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Skyvisions, ASE Certified Technician
Category: Lexus
Satisfied Customers: 14461
Experience:  Lexus Expert
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I have a 1996 lexus gs300. the harmionic balancer was wobbly

Customer Question

I have a 1996 lexus gs300. the harmionic balancer was wobbly and its time for a timing belt (147,000 miles, t belt replaced once at 70,000 miles. I am busier than a midget mountain climber and did not have time to do it myself, but I would have loved to. I wanted all OEM parts and decided to have toyota of Orlando do it. of course being 20 years old I had them do "the package", i.e. t belt ,water pump, all seals, t belt tensioner bearing and tensioner.
Parts were over $1,200!!! (the new harmonic balancer was close to $500)
When I picked the car up, it ran great, that is exactly as it did before.
After driving to work the next morning, less than 20 miles since tbelt job, I pulled into parking space, let engine idle in park while I assembled my phone, lunch bag ,breifcase, etc. as I sat in drivers seat. Just before I was about to turn off ignition, the car faltered badly and started to die. I gave it some throttle and it chugged and sputtered and poured white, very heavily scented with gasoline smoke out the tailpipe. When I removed my foot from throttle, it dried to idle but died. I had to work, so I very dishearteningly locked the car and went to work.
Since the t belt was just done, the only thing I could imagine happening was that the tech screwed up or the t belt tensioner broke and the t belt jumped timing (!!!).
After work, I started the car and it was back to its old self, nice idle, no smoke, and I thus assume my diagnosis of the t belt was wrong. It ran fine for about 28 miles (back home, to work the next day, and almost home again when it resumed running horribly and pumping white, gasoline stinky smoke out for the remaining two miles to my house.
I went online to read some blogs to confirm my suspicions and hear is what my current diagnosis is :either a bad ECU, or an injector sticking open. I plugged my OBD scanner in under dash and it says no engine or drive train data codes have been stored by car.
A reman ECU from Lexus is $1300! I am considering replacing the caps in ECU myself.
My question is: could it be another fuel injection component. It doesn't seem likely that an ecu would work well and then not intermittently. Also if it is the capacitors in the ecu, caps don't usually work and then not work.
Also forgot to mention car worked fine this morning after resting in garage overnight. I did not drive it however.
Thus problem is heat related, it failed all times after 10 miles or so when under hood temps are high.
Submitted: 1 year ago.
Category: Lexus
Expert:  Skyvisions replied 1 year ago.

at any time did the check engine light come on or start the Flash? Do you have the ability to be able to pull the spark plugs when it's running rough and you see the smoke and fuel smell from the tailpipe?

Customer: replied 1 year ago.
the check engine light comes on because I removed the EGR valve and plugged all holes two years ago. the Egr remains in the closed position, it is opened by vacuum which is blocked to it. This is not the problem. the obd scanner tells me "insufficient egr gas volume" which is correct, as there is no longer any exhaust gas recirculation.
No other codes come up.
The plugs were replaced by me when I did the valve cover gaskets roughly 5k
miles ago and were clean as a whistle.
They are very hard to reach and would not act intermittently.
Customer: replied 1 year ago.
If not a fuel system problem, the only thing I can think of is distributor igniter failing after too hot. but I think the engine would then shut down altogether
Expert:  Skyvisions replied 1 year ago.

I wasn't suggesting that the plugs are the problem what I was suggesting was when it starts running rough and acts like it's burning excessive fuel you would need to shut it off at that point pulled the spark plugs and see if any one cylinder or spark plug is soaked with fuel or covered with carbon. That would give you an idea if there was any particular cylinder or injector that was malfunctioning. Is extremely unusual to see computers fail. It's not likely the timing belt or any of the components because that would not come and go. However there are some sensors and some things that could throw the timing out causing inaccurate fuel injection time and Spark which could be intermittent that would be close or related to the timing belt that is what my thought process would be at this time. Without putting a fuel pressure gauge on it and checking what the fuel pressure is doing when the problem occurs and monitoring the cam sensor and crank sensor inputs to the computer to see if it's erratic would be the only way to test this or to start investigating as to what's going on. I could guide you through some specific tests but before you waste your time doing that if this was never an issue prior to having a timing belt done I would at least have them take a look at the wiring harnesses and things that are close to the sensors on the front cover area. Let me know how you'd like to proceed. It is also not likely sticking injectors.

Customer: replied 1 year ago.
Do you think Toyota could diagnose this accuratly without guessing? do you think their diagnostic devices are capable of telling the real problem? I do not know their capabilities as I have done my own work on the car for 20 years.
A few blogs I have read speak of the ECU usually being the problem. aparently there are a few capacitors which go bad after years of service.
Customer: replied 1 year ago.
they have offered to look at it because of the timing belt job, but I can see them charging me thousands to replace this and that.
That is\ why I am trying to diagnose the problem first.
Expert:  Skyvisions replied 1 year ago.

I can't directly answer your question cuz I don't know whether the dealership you're dealing with has somebody with diagnostic skills and knows how to professionally use an oscilloscope as I do. Unfortunately not all dealers are staffed the same. The capacitors that you referred to are probably the drivers that are bolted to the side of the ECU case. I have seen them overheat and Bubble Up and cause the injectors to spray erratically or not at all. It's worth popping the computer open and taking a look at them but if you don't have the time to do this you need to find a good diagnostic guy that can step by step go through all of the inputs to the computer that could cause extended fuel injection duration or mismanagement of the injection time vs. The spark. All of these inputs should be monitored with the scope I typically pick the top four and put it on a 4-channel scope and monitor it and record it when the problem occurs. This works great with vvt-i systems amd so on

as as I mentioned before I think it would be worth having the dealership that put the timing belt on take a look to see if maybe they didn't get one of the sensors or reluctor wheel for the cam and crankshaft timing. Something is very suspicious if this was never an issue prior to the work that you just had done. You cannot Overlook the basics and the obvious things that they were under the hood playing with.

Customer: replied 1 year ago.
Agreed. I will take it to them tomorrow and hope they have an expert like you.
Thank You, ***** ***** keep you informed if you like.
Expert:  Skyvisions replied 1 year ago.

I'll be around let me know what they say. What part of the country are you in?