LS400 Missfire - Just had a new starter motor

[ABTJ]

Hi all,

I’m aware misfires have been covered many times on lots of forums on these cars, however I’m stumped even after hours of searching.

 

Mine is a 1996 model, I’ve not owned the car for long, however it had full Lexus service history untill 2011, then was serviced by hand by the previous owner, allegedly.

The car was running fantastic, I did 500 miles no problem, apart from a slightly less enthusiastic starter motor, which after signs of giving up finally did, at a Lexus dealership. They quoted me a fairly reasonable price after some resurch, and decided it was above my skill level. 
 

This is day 2 of having the car back, I did 30 miles no problem, but then a problem started occurring with it misfiring under hard acceleration at around 5k rpm. This has now got much worse, and at medium throttle around 2k-2.5k rpm it splutters, but if you give it a bit more it runs smoothly untill around that 5k mark. There is a check engine light which is on 80% of the time also. The car feels slightly rough at idle, and on one start up, it reved itself between 1k-1.5k rpm repeatedly for 10 seconds until I shut it off, then idled normally.

Before the starter motor replacement the engine has always been strong and ran smoothly, with no light, untill I got it back.

I have a code reader arriving on Sunday which should help diagnosis, but I’m just at an end after waiting for 2 weeks for my car to come back, for it only to run worse than when I gave it in.

Any help would be very much appreciated, thanks all!

 

[The-Acre]

As frustrating as the wait may be I think you have to hang on until you've got the codes read, otherwise it's just guesswork.

[shanra]

Don't know what code reader you have ordered but being a 1996 it hasn't got OBDII. You can access codes with a paper clip placed in correct pins of diagnostic port on engine. http://www.lexls.com/tutorials/intro/codereading.html ignore 1990- 1994 OBD1 as it's for USA cars, yours is OBD1 also.

 

[shanra]

I would check the connections on both of your ignition coils as they would have come off for the starter replacement, also ignition leads as they would also have been disturbed. So many things it could be but really should take it back to the garage that did it.

[BigBoomer]

Since the problem is occurring since the Lexus dealership changed the Starter motor, and that involves removing the intake manifold, I would take it back to them if I was you. The problem is almost certainly something that they either did not reassemble correctly, or something they damaged during the starter motor swap.

[Malc]

especially as you must have paid them the neck end of £800 for the job .....  it's a whole day labour plus the new starter motor ....  oh! and the vat too

do tell please

Malc

[steve2006]

As George and John have mentioned take it back to Lexus, they did the work and the car was firing on all 8 cylinders prior to this work being carried out.

Given the age of the car the electrical connectors tend to become brittle particularly the injector plugs, LT coil connectors and the spark plug leads are easily damaged during removal.

[ABTJ]

Due to the garage being closed on the weekend I am about to call them now, however I’ve started it up this morning to begin pulling the codes, because Lexus (UK) anyway can’t read there own car 😕 

And it absolutely reaks of unburnt petrol, it is a roughly 25 min, 15 mile drive to the garage, do you think this would be safe?

many thanks.

 

[Malc]

25 minutes ago, ABTJ said:

15 mile drive to the garage

RAC service might provide the trip for you if you had the right type of cover 

Malc

[steve2006]

A 15 mile drive could damage the cars with unburnt fuel going through them particularly if you have already done the same from the dealer.

Recovery is your safest method.

Did you check the connections to both ignition coils as suggested?

[ABTJ]

Hi all,

so update here:

It went back to lexus and received a new oxygen sensor. I thought amazing, they took it on a test drive and all was well. So I picked it up, drove it home all was well. The next day I start it, drive 5 mins, and the check engine light comes on again and starts missfiring badly. 
 

It now seems that it’s only occuring when the engine is warm, but also the degree of the missfire isn’t constant and does it sometimes, other times it’s okay.  Oh and it still reeks of petrol when you rev it and when you start it cold.

I ran some diagnostics and received the attached. Mainly all sensors throwing codes, however this was not the case before it went in to have the starter motor. So it’s definitely something which has happened while the starter was being replaced. I’m just at an end now and wondering if anyone has any ideas what the problem can be as this Lexus dealer is f*****g useless.

Many thanks all, any help is appreciated.

 

[Malc]

Ben hi ... I'm simply thinking here ...  did you have good confidence in your previous independent ( or other ) car mechanics / servicing guys with your previous cars  ?

If so then it might be time to just bite the bullet and refer it all to them for some " loyalty " with an existing customer type scenario 

Clearly your Lexus Main Dealer can't cope with this situation ...  " old " school and what shoud be simple technology is quite beyond them sadly

Malc