RPM's fluctuating
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Dr. Wu 2000
New Member
I understand that the BBK throttle bodies have a idle air screw that you canroad rage said:When the car sits at idle (I warm it up) I can hear it in my house as it fluctuates. Also when I'm driving, I'll come to a stop and sometimes it will drop own to 500 rpm's and then go to around 700. Any ideas?
adjust to fix the surging at idle. I don't know if the MAC has that or not. The
idle air screw is on top of the throttle body and changes the position of the
butterfly when at idle. You may want to check that out if it applies
I am having to do that right now after my custom tune I had done. It may
take a couple times of adjusting and testing it to get it correct. Also, if it
is surging and you give it gas and then quickly brake, do you stall out ? I
have had that happen a couple of times
JonJon
Founding Member
I had that problem, I made it go away by adjusting the idle screw. The IAC had absolutely nothing to do with it since it died and I replaced it... but the RPM bounce was still there.
It doesn't drop at all anymore EXCEPT when I'm using the AC, but the drop is a lot less than before.
It doesn't drop at all anymore EXCEPT when I'm using the AC, but the drop is a lot less than before.
JonJon
Founding Member
JonJon
Founding Member
Replacing the IAC did NOT fix my idle drop problem. My IAC died and the new IAC still had the idle surge. I got an Accufab 75mm TB last month and adjusting the idle screw last week got rid of my idle drop (when coming to a stop). When I have the AC on it drops a little, but not as bad as before. With the AC off, it hasn't dropped since I adjusted the screwDrK MrK iV said:
pony_vert02
New Member
OR.... you can get a tune up! clean you injectors..check/replace your spark plugs.. do you notice any hesitation or drop in rpm's while driving?
stangman16
Active Member
I'm having this same problem with my '99 GT and it's all stock. Once I come to a stop the idle will surge to 400-500 and back up again to 700ish. Sometimes it doesn't do it, but most certainly when the A/C is on. I've replaced the IAC already due to it being faulty - How much do you adjust the Idle screw to fix this? I've tried injector cleaner as well. The car has about 75K miles and it's been doing this for the last 20K or so.
deftsound
Please ask me how much my supercharger cost
i have a 99 and mine startd doing it afte rmy offroad h pipe and straight through mufflers, i think its because the lack of backpressure
stangman16
Active Member
Wish I could pinpoint it that easily for mine, but I'm all stock - so I don't know what the deal is.
NaplesBill
New Member
- Aug 10, 2005
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Well, I have an '03 Explorer with the same motor as the 99-04 GT. I had a problem very much like everyone here is describing. It started a couple of days ago and just kept getting worse. Today I had to hold the gas and brake everytime I stopped to prevent the engine from stalling.
I decided to take a look at it tonight. I have an engine cover and when I removed it I kept hearing this sucking sound. It sounded like it was coming from the intake manifold. It turned out that the breather tube that connects from the passenger side valve cover to the intake plenum had a hole in it. I have no idea how the hole got there but I replace the elbow where the hole was and the problem is fixed.
It's the large breather tubing that elbows right at the intake plenum. There are two small cooling lines that connect at the same area on the plenum. It would stand to reason that a smaller whole or leak would cause less severe but similar symptoms.
I decided to take a look at it tonight. I have an engine cover and when I removed it I kept hearing this sucking sound. It sounded like it was coming from the intake manifold. It turned out that the breather tube that connects from the passenger side valve cover to the intake plenum had a hole in it. I have no idea how the hole got there but I replace the elbow where the hole was and the problem is fixed.
It's the large breather tubing that elbows right at the intake plenum. There are two small cooling lines that connect at the same area on the plenum. It would stand to reason that a smaller whole or leak would cause less severe but similar symptoms.
my 99 Gt was doing the same exact thing after installing a new plenum intake and throttle body, I replaced the idle air control valve (IAC) and disconnected the battery for a good 45 min. for the computer to reset ,after that works great the rpm hangs a lil bit but used to be worst, i also heard about a copper cap in the IAC tube you might want to look that up.
hotdog71
Member
IMO Important rules when it comes to GOOD quality TB's.
1, Never adjust the butterfly screw or any other screw as they are all factory set for your motor and will most likely not help. Unless you have bought 2nd hand TB and it was messed up before.
2, Never clean off the seal paste inside the TB that seals the butterfly when closed.
So far this has worked for me and many others i am sure.
1, Never adjust the butterfly screw or any other screw as they are all factory set for your motor and will most likely not help. Unless you have bought 2nd hand TB and it was messed up before.
2, Never clean off the seal paste inside the TB that seals the butterfly when closed.
So far this has worked for me and many others i am sure.
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