I am new to this sight, and soon to be new to the RX-7 world. I am about to purchase a 1988 RX-7 SE for around $900, interior and exterior are fair, it starts and drives just fine(thanks to me doing work on it). The car sat for 2 years untouched and undriven, It has approximately 119000 miles on it. The two main problems I am having with it right now are the oil pressure gauge(on the dash) pegs out to above maximum when started(I think it is a bad ground, but have not traced the wire to confirm yet) and it seems to have a intermintant idling issue. About every 5 starts, regardless of whether it is hot or cold if the rpms drop below 1000 it will die out if you dont give it any gas. If you give it gas and dont let it die when it happens and hold the rpms at 2000 for a minute or so it will idle fine. I have replaced the spark plugs, coolant temperature sending, I am fixing to replace the water pump, fan clutch and belts after I make the final purchase. I have already flushed all the old fluids and replaced with new. There is no smoke from the engine, and aside from the problems listed here seems to run good. So any help would be appreciated...

 

Okay, the gauge works by receiving ground, so if the gauge is maxing out it will never be a bad ground... in fact it means there is too much ground.

So I would be looking at a bad oil pressure sender or much more likely, someone broke off the senders condenser and then just hooked up the broken wire to ground.

And as a hint, 98% of the time suggesting a bad ground is like saying you have no clue about electrical systems at all. If there was a bad ground on this particular circuit either the gauge wouldn't work, or your engine wouldn't be grounded.

TPS should be checked first (it may be starting to fail) but also it sounds like the cold start circuit has been removed and possibly the intake temp sender is starting to fail, or the BAC is sticking.

 

yeah, I dont know much about electrical systems ... but thanks for the sugestions as to the idling issue.

 

Icemark,

If the oil pressure sensor wire was unplugged, and resting against the motor, wouldn't that peg the gauge? I thought that the sensor itself just varied the resistance, the lower the resistance to ground, the higher the reading at the gauge. Is this not correct?

Thanks...

 

Yep, that could happen too, but I would be pretty surprised as the way the plug works it really shields the connector.

More likely would be that if the sender wire is not hooked up, that the connector is ripped off and then it could sit against ground.

Pretty much if the gauge pegs on the 2nd gen, it is either the sender wire is pinched or connected to ground or the condenser is missing and someone hooked the condenser's wire to ground.

Or someone took apart the gauges, made the mistake of trying to remove the needle from the gauge and didn't assemble the gauge correctly... but in that case the gauge is pretty much pegged all the time, regardless of if the key is ON or not.

 

Lucky for me I work in shop with a mechanic who worked for mazda for 20+ years. The cold start reservoir was completely empty, so I topped it off with a 90/10 coolant to water mixture and bleed the system out. I also removed the BAC valve and thoroughly cleaned it. The car no longer seems to have an idling issue, but i guess time will tell... As for the oil pressure issue the sending unit looks to be intact and whole so I think replacing it will do the trick. One more question, does anyone know if Seafoam is safe for rotary engines?

 

Oh no, you mis-understood. The cold start system should be removed. There is actually a Mazda TSB that says remove it and cap it off if you find it on a car.

as far as Sea Foam, Mazda actually makes a combustion chamber cleaning kit that uses Sea foam for the RX-8, so it is safe to assume that it should be fine for a RX-7. But I would do the water treatment instead just because it will work better at cleaning and only costs the amount of a gallon of distilled water.

 

I already have a can of Seafoam laying around from my recently deceased Dodge Caravan. I am not familiar with the water treatment, but I'm sure it is on this sight somewhere just have to find it. This is a great sight, thanks for all the help and I will be posting pics soon of my new toy. I will warn you it is pretty rough right now but it just needs some TLC.

 

get an aftermarket gauge