EMATTOX_82FB

1982 Mazda RX7 GS, 5 speed. Stock 12A with stock Nikki

I am having a problem with the car falling on its face (sometimes dying) under load. It’s like I am hitting a rev limiter that doesn’t exist (bogging?). Sometimes it happens just cruising around lightly on the gas to hold speed, sometimes under hard acceleration. I have seen no consistency with what gear it's in or the speed I'm driving. I got up to 55 a couple days ago before it bogged, some days it wont do more than 20. The car has never had idle problems once warmed up, idles great at 1k and currently gets 3.9-4.1 PSI of fuel pressure. I'm also pretty sure it’s never had problems revving in neutral. Carb rebuild has no more than 200 miles on it. Accelerator pump squirts fuel. I think the car previously sat for roughly 20 years (haven't gotten around to changing all the fluids/belts), and I have put 1800 miles on it since purchased beginning of June. I’m not sure what it could be, I feel like any issues I haven't addressed (timing, vacuum leaks) would cause problems with idle or at least be somewhat consistent.

And yes, I have searched. The most common fixes to people who seemed to have similar problems were: Fuel filter, fuel pump, accelerator pump, carb rebuild.

Here is some details/storyline as far as my thought process and what I have done:
When this problem first started, it would happen strictly from 55+ mph or going uphill, no other issues. I finally got around to changing my fuel filter which was super nasty and clogged with red gunk. This worked well for a while and was the solution for a few filters, changing them every couple weeks. Funny enough at this stage it would never die.

Eventually I changed a fuel filter and it only lasted about 2 days before the problem popped up again, this time about 40mph. The filter was clearly clean enough to run but I changed it anyway, no change. I got a cheap fuel pressure gauge from harbor freight and discovered I was getting about 3 PSI. I then changed the fuel pump, looking back maybe not the right move but whatever. Now the car had good fuel pressure with the brand new pump (about 4.3 PSI). No change in the problem, even with good fuel pressure.

At this point I was trying to avoid a carb rebuild. I had broken the vacuum line off of the yellow solenoid which operates the shutter valve. I figured maybe it was closing when it shouldn't have been, and went down a wild rabbit hole trying to remove the flap in the intake manifold. I eventually succeeded in permanently removing that “feature”. In hindsight this wasn't necessary and ultimately made no difference with my issue.

Eventually the issue worsened to the point where I couldn't get out of first gear or past 10 mph. Frequently the car would die after falling on its face at 10 mph. Also to get going I would have to rev the engine up to 3k and then very slowly let out the clutch, otherwise it would just stall no matter what.

I finally rebuilt the carb, what do you know, it has super nasty red gunk everywhere. I did not touch the float seats, I saw sterling's rant about not messing with floats that once were in a working system. Cleaned all the jets, everything (to my knowledge). After a couple small hiccups I got the carb back on and running correctly. I thought for sure the carb clean fixed it, for a few days the car felt great, pulled nicely to past freeway speed on a 40 minute drive. Then the problem as described at the very top came back. I’ve been meaning to get the gas tank cleaned, but again I'm getting enough fuel pressure.

From what I have heard this is not an rare problem, I have tried all the common fixes I have found so far on here. I appreciate any ideas or tests you suggest, happy to answer clarifying questions. I am new to this so hopefully it's just something little I overlooked.

Thanks,

Elijah

EMATTOX_82FB

The only thing I can think of is maybe that there was some gunk in the fuel line that got dislodged and is clogging the carb up. Not sure why, but it feels like a long shot. By the way, did I post this question in the right spot?

diabolical1

iTrader: (3)

welcome to the board.

my first thought would be check the filter at the pick up (in the tank).

other thoughts are:
1. are your secondaries opening?
2. did you choose the right gasket in the rebuild kit?

EMATTOX_82FB

Thank you, I was unaware there was a filter in the tank but I am sure that would be pretty nasty. If this was clogged up that would affect my fuel pressure, right? (my goofy gauge is hooked up right before the carb). Anyways I would think my secondaries would be opening if I was able to make it to 55 a couple days ago, but I'm really not sure at what point those should start to crack open. I used the 79-85 kit from atkins rotary (where i've bought all my rx7 specific parts from) and everything seemed to work pretty well. To be honest I think there was a much larger chance that I messed something up than wrong gaskets. It was my first carb rebuild so I was going off a video and my shop manual that came with the car.

I appreciate the suggestions, I will look into that filter

diabolical1

iTrader: (3)

well, it would appear that you don't need to check on it since your car is an '82. i went searching to see if i could find a photo for you, and found this thread (and another) that states '79-'83 models did not use the in-tank filter.

https://www.rx7club.com/1st-generati...-sock-1136332/

your car can hit 70 MPH without working secondaries - much less 55 - it just takes longer. they should be opening somewhere around 3500 RPM, if i recall - certainly by the time you hit 4000. there is a rod that sits in a little bracket (we all refer to it as the "teeter-totter", so you can search with that term and reference photos should be available for you to see, on the board). it costs you nothing to check it out.

as far as the gaskets go, the rebuild kits that i've seen usually come with, like, 2 or 3 gaskets that look very similar to the average joe. however, they are different, and using the wrong one can lead to issues that include the secondaries acting weird. i've never bought a kit from Atkins, so i'm not familiar with the one they sell.

here is a recent thread that illustrates what i mean: https://www.rx7club.com/1st-generati...oding-1163836/

EMATTOX_82FB

Wow, thanks. Thats very interesting you can get going that fast on just the primaries. A couple days after the carb rebuild I was able to hit 85 while the car was acting normal (next day was the end of that). So they are at least kind of operating, or used to be. If you think the incorrect gasket (without the holes) would cause problems and dying at low speed, I will most definitely take the carb apart and have a look. It's for sure a possibility the wrong gasket is on there, I just don't have enough experience to know if that would kill the engine. Thanks again.

j_tso

iTrader: (2)

I was thinking the same. Can you see the fuel pressure gauge while driving or is it in the engine bay?

EMATTOX_82FB

Unfortunately it is in the engine bay, some well placed tape might be able to stick it to the outside of windshield. It holds steady at 4 PSI while revving in neutral. Also (terrible idea, I know) at one point the rear was on stands and got to about 15 mph, held steady at 4 there as well. I have never seen the gauge while its acting up though, which is what I imagine your getting at.

EMATTOX_82FB

OK, update. I've got the carb pulled off again. It surprisingly has the correct gasket mentioned in the thread you linked. more red gunk, which is super annoying (at least makes sense though). I think its getting past the fuel filter (I don't doubt there's some in the lines as well). I'm gonna try get my tank cleaned, lines cleaned. I'm thinking about swapping back the old needles as well, it seems like the new ones can cause a lot of problems. that's the last thing I want, more problems. Is there anything else you recommend while I am here?