If you get the blue light then it is suitably rich. The lambda voltages you describe are normal. Cold hesitation is normal. Hot hesitation is not normal.

AFM=MAF = airflow or mass air flow meter (same thing)
Sometimes people use AFM to mean a air fuel display.

[Edited by john banks - 7/1/2002 5:07:44 PM]

 

Ideas please?

I have had my STI 5 for about 6 weeks now and after 2-3 weeks I started to notice a very slight hesitation when cold. It was almost like the car was only temporarily firing on 3 etc.
This was a very light throttle and low speed as the car was very cold etc.

Anyway over the last few weeks it seems to have got more and more noticeable.

I fitted the Scoobysport downpipe to the Nur Spec R system at the weekend and it seems ever more noticeable now.

When the car is hot it is fine........

Is this a common problem????
Does it sound like a plug going down but coming back when hot???

Help please

 

Have you specs of the fuel type you use, last service etc...
Silly questions but could help resolve your problem

Tony

 

Mines a bit jerky when cold, I put it down to fueling and its perfect after about 3 mins. Its when youre not accelerating hard or slowing, just cruising with the throttle open slightly ??
Dan (STi5-R full decat)

Edited to say Optimax and Millers octaine booster

[Edited by DanTheMan - 6/30/2002 11:18:16 PM]

 

Dantheman

Yeah , absolutely right mate

Its when you are only slightly opening the throttle 10-20mph or as you say cruising slowly .

As soon as you fully open , it seems to be fine...

And it completely goes away when its hot

 

Legacy turbo I have just drives like a pig when it's cold. All the imprezas I have driven are the same: Feels like a bag of hardened snot when it's cold....then ya drive for 5 minutes and suddenly your clutch is fluid and doesn't judder (yes, I know I have warped my clutch...round of applause please) the turbo gets quieter (yes..I know I shouldn't be using it....but everyone has done it once) the exhaust sounds nicer, the accelerator gets more responive the blah blah blah blah

My Old Type RA had some weird jap sequential blow off valve and used to stall like a pig when it was cold too.

I just put it down to one of the joys of scooby ownership?

 

My P1 (Sti5 in drag) does the same it used to just do it when it's cold but now it does it when it's hot as well.

It's like it's clearing it's throat- it stutters a bit and then clears and off it goes all on a steady state throttle. I also run a full SS decat,ITG, as well as Optimax + NF at all times.I'm thinking about replacing some of the exhaust and/or the filter with the stock item and seeing if it improves matters.

Driving home last night my other half said it seems to be running a little rough! First time she's noticed anything about a car other than it's colour.

 

Mine has started doing this.........2 days ago. I replaced a faulty Lambda sensor. Since then it has being doing this, it feels like the engine is slightly starved of fuel and then it's back again........the car "pulses" under light throttle. Open her up and she's fine. My car is a UK Turbo with De-Cat and Dawes. I'm going to take the Dawes off to see if that makes a difference.

The thing is it didn't do this before fitting the new Lambda sensor. With a knackered Lambda does the car run rich? I know with the ECUTEK maps they richen the mixture low down the revs

 

I have recently noticed a slight hesitancy whilst driving a UK model MY99 The problem occurs more when the engine is cold but has recently become progressively worse when the engine is warm.

The best way of describing the problem, is when I am in 2nd gear driving along at around the 2000-2500 rpm with my foot just slightly on the accelerator when the car seems to momentarily loose power, and seems to start misfiring?

It tends to happen intermittently so sometimes it will happen and other times it will go away (as it did when I was trying to demonstrate the problem to a Suabru dealer). Seems non-existent when the Turbo cuts in above 3000 rpm's.

Suggestion was to start with the leads then take it from there. Found that the leads alone will probably cost around £100, so I'm hoping this will solve the problem!

 

fwiw - this is quite normal when cold as the JECS ecu works from static maps when it is in cold-start routine - ie isn't learning from the sensors - once warm it switches out of cold start routine - you should be taking it easy for first 10 mins anyway to avoid engine wear while oil is cold - I know it is irritating though - I have had this with sti 5 and same with current b4 (both JECS) - I usually change up to 4th gear when tootling at 30 mph as it actually runs more smoothly at lower revs/smaller throttle opening.

btw - note for 'sti wanna subaru' above - sounds like your AFM is faulty mate - could also explain demise of your O2 sensor too as you will probably be running too rich all the time - another big bill coming up.

Paul W

 

Paul,

Can you please explain.....

The car had a faulty O2 sensor, it's been replaced and the AFM is showing that It's sending a signal and from what I've read it's also showing as you would expect.

Are you saying the faulty O2 sensor has damaged the engine? When you say "big bill" you're making me worry

Cheers

Guy

 

sorry if I caused any alarm unduly but...

'big bill' as in replacing an AFM - not engine in general - not that big a bill but probably more expensive than say the O2 sensor was.

hunting or pulsing at idle is a classic symptom of failing AFM - if in doubt, get the car on a select monitor and monitor the afm output in realtime - it should be evident whether it is responding properly. In terms of the two items being related, overly rich running can cause an early demise of the O2 sensor (though they don't last forever on decatted systems anyway!) - thus it could be (though not certain) that an afm fault could cause O2 sensor to fail aswell. Have you had the exhaust checked with a probe - be interesting to see what the readings are AFTER the O2 sensor has been replaced and confirmed to be working - ie if still running chronically rich (even more so than normal) then you may have another issue.
Don't panic unduly though - running rich isn't itself a terribly bad thing and won't be doing any damage to your engine per se.

Paul W

 

Unlikely to be running rich with full decat, more likely to be too lean hence everyone's advice to run with Octane booster to stop det.

 

When you talk about AFM what are you refering to? I fitted a Dawes AFM with the MBC. I spliced into the ECU feed and ran the power cables to the battery. I don't see how this could cause a problem. Are you talking about the MAF?

The surging I'm getting sounds like what most people are experiencing, what I don't understand is that it felt to run better when the O2 sensor wasn't working. I checked the signal at the ECU feed before and after the Lambda was replaced. Before I got a steady 247mV @ tickover. The new Lambda was showing a pulsing. From what I've read this is correct for a working sensor. On WOT the Dawes AFM is showing a blue light and when hot green sometimes dropping to amber. Again from what I've read this is expected.

Cheers

Guy

PS sorry to hijack the thread............hopefully something may be helpful though

 

Cheers John, that's where I thought the confusion was coming from.

Don't you think it's strange though that the car ran better when cold with a broken Lambda