Lost and confused

[Hart1975]

Im having problems with my 93 lexus ls400. I know i need to replace my starter. Its got problems at times while turning my key. One day when first starting the car for the first time somthing happend that made a very rough idle. Like it was a misfire. As i drove the car it felt like the front of the car was bouncing up and down while my foot hit the gas. I figured i needed a tune up. So i replaced plugs wires and distributer caps. I thought about the ignition coils. But did not have the money and i was not sure if that was part of the tune up and what they where for ( i have never had a car like this one) so after the tune up the car had strong power but it still had the same problem. As i was diving it home the car got slower and my car would not move. I had to floor the pedal just to make the car move. But it was hard and slow and i made the engine smoke. It went in reverse just fine but would only inch forward. So i took it in. Found out that my car was working on 4 of the 8 cylinders only. So they replaced the ignition coils. My car started to drive again. However the problem is still there but in a different way.  The car drives but at a certain speed the jumping feeling starts up and it still feels like a missfire. Im sucking up gas very fast. I went from 14 miles to a gallon to 11.. And the engine still feels rough at idle and drive. now i took it into pepboys and they hooked it up to a machine and no codes came back and no check engine lights was on. They beleve its a cylinder head problem. I still feel like its a spark misfire problem. Another mechanic checked it out and still no codes or check engine light. I called up the dealership and besides telling me to bring it in and give the car a tune up ( i guess they did not understand when i told them i gave the car a tune up ) they had no idea the problem either. I feel i may have blown the new spark plugs due to force driving it home on 4 cylinders instead all 8 before replacing the coils. I do not have money to replace random parts in hope its whats wrong. I have a smell of fumes like my muffler coming from the engine.  The fumes smell heavly gross of paint thinner. What is this problem With my car ????????????

[1990LS400]

It's going to take a Lexus dealership or an indie repair shop that specializes in these cars to diagnose the problem.  Offhand, it sounds like you have a fuel/air mixture issue - maybe a throttle body problem - but only a knowledgeable technician can tell you for sure.

These cars are not cheap to keep running as they age. 

[vissine]

Does your mechanic know how to read codes from cars manufactured before OBD scanner came out? If I were you, I will find the way to read OBD codes myself before bringing to a mechnic and relying on their multiple guesses.

[threepwood]

Just saw this. Hope I am not to late.  I'm sorry to say this sounds just like my ECU (Engine Control Unit - it;s behind the glovebox) capacitor issue.  Mine is a 1992 LS400 and I went crazy replacing things until someone here pointed out the post where all these ECUs have bad capacitors and will fail sooner or later.  It's so common people on ebay are selling capacitor 'kits' for less than $20.  But you do need to know how to unsolder and resolder the new caps in.  It is very easy.  I'm told a new ECU cost more than the car is worth.  Don't buy a used ECU from a junk yard, I did and it was also bad.  My thought is it is probably  the reason the car was junked.  Good luck.