olsoncam

need some tech advice. Here's the case.
my '94 ls400 stutters and bucks when i'm trying to accelerate.
took it to the shop, and here's what has been done thus far:
1) rebuilt ECM put in, 2) new plugs, wires, caps, and roters. 3) complete carbon cleanout (fuel, intake, exhaust). 4) throttle body cleaned out. 5) fuel filter replaced. 6) instrument cluster rebuilt.
today when they finished up their work, they came to me and said that now the ECM is throwing a code that says that one or both of the Cam Sensors aren't working properly. oddly, that particular code never came up before they started the work on the car (plugs, wires, caps, roters, carbon cleanout).
So I took the car for a drive and found that my stuttering and bucking IS MUCH WORSE. turned the car around and returned to the shop.

fyi,
car has NO transmission issues and timing belt was replaced by dealership 30k ago.

any thoughts?

Losiracer2

its your coolant temp sensor. Replace that and you should have restored power and fuel economy

olsoncam

Thanks for the info!
How do you know it's the coolent temp sensor?

Losiracer2

Its most likely the cause since you took care of the ECU issues already with the refurb. one.

That's actually the first thing I did on my 97' since I read so much about it, and sure enough, the connector just crumbled in my hands, I couldn't even remove it in one piece. Underneath the plastic, I saw corroded terminals and contacts. I purchased an aftermarket one from O'reilly though since it was available and has a lifetime warranty. Ended up costing me 17 bucks I think

Banshee365

To be honest, I think the ECT sensor 'diagnosis' is a bit of a shot in the dark. I also highly doubt that is causing all of your problems. I would also only use OEM Toyota/Lexus for this sensor. You really should start by monitoring your sensors through a scan tool or even a unidirectional tool like the scanguage. If your coolant temp sensor is messed up it will show you right there. Usually the bad ECT sensor just causes poor fuel economy and things like that. It won't cause CMP codes and bucking and such. You've got something else going on. Did they or anyone clean the MAF sensor? How is your rear transmission mount?

olsoncam

They said the MAF sensor isn't cleanable. And we have not checked rear transmission mount yet.

How about igniters and coils? Should I have them check that out along with tranny mounts?

Banshee365

Im glad they know that the MAF isn't able to be cleaned. How does the engine feel and sound when revving in neutral?

olsoncam

Sounds and feels excellent revving in neutral. I tested that myself...Knowing the issue is probably while under load.

Losiracer2

I can be 100% certain that it will only aid in the drivability he's experiencing, especially if it has never been replaced. You should know this firsthand banshee, it can cause all kinds of problems and is at the top of the list of things to replace for a first time LS owner.

Even in a dry, desert climate which my 97' has been kept in, it still corroded and failed.

OE part is $45 and you'll probably have to wait 1-3 business days, or the aftermarket is $17-25 and will be in stock immediately for replacement and has a lifetime warranty. Hell, you could keep replacing these every 5 years for peace of mind if you wanted. My Import Direct one was manufactured in Brazil with love

They take about 15 minutes or less to access after undoing a few plug wires and right side coil depending on your model year LS.

Losiracer2

But this also seems to me that the timing of the car is physically off. When my mechanic did the timing belt, he messed up and was either 1 or 2 teeth off and my car would bog down after 3k RPMs.

Did they have to touch the Timing belt at all when servicing your vehicle for any reason?

deanshark

It could be that they crushed a plug wire, or coil wire, when they put it all back together. Did they use aftermarket wires? If so, I know most of the wires are a bit longer then they should be so it's easy to crush them while trying to stuff them under the covers.

Banshee365

Saying it COULD aid in performance is much more in the ball park than saying that the ECT sensor is his problem and is causing his issues. It's not.

olsoncam

UPDATE/RECAP:
Brought car in for stuttering and bucking going up inclines (car needing more power to maintain speed upon inclines). Check engine light would come on ONLY when the somewhat violent bucking would occur. Shop ran the code. Said it was my TPS. They tested the TPS to varify. Put in a new TPS and the shop tested it. recognized no improvement with the new one. So they took it back out and put my original one back in. Came to me and said the ECM is probably bad because of the false codes.

1) I then replaced the ECM with a rebuilt one from Foreign Auto Computer Company.
2) I also replaced my instrument cluster for issues at this same time.

stutter/buck Problem is still not fixed.

3) Speed Sensor #1 replaced with OEM.

Stuttering and Bucking Problem is still not fixed. Moved to Idaho at this point. Car had several of cases of stuttering and bucking while driving from Cali to Idaho. Took it to a shop to diagnose. NO CODES for them to read. But, we then did this:

4) replaced Spark Plugs/Wires/Caps/Rotors with OEM
5) Cleaned Throttle Body
6) Complete Carbon Cleanout system flushing
7) Fuel Filter Replaced. Checked Fuel Pump for issues. none found.

They put the car back together and then immediately the Check Engine light was constantly ON and the car stutters and bucked 10x worse. CODE read Cam Position Sensor failure. We looked to replace the cam position sensor, but found out that what really needed done was to fix a poor and brittle connection somewhere near the CPS (wiring issue).

8) Timing Belt Replaced. (old ones were 4 clicks off).
9) Re-Soldered a brittle connection wiring issue near/at the CPS. That problem solved.

Put things back together and then the Computer read CODE that the MAF failure. Shop established that a brittle connection somewhere at the MAF was the issue.

10) Re-soldered a brittle connection somewhere at the MAF. That problem solved.

Car is now back in my possession and running MUCH BETTER, as it should sense I just spent a ton of money on a TUNE-UP!!
HOWEVER, THE CAR STILL STUTTERS UNDER LOAD, ALMOST EVERY TIME IT NEEDS MORE POWER TO RESPOND TO MY ACCELERATION NEEDS OR TO AN INCLINING ROAD!!!!!

Where do I go from here? Please help. the Computer is giving us ZERO/NONE/NO CODES TO GO OFF OF. So frustrating.

other issues:
1) tail light needs replaced, 2) trunk release button in cap doesn't work anymore, 3) alarm system goes off from time to time without reason, 4) dome light won't come on when door opens sometimes, 5) door ajar light comes on in dash quite often (happens because of either door. i'll tug on one or the other of the doors and the light goes away temporarily).

My guess is that I have a WIRING ISSUE! Potentially a WIRING ISSUE with the Trottle Position Sensor. Any other thoughts?

Thank you all.

oldskewel

iTrader: (1)

Fuel pump? I replaced the one in my '91 with 190k miles recently and I now realize it vastly improved the performance of the car. I now have to be careful giving it gas after a stop to avoid burnouts, unless I want a burnout.

olsoncam

Today I went to pass a car on the highway. My car stuttered and bucks upon acceleration just like usual.
Except...She never recovered this time. Lost tons of power for the rest of the drive, car wouldn't accelerate over 65mph, engine started rattling at idol for the first time ever. And at a stop, white SMOKE started poring up from underneath the car. With strong smell of burning.
limped it to the auto shop. The same shop that I brought it to to diagnose this exact problem. The same shop that told me I needed the above prior post listing of $2000 worth of a tune-up.
​​​​
I'm afraid she's done.