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Discussion Starter · #1 ·
Hi guys!

I have AR 166 fl 2.5 v6, 2004, manual gearbox and have big problem. My car is idling between 1600 and 1900 rpm. When i start engine it works okay until i start drive, after about a minute idle is very high. Funny thing is that when i turn ac on idle drops to normal, about 800-850 rpm. Car is driving fine, pulls normally and everything else is ok. It happened after i change ignition coils. I checked every vacuum hose, cleaned throttle body, ecu and throttle reset, changed maf sensor, checked for air leaks and found nothing. Only trouble codes that i have is P0505 idle control system and i erase it and drive car, idle is still bad but there is no check engine light. Maybe you have some suggestion what to do, what to try, some help.

Thanks in advance
 

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Sounds like you’ve checked the obvious. Are the brakes OK? Sometimes the servo can fail and let a lot of air in. If the brakes are hard, then check the servo hose for integrity.

Do you have Multiecuscan? It will tell you if the engine is getting any weird readings. Have you tried getting someone to work the throttle pedal with the engine off (ignition on) and the intake off so you can see if the movement is smooth?
 

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Discussion Starter · #3 ·
Brakes are ok and i don't have multiecuscan, i have 2 different diagnostics but not original one. No i have not tried checking throttle flap with ignition on, but will tommorow, thanks for advice. When i was cleaning it i saw that it doesn't fully close, there is a slight gap between egde of the flap and body.
 

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It's normal to see a small opening of the throttle body with no power - this is the 'limp home' setting. The throttle has to be driven further shut for idle control/normal driving.

You can run it without the MAF connected, so to check the throttle is behaving, disconnect the MAF and remove the inlet convoluted pipe so you can see the throttle butterfly - see what it's doing.

An air leak still seems the most likely problem. Probably one of the inlet runner rubber seals to the plenum (they can get tucked under themselves at times) or perhaps one of the PCV pipes round at the back of the plenum - they are a bit awkward to get to and can split with age.

Switching on the AC loads it up quite a bit, so I can see how that fits with an air leak.
 

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Just tried this on my 3.2.

The throttle plate is not visibly open at rest - it is a little bit open, but if you can see a gap it is far too open.

Get a helper to switch the ignition on and push the accelerator to the carpet. The plate should be wide open, and clean all around. If the helper releases the accelerator, then the plate should snap shut - fully shut. Turn the ignition off and wait a few seconds. It will whine and hum for a bit, then open up ever so slightly to the resting position.

If that is all normal and smooth then I also thinking air leaks - but they tend to manifest as a high idle with no power and misfiring - and the ECU generally manages to get the idle down to about normal, so you just get a misfiring lumpy idle, not 1800 rpm.
 

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Just tried this on my 3.2.

The throttle plate is not visibly open at rest - it is a little bit open, but if you can see a gap it is far too open.

Get a helper to switch the ignition on and push the accelerator to the carpet. The plate should be wide open, and clean all around. If the helper releases the accelerator, then the plate should snap shut - fully shut. Turn the ignition off and wait a few seconds. It will whine and hum for a bit, then open up ever so slightly to the resting position.

If that is all normal and smooth then I also thinking air leaks - but they tend to manifest as a high idle with no power and misfiring - and the ECU generally manages to get the idle down to about normal, so you just get a misfiring lumpy idle, not 1800 rpm.
Those throttle bodies go bad at times. Try removing it and cleaning it with brake clean from both sides.
 

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PCV valve sticking will give an idle speed of about 1400 rpm. If not that, I'd test the tps with a multimeter.
 

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Discussion Starter · #8 ·
I also think there is air leak issue, giving the fact i was changing ignition coils. I've cleaned throttle body from both sides so its clean 100 percent. Maybe tps is faulty but want to try everything else before i buy it. You mean those 6 rubbers on intake plenum? Where are those PCV hoses and PCV itself located?
 

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Yes, the short lengths that link the chrome runners to the plenum. They can be fiddly. PCV Hoses are round the back of the plenum, PCV valve bolts into the back. Also check the hose that links the bottom of the oil separator back down to the block.
 

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Easiest check for the plenum rubbers - a bit of pipe as a stethoscope. With this, you’ll hear the air whistling in when you put it next to a leaking one.
 

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Discussion Starter · #11 ·
I will check PCV hoses and rubber runners, didn't think about that. Can i use air or brake cleaner to check it, spray a bit over?
 

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I will check PCV hoses and rubber runners, didn't think about that. Can i use air or brake cleaner to check it, spray a bit over?
Spray the hell out of it with WD40 or brake cleaner, if there are leaks, engine will change sound or bog.

EDIT: It would probably be safer to do it with WD40 since those engines run really hot, you do not want to start a fire.
 

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I usually use butane for finding leaks like this. Doesn’t make a mess like WD40 or the like. Safe enough in an open environment as it disperses rapidly.
 

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Discussion Starter · #15 ·
Thanks guys i will try this and if that isn't it try to find used tps to try with that. Just need to find some time that i'm not working:)
 

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Be methodical with this. Car was fine. You changed the coil packs. Now it isn't. Think about exactly what you did when you made that change, then carefully go back over every step, double-check that you put everything back as it was - all the earth straps, all the fixing bolts, all the hoses & clips clips, all the connectors.

Don't assume that because you checked something before it is OK - mistakes happen, we miss things. Assume nothing, start from fresh as if someone has presented you with the car as it is now. It is all too easy to bias yourself into missing stuff ("I checked that, it was OK, can't be that..."). I know this very well, having done it myself.

Yes, coincidences do happen, but why would you suddenly suspect the throttle position sensor? It isn't a separate replaceable part by the way - it's an integral part of the entire throttle body.

Error codes can be very helpful, but they can also be very misleading too, as unless they are obvious, like say a failed crank position sensor or similar, the root cause could be many things, the ECU can just be reporting a symptom, not the fault.

You'll find it.....
 

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Discussion Starter · #17 ·
I was suspect about tps because i cleaned it so maybe i did something that i wasn't allowed, i said maybe. Ofcourse i will go step by step but when i bought car it was happening sometimes, changed Maf because of throttle lag and it continued and gone by itself. Now after changing coils it happens again. One thing i know for sure is that i disconnected battery. Just one day off and i will try your advices.

And one more thing, when i'm accelerating between 4000 and 7000 rpm car is choking, stutter, but not always under those rpm it accelerating fine?

Thanks
 

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I was suspect about tps because i cleaned it so maybe i did something that i wasn't allowed, i said maybe. Ofcourse i will go step by step but when i bought car it was happening sometimes, changed Maf because of throttle lag and it continued and gone by itself. Now after changing coils it happens again. One thing i know for sure is that i disconnected battery. Just one day off and i will try your advices.

And one more thing, when i'm accelerating between 4000 and 7000 rpm car is choking, stutter, but not always under those rpm it accelerating fine?

Thanks
My guess here is the MAF?
 

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33_Stradale You mention you changed the MAF - did you fit a new genuine Bosch part, or one of the cheap E-Bay jobs? I ask, as the cheap clones are well known for causing problems. It doesn't help that there are plenty of cheap copies that are sold as genuine :(

You can maybe check the MAF again by disconnecting it and seeing if the stutter stays the same. If yes, it's almost certainly the MAF to blame as Mufasa says.

Good luck.
 

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Discussion Starter · #20 ·
Sorry for late reply i was working very hard last days didn't have time to read or work on the car.
Maf is genuine bosch i have 2 of them one new and one and one used but it was working okay on other car.
Today if i manage to find some time i'm goingbto replace hose that goes to intake plenum from valve cover that little piece with 90 degrees bank. Its plastic and i suspect that maybe here is getting air.
And for stutter i dont know what to do its not always but on hard acceleration only
 
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