I just bought a 93 Rx7 TT 5spd, car runs great, previous owner put a newer motor in it. The car breaks up at about 3k rpm and pops and misfires if you floor it, but if you rev it up slow it goes through the rpms fine. Also the car smells like its running really rich, i checked for boost leaks but didnt find any. I think maybe it has something to do w/ how the previous owner installed the motor. But i dont know what to check as I come from a dsm/evo backround. Any ideas to what it could be? really appreciate the help.

 

have you tried a simple tune up? spark plugs, wires, fuel system cleaning air filter, fuel filter etc, see if any of this helps, and also is there a check engine light on?

 

Check the map sensor the vacuum hose may not be installed on it correctly

 

What ECU? Any modifications to the car?

 

welcome to an life of both heartache and absolute joy!

 

Car has stock ECU, Blitz bov, some sort of hard upper and lower IC piping, exhaust. I tried putting fuel system cleaner through it, what kind of spark plugs do you recommend? and can someone link me or explain the spark plug order.

 

I had major break up at full throttle, but still good performance at light throttle last time I had my car on the dyno, a lot of the breakup was due to old plug wires, that weren't connecting that well anymore. I have some basically brand new wires if you want them, about 3000 miles on them...I'll ship them to you for $15, they are the stock NGKs, I will included a less than 3000 mile set of stock spark plugs as well so you can kill both of those birds cheaply and with one stone.. I have an LS1 in my car now and I am looking to dump these parts basically just to help people out. I am getting close to just throwing it all away as I need space in my garage and shipping charges are getting PRICEY.

Go with stock plugs, with your mods you shouldn't need anything different. The leading and trailing plugs are both marked on the plug and the rotor housing. You have to take off the intake elbow to change the wires, I usually had the best luck changing the plugs from the bottom of the car. There are tutorials on this site if you search.

There are MANY other sources for a breakup problem, but that is where I would start. You could have voltage issues off of your battery or alternator...it could be a tuning issue...it could be anything. But I would say, plugs and wires would be a good place to start. If you want to buy new ones, call Ray Crowe at Malloy Mazda, he gives great pricing to club members and offers excellent service. Search his name and you will find his number.


One more thing. I had a MONSTER 3000 rpm stutter in my car when the engine was warm and it had the stock ECU and the only thing that took it away was replacing the ECU with a Power FC (took me about a month of ownership...lol) This should be the first mod anybody ever does to their car. It smooths out EVERYTHING! Even with only light mods. The stock ECU, in my experience, is garbage. So it could also be that...

 

spark plugs and wires on this car are quite difficult. The spark plugs are VERY EASY if you do them from the bottom of the car. However for the wires, you cannot get them from the bottom of the car and the entire upper intercooler piping must be removed, along with 2 coolant hoses ( replace them if neccessary) attached to the throttle body, and remove the entire throttle body assembly, and lie it down on top of the engine manifold leaving the TPS still connected. DO NOT however completely removed throttle body, leave the TPS sensor plugged in to it, do not remove these 2 screws! (Other wise the TPS will have to be readjusted, or it may be damaged I learned the hard way!) Really as long as you leave the TPS plugged in, you wont have any problems. Unplugging the TPS from the connector, or not unplugging it at all is the best way to remove the throttle body
Heres some pics from my job

 

I am not sure how bad the hesitation is, but it is common on many FD's at around 3k, but since you say it is misfiring as well it probably is a sign of something worse.

 

I dont really recommend fuel system cleaner. It is kind of screwey stuff. I would recommend that you actually remove the injectors and have them cleaned. I have never really had any kind of luck with fuel system cleaners. I have ran them through countless fuel systems and not had any result (i'm a mechanic). The only thing i think they are good for is if you run them on a regular basis as some kind of routing maintenance. But even still i dont think they are usefull. It sounds to me like you are having some kind of problem relating to your map sensor. If you are new to the car i would recommend that you go through the basic maintenance things like plugs, wires, fuel filter, coolant flush (this one is kind of important because if the coolant is too old it becomes corossive and can damage the coolant seals in the engine which are the equivalent to a piston engine's head gasket). Having the fuel injectors cleaned by someone like kg parts, witch hunter, or doctor injector is a great idea. Then go and check the quality of your coolant lines, boost lines and vacuum lines. If the car has not had its vacuum lines converted to silicone i would recommend that you do that as well. If those things dont seem to correct your problem then i would recommend that you take the car to a competent rotary mechanic in your area. Good luck!

--Hank

 

thanks for all the feedback, the car barely has any of the vacuum lines connected, the map sensor on the firewall is connected and thats about it. I was told the emissions were all removed, theres no vacuum lines going to the wastegates, i tried to hook up the lines using a diagram i found on here, but no luck, alot of the things were removed, does anyone have a diagram for a motor w/ no emissions?

 

fixed my problem! searched all day and found a page w/ emissions delete vacuum diagram, and the resistor mod. got everything straightened out in about an hour or so! now she revs up like a kitten! it is still running kind of rich, any ideas?

 

My spark plug was light brown when I replaced mine. It also had some chips flaking off the tip where your is black. Are the spark plugs supposed to be black like that? What does it tell you when the plugs are light brown? Sorry to bring up an old post.

 

Is it doing it only after 3k rpms or does it do it as teh car goes into possitive manifold pressure(boost)? I am assuming you have a boost gauge installed? Could be a lot of things but we will help you figure it out here on the forums if you give us more info.

If it does it as the boost guages trasitions from vacuum to boost then the car is in limp mode. If it does it as the boost gauge hits 12lbs it is probalby fuel cut as you are over boosting the stock ecu.

Check for the two things I mentioned above. If it is neither, then replace your spark plugs and wires. Those are the first easy and cheap steps that can all be done within an hour. If that doesnt fix it come back with as much detailed info as possible.