car was running fine 3 days ago except for an ocasional stall when warm. was advised to check the mass air sensor so i pulled it off cleaned it out and replaced it. now the car idles at 1400 rpms, drops to 900 ( which is where it always ran before ) for a second or 2 then back to 1400. besides a vacume leek, what else would cause this problem? i already swapped in a known working icv and still same problem. could it be the throttle control switch thingy on the bottom of the throtle body? maybe the fpr? have a smoke test scheduled for next week but if i can get some hepl here, well u know. oh yea, there is also a lag time in decelararion when you let up on the throttle.
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You have an intake leak or coil/ignition problem. TPS is worthy to check but since it goes up and down without pedal assistance I would rule it out.
This is not FPR issue as far as I'm concerned. -
when i first start the car she idles at 1000 then in about 3 or 4 min. she slowly climbs to 1400. while at 1400 if you rev it up and lay off the peddle, she drops down to 900 for a second then back to 1400.
hmmmmm
would this point anybody in a certain area to look?sigpicComment
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Clean or replace ISC valve and clean yuor throttle body out.Your signature picture has been removed since it contained the Photobucket "upgrade your account" image.
garage queen 91 bmw 325is / 1972 Chevy El Camino 355 sbc 450hpComment
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Clean ICV, look for leaks around your intake boot.Originally posted by KingBComment
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what is the isc valve? i already swapped out the icv w/ known working 1, didn't help. cleaned out the old 1 and put it back on, still no good. brand new intake boot. cleaned the tb out as best i could w/o taking it off, no new gasket for it till monday. maybe bad throttle pos. switch???
this sucks, the car ran like a top for the 2 years i had it and now i'm going to g-fest and i have to roll up there with this shit going on.
grrrrrsigpicComment
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I ruled out ICV since you claimed that you cleaned it. I still think you have an air leak. Check all the hoses, get 10$ VAC gauge and feed it into air line if needle fluctuate you have 100% air leak in the system.
Go ahead and pull the plugs (replace them), try starting without MAF and check resistance on all the coils+tps+icv.Comment
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I ran into this problem not long ago. Thought my ICV was bad at first. I realized that while I was fixing my glove box I must have bumped the idle control unit and loosened the harness for it. At one point my ICV was not even vibrating anymore. The ICU is about 2"x2"x1/2", and is located to the left of the ECU/DME. If checking that connection does not solve your problem it could be possible that your ICU is bad, I read that the green ones are the most durable.Comment
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It is also possible that your TPS is bad and is not switching from the DME controlling the mixture back to the ICU and ICV.Comment
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I know that it measures how far the throttle is open when you have the pedal down. It also acts as a switch to switch between idle and throttle (ICU and DME/ECU) which I believe is why it has three terminals.
I may have a link saved in my favorites on my personal computer that helps diagnose the idle control module and I will post it if I find it.
I used this to check my TPS, which is from Pelican Parts;
Also ANY leak in the intake system, especially between the MAF and the throttle body will cause the idle to surge or even die. Another good point to check is the breather line from the valve cover to the throttle body.Now before we begin to re-install the boot and other items, we will need to check the throttle switch on the bottom of the throttle body. This switch is used to control the idle control valve. If this switch has a fault, it will cause the idle control valve to operate incorrectly. In order to test the switch, first remove the electrical connector from the switch. Just push down on the metal wire, and pull it off. Inside you will see three terminals. From the left, they are numbered 2 then 18 then 3. First, connect a digital multimeter between terminals 2 and 18. Now open the throttle halfway and slowly let it close. When it is between 0.20 and 0.60mm from it’s stop, check for continuity between the terminals. Now, connect the multimeter between terminals 3 and 18. Now open the throttle slowly. Check for continuity when the throttle switch is within 10 degrees of being fully open. If you don’t see continuity while testing the terminals, loosen the screws on the bottom of the switch, and adjust the switch until it comes within these values. If you still do not have continuity, this means that the switch is bad and must be replaced. Pelican can provide you with this switch if needed. If the switch is good, re-connect the connector onto the switch.Comment
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