1993 Lexus SC 400 Engine Replacement

  • 1993 LEXUS SC 400
  • V8
  • 2WD
  • 180,000 MILES
I got this car used a couple of years ago with pretty good mileage for a 1993. But its causing me some problems right now. Here goes:

About 5 weeks ago, I had the timing belt break. But I was driving at low rpm at the time. Got it towed to my mechanic and he said replacing the belt may work or it may have caused major engine damage. I elected to replace it with new bearings and get a new water pump($1700). Got it back and it ran fine for 2 weeks then the engine randomly died on me again. Got it towed to the mechanic and he said the lower end of the engine is damaged, and the cheapest option is too put a low mileage used engine in and the quote he gave me ($2500). After much thought, I decided to go ahead with it. And I said that would be all the money Im willing to put into this car.

NOW.I go out of town and come back 2 weeks later expecting to get my car back and he said they replaced the engine twice because the first one wasnt working that well. Then he tells me. The second engine cranked up and ran for 2 hours. Then when they drained the fluids and put new fluid in. It cranks but the engine stalls. But couldn't give me a reason why (All he said was he thinks its an electrical issue). Now. Some 2 weeks AFTER that. He finally narrows it down and says the ECM is fried and there is no output signal going to the fuel injector. He says its because a few electric wires were corroded.

I am unconvinced that the ECM failure is un related to them replacing the engine (All you need to fry a computer is a surge of voltage which can be caused by a defect in a sensor, or putting the wire in the wrong slot when the engine was being replaced). So I told him I am only paying the $2500 I originally said to get the engine replaced.

Am I justified in my approach. Or is the ECM failure absolutely 100% without a doubt not related to the engine being replaced (because If someone can convince me of that. Then I will pay for the new ECM)
Friday, December 11th, 2009 AT 3:24 PM

2 Replies

  • 108,854 POSTS
Well, chances are the ECM problem ( it that is the problem) is not related to the engine. I need to know some background info. The original engine that you fixed, he told you there was bottom end damage. Was the engine knocking? Honestly, the bottom ends rarely go bad on these engines.

Second, as far as the ECM, if there is no output from it to the injectors, I have to ask, the engine used to replace the original, does it have the same injectors? Is it a different year engine that could have caused damage to the PCM? Many times people will get different model year engines that are the same size and they fit right in. However, the manufacturer changes things such as sensors, injectors. This usually leads to other problems.

I guess the bottom line is, like you, I question what has been done since the original engine. I would ask what year engine was used in the replacement. Also, if he has your old engine there, has he tried those injectors? Keep in mind, the engine did run for some time, so the ECM did have an output. What is also interesting to me is that it took 2 weeks to determine there was no injector pulse. THat should have taken 10 minutes and one of the first things checked when the engine wouldn't start.

No, I can't guarantee (100%) that something didn't happen when the engine was replaced. I would like to know, if you wouldn't mind, was the original engine that "had a bad bottom end" knocking before you took it to them?

Let me know if you have other questions.

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Sunday, December 13th, 2009 AT 1:02 AM
  • 41,814 POSTS
Hi hassaan87,

Thank you for the donation.

This is sometimes very sticky and what we mechanics faces now and then.

Replacement of the engine should not be related to the fried ECM but as you mentioned improper installation or power surge can cause it to. This can be attributed to workmanship.

Mechanic mentioned corroded wires and if that is the case, it can cause the ECM to fry. During replacement of the engine the wires were removed and installed and if they were internally faulty, the movement could have caused the shorting and for this, it should not be faulted to the mechanic.

If there are no definite answer to the cause of the problem, the best deal is to strike a balance and both sides step back a little and come to a compromise to get it settle amiacably.
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Sunday, December 13th, 2009 AT 1:03 AM

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