carey83gsl

hey guys, so the other day i was driving my rx-7, i took it up to redline a couple times, and then about five minutes of normal driving after that, the engine began to run rough and it lacked power. the car didn't want to die or anything, it would idle fine, just a bit rough. but i could barely get it moving, and didn't wanna push it past 30 in 2nd at 4k-ish rpm (to maintain speed). it would barely make it up the hill to my house. but, the engine wouldn't die on its own...it would just idle a bit roughly, right where it should.

i've checked for spark and it appears to be fine. however, there was some very odd corrosion on the leading plug wire from the coil to the dist. cap, so i tried to clean it, and no go. switched cables from leading to trailing ignition, no change. the spark plugs are getting spark. just to be safe, i'm putting in a new cap and rotor and spark plug wires today, we'll see if those help. i also swapped out the leading coil and leading ignitor just to be safe.

i also checked the compression on both rotors, and both were right around 95-100 psi, and had consistent bouncing, so all the seals appear to be good.

i also checked for vacuum leaks as best i could, but there wasn't a hose that looked to be misplaced, cracked or broken. and i JUST replaced the fuel filter a week or two ago, and the air filter looks alright, i think.

anyone have any ideas? thanks!

mazdaverx713b

iTrader: (91)

ray green had an interesting thread regarding something similar.. here is the thread: https://www.rx7club.com/1st-gen-archive-71/engine-sound-apex-seal-gone-bad-754872/

read through it, it may help you.

carey83gsl

interesting, i'll read through it. his situation seems different though, because in my case, i can even start the car and it will warm up fine, but just a bit rougher than normal, and it won't rev.

i was searching, and ran across a thread where a clogged cat was cited as a cause for this problem. would this be something i'd just take it to an exhaust shop to have checked? would you guys just recommend another cat, or a pipe or something? i don't have to pass emissions again...

mazdaverx713b

iTrader: (91)

well, a full racing beat exhaust woud be preferable..however, you will want to check exhaust the flow first. get behind the car near the muffler and put a towel in front of the tips. have someone rev the engine a bit. the exhaust should about blow the towel out of your hand. you use the towel so you dont burn your hand. if the towel barely moves you have an exhaust flow problem. often times a clogged converter will back up an engine enough to produce enough back pressure, causing a sound much like a vacuum leak...

carey83gsl

great, thanks! i'll give that a try and post back.

carey83gsl

alright, i tried it, and there still seemed to be plenty of pressure coming out the tailpipe. enough to make a difference from idle, and really blow the towel around.

when it's idling, you can really feel and hear individual puffs of exhaust. maybe i'll just call the shops around here and see how much it'd cost to have my exhaust system tested. i'm also getting the new dist. cap and rotor today, i'll put those on and see if there's any change.

boostedHULK

iTrader: (1)

it sounds like you have carbon tracks in your dist. cap. you could be getting spark which is why it's running good, but not enough voltage to really run properly under a load. it sounds like that's what you've got goin' on. that wierd "corrosion" is probably carbon tracks. give it a try if ya get a chance.
Neil

Dr Rx

Bad trailing ignitor???? I've had it happen on my sa and it would start and run kind of smooth but as soon as you try and put any power down it barely had the guts to go, it felt as if the power was cut in half.

boostedHULK

iTrader: (1)

ya know, coming to think of it, when i still had the points, when my trailing points would start gettin' real messed up and needed filed they would act a lot like that too. But yeah, it really sounds like it's in the ignition somewhere.

mazdaverx713b

iTrader: (91)

your next step would be to test your ignitors and check for plug corrosion. check all ignition system components per the fsm....which can be found here: http://foxed.ca/foxed/index.php?page=rx7manual

carey83gsl

well, i've now replaced plug wires and distributor cap and rotor. no dice. i've also swapped out the leading coil, and the leading ignitor. i guess i'll check the fsm.

anyone else have any ideas?

mazdaverx713b

iTrader: (91)

you may want to pull teh fuel filter and chek for sediment build up even thoug it is new. i've seen them clog shortly after install. i would also pull and test the fuel pump. have you checked the fuel level in both of the sight glasses on the carb when the engine is running? often times, crud gets into the fuel bowls in the carb and subsequently clog the jets. it may benifit you to rebuild the carb. its very easy to do and only takes a couple of hours from removal to reinstall. i had the same problem and it turned out to be clogged jets. they were clogged from the build up of sludge in the float bowles. make sure you get that crud out, remove and clean the jets and air bleeds. make sure the accelerator pump is replaced as well..if you're rebuilding the carb i'm sure you'll do al of the above mentioned and then some. keep us updated.

carey83gsl

alrighty, i'll go ahead and check the fuel filter again. is the fuel pump a PITA to pull? could the pump itself be clogged or something? i guess there could be a large crud buildup in the tank...

i could go ahead and have a crack at rebuilding the carb. last time i tried, i managed to crack the float which caused some VERY confusing and VERY intermittent problems. is just a rebuild kit from schucks a good way to go? and the carb manual on the FSM page has everything i need, yes?

thanks again for all your guys's help. as soon as i get some time (got wisdom tooth surgery this weekend) i'll have a crack at the carb and keep you updated.

DivinDriver

iTrader: (15)

The mazda carb manual from the FSM page is way superior to what comes with the kits, or aftermarket manuals, or even the FSM itself (better pictures). 99.9996% right.

carey83gsl

haha alright. let's hope that 0.0004% isn't important.

mazdaverx713b

iTrader: (91)

the carb is very simple to rebuild. once you see the parts in the new kit it'll be a breeze

carey83gsl

update:

so, i decided that before i was going to rebuild the carb, i should at least check the fuel pressure. which was pegged at 1.5psi at the carb.

so i changed the filter (even though i changed it not too long ago), and checked it again, now it's about 2.25-2.5 psi, which STILL isn't enough which leads me to believe that either the fuel pump is going out or i have a clogged line somewhere.

any advice? should i just go ahead and get the new pump? is one of the universal, "carter" in-line pumps okay, or do i need something more specific?

oh, and is there a way so that every time i unplug a line at the back of the car, fuel doesn't spill everywhere? it's fairly annoying.

Thanks!

trochoid

iTrader: (6)

You didn't happen to fill up with gas just before this started did you? Before you tackle the carb, try a can of Seafoam. Your fuel pressure is a tad on the low side. Specs are 2.84-3.54 psi. If the Seafoam doesn't help, then I'd be looking at the fuel pump, after another check of the fuel filter. Another cause is the filter at the end of the pickup tube inside the fuel tank plugging, or splitting and the pickup tube itself is clogging.

I bought a 7 once that started and idled perfectly, but as soon as I gave it any throttle, it died, even after a new filter and pump. Turned out the pickup tube filter was gone and the tube itself was almost completely clogged. Dropped the fuel tank, pulled the pickup/return assembly, sandblasted and painted it, worked fine after that.

carey83gsl

I don't know for sure, actually, I'll have to check the gas gauge....if it's low enough on a tank, just put the whole can in? Actually, since replacing the fuel filter, even though the pressure went up a bit, the car won't stay running. It will start and idle for about 2 seconds, then die.

Also, when I unplugged the line going into the filter from the tank, gas was flowing (rather regrettably) pretty freely all over my arms and hands. Is there a more concrete test I can do to check for clogs between the tank and the filter, or is the fact that gas flows freely from it pretty conclusive?

I have a new fuel pump, but I also want to check power going to the existing one as well. What kind of current should be making its way to the pump?

Thanks again for all your help, guys.

NCross

iTrader: (18)

How dirty was the old filter? Try disconnecting the fuel line between the filter and carb and blowing it out with an air hose.

carey83gsl

the old filter didn't seem that dirty.

installed new fuel pump (**** carter one from schucks) and now it will start and run again, but same as before, and still has low pressure. I'll try blowing compressed air through it.

i called a mechanic, who said it was likely that the schucks fuel pump was to blame, and that i should get a genuine OEM mazda one. Thoughts?

carey83gsl

finally gave up and took it in to a mechanic.

and they subsequently found a vacuum leak of some sort.....basically, they plugged a vacuum line on the front of the carb (haven't had a chance to look), and now it runs perfectly.


*sigh*

oh well. at least it's working.

NCross

iTrader: (18)

Hopefully cost you less than $100 for them to look at it right?

carey83gsl

yeah, it was just under $100, thank god.