rough idle- running rich

Anonymous · February 4, 2004, 12:50

Hi Guys, done a search so thought as that came up with a blank I'd ask the question.

Firstly Jap Import 2001, SMT, 28k miles. Precats good, no main cat (only 1 O2 sensor)

About 2 months ago I put a blitz exhaust on the car to go with the Blitz filter.
2 weeks or so ago the car started to idle very low, almost to the point of guessing 5-600 RPM. The petrol (always optimax)consumption went up by around 10 mpg and she gets a little overrun in fuelling on decelleration. Other than this, the car is performing superbly. It has a brand new battery and oil is really clean and literally no consumption (if you know what i mean). No engine check lights and as I say running great. Now I may be wrong but these are not tuneable cars i.e. the ECU is responsible for fuelling and air etc. So if I made an educated guess the O2 sensor is screwed or an actuator has gone or something?
Anyone have any ideas, as at the moment I'm taking it to a tuning place I know which will run a diagnostic, but it may help to be able to point them in the right direction.

Thanks In Advance

Slacey · February 4, 2004, 12:55

May be as simple as cleaning the MAF... worth checking, especially as you are running a Blitz intake.

Anonymous · February 4, 2004, 12:58

thanks slacey hope so s:lol: :lol: s:lol:

Tem · February 4, 2004, 13:04

Instructions for cleaning:
m http://www.spydermagazine.com/2002/Marc ... _clean.htm m

Anonymous · February 4, 2004, 16:34

Thanks Tem

Give it a shot on the weekend s:)

s:)

SteveJ · February 4, 2004, 19:50

The blitz SUS is a wire mesh filter (no paper or cloth) and as such doesn't stop small particles like sand and oil etc from being ingested into the engine. Almost certainly your MAF will be seriously gunked up, and there is a question mark over the effect allowing the small particles to get into the engine (increased wear to valves & seats and the cylinder bores)

Anonymous · February 5, 2004, 15:11

Faintly off topic (sorry) is it normal for a cold engine, when first started to idle at around 1500rpm, dropping to 900rpm when warmed-up?

markiii · February 5, 2004, 15:14

seems about right for mine though 1500 is the extreme when it's very cold.

Anonymous · February 5, 2004, 15:15

Quote from: "Testcard"Faintly off topic (sorry) is it normal for a cold engine, when first started to idle at around 1500rpm, dropping to 900rpm when warmed-up?

yes.

Anonymous · February 5, 2004, 15:18

Thanks for that. Couldn't find/see anything in the manual about idle speed.

Anonymous · February 5, 2004, 15:20

Quote from: "Testcard"Thanks for that. Couldn't find/see anything in the manual about idle speed.

I had the same worry when i first got mine but was told its normal by members on here.

Hope that helps.

Anonymous · February 5, 2004, 15:25

That's good to know. Problem is, I'm still in that honeymoon period with the car where my knowledge base is limited, but growing slowly. I'm almost confident enough now to take it out of the garage for the first time s:wink: :wink: s:wink:

markiii · February 5, 2004, 15:32

In which case, a breif synopsis.

ignore what most dealers tell you as they are clueless.

read you manual (amazing how much is in there you don't expect.

Ask us anything you need to.

Consider buying the workshop manuals if your mechanically inclined. They are very very usefull.

Anonymous · February 8, 2004, 21:56

Help Guys

Ok report back....

Maf sensor is spot on
No ECU faults flagged up
According to garage fueling is spot on (even though I think consumption has gone up)

Not that i don't trust them to figure it out, but is there an idle actuator or the like in the 2. It strikes me that this may be where the rough idle lies at least. As for the fueling well maybe its the rough idle thats causing the lower mpg??

Any other suggestions greatly appreciated or I'm gonna end up spending money on a chip GEMS or MOTEC unit s:shock: :shock: s:shock:

Ouch so close to xmas!!!

Thanks in advance

Anonymous · February 8, 2004, 22:20

Quote from: "Testcard"That's good to know. Problem is, I'm still in that honeymoon period with the car where my knowledge base is limited, but growing slowly. I'm almost confident enough now to take it out of the garage for the first time s:wink: :wink: s:wink:

We've had ours a year, and she does now come out the garage now and again on weekends s:lol: :lol: s:lol: Oh and I still know NOTHING about ANYTHING. I have my friends here to help me with everything.

Anonymous · February 9, 2004, 10:11

They're a helpful bunch here, aren't they s:lol: :lol: s:lol:

Anonymous · February 9, 2004, 11:44

You say at the beggining of this thread you only have 1 O2 sensor? Do you mean this i.e you've got both banks re-wired so it's reading from just 1, or this a typo? s:? :? s:?

Anonymous · February 9, 2004, 13:15

QuoteYou say at the beggining of this thread you only have 1 O2 sensor? Do you mean this i.e you've got both banks re-wired so it's reading from just 1, or this a typo?

Hi Ian

Sorry I'm probably wrong, but I thought the Jap spec only has one O2 sensor rather than the UK spec.

Actually since you've responded the garage has said that the throttle has a flyby wire which corrects and sets the idle at its proper levels (ie the blip of revs on change down) and they feel it could be something to do with this. being thick, but does the idle get controlled by this or the ECU? I would have thought that the pedal position notifies the ECU to engage the SMT etc, and that the idle would be the ECU's domain.

I don't know s:? :? s:?

Anonymous · February 9, 2004, 13:35

Quote from: "adair69"
QuoteYou say at the beggining of this thread you only have 1 O2 sensor? Do you mean this i.e you've got both banks re-wired so it's reading from just 1, or this a typo?

Hi Ian

Sorry I'm probably wrong, but I thought the Jap spec only has one O2 sensor rather than the UK spec.

Actually since you've responded the garage has said that the throttle has a flyby wire which corrects and sets the idle at its proper levels (ie the blip of revs on change down) and they feel it could be something to do with this. being thick, but does the idle get controlled by this or the ECU? I would have thought that the pedal position notifies the ECU to engage the SMT etc, and that the idle would be the ECU's domain.

I don't know s:? :? s:?

No mate ours still have 2 O2 sensors but not the third one after the main cat.Thought thats what you may of meant.

Not knowing anything on the SMT i'll not speculate.Shout loud and hopefully Markiii or mph will bring their SMT knowledge in to play. s:D

s:D

Anonymous · February 9, 2004, 14:01

QuoteNo mate ours still have 2 O2 sensors but not the third one after the main cat.Thought thats what you may of meant.

Doh s:oops: :oops: s:oops:

Damn they do say a little knowledge is more dangerous.....!!! Thanks.

Anonymous · February 10, 2004, 14:46

Well for anyone who possibly has this problem in the future.......

According to the garage its now done, and running very sweet again. I t was the throttle body which they stripped down, (not easy to get to as i understand).
They were led to this being the fault after the logic in the previous post, and the fact that the readings were not quite right for the fly by wire. Anyway if your SMT runs rough at idle and cold start etc, then this would possibly be the first place to look (and the cheapest). I will update if the problem returns but they are confident its OK s:wink: :wink: s:wink: