200 RPM Idle :(
 

So, yesterday I took my car over to a friends house to show him the progress of bodywork and he lives down the road and on the way back I noticed that somehow my idle very randomly dropped to about 200 rpms. So I thought apex seal went or something crazy. When I got home, check compression on both rotors, and that was ok, then I checked all the spark, and that was ok. So I figured maybe I went over a bump a little too hard on the way home and something in the carb jumped around and finally clogged it after not being "cleaned" after about 10 years. So I took it off and the intake manifold and cleaned it out because there was some weird pink stuff in there and sprayed carb cleaner down every nozzle and small passage way and let it sit over night. I then also changed the fuel filter at the pump to make sure that was good and also checked the fuel regulator gauge in the engine bay and that read 8psi, like normal, and so when I got home I put the carb back together and put everything back on and still the 200 rpm weird idle. So right now I'm going to browse the Hayne's manual to make sure I did not miss any small filters and go through my fuel lines to make sure I didn't miss any. I did drain the fuel tank the other day because there was bad gas that accidently got put in my car so my guess right now is that something is clogged somewhere. When I put the choke on, the engine idles fine at 1000-1200 rpms, like it used to do. So if anyone has any ideas what might be going on that'd be a great help. Thanks.

Is the idle still smooth or the same as before? Use your ears and listen to the idle. Are you sure it's idling that low, or is the tach just off and you assumed the 200 rpm was correct? I've had mine idling at 400 and it doesn't sound much different than 750.

Another thing I noticed is that during revs it seems like there is a ticking thing going on and it goes faster as I rev it higher. I'm not quite sure how to describe it other than that when it idles at 200 rpms, it like ticks the same way when revving it but slower, it comes from the exhaust though, like it's the sound of the car. I don't think the exhaust is clogged because I run headers to resonator to muffler, but I will check the resonator right now.

The idle is smooth, and the tach reads at the lowest bar right before 0, so I'm just taking a wild guess. The idle is extremely low though.

I think a good way to describe how it drives is that it sounds exactly like an ATV, and it will sputter/hesitate/backfire at low rpms, but when full throttle comes around, it still throws me back into my seat and sounds like nothing is wrong. Any ideas?

Check all of your ignition again. The ticking almost sounds like an ignition event. Spark leaks are best found in poor/dark lighting.

Will do. Should both leading and trailing have the same big spark or would the trailing have smaller? The trailing had smaller when I last checked, and that makes sense to me because why would it be as big if the holes for the trailing plugs are so small?

IIRC trailing spark is not as strong on mine, so that's probably fine.

What does the timing light say about spark consistency? Does it look like it's skipping?

Well I checked spark and all is good in that region, but not quite sure about timing. I don't think the timing changed at all during a drive though, but who knows. I've narrowed it down to that something must have happened when I went over a bump on a back road a little too hard and something went wrong then. I got a new brake master cylinder coming today, so I will replace that and if I can get a buddy over I will probably drop the gas tank to check to make sure nothing is clogged in there. Any ideas on what might have gone bad when I went over a bump?

Sounds like its ignition related. Are your sure both leading plugs are firing when its
idling?

The way you describe it, it sounds like its running trailing alone until you
accelerate. The rotary will run on trailing alone just not as well.

Spark should be the same between leading and trailing as both use identical parts. If the size of the hole in the housing had anything to do with it, the trailing spark would be hotter due to the smaller hole, think about it.

Hmmmm, that's true, didn't think about that, but the thing is the car ran fine with the spark the exact same as it is now. When it's "idling" now and i remove the trailing ignition, I can hear the difference, so I know the leading is definitely working the way it should. When driving the car at full throttle, the car sounds like it normally would and accelerates like it should, but not at low rpms/ low throttle. It sputters and bogs until full throttle. I'm currently in the process of dropping the tank, but it seems like when I drained it that the fuel came out like it normally should so I'm debating if I should go any further. I'll work on replacing the brake master cylinder until I hear further from you guys. Thanks.

What do you mean you can hear the difference when you remove trailing? Trailing barely does anything, so removing it shouldn't really have much effect. I know some people run without trailing just fine.

I mean I can hear a very slight difference. Like very slight.

when its dark out, raise the hood and run the engine. look for jumping spark on or around the coils, distributor, plugs, and wires.

Okay, I'll check that tonight then and let you know.

Wiggle your injectors and see if it smooths out.

Just checked and there was no jumping at all. I did replace the cap and rotor and cables very recently, so I'm pretty sure they're all good. And the engine has a Mikuni side draft carb, so no injector problem, but thanks anyway. I'm going to probably end up taking off the carb again tomorrow and respray it down with carb cleaner and see what happens.

My bad I did read that earlier but mind was in diagnostic mode and forgot that important detail.

Make sure your dizzy cap is on straight. They can get off-center and the rotor starts chewing the inside of the cap up. Will make a ticking/buzzing sound if its slight.

I'll check that out later tonight when I get home, but the "ticking" sound is from the exhaust. The tone of the exhaust is like the exact same as a fourwheeler. It's really wierd.

next thing i would check would be the exhaust flow. this will ensure your converter is not plugged. if you run the engine and place a towel over the tips, the towel should move very freely. i can post a pic if you'd like. the ticking could be a loose and swinging split air tube or a loose heat shield on either the underbody or on the conveter (if you have one..for some reason i keep thinking you have a 79..which wouldnt have a converter..)

Yeah, the car is a 79 with a newer engine, either 83 or 82, but my exhaust system is RB headers to a resonator to a muffler, so I don't think it would be caused by the exhaust system being clogged anywhere. I could take off the connector right before the resonator and remove that so I'm running straight pipes just to see if it would make any difference if you think I should do that.

Well this afternoon I took of the intake manifold and carb and tore the carb apart again and did a pretty thorough cleaning and found a thing that was loosened and put it all back together and back in with no success. This is really starting to confuse me. When I pull the choke, the car goes to a normal idle with no problems, but there is an occasional backfire. The problem was caused by going over a bump on a back road a little too hard. Fuel is getting to the carb with no problems at all, I've made sure of this. There is spark on all four plugs, but I'm not sure about the timing. The carb was cleaned out so there shouldn't be anything wrong with that unless I missed something. All apex seals have compression. Any ideas on this problem?

timing should not be affected at all. i know you mentioned a newer cap and rotor..but did you check to make sure the cap didn't get cocked? my tender blue 85 that i sold last year had a similar problem and i had recently installed a new cap and rotor and, who knows how the cap got cocked, but it did, and this is what i found(mind you the engine would still run mostly fine)

http://i636.photobucket.com/albums/u...b/DSC07204.jpg

http://i636.photobucket.com/albums/u...b/DSC07206.jpg

Just pulled the cap off and everything is good, looks like new. and rotor looks good. No excessive wear or anything.

And the fuel pressure regulator in the engine bay reads like normal. So I'm kinda confused with that because this sounds like a fuel pump problem or something.

vacuum leak? have you tried to just reset the idle speed and mixture?

I checked the vacuum lines and couldn't find any that were unplugged, but I will go over them again just to make sure. I also messed with all the screws that looked like the adjusted something and there was no dramatic change in anything, I will grab a picture then so you can see my carb, there also might be one in one of my albums. I'm heading out to dinner so I will get one in a bit.

Well here are the pictures, As you can see on each side it looks like there are 3 ''screws" for adjusting things. I'm not quite sure which one does what but they are mostly screwed the whole way in because that's where they were when I got the car so I haven't messed around with them at all besides when I just screwed them out to see if there would be any difference in the idle. There is another screw on top that adjusts something right where the fuel goes in, my guess right now is the idle for that one but I don't know. I really need to get this car running asap because my brother comes home from out west in a couple of weeks and I won't have a car to drive once he gets home if this isn't running. Thanks for all the help.


https://www.rx7club.com/attachment.p...1&d=1287327559
The whole carb

https://www.rx7club.com/attachment.p...1&d=1287327559
Side of the carb where it attaches to the intake manifold. (I cannot determine the maker of the intake manifold)

https://www.rx7club.com/attachment.p...1&d=1287327347
3 screws on right side of the carb. By right side I mean looking at it from passenger side of the car.

https://www.rx7club.com/attachment.p...1&d=1287327559
Left side of the carb. There is a vacuum hose in front of the 3rd screw.

https://www.rx7club.com/attachment.p...1&d=1287327559
Top of the carb where the fuel enters and there is a screw right beside there that adjusts something.


Any and all help is appreciated. I might end up tearing apart the carb again today and if I do, I will snap some pictures. If there is any picture requests of a place or piece, please let me know. Thanks.

i don't know anything specific about the mukini, but i have gone to weber school... if i were you i'd try to find a diagram of the carb, just so you know what does what. don't be afraid to play with it either, once you know what each part of the carb does it really takes away all the "magic"

1. looks like the idle mixture screw. if the carb was jetted properly, and is idling on the idle circuit this will affect the idle mixture. carb these get turned in gently all the way, and then backed out. if its a factory car its usually 2.5 turns. since yours isn't factory, just turn the 2 of them so they are even, and it runs the best. all the way in is lean, all the way out is rich.

2. dunno, if you're lucky its an idle air bleed. setting it kind of requires a baseline from #1 and the idle speed screw, or throttle stop to be set right. if you do decide to play with it, mark where you are now, so you can put it back. unscrewing it = more air

3. probably a plug, the transition holes are under there, that's how they drilled em at the factory, since its a screw, it makes it easy to clean and inspect.

if you want the "how to tune the carb" paper, PM me your email. you will have to translate from weber to mukini too. all these carbs have the same parts, they just have different names

Well, I did some researching early this morning and found 2 great resources for Mikuni Carbs. If anyone wants to post these somewhere and have them saved in the archives for other people who have a hard time finding things for their Mikunis, that would be good.

http://www.mikunipower.com/PHH01.htm

http://www.wolfcreekracing.com/index...d=21&Itemid=30

I didn't get much time to look through and read too much because I went with my dad to SAAC Shelby meet in Hershey today and I just got back. There isn't much daylight left and I want to drain the tank quick and put in new gas and see what happens. I will read through them later tonight once daylight runs out. I found out mine is the PHH 44mm, and even though Wolf Creek Racing is all about Datsun's, they have some good info.

Well I drained the tank tonight and walla, no success. :( But I did take some videos so you guys would get a better idea of what was going on. Here they are...


http://www.youtube.com/watch?v=_ft-oH70Rr8
In this video, I have the choke on, then I take it off, the idle drops way too much...


http://www.youtube.com/watch?v=5YK6jOzVfrU
In this video, I rev the car, and at first it bogs down, so I let off or else it would die, then I get it to rev up to about 3000rpms...


http://www.youtube.com/watch?v=1w1MF1-hZzk
In this video, I unplug a vacuum hose connected to the carb and nothing really changes, I followed where it goes and unplug those places and nothing really changes. (The hissing noise is the choke because I can't work around the engine when it shakes so bad at low rpms.)


So do these videos help out at all? Sorry for bad quality, my camera isn't the best.

that vacuum line at the dist has no vac at idle. it's port vac and increased with rpm to advance the dist. as for why it's idling so low, no clue. unless u just need to adjust the idle screw on the throttle itself.

Okay, thanks for clearing that vacuum hose up. I don't think its the idle screw because why would the car bog and sputter? I'm really confused.

dunno, but its a carb, at some point you need to get in there and mess with at least the idle speed and mixture....

its too bad you're so far away, it looks like it would be fun to play with.

Yeah, it's really a pain how there are no close people around here who have RX7's (specifically 1st gens). All my car buddies have 240sx's, haha. There is a small rotary shop over in E-town, but the guy there doesn't know much about carbs or much about 1st gens. They mostly do work on second gens, and they do a good job with them. In Lancaster City there are some Puerto Ricans in there that like RX7's but I don't think they would really want to come all the way out to where I live and help, and it's really hard to get a hold of them. I'm going to tear apart the carb again today and see what I can find. I'll have the spec sheet this time too with all the little parts ID so that will help. If I can, I will update later tonight. I'll grab some pictures too if I remember.

Well, I got to tear apart the carb yesterday, and it was helpful to have the manual. I was over at a buddies working on a lip for his 240 so I didn't get to grab any pictures. I think today I'm going to put it back on and run the car for a little bit and then take off the top and see what the floats look like. If there is gas in there, then I'm guessing that a passage way is clogged.

I also wanted to add that the only way you can get it started is if you pull the choke the whole way, but won't start with applying gas using the pedal. Is there any carb experts out there that know what this problem sounds like?

This afternoon I was able to mess around with mixtures and the main jets and that stuff and so far nothing has changed. The floats were both filled well. I really don't know what this problem is anymore. I really need help here, all my knowledge is about spent. I'm just going to go over the basics for the rest of the afternoon and see if I missed anything. I really don't want to take this to a mechanic because I know that all mechanics around here know nothing about my car. I'm officially begging for help here. :(

I did put some MMO in a couple days before the problem began, and the exhaust was shooting some small black carbon chunks out. Could this be the exhaust being clogged? Why would it not idle right if the exhaust is clogged though? And why would it sputter and bog too?

So I took off the headers to make sure it wasn't the exhaust being clogged, and it wasn't. Rotaries are also very loud with no exhaust system, haha. The one intake manifold nut stripped last night so I have to use a dremel and cut that off when I get the time. I finished bleeding the brakes and they're good. But so far no progress on what the problem is.

No luck yet, I dropped the tank and found out that I couldn't even get to the inside of it because the one screw was rusted and I didn't want to strip it so I put it back in, and the one nut on the intake manifold got stripped so I have to use a dremel to cut it off later this week and I found out I have 2 exhaust leaks that I have to fix sometime. I talked to my one buddy who is a mechanic and he's like I have no clue what the problem might be so he will be over to check it out one day this week hopefully, but so far nothing is working....

Problem solved, the air jet was loose and when the car accelerates it spins and it was off because of that. I'm not quite sure how to keep it in place, I almost want to use glue but that's bad, any ideas on what to use to hold it in place?

Which air jet?

Normally, gentle torque is enough to hold them in place. You could probably use a SMALL drop of low-strength (blue) Loc-tite if you had to.

Being as the jets are all made of brass, you don't want to make it too hard to get back out again.

It would be number 28 on this page, http://www.mikunipower.com/PHHCarbs/PHHservice23.jpg , I'm not at home right now so I can't take pictures but you can find the part name on page 24 here, http://www.mikunipower.com/PHH01.htm , there are two of them and they both move pretty freely when I apply throttle.

It's both of the pilot jets, they spin almost like they're free when I apply gas.

Gently lift the jet out of the carb and match it to the picture in the diagram you posted. Make sure the jet is not broken, and the threads are not stripping on either the jet or the carb itself. If you still have a problem, try the blue loc-tite as DivinDriver suggested, but be careful not to let any drip into the carb, or the inside of the jet--for obvious reasons. Given all the vibration from such a low idle, sounds like you are lucky you still have the jet. Let us know how it turns out.

I used the blue loc tite the other day and it turned out good, car idles very well and drives great. :)

Beauty!