Pulsing Idle
 

So my car is being really annoying now. When the car is cold everything seems fine, except no accelerated warm up. However, when the car warms up the idle likes to pulse between 1k and 1.5k rpm. This is very embarrassing in traffic and at stop lights.

So, to ad to other problems, I have a single turbo set at 13 psi, stock primaries and 1300 cc secondaries. I took the car down to Tri-Point to have them tune it and they couldn't get the car over 167 hp, no that is not a typo. They said the fuel trim and timing were fine. They suggested that my Trust car back was causing flow issues since it seems to be disintegrating inside. I am picking up a Racing Beat single tip exhaust on Monday.

Does anyone else think the bad idle might be because of the bad exhaust as well?

Also, I did notice that the plug to my IAC valve came off last weekend and kept coming off. I zip tied it on and it's still connected, but I still have this issue. I don't know if the previous owner disconnected it and reconnecting it caused this problem.

Do you have stock cats still? They could be clogged. how does it idle below 1000k? Vacuum bounce? Have you checked compression lately?

Have a down pipe, but still have the second car. Tri-point said it looked good, but the muffler was shot.

The car doesn't really idle under 1000 rpm at the moment. When it's still cool it sits at around 800 to 850

And compression is the same as when I bought it back in January 112 psi rear and 95 psi front. Tri-Points isn't to sure why that is. I suspect at some point the previous owner replaced the rear housing but not the front. Tax returns next year will bring all new housings and an Arkins over haul kit.

Vacuum leak.

Not that I've found yet. Do you have any suggestions of where to start looking? I no longer have the rats nest so there aren't nearly as many hoses.

This seems to be a real issue right now, I saw two other similar threads on this scrolling down to mine.

I just noticed an other symptom. The car idles fine when it wants to, but when it decides it wants to do this pulsing idle, it runs my rpm's up to 3k with out my putting my food on the accelerator, then it drops back down to 1 k and pulses between 1k and 1.5 k. This really sucks while being stuck in traffic or the all to common red light.

Created a video to help show the problem.

Its a vacuum leak.

Okay, a vacuum leak from a particular spot? Do you have an idea of where to check? If it was a vacuum leak wouldn't this be a constant problem instead of an intermittent one?

It really is random as to when it decides to do this. However is seem to happen more often on a hot start instead of a cold one.

Vacuum leak use the clean throttle spray and spray the vacuum hose !

Then what, then engine does something?

Idle will change when the vacuum leak ingests what amounts to fuel. I'd start around the UIM, especially around any ports. You can also use a mechanic's mirror to visually check places without removing things.

Okay, so I found some Vacuum leaks I will fix tomorrow.

These should be capped
http://i291.photobucket.com/albums/l...ps0106a975.jpg

And what is this and where is the hose that goes to it?
http://i291.photobucket.com/albums/l...psbafc9597.jpg

Cleaned the IAC tonight also. We'll see if that helps tomorrow, it didn't seem that bad.

That is your double throttle control. See link below:

Banzai Racing FD Block-Off Plates Location

Based on your photos it looks like you're overdue for a full vacuum hose job. I'm surprised TriPoint didn't catch all these missing vacuum lines. Those connections should have a vacuum line or be capped depending on your setup.

The car is a single turbo and the rats nest has been removed. This was all done prior to buying the car. I've had it since January, but the idle problem just popped up about a 3 weeks ago. Also the car dynoed at 167 hp???? This is also a condition that started about 2 months ago and is a real head scratcher. I'm going to pick up the plugs for those nipples tomorrow.

Found this on-line, but the hoses are no where near this configuration now.
Attachment 667131

You didn't find any vacuum leaks. The four pipes in the picture go straight through the the LIM for sequential turbo control and EGR. The other picture is the disconnected double throttle. With the engine running, spray carb cleaner on areas that can leak like the LIM to block. It is very common to leak there because of the crappy paper gasket. When you get the carb cleaner in the leak it will be obvious.

Will try that tomorrow if the car continues to act up. Cool thing is my cousin just started working at tri-point last week.

Humm, looks like the previous owner blocked off the ACV (air control valve)

Since it's already been disabled, and after getting your idle stabilized, you may want to consider removing the double-throttle.... How to Disable or Remove the Double Throttle

Okay, so I capped off the four nipples in the pic, I also found four more on the outside of the intake manifold close to the turbo and caped those off as well. I haven't had a need to drive the car yet so I'll post up as soon as I get the car up to operating temp. I did notice in the garage though, I still have the same problem with the deceleration. If I rev the engine up, then take my foot off the gas, as the rpm's drop, they drop to almost zero then bounce back up to about 1000 to 1100 RPM. I just cleaned the IAC valve last night, so I have no idea why it's still doing this.

http://i291.photobucket.com/albums/l...ps0106a975.jpg

http://i291.photobucket.com/albums/l...psd145111a.jpg

http://i291.photobucket.com/albums/l...psc6c0a60b.jpg

http://i291.photobucket.com/albums/l...ps38a06af1.jpg

Uploaded an other video to show what the idle is doing now

You capped off both ends of the same pipe.........4 times!

Same pipe four times???? I've never seen a four sided pipe before. I was just going by what the vacuum hose diagram showed. I believe those pipes went to the twins when they were on the car, some sort of boost/vacuum information and the rats nest. I don't think they would run solid pipes through the intake.

And basically the video I posted is what the idle does before it reaches operating temp and when it hits operating temp is what you see in the second video.

I also just went down and sprayed the entire area around the UIM and LIM with carb cleaner and nothing happened. I imagine I fixed what ever vacuum leaks I have with the capping.

There are four pipes that run through the LIM. You put caps on both ends of four pipes. The pipes do not see intake manifold vacuum or pressure. The four pipes are a means of controlling the stock twins and the EGR valve via the rat's nest. Since you don't have a rat's nest or twins where are you going to get the vacuum from? Take a piece of four mm hose. Put it on the top nipple either side. Plug the top nipple on the other side with your thumb. Suck on the hose creating a vacuum. Let go with the thumb. You capped both ends of four pipes and proclaimed you fixed a vacuum leak. You did not fix anything. JDM intake manifolds don't have any pipes going through them. They go around.

So, I managed to drive the FD for a bout an hour. A side from the idle wanting to die on me that car seemed to work okay. Then I got out of the car for 5 min, when I got back in to start it, it did that thing where it jumps up to 3k rpm, them fluctuates between 1.5k and 2k rpm. I then drove on the freeway for about 35 min and by the time I got off the freeway the idle was fine. WHAT THE HELL IS WRONG WITH MY CAR?????

That's just weird, I wonder why they decided to do that??? Right now I'm just trying anything that might help me fix this problem.

So the pulsing idle is back with a vengeance. Someone please help me here, I'm really starting to get pissed off at the car. I've got a TPS on the way hoping that will help. I'm wondering if I didn't clean the IAC valve enough or something. Is there a write up on the specifics of cleaning that damn thing? Or are they known to go bad????

Could it be the MAP/BOOST sensor. Has anyone had this problem before and figured it out????

Typically with the boost sensor unplugged the car will barely run if it starts at all. Yes I've had the problem you describe...it was a vacuum leak.

a block off plate kit would be a great place to start. you still have the split air pipe it looks like. the thing that the air pump fed into and it looks uncapped and open. it seems as though a vacuum leak is for sure what you are chasing after. since you are singled already, this should be trivial. take off the uim and look around. use this https://www.rx7club.com/3rd-generati...-turbo-749702/ and you will be very easily able to find the leak.

the 4 pipes that you capped off, those pipe do nothing more than pass through the lim. if you could shrink down small enough, you could walk in on one side and out the other. they are just a means of connected the vacuum lines from the twins to whatever under the intake manifold so that the hose dont need to wrap around. pretend as is they werent even there.

as stated earlier, they see no vacuum or anything. they just exist.

Where abouts did you find your vacuum leak. I've sprayed carb cleaner all around the intake manifold and nothing happened. I actually posted a image I've been using earlier in the thread that shows the vacuum hosing for a single set up. It has been very useful in helping me understand what is going on under the UIM. I just feel like I've tried everything to find a vacuum leak and am coming up with nothing. The split pipe you mentioned is hooked up to nothing on the back either. There is no hose that goes down to a cat.

I tried cleaning out the IAC valve again last night, so we'll see how much that fixes things. The first time I cleaned it, the problem went away for a few days.

Yup, cleaning the IAC didn't help after all and I have no idea where my vacuum leak could be. I've tried the spraying carb/choke cleaner all over the place.

Also, I'm not saying that it's not, but if it is a vacuum leak, wouldn't the idle be doing this all the time instead of just when the car is fully warmed up?

So i just got done spraying the crap out of my engine bay with carb/choke cleaner. Everywhere I could think of, under the UIM, the throttle body, behind the IM, down by where the runners go into the block, checked my hoses based on the single turbo diagram. Nothing....Idle continued to pulse. No chenges in idling even for a moment. Unless someone has another idea of where to check for vacuum leaks, I'm at a loss. I just want a good running car, this fluctuating idle is not good in heavy traffic and the back to back red lights we get here in Los Angeles. This is my only car.

So I tried to check my MAP today with a volt meter, but I couldn't get the needs into the back of the plug, I even tried sicking safety pins in there and using those to connect to the volt meter, but couldn't get a reading. I was going off of the manual page F-167 and guessing by the pictures the A terminal is the one closest to the fire wall.

My FD had this same hunting idle, it turned out to be the gasket that sits between the intake manifold and the engine block. If I were you I would order a lower intake manifold gasket and upper intake manifold gasket, as well as throttle gaskets, then spend a weekend replacing them all from start of the throttle through to the block.

Not a horrible idea. Could this also be the cause of me dynoing at 167 hp?

Hard to say for sure if you have other issues going on at the same time that you don't know about, but I can confirm that mine was significantly punchier with the stock twins after replacing the LIM gasket.

Do you have a PFC and Datalogit? I watched the video again and it looks like your fuel cut is set too low. Also check your TPS with the Datalogit. You can see the PIM, should be between 3000 and 4000 at idle on a stock port. Hope this helps.

I do have a PFC, but I don't have a datalogit. I've not changed anything on the PFC since I got the car and this problem just started up about a month or 2 ago. The car also came with a street port engine, stock primary injectors and, I believe, 1300cc secondaries.

I currently have coming to me in the mail a TPS, a IAC valve, a upper intake manifold gasket, and lower intake manifold gasket and a throttle body gasket.

Hopefully at least one of these items will get my car back into daily running form.

P.S. I ordered up all the gaskets from Atkins Rotary and they were totally cool. I told them I was on the rx7club forums and they knocked off my shipping costs.

If this doesn't work, I'm offering anyone local a couple bottles of my homebrewed beer to help me figure this out.

I might have to just buy a bunch of silicone tubing & new gaskets myself. I am having a vacuum issue too.

How did you clean the IAC?

Thanks,
David

Fortunately my rats nest is gone, so it was real easy to get a 10 mm socket wrench in there to get the nuts off. I then sprayed MAF sensor in there, then I filled it with MAF sensor cleaner and worked the plunger with my finger until it started sliding smoothly.

Thank you! That makes sense and easy enough. I think I will be redoing the vacuum lines this weekend. I will clean everything then too. It is so weird, I drove it just now and it was perfect, amazing, an absolute dream, but last night would have no power and sputter/bog down if you pushed on the pedal more than about 30%.

Only difference is the ambient temperature outside. It's a really hot day and was cool last night.

-David

I'm also having the same problem right now along with the idling issues.

Unless it's a basic mechanical issue like a vacuum leak, this will be very difficult to diagnose without you taking Datalogit logs.