PVC Cause High Idle?
06-19-08, 09:39 AM
#1
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PVC Cause High Idle?
Pretty simple and straight forward question here. Would a disconnected PVC line cause a high ilde? I recently finished a fresh rebuild and have put everything back together and started the car. I am having a problem with my idle though. When I get it started it idles at 2000 RPM and if I turn the bleeder screw all the way tight and then mess with the TPS screw I can get it to start bouncing from 800-1500 but it doesn't sound very good. When I loosen these back up to pre rebuild positioning it goes back to 2000RPM.
The reason I ask about the PVC(which I THINK is the pipe that feeds back into the oil filler neck) is the last time I looked I didn't have that line feeding back into the oil filler neck. It was basically not connected to anything at the time. Since then I have put it back into place on the oil filler neck but I haven't gotten a chance to start the car since. I was searching for a few ideas as to what was wrong with my idle and found one other person in a older thread bring up the PVC. Could this have been my problem? If not what else do you suggest I check? Is there a way to check if my have a major vaccum leak somewhere? Any help would be very much appericiated.
The reason I ask about the PVC(which I THINK is the pipe that feeds back into the oil filler neck) is the last time I looked I didn't have that line feeding back into the oil filler neck. It was basically not connected to anything at the time. Since then I have put it back into place on the oil filler neck but I haven't gotten a chance to start the car since. I was searching for a few ideas as to what was wrong with my idle and found one other person in a older thread bring up the PVC. Could this have been my problem? If not what else do you suggest I check? Is there a way to check if my have a major vaccum leak somewhere? Any help would be very much appericiated.
06-19-08, 12:05 PM
#3
The presence (or lack thereof) of a PCV line by itself won't cause a vacuum leak or high idle - unless you didn't plug the opening at the UIM that it normally fits into.
If you had everything apart, you probably need to go through the 3 or 4 throttle body mechanical settings to make sure they are OK. You also need to check the throttle cable to check that it isn't holding the throttle plates open. Once you have those items sorted check the TPS settings. The mechanical settings on the throttle body affect the TPS so make sure those are OK first.
By the way, don't "mess with the TPS screw". You adjust it using a volt meter. Check the FAQ for a thread on adjusting TPS and other threads on idle. Plenty of good info already in various threads on here.
If you had everything apart, you probably need to go through the 3 or 4 throttle body mechanical settings to make sure they are OK. You also need to check the throttle cable to check that it isn't holding the throttle plates open. Once you have those items sorted check the TPS settings. The mechanical settings on the throttle body affect the TPS so make sure those are OK first.
By the way, don't "mess with the TPS screw". You adjust it using a volt meter. Check the FAQ for a thread on adjusting TPS and other threads on idle. Plenty of good info already in various threads on here.
06-19-08, 12:59 PM
#4
RX-7 Bad Ass
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First, it's PCV - Postitive Crankcase Ventilation. Not Polyvinyl Chloride 
.
A high idle can ONLY be caused by air getting around the throttle body. Either the throttle isn't fully closed, you have a vacuum leak, etc.
The car stock will idle about 1500 RPM until it warms up - this is the thermowax doing its job.
Read the stuff in the shop manual about idle and adjusting idle.
But, to answer the original question, an unplugged PCV can cause a high idle as it's a post-throttle-body vacuum leak, MAYBE. But, you should be throwing that thing out - do some searching on PCV, the '95s eliminated the PCV valve, it's not needed. Just cap the one nipple on the oil fill neck and the intake manifold - cap the intake manifold hole WELL, it's a large cap that can easily blow off. Glue it on and clamp it on as well. With that done, you should just have the one hose coming from the oil fill neck going down to meet with the metal line that goes over to the turbos - it eventually feeds into the primary turbo inlet duct.
Dale
.A high idle can ONLY be caused by air getting around the throttle body. Either the throttle isn't fully closed, you have a vacuum leak, etc.
The car stock will idle about 1500 RPM until it warms up - this is the thermowax doing its job.
Read the stuff in the shop manual about idle and adjusting idle.
But, to answer the original question, an unplugged PCV can cause a high idle as it's a post-throttle-body vacuum leak, MAYBE. But, you should be throwing that thing out - do some searching on PCV, the '95s eliminated the PCV valve, it's not needed. Just cap the one nipple on the oil fill neck and the intake manifold - cap the intake manifold hole WELL, it's a large cap that can easily blow off. Glue it on and clamp it on as well. With that done, you should just have the one hose coming from the oil fill neck going down to meet with the metal line that goes over to the turbos - it eventually feeds into the primary turbo inlet duct.
Dale
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