knifehitz

Hi guys, after digging through the FSM and searching all over the forum I'm hoping that someone might be able to point me in the right direction.

Just bought a 1985 GSL with 27K original miles. Before I purchased, it had the cap rotor, wire set, spark plugs and fuel filter were replaced, oil changed and I had the coolant flushed yesterday.

The car is 100% stock, 12A motor, visual inspection shows nothing wrong, everything is remarkably clean.

The only issue I've had while running the car is a hesitation right at 3000 rpms, usually in 2nd gear is the worst. Idles right at 750, etc. Acceleration below and above 3000 rpms is just fine, it is consistently hiccuping right at that mark.

From what I've gathered, if the problem was the fuel pump or filter the issue would be over a wider range rather than just one RPM mark. I'm thinking that this is related to the carb, but I'm a bit stumped as to what component I could test without having a rolling road tester.

Any results I can find for "3K hesitation" do not deal with a completely stock 12A engine with no turbo. I'm wondering if this sounds like a problem that anyone else has had, or if there is something obvious I'm not thinking of. I can't find any vacuum leaks from my inspections. My next steps are going to be running some fuel system cleaner in the next tank of gas (I'm still on my first tank for the car) and revving a bit hard around town to try to clear out gunk. Given the good operation of everything else, I'm hoping that I don't have to disassemble the entire carb. Visual inspection shows everything looking pretty clean inside and out.

I'd be grateful for any tips or obvious things I might be missing. Thanks!

Cookboy

iTrader: (10)

Good plan. Seafoam that baby, take a several hour trip, burn through a tank and do it again. Keep an eye on your fuel filter, see how it does.
Check back in with progress, and a pic of that low mileage unit. Must be a beauty!

diabolical1

iTrader: (3)

welcome to the board.

I suspect something causing a slight hiccup while your secondaries are coming online. you may want to investigate that.

Rhyno2050

i agree with diabolical1, its gonna deal at the moment when your secondaries kick in, give a check to your trailing coils, cables, plugs,...but in my opinion it wouldnt be the fuel pump

Coltdaddy47

Quick story i just went through the past week. Bought used 12a put it into car. Timed it without timing light. 2500 to 3g rpm max. Tried everything. Come to find out previous owner put front pully on 1 bolt off. The stud did not line up with the stud hole. Car started right up and ran fine to those rpms but no further. Found that out and moved it 1 hole over and retimed it with no problem. Car runs amazing now. I say this story because you said previous owner did a tune up with the cap and rotor and may have messed something up. May need a carb rebuild to freshen it up as i would think if it had that low of miles it probally was never done. Diabolical1... doesnt the secondaries come in around the 4g mark?

diabolical1

iTrader: (3)

generally speaking, yes. at least, that's what I observe with most Nikki-powered Gen I cars. however, on my '83 many moons ago, I went through about 5 12As in 7 years. for some reason 2 of them would start opening up right around 3500 RPM (maybe a hair sooner). at the time my level of curiosity was not as it is now, so I never felt the need to find out why. oh, and it was the same Nikki used on them.

since he implied the engine is revving and making power in the upper ranges, I assumed the secondaries are functional; and since what he described seems like a momentary thing, I figured maybe there is something funky going on with the vacuum signal (maybe the linkage) and offered my posted suggestion.

knifehitz

Thanks for the tips guys. I ran some Chevron fuel treatment through one tank and it didn't seem to do much. Last night the tank ran out again so I was able to throw some Sea Foam in there. Even after just a few miles that seems to be easing the hesitation a bit.

My idle seems to be just a bit rough, and it's a little bit tricky to start first thing in the morning. Have to give it just a bit of gas on the pedal, and then after it catches then pull out the choke. I think it floods out if I pull out the choke first. After it starts there is absolutely no problem when the choke is out, and the hesitation is definately at 3K alone, no problem once it revs past that point. Almost certain that the carb is just a bit gummed up from years of infrequent use and low RPM driving.

If a couple tanks of Sea Foam don't make it all better I'll dig into the carb and vaccuum systems.

Will let you know how it goes, hopefully this weekend I can take her out for a couple hours of serious revving! Here's some pics in the meantime:

archaphil

iTrader: (1)

that car is in beautiful shape!

diabolical1

iTrader: (3)

good Lord, your car is gorgeous. however, of particular note, your interior is pristine. take care of it.

knifehitz

After putting a few hundred miles on the car with some Seafoam in the tank it seems to have eased the hesitation a bit.

Funnily enough, the heater / AC blower didn't seem to be putting out much in the way of airflow, but after a several hour drive yesterday something clicked over and all of a sudden in started putting out proper airflow.

Still blowing the dust off, so to speak, but everything seems to be coming together. After another tank or so I'm going to adjust the idle mix / speed on the carb and check the timing. I'll probably replace all the vaccuum lines to be on the safe side as well, but I plan on keeping everything as stock as possible on this car.

I guess the guy who arranged the sale never removed the craigslist ad after I bought it, because someone else posted about it in the Northwest section a few days ago but I don't have enough posts to reply in that area

https://www.rx7club.com/nw-rx-7-foru...5-rx7-1038023/

And yes, the interior is in immaculate condition. It will be well cared for and loved for many years to come, for sure!