Yaris sedan sputters after a cold start!! CT Scott pls help if you're out there!!!!

[tyrone_yaris]

Hi,

For some time now my car sputters for several seconds after a cold startup but then it idles fine and runs fine. If I stop and start the engine again the next time, it starts fine without any sputtering afterwards.

Usually happens when the car is parked overnight or for a long period say 7-8 hours. Replaced all 3 spark plugs with Denso Iridium, did a throttle body and MAF sensor clean too. Also put in another battery to see if it was a battery problem but still the same sputtering after a cold start.

What could be the cause of this? CT Scott I wish you could give your opinion too.

Thanks

Tyrone

[CTScott]

Since it only does it on a long-cold start, it almost seems like the fuel system is having trouble getting up to pressure. Other people from your part of the world have had issues with the fuel filter being plugged, so that would be my guess.

[tyrone_yaris]

Thanks Scott.

Yes we do not get the best quality fuel out here at all places.

Should I just go ahead and replace the fuel filter? Btw did a scan using the X431 but it did not show up any error codes either, just a rough idle code P1605.

[CTScott]

Replacing the fuel filter is a bit of a hassle. If you could get someone to scan it with the Toyota service tool on cold start, if the filter is really plugged, you'd see it be lean, rather than rich, as it should be during a cold start.

[tyrone_yaris]

Thanks once again.

Ok; Will see if I can get it scanned as you advised and update you accordingly.

[tyrone_yaris]

Originally Posted by CTScott

Replacing the fuel filter is a bit of a hassle. If you could get someone to scan it with the Toyota service tool on cold start, if the filter is really plugged, you'd see it be lean, rather than rich, as it should be during a cold start.

Hi CTScott,

A friend of mine just got an X431 scanner so I asked him to help out. But he couldn't figure out how to tell if its lean or rich when he connected the scanner. Can you guide as to what parameter on the scanner to look for?

Is there any other way of telling if the fuel filter is plugged??? I really need to solve this starting issue. It's like as if the engine is gonna shut down but then it picks up after several seconds.....

Thanks

[tyrone_yaris]

...Oh and if this also helps...my fuel avg is not good either. Getting about 9-10 km / liter.

[CTScott]

The scanner would need to be one that can read more than just trouble codes. Normally the Yaris ECM runs the system very rich when starting (about 18 for the AFR), whereas once it is warmed up it aggressively keeps the system at 14.7 for the AFR.

[tyrone_yaris]

So if its below 18 shld I presume its a plugged fuel filter?

[CTScott]

Originally Posted by tyrone_yaris

So if its below 18 shld I presume its a plugged fuel filter?

Yes

[tyrone_yaris]

Originally Posted by CTScott

Yes

Thanks will keep you updated.......

[seth_man]

other way around, less than 14.7 would be rich and above 14.7 is a lean mixture, cold start air fuel ratio on our cars running properly near freezing should be in the low 12's and will vary a little with ambient temperature

[CTScott]

Originally Posted by seth_man

other way around, less than 14.7 would be rich and above 14.7 is a lean mixture, cold start air fuel ratio on our cars running properly near freezing should be in the low 12's and will vary a little with ambient temperature

Yeah - That's correct - I must have been half asleep when I posted that this morning. 13.8 (which is rich) is the AFR that the ECM targets during cold start. 18 (which is lean) is actually the AFR seen during DFCO.

[ciscobear]

tyrone? I thought you had a Belta? Did you do as I suggested? Another member had a similar issue and it turned out to be her grounds. We suspect the vehicle might have been in an accident and the grounding points were painted over.

[tyrone_yaris]

Originally Posted by ciscobear

tyrone? I thought you had a Belta? Did you do as I suggested? Another member had a similar issue and it turned out to be her grounds. We suspect the vehicle might have been in an accident and the grounding points were painted over.

Ciscobear, no I'm sorry it must have slipped my mind...could you pls repost it here again and I will try. I'm zero where these cars are concerned so you'' probably have to explain it as simple as possible :)

CTScott, another mechanic had a look at my car y'day evening and started it. He didnt have a scanner but when he started the car and I explained to him the situation, he said its the fuel pump and not the fuel filter. Reason being that the car runs smoothly after that and there are no jerks or problems in the pick of the car. He says since its only on cold startup it seems to be a problem of the fuel pump pressure initially as it starts up.

[CTScott]

Originally Posted by tyrone_yaris

Ciscobear, no I'm sorry it must have slipped my mind...could you pls repost it here again and I will try. I'm zero where these cars are concerned so you'' probably have to explain it as simple as possible :)

CTScott, another mechanic had a look at my car y'day evening and started it. He didnt have a scanner but when he started the car and I explained to him the situation, he said its the fuel pump and not the fuel filter. Reason being that the car runs smoothly after that and there are no jerks or problems in the pick of the car. He says since its only on cold startup it seems to be a problem of the fuel pump pressure initially as it starts up.

I would think that if the fuel pump had an issue that it would be visible on more than just start-up.

[tyrone_yaris]

Originally Posted by CTScott

I would think that if the fuel pump had an issue that it would be visible on more than just start-up.

CTScott, I just wanted to confirm from you before jumping to any conclusions. What would be the tell tale signs of a fuel pump issue if it were so, if you could pls let me know?

[tyrone_yaris]

Originally Posted by ciscobear

tyrone? I thought you had a Belta? Did you do as I suggested? Another member had a similar issue and it turned out to be her grounds. We suspect the vehicle might have been in an accident and the grounding points were painted over.

....and yes the Belta is what I have. It was imported at 43,226 km but I believe its called a Yaris in Canada/US so thats how I mention it when I post on these forums