I have a 138k mile 87 NA car that shows 100 psi on the front rotor and 105 psi on the rear rotor, with all pulses being even. The car runs fine a lot of the time but recently I am having problems driving it when it is first started. The car starts right up always but recently, instead of revving to 2500 on startup and then running fine, now it will only rev to about 1500, and then the idle immediately starts porpoising up and down constantly. It will do the rev up, down, up, down for about 2 minutes, then you can hear the engine note suddenly smooth out. However if I try to drive it at this point, as soon as I let the clutch out it starts revving up and down and it makes no power at all and wants to die. In neutral, I can not rev over 2000 or it will start the same pattern of revving up and down on me.

If I restart the car several times, it will suddenly run fine and make power and rev fine up to redline.

Any ideas? I thought maybe the weather is revealing a problem but it was pretty warm today, almost 60 degrees. The previous owner tells me the car was getting very poor gas mileage and making the front cat glow.

It won't always have these bad cold start manners, sometimes its totally fine and I can just power down the road 30 secs after starting, but lately not so good

Thanks

Steve

 

cats could be clogged, could be the cold start is misfuntioning i would take it out and use a block off plate since mazda put a recall on them. you could also have a bad AFM or your BAC could be functioning wrong.

 

the surging idle is almost certainly the TPS. check and adjust it properly.

 

+1 on the TPS
Search on how to Adjust your TPS..there are Pages on it
..and I would be checking the Catalytic converters to see if the are Not Toast.
If the original Cats are on the car,I would look into replacing them.
By the way,try NOT to "make power" after a Quick Start up and Go situation,especially when Cold.Letting the car warm up a bit is Good Rule of thumb If you want to keep the engine healthy.Otherwise you can Plan on getting the engine rebuilt soon.
Good Luck.Welcome,Rotor on!

 

Thanks. I will be working on the exhaust soon but since this problem comes and goes, I think it may be engine management related and not something that is unchanging. I will check the TPS setting. I do a lot of work on (piston) engines for a hobby and am well aware not to run a car hard when cold. I should be able to drive it cold though, where this car is not allowing me that. Multiple re starts in succession when the problem rears up, resolves it so I think I am looking for a sensor or connection. When the car is in its "unhappy" mode I can hold the pedal all the way down and the engine will quickly hit 2000 rpms, then drop, then keep doing that. I can make a video of what it is doing.

What's the deal with the cold start on these cars? I have dealt with a cold start injector on another make and platform but when you deleted the (also problematic) cold start injector on that other car, the ecu had to be reprogrammed such that the injector pw was compensated to allow a richer cold start once the injector was removed. Is that the case if the cold start is deleted on this car?

 

nah..you get rid of the cold Start on the car.you will just have to sit in the driveway a little longer to keep the car from stallin.I kept mine onmy N/a because I am in Canada..it gets a Bit Cold up here..(excuse me while I rub up against this Grizzly to keep warm will ya?)
Oh.. I got an Idea..Look up "rats nest removal."..That is all the stuff you can take off the engine that has to do with emissions,etc..it takes the engine down to it's bare Minimum needed to operate.It makes the engine a little bit neater,drops a couple pounds on it..
the Best Stuff to Peruse through is the Sec Gen Specific and Archives.It has anything done to the engine already Documented...alot of good Info.Trust me,.I just read for like 2-3 months after I got my First FC.and I did learn alot.(but nobody told me about the maxed out credit cards!).Cheers.Good luck.,STYX!

 

A glowing cat can also be a function of an air pump not doing its job correctly. Also check if your O2 sensor is up to speed. One way of checking the O2 sensor is by "pulling codes" but the engine needs to be hot for the sensor to work properly and thus throw a code that it is not working properly. The link below explains how to pull codes and narrow down the possible source of your problem.

http://www.teamfc3s.org/info/article...odes/main.html

 

Thanks. I am not deleting any emissions equipment, I want to keep this car running as clean as possible and an air injection system shouldn't be that much of a hp drain on the engine. The air pump is making pressure, I have checked if off the car. O2 is newer, within the last 20k miles according to the receipts and service records. I have only put about 25 miles on this car since getting it so I have had it up to operating temp, but not for long.

 

One more thing to add is checking the input and output values of the emissions control unit(ECU) check page 30 of the link below. This section of the FSM will also detail how to check the condition of the many sensors, valves and whatnot that are part in parcel of the rotary engine.

http://www.cochran-racing.com/FSM/s4...SYSTEMS_NA.pdf

 

I found that the electronic plunger that pushes against the throttle shaft, was disconnected (I think by me when I was working on the front auxiliary recently). I plugged it back in and the car has the 2500-3000 rpm rev when it starts now and I can drive off immediately without any hiccups. Not sure if this was the actual cause of my problem or if it was a fluke, but I did a bunch of cold starts yesterday and the car was fine. It seemed like the car took a few miles to relearn the warm idle speed once I plugged that plunger back in, it was hanging the warm idle around 1100 for a little while but it has come back down to normal and seems to be good now.

 

Oh dear god, guess what the "plunger thing" is that I had disconnected -- it was the TPS. I have worked on plenty of american made EFI cars but I had not seen a TPS like this before, I assumed it was an idle speed compensator of some sort.

That was *probably* why I couldn't drive the car after working on it. It runs great and I have been driving it around after work with no problems.

Woopsie!

 

Did you ever check the resistance(ohming it) of that "plunger thing" and if so what were your readings.

 

I have not messed with it, the car runs great, has the proper cold start 3k rpm flare, and idles at 750 rpms once warmed up so I did a victory dance and decided not to screw anything else up the other night. I will check it though

 

Look into the O2 sensor issue. The car will tend to appear to run fine with the O2 sensor inop (runs in a limp home, default rich mode), but that will eventually cook your catalyitic converter, and maybe foul the plugs and make for excessive carbon buildup. You can put a 12v led between the two center pins of the test connector; when it is lit the ECU is seeing a rich mixture, and not lit means it is seeing a lean condition. Once warmed up, and then run at 2000 rpm (steady) or so, it should blink on and off about 8x per 10 sec. The ECU does not always recognize that the O2 sensor is gone, and may or may not thow a code.