I bough an old beater Rx7, 1st gen, 122k miles. Anyway on the way home it started backfireing horibly and I couldn't get it all the way home. After some new plugs and some more gas, it seemed to be fine. Turns out the guy who had it last put in a new fuel pump/filter and didn't tighten down all the bolts...so that probably causes a gas pressue drop and leak, so that's it right? End of story? wrong.

Finally got the tag for it today. Went out, got about 10 gallons of gas, drove it around, seemed fine and strong...until I took it up some steep hills. It had trouble getting up..but I made it to the top and back down, but then as I was just driving around, I'd lose power...I'd push down on the gas and the rpms would drop...I'd let off and it would kick back up again, but just barely...the car was struggling...I tried differnt gears, shifting...it just kept wanted to putter and stall and you'd ocasionally hear a put.put.put..bang sound out of the exhost (and it totally loses all power while doing this)...it will do this if I'm parked and reve it up to around 5,000 rpm too.

So what's the deal? I feel like I'm losing fuel pressure. I wish I had a fuel pressure gague to be sure. I just really hope I didn't buy a Lemon. Any suggestions would be helpful.

TheBattlePenguin

 

Buy a fuel pressure gauge and check the pressure, it sounds like you are flooding and not leaning. Pressure should be no mre than 4psi (3.5 recommended) also check the vaccum hoses going to the distributor timing advance and make sure there arent any leaks (at any vaccum hose)

peace

 

still sounds like starving for gas problem, if he changed all the above mentioned items, and still acting like this, i would look into the carb,,,clogged screens inside the top of the fuel rails, worn or ruptured accelerater pump diaphram, even check the metal fuel check valve for clogs in the fuel return line by the carb.....pull the fuel line off and turn the key to see how much gas is comming out,,,may even be a cat conv clogging,,,just some suggestions to look at,,,let us know what u find,,good luck,,,,go vols...

 

i have about the same problem as you man... car backfires and has no where near as much power as it used to. I think its either a carb problem or exhaust leak. I know im getting fuel, my pressure is set to 4 psi, but maybe i will turn it down to 3.5.

 

didn't work *sigh*

 

check the glass on the carb...... see if it has fuel when its doin this.... dunno....

 

I just had virtualy the same problem and my cat was clogged. I couldn't go up hills and it had no power. I checked evrything with no solution until i decided to loosen the bolts before the main cat, and holly **** it drove like a bat out of hell. On Saturday i took off my cat and used a crobar to break up the inside and dump it out. My car runs better then ever.

These cars have always had issues with the cats as soon as they get close to 100,000 miles. They were an early, early cat system.

I will guarantee that if you check your cat will be clogged.

 

don't have cat... ripped it off a long time ago

 

Man that sucks, it sounds identical to the problems I had. What about your igniters, coils or your fuel filter.

 

I have a msd 6al, new coild, new fuel filter, new fuel pump...

 

That's gotta be it then. I have a 13B fuel injected engine, so it's obviously not a carb problem and the deal is I don't really lose power until I go up an incline. The cat on my looks totally rusted out anyway and it's only hanging by one of it's support rods.

Tomorrow I'll try checking the cat (and probably the rest of the exhost as well) and chainging the oil and air filter. Hope this works.

 

have you checked the carb screens? both of you, lol.

battlepenguin- start at you're cat and work from there.

 

I pulled off all three cats and guess what..the previous owner had all ready taken a crowbar to them...they were all completyly hollow. I'm going to run it tomorrow like it is with all the cats off (I'd do it tonight, but don't want to wake up the family). If it doesn't help I'll try some fuel injector cleaner and go from there. BTW, how much psi should be on the fuel lines if you've got a fuel injected engine (at idle).

The Penguin

 

Every time I change gears my RX back fires. Does anyone know how this can be fixed?

 

RuggyLuague - It's suposte to...Rx7s always backfires when they shift, espically if you or someone before you gutted your cat. You can probably get rid of it by just buying a new cat. BTW, by backfire you mean small little backfires right? Anything really loud could be a sign of blockage or other problems...like I'm having.

Everyoneelse - tried driving it around with no cats at all...loud as anything. Anyway, it drives fine for about 5 minnutes until it warms up...then it always struggles and loses power between 2500 to 3000 rpm...I can keep pushing down the gas and the rpms just drop and the engine feels like it wants to stall...I'm open to more suggestion. I'm pretty sure it's fuel related.

 

sounds like the injectors are stuck open and you just start flooding it. during warm up the engine is choking and adding extra fuel so it isn't noticable until up to operating temp. try running some injector cleaner through. also could be the air intake sensor (it isn't a map on these is it?) i remember a guy who had problems with this and i believe did the same thing yours is doing. thats all i have right now.

rugby- punch your cat through and disconnect the airpump. if you don't want the single belt squeal then just take off the short hose between the airpump and acv. that way it will just pump air into the engine bay. the thing is that your car slowly detunes, you're letting that extra bit of fuel through, the airpump pumps in air, mini combustion in the exhaust, and pop or boom in a backfire. deleting the airpump gives the fuel no air to ignite.

 

Ok, to reiterate. What I've tried

New air filter (old one kinda disintegrated)
Removing the entire exhost (all three cats)
Fuel Injector Cleaner (with a full tank of 97+ gas)

And what still happens:
at about 5,0000 at idle or around 2,000 uphill (and by uphill I mean like a tall speed bump) or 2,500 on level ground it will start puking and sputtering until I let off the gas...if I add gas I either maintain power or it drops, never increases.

What it probably is:
The gas tank is full and the fuel filter is new and it's pumping fine at lower rpms. I think the engine either isn't getting enough gas (air flow sensor detecting the wrong ammount of air) or there's an air leak somewhere in the intake keeping air from getting in...

I'm gonna look in the Hayne's manual and see how hard is is to get to the airflow sensor and try that route. Any other suggestions are welcome.

 

I had a similar problem and it was the leading ignitor. You can try swapping the leading and trailing to see if that makes a difference. The car should run good with only the leading but the tach will not work. With just the trailing the tach will work but will be way down on power. Only takes 5 minutes to try.

Hope this helps.

Mark

 

Yes, it is mainly small little backfires that aren't loud but it has only recently started to happen and I am not a car expert so I sought the advice of you guys.

 

Also, I am filling the car with water constantly as it is always flashing on the monitor that I need more water. When I go to fill it up the cap has blown of the clear water container and the water level is dangerously low.

 

chack the intake air flow meter and make sure it sin't sticking.

rugby- is your car smoking white? have someone drive behind you and check.

 

Sounds reasonable to me.

"at about 5,0000 at idle or around 2,000 uphill (and by uphill I mean like a tall speed bump)... or 2,500 on level ground it will start puking and sputtering until... "

I know you're looking at fuel, but you get similar symptoms if an ignitor is not firing. Or the plugs are fried. It will rev at idle, but with any load it bogs.

It could be that the guy did not replace the pump and filter with proper replacements, but I would check for leading and trailing spark with a warm engine before looking too far into that. He might have replaced them without knowing the ignition was the real problem and all you need is a set of plugs or an igniter.

At any rate, you asked for fuel pressures for the 13B:
Pump outlet pressure is 50-70 psi. (No flow)
Regulated pressure is:
37 psi (no vacuum applied to fuel pressure regulator)
28 psi (with vacuum applied)


It's not likely the injectors. When they get sticky, the engine runs well, and they leak when the engine is off, bleeding off the fuel pressure. Then you have hard starting and flooding problems.

Good Luck, John.

 

Think i might of found my problem.... solid core wires with my msd... *DOH*

 

guys, well i have to agree that it sounds like severe flooding, check your plugs to see what they reveal.

also, has anyone checked to see if their lead and trail wires are not crossed? also ignition wires, caps and rotors are worth replacing (can't hurt) ...

 

Hey rugby my 81 used to boil over like that all the time. I replaced the thermostat and it got a little better, but would still boil over on long trips, I had the radiator rodded out (removed all the deposits of calcium etc) and never had a problem with it again. But listen to jeremy first with the visual of the exhaust.

peace