high/erratic idle, bucking, stall.....

[Saleen4971]

left work today, and i had a high idle - with a bit of a surging to it. somewhere around 1000-1500 rpm was the range (until it warmed up a bit)

bucking seemed to be under some load, but not always. oddly enough, it seemed to happen in the 30-40mph range regardless of gear. as it got up to operating temp, the bucking wasnt as bad, but still present.

shortly after leaving (1/2 mile down the road) i lost all power.....then it came back......then gone again, and stalled out. crank/no start for roughly 20 seconds.

the idle issue and bucking/hesitation persists, but it has not stalled again.


idea on where to start? the only change that i made was to "tidy up" my HID harness, and i see no reason that would have any affect.


TIA

 

[Johnf78]

Any codes?

 

[Saleen4971]

no CEL, sadly i had to leave so i couldnt grab the scanner, and my cheap bluetooth adapter doesnt work with this car, so using torque is out. its possible that there may be a pending code or two - i am going to try and get over to my shop tomorrow or sunday to check, but that may not be possible

 

[Dino Dino Bambino]

I suggest you thoroughly clean the inside of the throttle body as your first measure.

 

[Saleen4971]

And this morning its running perfectly.....

 

[07 Boss]

And let your car warm up before driving it.

 

[Saleen4971]

.......if I have to do that, then there is something wrong.

 

[07 Boss]

.......if I have to do that, then there is something wrong.

Really? Every car I've ever owned, new and used, ran better when warmed up.

 

[cdynaco]

I suggest you thoroughly clean the inside of the throttle body as your first measure.

Yep. Throttle body, and MAF. If it persists check O2 sensors.

 

[Saleen4971]

yeah it runs better, but there is no reason why i shoudl have to wait for it to warm up. this isnt the 70s - fuel injection is a thing. its a good thing.

when i have time at work i will clean the MAF, TB, and swap plugs.

O2 sensors when the bank allows it - lots of expenses these days. once the wedding is over with, there will be some extra cash available

 

[Dino Dino Bambino]

And let your car warm up before driving it.

The engine should run perfectly even when cold thanks to EFI. If it doesn't, as Confucius would say, "Sum Ting Wong".
Looks like the OP already knows what to do except decide how to divide the expenses between the two wives. ;-)

 

[07 Boss]

The engine should run perfectly even when cold thanks to EFI. If it doesn't, as Confucius would say, "Sum Ting Wong".
Looks like the OP already knows what to do except decide how to divide the expenses between the two wives. ;-)

Well there is a certain range where engine efficiency is at its best. Using deductive reasoning it must not run as efficiently when not in this range. EFI makes it run better but you still need to get plugs up to temp. Sensors need to heat up before they read properly. Cold start up usually has a slightly richer fuel mixture. In theory you should be able to start her up and drive away, and in most cases this is true. But even then you can't say it is running like it should. It won't make the same power as when it's warmed up. So if it's not running at 100% it may stumble when you load it at low rpms and light throttle, especially cars with blowers.

 

[cdynaco]

Cold start up usually has a slightly richer fuel mixture. In theory you should be able to start her up and drive away, and in most cases this is true. But even then you can't say it is running like it should. It won't make the same power as when it's warmed up. .

Of course there's an optimum running temp. But at cold start, even with ECU richening, it should not be running like "erratic idle, bucking, stall...".


Most the time these issues are solved with cleaning throttle body and MAF. Pretty common posts.

 

[Saleen4971]

The engine should run perfectly even when cold thanks to EFI. If it doesn't, as Confucius would say, "Sum Ting Wong".
Looks like the OP already knows what to do except decide how to divide the expenses between the two wives. ;-)

:-D two wives? Try three! Between the lady, the blown mustang, and the blown jeep I've got my hands full and bank account empty.

 

[Dino Dino Bambino]

Well there is a certain range where engine efficiency is at its best. Using deductive reasoning it must not run as efficiently when not in this range. EFI makes it run better but you still need to get plugs up to temp. Sensors need to heat up before they read properly. Cold start up usually has a slightly richer fuel mixture. In theory you should be able to start her up and drive away, and in most cases this is true. But even then you can't say it is running like it should. It won't make the same power as when it's warmed up.

All of that is correct but an EFI engine shouldn't stumble, stall, and have an erratic idle when cold.
Yes, it'll have a higher than normal idle speed on cold start up due to the rich A/F mixture that's required until the O2 sensors warm up, but the engine should still run like a Swiss watch.

 

[thump_rrr]

yeah it runs better, but there is no reason why i shoudl have to wait for it to warm up. this isnt the 70s - fuel injection is a thing. its a good thing.

when i have time at work i will clean the MAF, TB, and swap plugs.

O2 sensors when the bank allows it - lots of expenses these days. once the wedding is over with, there will be some extra cash available

I bought my front O2 sensors for my 05 from Summit Racing.
$32.00 each
http://m.summitracing.com/parts/BCH-15716

 

[Saleen4971]

I will only run OEM electronics, unless there is an aftermarket upgrade. Had too many issues with picky vehicles

 

[thump_rrr]

I will only run OEM electronics, unless there is an aftermarket upgrade. Had too many issues with picky vehicles

I'm running 543rwhp on stock internals.
If there was anything wrong with the Bosch O2 sensors it would have shown up in my car.
http://www.s197forum.com/forum/showthread.php?t=116194

What mods, mileage, tune?
Any previous issues?
What plugs, fuel filter, and how old are they?

 

[Saleen4971]

Like I said, it never had an issue since then....

Just put a new set of ht0 at 030, and fomoco fuel filter yesterday.

Frpp axle back, Vortech ho, 65k

I'm a bit anal about certain things - especially with this car

 

[joe_momma]

Any chance of an air leak? You said you were tidying up some things, maybe bumped something?