THC

Gentlemen,

I have stated what the car is many times so I will be brief this time. 1983 12A,

Problem has been missing at any steady RPM, particularly at 2500 cruise range.

What has been done to date: Cleaned & refurished the fuel tank and system, replaced corroded carb with another earlier unit. Replaced ignition wiring, plugs w/ NKG, Swapped Rotor cap form the 84 parts car, Coils test within proper range.

Results: runs much better, accelerates well, lots of power, smoother ect. But still misses at the 2000 through 3000 RPM range, runs great when accelerating.

PROBLEM PERSISTS
Continuing problem with engine missing @ any cruse, low load condition. That is operation on a level surface. The miss goes away as soon as a load is applied as in ascending a grade. If load metering of fuel is the problem, then where in the carb do I need to pay particular cleaning attention??

The exhaust presently terminates 20" past the Cat. Could the lack of back pressure be a source for the low load missing??

I disassembled the carb air horn, removed all the jets and cleaned, blew out, checked for obstructions and found none. I did not remove the center carb housing and clean the section containing the idle mixture screw. Do you believe this is the problem source??

I have had to buy parts to refurbish the brake master cyl and a new left rear wheel cylinder. Later this week after installing these components, I will have a stock exhaust installed. The exhaust supplier tells me the engine must have back pressure for the engine to operate properly. I really wanted to open it up a bit, at least to be able to better hear the engine. He further tells me I will see much improvement in engine operation and driveability with a proper exhaust installed. What are your thoughts on the above??

Best regards,
THC

REVHED

In my experience low load/light throttle missing is usually due to running rich.

First, what fuel pump are you running? Excessive fuel pressure can cause these kinds of problems. Also, make sure that the float level in both bowls is in the middle of the sight glass. Then, adjust the mixture screw by turning it in clockwise until the idle starts dropping and then back out maybe 1-4 to 1-2 a turn. If the problem is still there it's possible the carb jets may have been altered or you have a problem with the one of the external carb/emissions devices. I had similar problems before I ripped all that crap out.

As for the exhaust, if you're at all interested about the performance of your car do not put a stock exhaust on there. When the good people at Mazda designed it they had three things on their mind... cost of manufacture, emissions and noise level. A free-flowing aftermarket exhaust can yield big power gains even on a stock engine. Besides, no engine wants or needs backpressure. So, I suspect he might be telling you these things just to make a sale.

THC

Revhead,

Thank you for your thoughts. The fuel pump is a carter and the pressure is identical to the OEM pump. Unfortunately the cheap gauge I purchased is 2 psi off and falsely led me to believe the pump was bad. I have found an accurate gauge is about $45.00.

I will check the float level, it very well may be off. I will go through all the environmental crap!! Is there a diagram anywhere I could print out which I can use to bypass the emmissions crap and use this to possibly isolate the problem??

I have to have the emmissions crap as we have emmissions inspections here in southern Indiana across the river from Louisville, KY. I want to use this car as a daily driver and do a few auto crosses, SOLO II events. The goal is to beat my son who is 17 and drives a 92 Miata, HA!

There is an 84 Rx7 comming up at a Goodwill auction in October and I hope to get it at a reasonable price. My 83 has very little interior left. The 84 is in much better shape.

If anything the project is teaching me patience. In a couple of years, I hope to begin receiving social security and if I keep working I will have money to spend on the Rx7's.

Thanks,
THC

REVHED

Are you running the Carter without a fuel pressure regulator? If so, that could well be your problem as it produces quite a bit more pressure than the stock pump. I tested mine once and it was about 6psi at the carb which is too much.

CrazyJoe12a

Well if you're who I think you are, We have had MAY discussions at our local AutoX's. This is Joe with the Silver, loud 1st gen When you mentioned your son with the 92 Miata, it kinda gave it away. Well I'm glad to see you found the forums. If you still have my phone # don't hesitate to call if your still having problems. I'd LOVE to see another 1st gen out there with us.

Anyway, i'll be out there on the 22nd, hope to see you there!

THC

Joe,

I am the who!! This is fun. Must give you a call.
Am looking at another that has a blown engine for $150.00.

talk to you later.

THC