99 lexus ls400 no hope

[Abe Scott]

I have a 99 lexus ls400  I have swapped engines condition existed before swap I replaced plugs and cops before

swap replaced map sensor , changed upstream and down stream o2 sensors. also replace throttle body Injectors have been replaced all that has been done my time and money. I forgot replace tsp yesterday. Help me please I have followed theads and post. I am close to dismantaling  this thing code for random misfire. vsv and cel are on not alway at stratup  but    

[paulo57509]

Your post is confusing.  Example: You mention "throttle body injectors..."  LS400's don't have throttle body injection.  Calm down and try to re-group.

What symptoms are you experiencing?  Describe in detail.

You have trouble codes?  What are they?  Not just their description but the actual codes.

 

[Abe Scott]

sorry for the confusion I meant the the throttle body and the injectors which are in the fuel rails

[Abe Scott]

trouble codes are just always random misfire with P0305, 307 and so on. no code for any remotely like o2 sensor

[Abe Scott]

again sorry for the confusion. Okay the the random misfire occurred before the swap of engines and it exist today. Random misfire and code for random cylinders. I did replace the injectors, the throttle, the cop and plugs. I played the parts game the o2 sensors have all been replaced, the MAF sensor has been replaced, VVTI controls have been replaced, fuel pump has been replaced and TPS.  I don't what to do next I have owned the car 1 year and 7 months I have not been able to drive it more 22 miles at any time.  rough Idle. sometimes limp, sometime poor shifting trans, VSC and CEL same codes for random misfire. sometimes CEL flashes. I have use my scanner and 2 other same results random misfire Code

. 

Edited July 11, 2021 by Abe Scott

[paulo57509]

19 hours ago, Abe Scott said:

trouble codes are just always random misfire with P0305, 307 and so on. no code for any remotely like o2 sensor

Are these the only two trouble codes?  While these code are generic, they really aren't random misfire codes.  They specifically point to cylinders 5 and 7.

https://www.obd-codes.com/p0305

https://www.obd-codes.com/p0307

I don't know what parts were replaced when you swapped engines.  But since you mentioned the same issue(s) was present before the engine swap, you can discount the "new" engine being the problem.  Read the links above and thoroughly address each item under "Causes".

I've attached pages from the Lexus shop manual for the trouble codes you listed.  These are from my 1998 shop manual but they should still apply to your 1999 model.  Hopefully, these will help.

DI-61 Engine - DTC P0300 - Random_Multiple Cylinder Misfire Detected.pdf

18 hours ago, Abe Scott said:

again sorry for the confusion. Okay the the random misfire occurred before the swap of engines and it exist today. Random misfire and code for random cylinders. I did replace the injectors, the throttle, the cop and plugs. I played the parts game the o2 sensors have all been replaced, the MAF sensor has been replaced, VVTI controls have been replaced, fuel pump has been replaced and TPS.  I don't what to do next I have owned the car 1 year and 7 months I have no been able to drive it more 22 miles at any time.  rough Idle. sometimes limp, sometime poor shifting trans, VSV and CEL same codes for random misfire. sometimes CEL flashes. I have use my scanner and 2 other same results random misfire Code

. 

I believe if you fix the misfire issues at cylinder 5 and 7 these other issues will go away.  These other issues are a result of the two cylinders misfiring.

Typically, a flashing CEL (vs. a steady on CEL) denotes a serious issue where engine damage is imminent.  I had a code P0303 on my GMC and found the injector stuck open - flashing CEL was pointing to imminent damage to the catalytic converter due to raw fuel getting into the exhaust system.

Edited July 11, 2021 by paulo57509
Formatting

[Abe Scott]

Thank you for the codes these are the codes especially P0300 for random misfires I have been getting.  Thank you again still can't seem to solve the issues with the misfires. as I said I replaced part that may cause this condition. 

[Abe Scott]

again sorry for the confusion. Okay the the random misfire occurred before the swap of engines and it exist today. Random misfire and code for random cylinders. I did replace the injectors, the throttle, the cop and plugs. I played the parts game the o2 sensors have all been replaced, the MAF sensor has been replaced, VVTI controls have been replaced, fuel pump has been replaced and TPS.  I don't what to do next I have owned the car 1 year and 7 months I have no been able to drive it more 22 miles at any time.  rough Idle. sometimes limp, sometime poor shifting trans, VSV and CEL same codes for random misfire. sometimes CEL flashes. I have use my scanner and 2 other same results random misfire Code

. could a short in the wiring harness cause this condition of misfiring. It's the only thing in common before and after engine swap.  

 

[paulo57509]

7 hours ago, Abe Scott said:

again sorry for the confusion. Okay the the random misfire occurred before the swap of engines and it exist today. Random misfire and code for random cylinders. I did replace the injectors, the throttle, the cop and plugs. I played the parts game the o2 sensors have all been replaced, the MAF sensor has been replaced, VVTI controls have been replaced, fuel pump has been replaced and TPS.  I don't what to do next I have owned the car 1 year and 7 months I have no been able to drive it more 22 miles at any time.  rough Idle. sometimes limp, sometime poor shifting trans, VSV and CEL same codes for random misfire. sometimes CEL flashes. I have use my scanner and 2 other same results random misfire Code

. could a short in the wiring harness cause this condition of misfiring. It's the only thing in common before and after engine swap.  

 

More likely an intermittent or an open connection.  I would carefully inspect the coil connectors and injector connectors back to the ECU.  I would focus on #5 and #7 cylinders first.  Funny as it sounds, wiggle testing the connectors is a legit test.

When I did my timing belt I also replaced the cam cover gaskets; removing the coil connectors, every tab of every connector housing broke off from becoming brittle with age and heat.  Not a big deal but I replaced the housings anyway.  I inspected the injector connectors as well - just prying open the convoluted sleeve from the injector wiring harness, several wires from the injector connectors broke off.  Also, insulation from the wires were brittle and broke off exposing bare wire.

Since you seem to be just throwing parts at this, perhaps the next thing to try is another ECU.  However, there are issues with replacing junk yard ECU's; they need to be programmed to work with your key transponder.  Read here:

https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/656360-all-my-crazy-lexus-issues-solved-ecu-leaking-capacitor.html

There are also places that will inspect, repair, test and return your ECU.  Just do an internet search for, "lexus ecu repair".

 

[Abe Scott]

thank! you I will inspect the injectors connectors and wiring I have already done the coil connectors. 

 

[Abe Scott]

I inspected the injector connectors, checked continuity from ecu to connectors Just to be sure I am changing the connectors. I did find a vvti connector not latching. will continue testing 

  

[Abe Scott]

I did not find evidence of broken wire or shorted connection in the wiring harness. so at this point I will retrace everything that I have done, perhaps I have over looked something. I will start with

 ecu

 

[Bykfixer]

If it still drives take it to a shop and pay the $125 diagnose fee. That'll save you a ton of aggrevation and quite possibly money too. 

I've swapped motors and rebuilt cars stem to stern but when I can't figure something out mine goes to a place who can. It could be as simple as a vacuum leak, valves out of adjustment or something the monitor can find. 

They have machines now that can tell you all kinds of things you'd never find at home. My mechanic was working on a van that kept running hot and the machine discovered the engine was low on motor oil. 

[Abe Scott]

Update: I think I have got it after all the work, time, and money spent. I started checking again I found an unbelievable vacuum leak around lower intake manifold. replace gasket today runs great thanks for all of the support. something that simple fix. when the engine was swap the starter was replaced. The gasket moved or something apparently cause a vacuum leak. I had no idea a vacuum leak could cause random misfires. I was sure it was an ignition problem. 

[Lexus Owners Club]

Thanks for the updated information Abe Scott 

Very useful for anyone else suffering with this issue in the future

[Bykfixer]

Good info, thanks. 

Way to hang in there. 👍