4.6 Rough idle, odd whirling sound

A

acameltoe

Guest
You may have seen some of my recent posts tracking down some codes after swapping out my 4.0 for a 4.6.

All the codes were resolved tracing them to the CVS not being plugged back in and removing and cleaning out one of the SAI valves.

I still have been having a slightly rough idle when stopped at lights or after driving for a while in drive with foot on brake, neutral or in park. It is like a bit of a stutter or shake say once a second or a little shorter. Cannot see it in the tach. I checked the throttle cables and they were a bit too slack from when they re-assembled so I re-adjusted them back to where they should be, but it didn't seem to change. I was thinking possibly the tensioner or alternator pulley as there is a bit of a higher pitch Rrr Rrr Rrr about every half second when at idle only. Not really screeching or anything, just a strange sound Almost like the sound a pigeon makes lol. My 4.0 did it as well and I thought maybe it is an ancillary or pulley they put onto the now engine? TPS?

But...

Today when I got home from work it was raining for last half of the drive and when stopped at home idling it was doing it and I seemed to notice the dash light behind the odometer looking as if it was dimming a bit in time with the stutter, then I heard a strange whirling sound. Like an electric motor spooling up or something. Heat was on low and it wasn't the heater blower, and it wasn't the condenser fan. Almost sounded like the SAI pump based on where it sounded like it was coming from while in drivers seat, but it sounded much louder. I have never really been able to hear the SAI pump without really straining to hear it. This was the first time I ever noticed that sound though. Never before engine swap or after when idle was rough.

I'm getting no MIL light or codes, and other than that the truck is now running very well after reprograming the ECU for the 4.6 and the adaptive values getting used to how I drive.

Any one have any ideas?

Thanks,

John
 
A

acameltoe

Guest
I did some more searching and only things I could find were about trying to clean TPS, so I will try that later today and see if it effects the rough idle. I also could only find posts with similar noises being SAI pump or a vent in the dash opening or closing which is a possibility I guess. Is there anything that would cause SAI to come on after car is up to temp. I saw some posts saying it might come on for a few seconds at stops, but that doesnt make sense to me if it is already up to temp it shouldn't as far as I know.

When I started it this morning, similar conditions as last night, cold, damp, the SAI pump sounded normal at startup, no wierd whirling sound. Idle was still a bit rough at stops once warmed up which seems to be a factor. Doesn't seem to do it when first started and not up to temp. coolant temp sensor perhaps?

I did not notice any lights dimming or anything on ride in this AM in time with the stutter. Still no MAF or codes.

Any suggestions where to look? Similar experiences?

Thanks,

John
 
A

acameltoe

Guest
Well, I cleaned TPS off. Didn't seem too dirty, but tried it anyway and still no change.

Plugs were brand new champs when engine was swapped. Wires are Magnecors and look good. MAF is only a couple months old.

Still no codes. Last one was P1415 SAI code, but after I cleaned out the valve on that side it has not thrown a code for the last 5 days, 380 miles and many cycles. But still that wierd idle burp and heard that strange windup sound again a few times in traffic today.

Anyone have any input? Alternator? Coils maybe? 02 sensors getting tired after the exposure to coolant when the 4.0 went south?

Can't seem to figure it out. :banghead:

Thanks,

John
 
A

acameltoe

Guest
Hi PT,

The dimming Im not really sure about. I only seemed to see it once and hasn't happened since. The belt is pretty new, a few months and noise was present before belt change on old engine.

When you say pull it do you mean torque the tensioner to make it tighter?

Could the alt cause the strange idle? I had the regulator in it rebuilt this summer and up until the engine swap it seemed fine as well. no strange idle on the 4.0

Thanks for the suggestion.

Hope all it well. I saw the post the you had been hospitalized.

John
 
A

acameltoe

Guest
Glad to hear you are doing better.

I will try taking the belt off this weekend. Probably won't have time tomorrow.

Do you think the noise could have anything to do with the stutter/rough idle at stops? Just seems weird that that sound was present on the 4.0 before the swap to the 4.6 but did not effect idle at all and never heard that weird whirling sounds before swap.

Still want to solve the noise either way so I will try with belt off this weekend.

Thanks

John
 
D

D.WILLIS

Guest
You Worry Too Much Dont Go Here Till Ya Get Stumped..er Clodded Injectors Gas Has Gotten Worse Lately...mine Blubbers At Idle Bad Gas And I Never Use Supreme Because Nobody Else Does So Ya End Up With Water In Yer Fuel From Condensation When Ya Get It At The Station And It Builds Up Over Time
 
SGaynor

SGaynor

Well-known member
Dec 6, 2006
7,148
162
52
Bristol, TN
Not sure on a Rover, but I had a Suburban that did what you described. I was thinking it was the alternator, but the fix was to clean the throttle body - had a lot of varnish. That's a simple fix. I now clean all throttle bodies once a year as preventative mantaince.
 
D

DISCODOWN

Well-known member
Dec 4, 2007
284
0
Phoenix, Arizona
alt weak or going can cause all kinds of freaky stuff...other ancilliary belt drivens too........and pigeon sounding? [weird] noises.
i am with p.t. -pull off the belt....post results.
 
A

acameltoe

Guest
Thanks guy,

Will try pulling the belt and seeing what happens over the weekend.

I cleaned throttle body and TPS already and have been running 93 gas since swapping the engine. Also ran some Techron through it for a few tanks since I did not know condition of the injecters on the 4.6 so I don't think it is the gas.

Question: How long can I run it with belt off? Do not want to overheat it. Obviously I wont be driving it that way, just idle. Since it seems to happen only after warmed up I guess I should drive it a bit, then once it is up to temp and doing it at stops go back, park it and remove belt to idle and listen.

Thanks,

John
 
A

acameltoe

Guest
OK, Thanks. That is what I figured but wanted to make sure.

Will try to get some time tommorrow to stack up on vitamin Guinness to fight off the cold, and test it out before we get whacked with another snow storm Saturday night and Sunday.

Thanks,

John
 
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