MikeFB

First problem- there is a sputtering and loss of power under a load that happens after about 15-20 minutes of driving. It seemed like either dirty gas or overheating.

The temp gauge only got up to a couple notches past C, which I was told is normal for these cars. I took the radiator cap off and let it run for awhile, and didn't see the coolant moving very much. I thought maybe a clogged coolant passage or a bad waterpump? Then I checked the fuel tank, it had rust in it so that's what I focused on.

I had tried to flush and coat the original tank with a POR-15 tank repair kit, but it was so rusty I had tons of holes afterwards. I instead used an 8 gallon fuel cell I had from a previous project. I plumbed the vent to the gas fume line with 1/4, did the main line in 1/2, and the return in 3/8. Finished it up today, no leaks and it works great.

Took it out for a drive afterwards, and sure enough the car started surging and sputtering after about 15-20 minutes. It got worse the more I drove, so I limped it back home asap.

Time to check into the cooling system a little more thoroughly?

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Second problem- When I started the car today for the test drive, the shifter wouldn't go into any gear. I tried for a bit to gracefully get it into reverse to back out, and finally had to just quickly jam it in to avoid any grinding. The car started moving with the clutch all the way in. I backed it out this way, then had to pop it out of gear to avoid stalling when I stopped in the street. I had to force it into first to get out of a neighbor's way, then second was hard as well. I got about two blocks away from home and then it was fine- normal clutch operation, normal shifter.

What could be wrong? Throw-out bearing sticking? Clutch out of adjustment? I'm not even sure what an RX-7 has for clutch actuation...mechanical, hydraulic?

Rx-7Doctor

iTrader: (13)

#1 problem. if you had a overheating problem and it started to do what you are describing. It would be rebuild time.

You need to be able to pinpoint the area of trouble first.
1). Fuel or lack of. When it acts up you need to verify if there is adequate fuel pressure and volume.
2). Do you have a failing ignitor when this happens. Need to verify adequate spark when it happens.

Is it happening under a load or can you duplicate the sympton by letting the engine run while you are in the driveway.

2nd problem.
Sounds like the clutch hydraulics may be failing.
Pull the boot back on the clutch slave and make sure their are no signs of leakage. On the clutch master you have to look inside the car for signs of leakage.

MikeFB

The car runs great for about 15-20 minutes, then it will start to spit and sputter. Starts out small, like a slight hesitation and hiccup at the upper range of a gear. As I drive more, it gets more frequent and more severe, eventually to the point of completely stalling out.

Edit: What i'm trying to explain here is that at first it happens under a load, while accelerating through a gear, then eventually it gets bad enough that I can't even free rev it and keep it running. When I first bought it I had almost gotten home, then I had to stop several times and let it sit. After a few minutes I could start it again, and get up enough speed up to coast a few more blocks through a residential area before I had to shut it off again. I had to do that like 6 times to make it back home.

When I drove it today after finishing up the fuel cell install, I know it had an adequate amount of fuel in the cell. As for the fuel pump and filter, those were new when I picked up the car. I realize new parts can fail, and it's possible the short run time with the rusty tank before I removed it could have possibly ruined them prematurely. I haven't checked the injectors, not sure how I would.

If it was injectors, wouldn't it have a problem at all times, and not just after 15-20 minutes of driving? Same thing with an ignitor? Do these things get hot after a certain amount of time in operation?

84stock

iTrader: (5)

Sounds like a plugged cat to me.

Man_in_black49464

iTrader: (1)

get the cat out then try agian.

Doc is on to something after 15-20 min the thermnostat would open up letting more coolant flow and chances are if it gets worse then you have a bad coolant seal thats leaking into the chamber.

Rx-7Doctor

iTrader: (13)

Like I stated in the previous post. Perform the tests that I have stated. Try to get it to act up while you are at home.

Without testing your wasting your time.

mazdaverx713b

iTrader: (91)

perhaps, if the coolant temp sensor is bad, it could be causing the engine to run rich, thinking that the engine is cold, and adding more fuel to the mixture, thus causing the stumbling you are experiencing. you'll need to test your ignitors seperatly. test the coolant temp sensor for s/g.

bliffle

If it's an internal coolant seal leak then one would expect clouds of white smoke at startup in the morning. Does it produce clouds of smoke when you start it in the morning?

MikeFB

Yup I understand the basics of troubleshooting- fuel and spark.

Kinda busy till this weekend, then i'll check them out more thoroughly.

I did a quick test today letting it idle in the driveway for about 20 minutes. It never did sputter like when I drove it, but it would have a slight miss if I held the throttle to about 3000 rpm. For a few seconds it would be fine, then it would miss and drop a couple hundred rpm, then do it again every few seconds until it was back down to idle speed.

BARF1

A plugged cat would make the car run like crap or not run at all all of the time, it wouldn't get worse as you drove then fix itself when it cooled down.

mazdaverx713b

iTrader: (91)

does the rpm jump at idle as well? also, have you checked adjustment of your tps?

Rx-7Doctor

iTrader: (13)

The TPS will not give the type of symptons that he is having. It will give other ones though.

The heat and load things are the key here.
The leading ignitor can cause a similar problem if has a poor connection or is starting to fail.

That's why the problem needs to be recreated at a time that testing can take place.

I've been here with a similar problem with one of my SE's. However it turned out to be the oddest longest diagnostic event that I have ever dealt with. At the end it turned out to be a defective distributor rotor that was only a few months old.

MikeFb,
What you can do is the pin test at the ECU. You don't have to get it to act up completley, just get it up to operating temp.

dean7

Where you at in Nebraska Mike? Im from omaha, and have a couple friends also that have rx-7's... if its an SE, I just took off my stock exaust from the header manifold, to the straight pipe. It worked great for me, and had enough pressure to open up the secondaries... if you want we can put mine on your car and see if that works... Otherwise, A quick ride in the car and I might beable to help ya (done alot of work on Rx-7s) .. Got a 85 se that im putting a new engine, tranny, carb intake, race exaust in this month
Dean
Numbers 290-9770

dean7

So hows she running now?