New cats installed - rough morning idle and higher fuel use.

[ezyb]

Hi guys

I recently got some Magna flow Hi flow metal cats installed on my VT, and ive noticed when i start it in the morning the idle is very rough and fluctuates a few times...like its about to stall then revs out, untill its warm its ok. Also ive noticed im using more fuel.

Car has been mafless tuned, has OTRCAI, custom 2 half exhaust with try-y extractors.

What do u guys reakon?

Cheers

[macca33]

Again, the first thing I'd check would be the Oxygen sensors, the removal/fitment of new cats may have disturbed them.

Also check the usual plugs/leads/air filter, etc...

Cheers and good luck with it,

Macca

[HARMSY]

Again, the first thing I'd check would be the Oxygen sensors, the removal/fitment of new cats may have disturbed them.

Also check the usual plugs/leads/air filter, etc...

Cheers and good luck with it,

Macca


Sounds like macca could be on the mark with this one.......had the same sort of sensations when my sensors went bye bye and it wasn't long after i played with the exhaust....

wazza

P.S. If it is the sensors, you can get non genuine made by boche (spelling???) which are a hell of alot cheaper and do the same thing, something i found out after i out genuine holden ones in :cussing:

[BLACK 346]

Yeah, Bosch mate, that is what I have in mine now (tks Brad).
My first thought was O2 as well, do you have a check engine
light, I did.

[ezyb]

Yeah, Bosch mate, that is what I have in mine now (tks Brad).
My first thought was O2 as well, do you have a check engine
light, I did.

Nah i don't mate...i did have a check engine light about 2 months ago and that was for the oxy sensors...i changed them...got the car tuned.

Just now after i got the cats put in.

[Dacious]

I'd put the car back into 'learning' mode - the cats will probably have reduced backpressure and leaned it out. It they are really low-restriction you may need a re-edit. Not unusual with f-i or carbs to get what you describe. Used to be able to adjust the idle mixture/needles on carbs, not now!

[ezyb]

I'd put the car back into 'learning' mode - the cats will probably have reduced backpressure and leaned it out. It they are really low-restriction you may need a re-edit. Not unusual with f-i or carbs to get what you describe. Used to be able to adjust the idle mixture/needles on carbs, not now!

Learning mode - Reset the PCM?

Re-edit...gee whiz...

ill get in touch with my tuner.

[Dacious]

I'd say if it drives OK off-idle and feels like it's got plenty underfoot it's only the idle table needs tweaking, not a full re-edit. Pays to get him to check, anyhow. If he ran a little close to the wind with the last one you might get some pinging.

Whenever I changed exhaust on my bikes I got the same thing - usually affected low-speed and idle most. If it is lean down low, you'll be putting you foot down more, hence worse economy. Yes, reset PCM is what I meant.

[ezyb]

I'd say if it drives OK off-idle and feels like it's got plenty underfoot it's only the idle table needs tweaking, not a full re-edit. Pays to get him to check, anyhow. If he ran a little close to the wind with the last one you might get some pinging.

Whenever I changed exhaust on my bikes I got the same thing - usually affected low-speed and idle most. If it is lean down low, you'll be putting you foot down more, hence worse economy. Yes, reset PCM is what I meant.

Cheers mate.

[Madmik]

Yeah i'm also getting this problem. Mafless tune 80mm TB & cams. Cold start in the morning have to hold throttle for ten seconds until picks up. Can stall when reversing (poor idle) and whn rolling ie 10km/hr dwonhill throttle off and no matter what gear the revs drop off quickly then jump back up again in a pulsing type way, instead of slowly dropping as speed drops off???????
Any thoughts on this..........And how do you go about resetting PCM will this affect the Custom tune??
Adam

[ezyb]

Yeah i'm also getting this problem. Mafless tune 80mm TB & cams. Cold start in the morning have to hold throttle for ten seconds until picks up. Can stall when reversing (poor idle) and whn rolling ie 10km/hr dwonhill throttle off and no matter what gear the revs drop off quickly then jump back up again in a pulsing type way, instead of slowly dropping as speed drops off???????
Any thoughts on this..........And how do you go about resetting PCM will this affect the Custom tune??
Adam

Hey champ

Dont know whats causing your problem, prob worthwhile taking it back to ur tuner.

As for resetting the PCM - do a search on the forums...there's a step by step guide showing you how to do it. It will have no affect on your tune.

Good luck