siccas

Hello Club Lexus,

I have a 91 LS. The car is having a problem with accelerating and it sputtering while trying to accelerate. The more gas I give it the more it falls on its face. The throttle has one or two sweet spots sometimes and it will go nicely. One is up top barely on the gas and the other is about a 1/4 down and this isn't all the time. Some times it wont go at any throttle position. But if if it dose get the sweet spot and I slowly ease into the gas cant do more the a little less than half. It will do much better. Also some times as I'm just driving down the road about 40 it will randomly miss or sputter. The Tachometer is also off bad idle is 0-200 and red line shift point is about 4500rpm. The car doesn't stall at all and always starts right up. Has no CEL or stored codes.

I got the car from an older couple and it was from Texas. So its super clean and has 245k on it. They have had it for 5 years and parked it every winter. This winter after being parked they started it up and it was running bad. So I bought it. I also own 2 SC300's 5speed (93&94) and an Avalon (95). I also had a 96 Avalon and a 96 Tercel. So I'm not new to Toyota/Lexus. This LS tho has got me stumped and running out of ideas.

Here are a few things I have done to narrow down the problem that I cant seam to figure out. First thing I did was pull the ECU. Put a LED shop light behind the boards to check the caps. They all look good the ECU looks like new.

After that I changed the fuel rail dampener. Because the fuel rails were loud and noisy. Well the problem still there and the fuel rails were quieter but still loud. Then I bypassed the fuel pump ecu/resistor. This also did not do much but the car did work a little better with the same issue.

Then I did a compression test (190PSI on all 8) and did one distributor cap and all the wires. I cleaned the spark plugs at this time as well. The problem got no better.

So still scratching my head I decided to change all the fuel injectors and fuel filter. Problem is still there.

At this point I have began to unplug things. When I unplug the TPS the car will idle up about 100-200 rpm and smooth out but still drives and sputters the same with acceleration. The shifts become bad from the ecu not knowing where the throttle is but the car dose seam to be easier to drive with the sweet spots. Funny thing is even with the TPS unplugged the car still doesn't throw a check engine light. So I tried unplugging the MAF/AFM and coil packs while it was running to see if it would throw a code. Well it threw all 3 codes for the things I unplugged except the TPS. I am still driving it around with the TPS unplugged because it is a little bit easier to drive but the problem is still there and has no idea what the correct shift points are.

Another thing I am thinking of trying is the knock sensors. There was a mouse nest in the vally of the block under the intake manifold. If you know 1UZ's this is a ***** to get to these to even try and test. Im thinking they may have gotten chewed up by a mouse. But once again no codes or stored codes.

I am running out of options and ideas. I think I am going to order a TPS just for ****s and giggles to see if that works. Then maybe move on to the knock sensors and fuel pump. I need to do a timing belt but i don't want to dump bunch of money in the engine b/c i could buy an engine for like 800$.

So if any of you have had a problem like this and fixed it I would love to know. I have spent hours on top of hours reading threads and looking up this problem to find tons of different people talking about problems similar to mine. But nothing has seem to get me any where. Club Lex Please HELP

Yamae

No code is often caused by a failed ECU. It can't be fully checked by your methods, I must say. I'd simply replace all those infamous capacitors as a preventive measure in a case like yours and start the real trouble shooting reading codes. Those QAS capacitors never last a quarter century too.

In the past, the capacitors change fixed almost all the failures of no code problems as well as to get the better engine running. And an additional trouble shooting was not needed in most of the case.

So I suggest you to replace all those capacitors if those are printed Nichicon PR(M) or PF(M). And then read the code and start the real trouble shooting. I guess you might be getting the code 52-55.

siccas

Yes I was thinking about doing it any way. I know its tricky to do if your not used to it. I do a lot of soldering on wire at work but nothing on boards. I know this is 2 different worlds. I have soldered on electrical boards be for only about a dozen times maybe. I think I may be ok to try. I just do not want to screw up the only ecu I have. I have heard of people having bad caps with out them leaking but very few and far between. I would rather have a pro do my ecu but I have seen pretty bad jobs and I am not made of money. Do you know of any good company's that do it, if I decide to not do it myself. I have read of a lot of rip offs and also poor jobs almost makes me want to just go for it my self from what I have read and seen online. I found some on e-bay but I don't want cheap-o's. Is this one a good set of caps? and could you point me to a few places that would do a good job on my ecu?

http://www.ebay.com/itm/181667351248?_trksid=p2055119.m1438.l2648&ssPageName=STRK%3AMEBIDX%3AIT
Thanks for the fast input I see your posts online a lot. You seam to know your stuff. I am still open to any other opinions and options as well please.

siccas

Hey Yamae
Well I changed out all the caps with new ones. Problem is still there and no engine light. Please try and shed some light on this for me. I am starting to lean towards the TPS. I also have read a lot about these first gen LS's not showing or storing codes. But it has all new caps. I plugged the TPS back in be for I plugged in the ECU and started the car. Then I let it idle till it was about a quarter of the way up on the temp gauge. Could clogged cat cause this? Or TPS? I will say even tho the problem isn't fixed my engine dose seem to run better. I am glad I changed all them caps. I am going to do it on my SC next. Please let me know if you have any ideas. I dont know if my post is not tagged well or what but I don't seem to have any one looking or commenting on my Thread.
PLEASE HELP!!!!!!

Yamae

Don't be discouraged, siccas. As you wrote,

> I will say even tho the problem isn't fixed my engine dose seem to run better.

You just have eliminated the ECU issue and now you can start a real trouble shooting. But no code does not leads you well. I don't know why it doesn't provide you any code but at first, I suggest you to check the resistance and the continuity of the resistance change of your TPS when rotated. Does it show as is explained in the service manual? My manual is for after 94 and it has a drawing like this below. I hope a 91 LS is something similar.

Anyway measure the resistance and see it has no glitches. Between VTA and E2, you should have smooth resistance change when the throttle is rotated.

siccas

Thanks Yamae
Im going to check the tps with my meter after work i will let you know what happens.

dicer

Now for fun change the fuel filter, and check fuel pressure.

dresmoove

I'm not as mechanically inclined as you but I can say that when my knock sensor was bad (I know we have two but only one was bad) that my CEL didn't necessarily come on all the time yet my 92 LS would feel like I had to push the gas all the way down before it even tried to get up to speed. I replaced both of them and then got a tune up. Problem solved.

k7q

iTrader: (37)

Not sure if I miss read, but did you check the coil packs? I had a bad coil pack on my sc and was doing the same thing. Sputter and wouldn't accelerate.

siccas

Thanks for the post dicer
I changed the fuel filter when I put new fuel injectors and fuel dampner in. I didnt change the fuel pressor regulator tho. I should check that too.

siccas

Thanks dresmoove,
I have thought about the knock sensors they went bad on my old 96 Avalon. Car ran horrible when they went bad too. At least that had OBDII and made life so much easier. Only problem I have with doing them is the amount if time it takes to get to them. And I hate putting on old parts. I like to put new things on if I am taking it off. At least the gaskets.

siccas

Thanks k7q,
I did check them and they were sparking when I had them unplugged and turning over the motor.

siccas

Thanks For All The Interest guys. I am going to keep testing and changing things and as soon as I find it I'm Going to post it on here and let every one know what it was lol. Even if I have to change everything lol. I checked the MAF/AFM today and it tested a little funky. So I swapped in my SC300 MAF/AFM and everything was the same. In both cars worked the same. So It is defiantly not the MAF/AFM. Im going to check the TPS and IACV tomorrow. I found a bit of info on it.
This is the Thread I found and I am using these steps to test.

https://www.clublexus.com/forums/per...on-issues.html

I feel this is very informative and even if it doesn't help fix my problem its good info to have.

Thanks for all the input guys keep them coming. I'm about ready to just change all the stuff we have talked about on here.

dicer

It is easier to have the car in front of you when trying to figure this stuff out. It could be lots of different things causing the problem. The symptoms you mentioned sounded like fuel starvation. Not saying it couldn't be a wire pulling apart when the engine moves or twists when accelerating. It could be an rpm signal thing too. This is the fun of computer controlled car systems, just so many things can cause a problem. With out the knowledge and the right test instruments its a very difficult deal to do.
Oh and you could do the engine change you talked about, and still have this problem your having that's a 50, 50 deal.

siccas

I defently hear where u are comming from. I checked the maf and it was good and the IACV too it was also good. Havnt checked the tps just yet I have a bunch of stuff going on right now. Im working on the inteior of my SC and wire tucking an RB25 into a S14. And still trying to get all these other things that I need to tend to on the wifes avalon. But I am going to take some time soon and just remove the TB to test it and be as acurate as posibble.