Vacuum thumping noise

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Mar 28, 2010 | 03:05 PM

#16

pawpaw

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From: SW Va

Ok you say you've re-installed the OEM IAC & everything is back to stock, does that mean the stock MAF sensor & air filter ar in place also????

Have you pulled & checked/cleaned the PCV valve????

Disconnect the IAC electrical connector & post what happens to idle quality & to the rpm surge at 1200 rpm.

Mar 31, 2010 | 09:35 PM

#17

hella 4.0

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Yes everything was back to stock, MAF sensor, Airfilter, everything. I pulled the plug on the IAC and my idle slows down. When I raise the RPM's up to 1200 I am able to hold steady there and run it all the way up to 2000 with no erratic changes, nice and smooth control of idle. With the A/C on the idle is not as stable when the compressor cycles on and off. Engine seems as though it will die. Common sense to me, IAC is unplugged, it doesn't know how to idle :-P

I am not sure if I found the PCV valve or not, I located a plastic item on the rear of the driver side valve cover. It had wires plugged into it, I unplugged them and removed the hose from the plastic fitting. I untwisted the plastic piece and pulled it out of the valve cover. It has sludge on it, it rattled and there was as small amount of oil in the plastic piece as well as in the hose that was connected to it.

I hope I am doing something right

Mar 31, 2010 | 09:50 PM

#18

pawpaw

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From: SW Va

With the IAC unplugged the idle should drop & maybe it'll stall, that's normal & as it should be.

OK, so with the IAC unplugged & the A/C off, you can run it up to 1200-2000 rpm without any surge, did I read & understand that right????

With the IAC connected & the A/C on, if the IAC is working correctly, it should compensate for the A/C compressors load when it switches on, so the engine doesn't stall. If not, then the IAC is acting out, or it isn't getting the correct duty cycle up command, from the computer for some reason.

Mar 31, 2010 | 09:54 PM

#19

hella 4.0

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Yes you read that correctly. And yes, with the IAC connected and the A/C on, the engine does compensate when the A/C cycles on and off.

Any idea what that plastic piece was I pulled off?

Mar 31, 2010 | 10:52 PM

#20

pawpaw

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From: SW Va

Not sure what the plastic piece is, but I believe your OHC engines PCV valve is located in the hose, or maybe the plastic piece, anyway I believe it's located on the drivers side, firewall end of the engines valve cover.

Maybe try cleaning it with the MAF sensor spray cleaner, or other plastic safe spray cleaner, to remove the sludge.

Sice you don't have the CEL lit, I was thinking maybe the PCV valve was sticking open at the 1200-2000 rpm range & messing with the air/fuel ratio & thus messing with the idle speed & causing the rpm surge.

Sounds like the "thump you were hearing was caused by the replacement air filter, as all is quiet now, with the stock air filter & intake plumbing back in place.

The thump & idle surge happening at the same time/rpm, may have just been a coincidence & probably was, as you previously posted the rpm surge was happening before you messed with the air intake & filter.

Keep us posted on your idle speed surge trouble shoot.
Will be interesting to hear what you finally discover is causing the rpm surge.

Apr 3, 2010 | 04:33 PM

#21

hella 4.0

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Okay, time for some much needed investigation.

I am going to check out the PCV lines to make sure they do not have holes in them. I have been doing some in-depth reading here and found similarities in other symptoms with other rangers. Such as the 2000 rpm start-up.

I'll keep you all posted on what I find, if anything.

Thank you PawPaw for all your hard work, dedication, education, and patience to my cause! I am pleased to brag about this forum to my buddies.

Thank you,

William Keene.

Nov 4, 2010 | 08:09 AM

#22

hella 4.0

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I know what I did wrong.

Hey everyone,
In reference to my thumping sound, coming from the intake/IAC, I know what I did wrong. I was looking into getting a tuner from SCT and came across some helpful information about what to do when switching MAFs or changing the size of the MAF housing. PCM RECALIBRATION IS REQUIRED. I must have goofed something up with the PCM when I installed the Spectra MAF sensor adapter housing. I did not use the supplied re-sizing cones that correctly metered the amount of air flowing past the MAF. In which case my PCM didn't know what to do so it stopped sending fuel and now the truck is running lean; which is why my tailpipe never has any black soot; even though I am running 91 octane (I know it's not necessary, but it runs smoother

). So.. in a nutshell, if one wishes to change the MAF or the MAF housing, PCM RECALIBRATION IS REQUIRED

!

Thanks again for all the help everyone! I hope somebody learns from my mistakes.

P.S. Now.. let's see if my wife will let me get that tuner!

Nov 4, 2010 | 08:50 AM

#23

pawpaw

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From: SW Va

OK, good find & feedabck on your problem. Is it running ok now????

If your into chips, tuners, ect, maybe look into Bama chips, as they have experience with tuning Rangers.