File

My rx7 has been acting up latly.. in fact its starting to make a weird thumping noise that i can hear in the airbox and in the exhaust... my idle has droped down (automatic tranny) and even sometimes my can has been known to die when coming to a stop if i dont slid it up into netural to bring the rpms back up. my exhaust also smells ALOT richer at all times and will sometimes have a little harder time trying to start up. keep in mind my rx7 is a 1993 with full factory exhaust.

First thing i checked was my spark plugs, i removed them and they looked clean. so i cleaned them up anyways just to make sure. that made no difference. and the only thing i can think of now that might be the problem is one of my cats is all F'ed up.

I wanted to know if anyone else has had these problems when their cats got clogged OR if you might think i have a different problem. please help me.

Mr. international

you might want to go ahead and replace your precat, they have a tendency to clog up also. I had problems with my main cat, which was causing my car to overheat. Thats BAD for rotaries! I replaced them both along with a full exhaust,and havent had any problems since. Also keep in mind that rotaries naturally run rich like you mentioned, do you smellit in the car, if so you might have an exhust leak somewhere under your car. I'm sure you have already thought of this, but i just thought i would share my past experiences . Good luck. :-)

kraked

I like to tell ppl to clean their throttle bodies when they have an idle problem. I did that on my fd along with a sparkplug/wire replace and it seemed to fix everything. You may want to check the TPS to make sure its set correctly.

mibad

O2 sensor connected?

File

Im also getting worse gas milage too... each tank gets less and less... something is happening to my FD and i cant figure it out. the rich smell just started the same time everything else did. it always smelled when it was cold... but never smelled when its been warm... now it does. its makes that thumping/missing/backpressor sound in my exhaust/intake. and no i dont smell the fumes inside the car.

BobfisH

describe the sound in more detail...

How many miles has the car done on the current motor? Decreasing gas mileage is a sign that the motor is on its way out. Have you had a compression test? Does the car drive ok otherwise?

Suggest also checking your earths, remove, clean, and reattatch them. Bad earths can cause them to conk out when stopping.

File

the motor runs perfectly fine when you are driving... the noise goes away above 1,500 rpms. but lower rpms just suck. what are earths?

I dont know how many miles are on the current motor. i know its not the original motor considering its got 103K ont he chassis and its a automatic... there is no way it can be the original motor; so says all the rotary shops i've talked to.

silver_7

not to be on the negative side....but my 1st motor died at 130,000. Check to see if ur airpump is working.....with that not working I was told that might help to clog ur cat and give u a lower idle. See if its turning on and off when it should. Check the TPS. U already did the plugs did u also change the fuel filter as well?

tcb100

"earths" is Brit for grounds.

If the car starts running rich it will drop your idle down but your o2 sensor ought to try to compensate for it. Decreasing gas mileage is also a sign of a bad o2 sensor. Try that first, it's cheap.

Would not explain "wierd thumps" though. If you cat is clogged you will have trouble making boost.

rajeevx7

iTrader: (11)

Earths (to a Limey) = Grounds (to a Yankee)
It is just about impossible to get the car to boost a consistent and correct pattern with a clogged cat...because of the blocked flow. When mine clogged, it would not boost past 5psi. Saying that, it still really doesn't sounds like a clogged cat to me. The pre-cat usually goes first because it gets much hotter then the next. Also, like ^^ said, spraying TB cleaner in supposedly helps in cleaning caked up carbon out of the housings on its way through the system, just premix with the next startup.
But, check your MaP sensor connection. That would also cause your same problems (it's my bet)

File

okay, i just dug into my engine bay a little bit. i checked the connection on my o2 sensor and its plugged in and everything. but that doesnt mean it isnt broken. i also started to dig into the vacuum lines a little. i removed that black vacuum chamber thats betweent he manifold and the intercooler pipe. under the vacuum box i found a blue female plug unplgged. i couldnt find any other unplugged plugs near it though. all my vaccum lines and plusg seem to be connected.

BTW my car isnt boosting anything higher than 5 psi. my second turbo does not even boost 1 psi. i checked those two connections under the manifold and vacuum box that control the turbos... i heard there should be a plug with a white strip... i dont know if its supposed to be on the left or the right... my plug with the white strip was on the drivers side. so i switched the two plugs just to make sure. i road tested my car and i didnt notice any difference. at all.

tcb100

If you look carefully, there is a white paint mark on the side where the white strip connector is supposed to go.

Stick a voltmeter on the o2 sensor once the car is warmed up and in closed loop. The stock o2 sensor is a single wire so stick a pin in at the connector for your positive lead and ground the negative lead somewhere in the engine compartment.

You ought to get fluctuations with the voltages running .200 to .800 with an average around .400-. 500 as the O2 sensor picks up, and signals for, rich/lean conditions.

If voltages flutuate, it's working. If the voltage is flat, replace the sensor, but make sure you have good connections on the meter leads.

If they stay at the higher end, something is causing the engine to run rich, at the low end, something is causing it to run lean.

My experiences with clogged cats were on-again, off-again inability to make boost and it sounded constipated. If you never make boost it's still a possibility but you should have noticed the cat coming apart over time. It's usually not a one time shut-down thing.

And obviously, check your hoses, hoses, hoses and make sure your map sensor is hooked up.

CantGoStraight

Since you still have the full stock exhaust, is it possible the motor was replaced and you actually have 103k on the stock exhaust system ? ? ? ? You can dump the precat and still pass smog (if you need to) on the stock main cat once the car is warmed up. I'm leaning towards restricked exhaust if your gas milage is deteriorating as well as idle and stalling.

File

This might be a dumb question... but i should disconnect the o2 sensor after my car is warmed up and still running?

Anyone know what that weird blue plug is that i found? and where is my map sensor? ever since i bought this car ive been working so much that i cant find time to work on it. sorry if i sound a little new... this is the first FD ive owned. But i do build my own cars so i know i can fix my FD myself as long as i know what to look at that could be causing the problems.

mibad

Download the factory manual. Do a search on this site and you'll find a link to it. Weird blue plug isn't used except on california cars. No reason to unhook your O2 sensor. If it's not working unplugging it wont make any difference. If the O2 sensor has never been replaced then it's about time. A Bosch sensor is about $120. I'd take the precat off and check to see if air flows freely thru it. You can replace the sensor while you have it off.
The map sensor is the little black gadget on the driver side firewall. It has a 3 wire plug and a vacuum line connected to the bottom of it. Check all your vacuum lines to make sure they aren't brittle.