henryhill

i have a 97 ls400 with 192k miles. all maintenance has been done.basically stock with coilover and muffler and resonator delete. when i accelerate up to 80mph around 3k rpms it drops 500rpms and then catches back up. what should i check? injector cleaner? ect? i noticed my pcv grommet is ripped and ill replace that.

henryhill

i also notice this during acceleration at 2k

lexmoose

I notice this on my 96 at around 3k, but only when force in 3rd gear. Let say I give it a bit more gas to pass someone it will drop RPM for half a second and then go just fine.

Since a few days it's much colder outside in the morning and when I first start the car there's now a strong smell of fuel. Wondering now if there's something wrong with the car and if those 2 issue could be related...

RA40

iTrader: (6)

Check for any error codes first. That is a broad area to diagnose from fuel to ignition. If the ECU has not been checked, this is Yamae's test to determine if the caps in the ECU are in need.
https://www.clublexus.com/forums/ls4...-by-yamae.html

lexmoose

In my case no code on the obd reader, caps have been replaced and the ECT is new.

henryhill

this is exactly what happend to me! as for the smell of fuel it is normal when cold. all cars do that to warm up faster thus using more fuel

henryhill

i observed that in first and second gear in lower speeds its smooth all the way to redline. but on the freeway when i try to pass someone as i step on the gas, it drops 500rpms at around when i hit 3k

lexmoose

Yes but the smell is like that old 70's pickup (454) I used to drive for work. That thing was backfiring so bad after getting of the highway... Memories

Sorry for the thread jacking, back to the RPM drop at 3k. Wondering if it's a "feature" or a real problem.

Gene01

It is NOT normal to smell fuel under any normal circumstances (not like you have poured some into the intake).
You have a potential fire hazard, and should investigate the cause.

henryhill

i also noted that in neutral, 1st n 2nd gear its smooth under throttle. just on the freeway like you said, the acceleration drops like that. is this a transmission issue?

Yamae

Sounds like a pressure issue to me. Did you check the fuel pressure?

If it's OK, I will check the the negative pressure of the intake manifold and the positive pressure of the exhaust manifold. If the problem is started when you deleted the muffler and the resonator, it may be because of the back pressure issue. The cam overlap effects the exhaust line pressure to the intake line pressure.

lexmoose

Humm nope didn't check the fuel pressure... Is there a release valve on the 1uz where I can plug the fuel pressure tester or I need to install a T adaptor?

Also just like OP I have done the muffler delete (not the resonator) but can't tell if the issue start after I've done the delete

henryhill

hmmmm the back pressure sounds reasonable... cant tell if it started when i got my exhaust done tho. how do i check the intake and exhaust pressure like u said?