fuel rail schraeder valve to see if it is in spec. If out of spec this could be caused by a clogged filter or faulty fuel pressure regulator. This test will also indicate a possible issue with a leaky fuel pump if that is the problem although I tend to doubt it as they usually fail catastrophically or simply work.
8. Leaky o-rings on the injectors are definitely not your problem - they will cause a slight lean condition and usually a slightly rough/fast idle as fresh air leaks into the intake past the injector. Under full throttle the amount of leaked air would not be sufficient to cause the major problems you are describing.
9. Also, sometimes the issue is easily overlooked yet obvious as an example, this problem could also easily be caused by a loose intake hose between the air cleaner box and the engine allowing a lot of air to enter the engine unmeasured by the MAF and possibly causing a major lean condition.
10. Double check all fluid levels especially engine oil and transmission fluid.
11. If you are going to replace parts, always replace the easy/cheap ones first!
If you are not up to doing your "homework" and getting a little dirty, you can either a) keep replacing parts or b) bring it to Lexus and allow them to run the full range of tests or c) bring it to a competent mechanic for the same.
Best of luck,
ABS
Last edited by abs; 01-02-08 at 11:09 PM.
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tu2 (10-10-21)
01-03-08, 12:12 AM
#54
the ecm on my 1995 ls400 went bad. so i got a new one for 1k and it runs better than ever. like a champion, i have notice a few people that have the same problem as you. so if you can find someone with a good operating ls and use their ecm. be your best shot to maybe fixin your problem
02-10-08, 12:01 AM
#55
So, I'm still "In Pursuit of Solution" to my problem, and I was browsing SC forums from the beginning, and I found this post in a thread about a problem similar to mine:
And then this post in a SAFC-II discussion thread:
Seeing that SC300T is basically having describing my problems in his old post, I sent him a private message, describing my problem and looking for suggestions, and if using SAFC would be a possible solution, and he was kind enough to send me a reply.
Originally Posted by SC300T
The low speed hesitation could also be attributed to the inherent bad fuel/timing maps built into the ECU from the factory. On early V-8s, low rpm/high load maps cause the engine to ping and activate the knock sensors which scale back the timing and reduce power. What you need is a way to add fuel during low rpm/high load conditions. During light to around 2/3 throttle, the ECU is in closed loop with the 02 sensors controlling fuel/air mixture. Above around 2/3 throttle, the ECU ignores the 02 signal and defaults to its own maps, which are poorly calibrated at low rpm.
There are several ways to get the car to run better... The best one I know of is to buy an Apexi S-AFC fuel computer to instruct the ECU to add or subtract fuel from the curve under these conditions. The S-AFC costs around $300-$325. The car will run alot better and may even make more top end power if you've got exhaust and intake mods.
Other solutions are:
Split-Second ARC $269
Simple box that Adjusts air/ fuel
Or the TSC1 $82, which fakes the coolant temp signal into thinking the engine is cooler and therefore adding more fuel to the maps.
(won't hurt normal fuel economy in closed loop).
www.splitsec.com
There are several ways to get the car to run better... The best one I know of is to buy an Apexi S-AFC fuel computer to instruct the ECU to add or subtract fuel from the curve under these conditions. The S-AFC costs around $300-$325. The car will run alot better and may even make more top end power if you've got exhaust and intake mods.
Other solutions are:
Split-Second ARC $269
Simple box that Adjusts air/ fuel
Or the TSC1 $82, which fakes the coolant temp signal into thinking the engine is cooler and therefore adding more fuel to the maps.
(won't hurt normal fuel economy in closed loop).
www.splitsec.com
Originally Posted by SC300T
That really pisses me off to see the stock ECU go 16.9 A/F at low rpm/ high throttle position. I suspected that the earlier V-8s went lean and was causing alot of pinging... NO WONDER!!!! Drivability should be 2x better with the A/F where it should be. I that situation, the knock sensors go off, it pulls timing then the whole thing basically bogs until around 4000rpm.
I had a 93 LS400 that would ping and bog until around 3500-4000rpm. Finally got so frustrated that I gave the car up. The dealer never helped. As suspected, this was the real reason. Lexus just didn't want to own up to it. I'd consider this $320 upgrade to be essential for any early SC or LS.
I had a 93 LS400 that would ping and bog until around 3500-4000rpm. Finally got so frustrated that I gave the car up. The dealer never helped. As suspected, this was the real reason. Lexus just didn't want to own up to it. I'd consider this $320 upgrade to be essential for any early SC or LS.
Originally Posted by SC300T
I haven't followed this much lately, but yes your assumptions are correct.... Any device you can put in-line with the MAF, i.e. S-AFC to modify the amount of airflow the computer sees will trick the ECU into richening the mixture while open loop, i.e. above 2/3 throttle. It should fix your symptom.
One more thing... The reason that the car runs well when you pull the MAF lead to the ECU (and get CEL), is that the ECU is defaulting to a base fuel map. The maps that are stored are gradually changed by the ECU. There is a long term and short term fuel trim function that constantly is changing the map. Apparently, as LS400 vehicle wear, this trim function of the fuel map in the ECU is wanting the mixture leaner and leaner.
You'll also notice that if you drive in cold conditions just after startup when the engine is not yet fully warm, if you really get on it, the engine will have plenty of power. This is because the fuel trim isn't taking out as much fuel when the engine is cold, and the ECU wants the engine to run a little richer. Try an S-AFC used on ebay or something. Isn't that expensive. I think you'd like the results.
Its the ECU programming that is at fault. A new ECU will still learn the same thing. These engines didn't do that new from the factory - there is something as the car ages that causes leaning.
For your application, any simple fuel controller that will add fuel (by manipulating the MAF signal) will work.
One more thing... The reason that the car runs well when you pull the MAF lead to the ECU (and get CEL), is that the ECU is defaulting to a base fuel map. The maps that are stored are gradually changed by the ECU. There is a long term and short term fuel trim function that constantly is changing the map. Apparently, as LS400 vehicle wear, this trim function of the fuel map in the ECU is wanting the mixture leaner and leaner.
You'll also notice that if you drive in cold conditions just after startup when the engine is not yet fully warm, if you really get on it, the engine will have plenty of power. This is because the fuel trim isn't taking out as much fuel when the engine is cold, and the ECU wants the engine to run a little richer. Try an S-AFC used on ebay or something. Isn't that expensive. I think you'd like the results.
Its the ECU programming that is at fault. A new ECU will still learn the same thing. These engines didn't do that new from the factory - there is something as the car ages that causes leaning.
For your application, any simple fuel controller that will add fuel (by manipulating the MAF signal) will work.
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Anonalon (08-14-22)
02-10-08, 12:37 AM
#57
I don't know... The car starts and driver beautifly other than this hesitation problem. There is a CEL if I disconnect the MAF. But when I was replacing the O2 sensors, I had the old sensors removed and then I had to drive to a Radio Shack, the CEL didnt trigger until after about 30 minutes of driving. Is it suposed to be this way, or my ECU is just too slow to react to O2 sensors input?
There a youtube video that shows LS400 0-60 acceleration, it takes about 12 seconds, and this is pretty much what mine is like. It's speedo is in Kilometers, so when it reaches 100km/h that's roughly equal to 60mph. http://www.youtube.com/watch?v=N6ISQDjrpzA
I suspect that a lot of peopel with LS400 and SC400 are having the same problem, but aren't aware of it, because they think it's suposed to be this slow.
There a youtube video that shows LS400 0-60 acceleration, it takes about 12 seconds, and this is pretty much what mine is like. It's speedo is in Kilometers, so when it reaches 100km/h that's roughly equal to 60mph. http://www.youtube.com/watch?v=N6ISQDjrpzA
I suspect that a lot of peopel with LS400 and SC400 are having the same problem, but aren't aware of it, because they think it's suposed to be this slow.
02-11-08, 11:47 AM
#58
Lexus Champion
Yep, my 0-60 acceleration is about 12 seconds too.. Its weird though, sometimes the car feels much faster than that.. but when you actually time it and type that out, you realize how slow it is.
02-12-08, 10:53 AM
#59
Lexus Champion
12 seconds 0-60? holy ****! mine still squeels the tires and lays it down if i take off from a stop. i bet mine still does 60 in 7 seconds. it's still slow to me though , considering i have 2 turbo cars i drive too.
are you guys using premium? lol....
are you guys using premium? lol....
