Hi I just wanted to first off say wow, what an amazing board, the information here I have been reading through is nothing short of amazing. The knowledge some of you have regarding the RX is off the charts!

Ok here is the problem, I have a 1994 RX7 Touring, I recently had work done and now nothing is the same. I will do my best to explain the symptoms. Hopefully someone will be able to shed some light on this for me.

The work I had done was getting a faulty EGR vavle sensor replaced. The check engine light would stay on until this was replaced. In order to replace the faulty sensor, I had to buy an entire new EGR valve. Apparantly it is pretty deep in the engine, and the mazda dealer had to take apart a lot of things to get to it.

I get my car back, and here are the problems I am seeing.

IDLE
When starting the car, instead of going to 3000rpm when I start, it goes to 2700, then 3000, then 2800, then works its way back down to 1000, at that point, it goes from 1000 to 1500, stays at 1500 for 4 seconds, goes back to 1000 for 4 seconds, back to 1500 for seconds, back to 1000 for 4 seconds, it repeats this cylce about 6 times then goes from 1500 to 800 where it stays relatively steady. The other idle problem is when I am slowing down. Lets say I am in 4th gear doing 50, if I hit the clutch, the RPM's fall to 2000 and stay there for a bit, then very slowly work down to 1000. When I stop at a light, it stays at 1500 for a bit, then slowly works its way down to 800.

KNOCKING
On a cold start the engine seems very instable, I hear a knocking sound and feel a lot of shaking, at times it sounds as if it could stall, but the RPM's are not reflecting a stall. I cant tell if the knocking is my exhaust or engine itself. After everything warms up it sounds fine.

HESITATION/BUCKING
Normally i start the car and let it heat up completely before I drive it. This bucking happens a lot for the first 15 minutes of driving. I will go to 4000rpm in 1st, shift into second give it 1/4 gas, and it bucks about 6 times before finally smoothing out, it feels like i am nailing the gas and taking my foot off really fast 6 times. Same thing happens in 3rd and 4th gear. After driving more, this seems to go away a bit.

Hesitation is happening all the time now, I cant shift smoothly through the gears unless I bring the rpm's to around 5000+ before I shift. Once the turbo does engage, it is smooth as can be, but when I shift around 3500-4000rpm into the next gear, i hit the gas 1/4 down, i feel it catching, then it hesitates with a slight buck, then takes off without any problem. It is very frustrating. If I run through the gear slowly without letting the turbo kick in, I have no issues at all no matter where I shift.

I have replaced the spark plugs, no help. I am about the replace the wires with MSD high performance 8.5 wires, maybe that will make a difference.

I am pretty much at a loss here, what used to be a joy to drive turns into a swearing fit everytime I shift. I have brought it back to the mazda dealership 3 times and they cannot fix this.

The car as 85k miles on it and prior to this the engine was in perfect shape, I have always babied the car, proper warmup, proper cooloff, etc......

Any advice would be greatly appreciated.

Thanks!

RXJoey

PS where can i get an oem r1 rx7 strut bar to mount over the engine? and will this really make a difference? I cant imagine it handling any better than it does right now. If no oem avail, what is a good aftermarket alternative?

 

To be honest, i am no expert, just a mechanic. I would have to guess fuel pump issue, if you didnt mention anything and just gave me the car to drive. Seems like when you shift and the secondaries come online, your ok, just if you shift and the primaries are on does it buck. Also, if you havent done the rats nest with hoses yet, now would be a good time to do so. Although i would love to explain a few things to you, i hate typing, so gimme a call if you have more questions. 315-725-9901. I'm not busy now, if you want some help.
Josh

 

damian had a thread on the tps sensor and adujstment, I would check that out, and search it is a common problem

 

I can't say what your problem is, but it is very unlikely to be a fuel pump problem.

A front strut bar will really solidify your front end. It will help your handling. Any strut bar that fits well will do a fine job.

 

The symptoms sound like the TPS is out of adjustment. It can't hurt to readjust it.

Damian's write-up:
https://www.rx7club.com/3rd-gen-archives-73/fixed-my-idle-problems-backfiring-bucking-more-242321/

PS: I hate to think what the dealer charged you for an EGR valve. I would have bought as many as 2 or 3 used ones (very cheap) before resorting to that. Also, IIRC it's right above the turbos and attached to the LIM, which isn't hard to access at all.

Dave

 

Well, not nessesarily fuel pump, but delivery... If you have a vacuum line that comes off, the tps and IAC need to compensate for the extra air that is going into the engine... hence the idle surging...

Once the computer levels out after 4 or 5 trys... it should idle ok. Until you touch the throttle again, and change the need to a new mixture. The computer isnt designed to run with a vacuum leak. Especially an RX ECU.

Like i said i am no Wankel expert, but i am tying to diag a drivability problem online. After checking all your vacuum lines, make sure your solinoids are good. this takes a little time to figure out, and lots of patience. I don't know enough about the 13b in particular to lead you to a more exact road, but generally speaking, start with vacuum lines, all 45 feet of them...

 

just to bust your chops...

if you had been reading as much as you say you have, you should know not to take your car to the dealer

you can find a used strut bar here in the Parts for Sale section

 

I'm wondering if you might have a vacuum leak from them doing the EGR valve. Any air leaks after the throttle body will mess up your idle and make the car run weird.

If they did the job, and it's been crappy afterwards, they didn't do the job right. In that case, they should fix it and get the car running right. It was running properly before, but just with a CE light from the EGR.

Once you get that ironed out, you need to either learn to work on the car yourself or find a rotary specialist near you. Seems like there's someone in SC that's a specialist, can't remember.

Dale

 

Get the vacuum diagram & check your vacuum hose carefully to make sure they are all attached and attached correctly.

Also make sure your Idle Speed Control is plugged in.

The dealer unplugged something or hooked up hoses incorrectly.

Before getting a strut bar, replace your vacuum hoses.

 

maybe a clogged fuel filter??? It make not fix the whole problem but at least you will have one element solved.

 

Thank you VERY MUCH everyone, I have a lot to go with here. One thing I left out that is probably very important.

There is a strange grinding sound behind my dash ever since this work has been done. I hear it at ide and when i am decelerating. It sounds like someone is sticking a piece of paper in a fast spinning fan, only way I can describe it. I only hear it in the RPM range 750-2500. If i am at idle and hit the gas, as the rpms fall i hear it through that entire range. While at idle the sound will at times go away for a few seconds, then come back. Sometimes it is loud, sometimes it is soft. I found out while trying to troubleshoot this the other day that when the sound is audible I can actually feel the vibration with my foot if i have the brake depressed. Pumping the brake also seems to exacerbate the symptoms. Any thoughts on this? Could this sound be tied to my hesitation, idle, bucking as a result of the valve I had replaced by mazda?

Thanks again for the great replies. I am very happy I found this forum.

RXJoey

 

the car will buck within the first few minutes driving it because of the fuel maps the ECU is running for the warmup/startup cycle. thats nothing to worry about, if it does it ALL the time then thats something to worry about.

 

Hopefully that sound isn't something foreign that suck down your turbo while the dealer was working on it.

 

My car does the same thing (rpms not dropping) and I hear that noise on decel to. It kinda sounds like a bogging noise under the hood. I checked the TPS already and it is fine. Any ideas?

 

You got to take it back to the dealer, I know you've done it three times but they've screwed something up when they put the car back together. Don't take the car back until it runs right!

 

Turns out the noise behind the dash was the brake booster hose. When I had the feul line recall done, i guess this hose was part of the many they replaced. They threw that old hose away otherwise I would of had them put it back on. This is the 3rd one they have put on now, this newest one has made this ticking/grinding sound louder and more consistent than the previous.

If you open the hood and grab the hose the tapping that you can feel is consistent with the speed of the sound you hear in the cabin. Apparantly there was a TSB on this, 011/97.

I am not sure why I couldnt hear a peep with my original, and now seemingly every one I come across I can hear very easily inside the cabin.

Are all these hoses defective? Is it just the nature of the hose and I got lucky that mine didnt make noise in the first place? I dont know. I am going to try modifying where the hose line connects to the fire wall with the flange nut and rubber mounting that the TSB suggested and see what happens. It is supposed to damped the sound a lot.

All in all this is very frustrating.

RXJoey

 

The TSB takes less than 5 minutes and it does work. You'll still hear a faint hint of it occasionally, but it's a lot better than without it.

 

Some people (myself included) have solved hesitation/bucking issues very similar to yours with an aftermarket ecu. Of course, this is a somewhat of an expensive "fix". You might want to try adjusting your TPS, and if that doesn't work, search the forum for hesitation/bucking threads and their fixes. BTW, before I got an aftermarket ecu, I tried various things such as adjustment of TPS, and various maintenance items. None of them worked.

I dont have data to back this up, but I believe that these problems are caused by the stock ecu not delivering fuel properly at certain levels of throttle. So the hesitation/bucking is caused by the ecu cutting or oscillating the fuel level. I feel that it is due to fuel cut because it doesn't display symptoms of running overly rich. This is the reason why you experience the bucking at around the same rpms and at all gears.

The pfc requires clipping of emission related wires from the harnesses. I also have a theory that the emmission related crap is also causing problems on the stock ecu.

I was set on buying an oem strut bar, but due to lack of availability (and impatience) I decided to buy an aftermarket one. Osumo3 is selling adjustable GAB strut towers for $80 + shipping. I felt this was a deal I couldn't pass up on.

https://www.rx7club.com/showthread.php?t=425330