Strange Engine Trouble

[paul200]

Hi im new to the forum here and hoping that someone on here has experienced the same symptoms my car has in order to help me figure out what is wrong.

I own a 2001 sport, car has 95k on it and recently developed a misfire so to speak. There are no codes showing on obd11 scanner.

Symptoms are as follows

Car is down on power acceleration is sluggish.

Between 2-3k rpm the car shudders (misfire assumption)

Experiencing poorer mpg.

If anyone is able to help it is greatly appreciated! Many thanks.

[paul200]

May i also add that the car has undergone a full service. Also upon crossing into vvt there is a rattling noise, however i assume this may be down to tappets needing set

[scudney]

Sounds like one of your coils might have gone.

[IHgs300]

As above or new plugs needed. iridium plugs are the most suited to the IS engine.

[ChrisIS200SportTTE]

I'm going to against what's been said previous (sorry)

If it was plugs or coils it Would throw a misfire code surely.

Because you mention it rattles on crossover to vvti I think it's something to do with your air intake. I say this because there is no such thing as vvti crossover. Vvti is always on. The "lift" or "boost" you feel around the 4000rpm mark is the ACIS (acoustic control induction system) working. Basically it opens a valve on the intake at 4000rpm. So if it's rattling then (when the valve opens fully) and if it's shuddering at 2-3000rpm (that would indicate it's not getting enough air or fuel so I'm thinking air..) I'd say something is up with your intake or the ACIS valve?

[paul200]

Were is the acis situated?

[ChrisIS200SportTTE]

http://en.m.wikipedia.org/wiki/Acoustic_Control_Induction_System

It's on the intake. I don't know where exactly as I've never had to get to it but I know some modify this valve so it's permanently open (don't see the value in this myself) so it can't be too difficult to get to. I can find out exactly where it is later...

[paul200]

Cheers for that, will have a look tonight, tomorrow and post my findings.

[paul200]

Ok so ive removed the valve from the acis, and also cleaned the ocv. I have had the car checked, there is no codes present on the system and coilpacks are all ok. There is a slight improvement on the 2500 rpm shuddering however at top end revs seems to take forever to pick up. Also my mpg has extremely depreciated! 80 miles to half a tank.

[paul200]

http://www.lexusownersclub.co.uk/forum/topic/85543-flatspots-and-sluggish-acceleration/

The above link explains my issues abit more accurately!

[North west beast]

Try new plugs denso iridium ik 20 or 22 s .

Maybe use better fuel if not already .

I let my transit run low on fuel the other week , I filled it up at asda and it's lost 50 percent of its power.i put injector cleaner in twice with bp fuel and it's nearly back to normal now .

Worth trying the cheaper options first .

Opie Oils sell upgrade plugs etc , they give good advise too .try them mate .