1994 LS400 strange starting problem

[garagestmarien]

Last year after many faults I found and repaired the dreaded ECU capacitor problem.

For the last year the car has run perfectly.

But, over the last few months it has developed a random strange starting problem.

Many times it starts up okay, occasionally it seems like the engine locks up for a second. If I let the starter keep going it then turns over normal, but starts with a bit of a loss of power, then kicks in and is fine again. Sometimes if I am quick enough and it locks up when starting, I let the key go and then start again and it starts as normal.

Last year when I had the ECU fault, everything was replaced, timing belt, rotor arm, dist. caps, leads, plugs and the temp sensor for the gear box. Throttle body was cleaned, oil and filter changed (Mobile 1 5w30) and everything else was set as per the workshop manual and of course all new caps in ECU.

I am scratching my head as to what this starting problem could be, can anyone help / advise.

[Cotswold Pete]

My only thought is possible issues with fuel line/fuel pump, as you have already had throttle body cleaned, which is typical of the symptoms you describe.

Other things I can think of is are you getting poorer MPG, might be the oxygen sensor.

Other sensor issues I have had in past (not on LS) is the crank sensor playing up, making for random starting issues.

[garagestmarien]

Sorry, I should have added. Fuel line was checked and new filter fitted.

Also, I have built a new exhaust (cats to tail pipes) including new sensors front and rear for each bank.

Fuel economy is as normal for this car.

[runsgrateasanut]

Could this be a Battery issue?.  Recently on our trip to Dover to catch the Ferry our Alternator packed in and I was surprised how far the Car could drive just on Battery power. If your Battery is dying it may be the cause.  Just a thought.

[garagestmarien]

Thank you runsgrateasanut, 

Last August I fitted a new alternator and Varta blue Battery. Charging and Battery power is fine.

[ambermarine]

Hi John

It sounds like you have put a lot of money and time into your car and the idea of giving up on it will probably never enter your head ,my view is with so much invested it is worth going into a a Lexus dealership and getting it checked on their equipment whatever it is can only be a minor problem as the engine runs normally most of the time.

[runsgrateasanut]

Not sure my 2nd pm reached you so, have you checked the Vacuum line from the MAF conduit to the ICV.  It can get broken.  ICV used to be my betanoire with Mercedes S Class.  Had the ICV off more often than on!.  Steam jet cleaned it in the end.  Not had a problem with Lexus but the small connecting pipe did get damaged and was not sealing correctly.  Glued it back into the hole and fine ever since.  

[garagestmarien]

I have not checked this vacuum line, but I will. However, I am not too sure this will cause the starting issues I have.

[plexus914]

How about repairing starter - solenoid contacts and plunger?