I have a 3rd gen rx-7 and have been having bad idle problems..it idles really low and lumpy and feels like it's going to stall. It started one night after I was driving the car and I was stepping on it half throttle and i felt a slight stutter and could hear it in the exhaust, but drove fine as i continued to drive regular. When I got to the stop sign, it started idling really bad and kept wanting to stall. There's no error codes on the ecu and I've checked for obvious vacuum lines off to the map sensor and everything. I even replaced the MAP sensor and still no luck. If I rev the motor up it hesitates a bit and sometimes backfires.

I noticed today that the blow off valve is staying open even at idle and there is a constant stream of air coming out. Could this mean a vacuum leak or the blow off valve is stuck open? Could this cause my bad idle??

I'm going to check my compression later on today just to make sure that's not part of the problem and then try to check for any vacuum leaks and if anyone has any idea of why my blow off valve is staying open, I'll take off the intake manifold to check for leaks.

If anyone has any ideas please let me know.

 

Try resetting the ECU and see if the idle settles down

tom

 

Your bov should stay open when idle, beause you are applying vac to it..

 

Check the TPS, change the plugs and clean out your TB. By the way, the problem is not the BOV.. if it's venting after boost then it is fine.

 

I've reset the ecu many times and no luck. I checked the compression and the front rotor was mid 90's and the rear was low 90's but that was with a piston compression tester with a check valve so I'm not sure how accurate it is. And the blow off valve is venting at idle without revving or anything. Air is constantly and forcefully venting from it, which it has never done the whole time I have owned the car, you can hear the air coming out over the loud lumpy idle of the engine even. I will try checking the TPS tomorrow. I bought new spark plugs and tried and still had no luck.

 

You're not making any boost at idle! Maybe it's your air pump and not the bov?

 

I think you're confused on when the blow off valve opens. It opens when it sees vaccum. At idle, you seen nothing but vacuum. When you shift, you see vacuum in the manifold, so it opens the BOV, that's where you hear pressure being released.

Oh, nevermind, I see what you're saying. You don't think there should be enough pressure from turbos to vent as much as what he's describing.

 

It's not the airpump, I've had it removed for over a year now with no problems, that's why I'm confused about the blow off valve being open. It's venting at idle without being driven or revved up, as soon as I turn my car on air is venting out of it..you can put your hand over it and air is coming out forcefully. Could the blow off valve be stuck open somehow or a vacuum line off causing the pressure to be off and opening it??

 

I'm going to take off the vacuum line from the bov to uim and put a vacuum cap over the nipple on the manifold and turn my car on to see if the bov still vents at idle without any vacuum to see if the bov is stuck open or it's something vacuum related.

 

I took the bov off and it was fully closed. I put it back on and disconnected the vacuum line and plugged the uim vacuum nipple and turned on the car. No air was venting at idle anymore so this means the bov isn't stuck open and it's something vacuum related causing it to stay open at idle under no boost. I'm guessing whatever is causing the vacuum to keep the bov open is also causing my rough idle. Does anyone have any ideas what could cause this??

 

You've never mentioned you vacuum reading while it's idling. What is it ? ? ?

 

Yeah my Engrish sucks.. esp when insomnia strikes and I'm tired as ****.

Anyway.. theres a whole section on troubleshooting vacuum leaks... unfortunately vacuum leaks suck. Could be any part of the rats nest, maybe a cracked elbow... etc..

According to the forums, people have used both the Doctor's stethescope AND/OR propane with success.. Becareful with propane!

 

so a vacuum leak could cause this?? and I will check the vacuum at idle tomorrow during the day and start checking out the rats nest

 

Let us know how much vac.

 

vacuum at idle is around 14-15

 

how did you measure the vaccum ...at 14 -15

 

boost gauge

 

The bov quit venting at idle just out of no where today.

I forgot to mention before as the idle is bouncing up and down there is a clicking noise. It sound's like it's coming from around the intake manifold. Does anyone know what this is?

when the car is in neutral it it idles bad, but doesnt try to stall, when I put it in gear and try to drive the rpms drop even more and it feels like it's going to stall out. Whether in gear or in neutral the engine cause the whole car to shake.

 

dude, ive just done a fresh rebuild on my car and i have the EXACT SAME PROBLEM, lumpy idle and a clicking coming from the intake manifold. Just now the cars developed an almighty screech from one of the drive belts too though - so ill fix that, and let you know how i get on with troubleshooting the bad idle and clicking.

Have you recently done any mods to your car? if i know where has been fiddled with recently on your car (where the problem started) it might help me with where i need to look!

 

dude same here except i have a 89 gxl n/a, crappy idle and the same clicking noise next to the intake