Engine misses during higher speeds?
09-26-01, 07:50 PM
#1
Passenger
Posts: n/a
Engine misses during higher speeds?
Hi, I have a problem with my 1985 RX-7 GS and no one around here especially the local dealer has been able to offer any advice. My RX-7 is in excellent shape, has only 65000 miles and is my weekend car, except it has become unreliable. Here's the problem scenario:
The car will all of a sudden start to miss and then normally stalls. This usually happens at higher speeds (over 40) in fourth or fifth gear. It very rarely happens in the lower gears although it has done it in second gear. After the car stalls, it will restart after sitting for a few minutes and will allow me to get up to speed, then it becomes a hope whether or not the car will run fine for awhile. The other thing that I have logged is that the missing happens on uphills only...which adds to the mystery of this one.
To me (an engineer but not a car mechanic), the problem seems fuel relates meaning that there may be some significant particles in the gas tank. I have used some gas cleaners and the mechanics at the dealer have done some testing on the gas line but have found nothing.
Does anyone have an opinion on this situation or a recommendation on what I should do to solve the problem.
It is highly frustrating to have a great car sitting and not being able to enjoy it...other than looking at it!!
I appreciate your thoughts.
Thanks,
trex...hickory, NC
The car will all of a sudden start to miss and then normally stalls. This usually happens at higher speeds (over 40) in fourth or fifth gear. It very rarely happens in the lower gears although it has done it in second gear. After the car stalls, it will restart after sitting for a few minutes and will allow me to get up to speed, then it becomes a hope whether or not the car will run fine for awhile. The other thing that I have logged is that the missing happens on uphills only...which adds to the mystery of this one.
To me (an engineer but not a car mechanic), the problem seems fuel relates meaning that there may be some significant particles in the gas tank. I have used some gas cleaners and the mechanics at the dealer have done some testing on the gas line but have found nothing.
Does anyone have an opinion on this situation or a recommendation on what I should do to solve the problem.
It is highly frustrating to have a great car sitting and not being able to enjoy it...other than looking at it!!
I appreciate your thoughts.
Thanks,
trex...hickory, NC
09-26-01, 09:36 PM
#2
EliteHardcoreCannuckSquad
Join Date: Apr 2001
Location: Ontario, Canada
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First off, most Mazda dealers know absolutely zippo when it comes to our cars. They will tell you all kinds of wacko things, and are absolutely useless, except for getting parts.
If you want to take your rex to a shop, find a competent rotary mechanic who is recommended by other rexers in your area.
I'm no pro like some of the guys here, but I'll throw out a few suggestions based on the experience I've had with mine.
No offense, I'm sure you've already done this, but have you changed your fuel filter? If it was bad, it would cause the exact problems you described. It would run fine after sitting for a while, then after driving for a few minutes it would stall. Then it wouldn't start at all. After a while, it would start up, but run badly. The next day it would again run fine for a bit.
This happened to me once, I got stuck out in the middle of nowhere in the middle of the night, and now I always carry a spare in the car.
It is located on the driver's side rear of the car, and is very very easy to change, check the thread "what fuel filter should I buy" for instructions.
Other than that, I guess check your fuel pump. There is an easy volume-test procedure described in the Haynes manual. Just pull off the main fuel line from the carb, and stick it in a container with volume markings. It should pump out about 1.2-1.5 litres or so in one minute I believe. There is also a one-way valve on your fuel return line between your carb and the firewall. I'm told this can become clogged, you can check it by removing it and blowing air through.
What about your ignition system? Going up a hill in 4th gear is a high load condition where problems would first start to appear. Have you replaced your plugs, cap&rotor, wires, coils, and checked your distributor for correct operation? Is your timing set properly? All of this stuff is really easy to do.
I guess my advice is to make sure all the easy stuff is ok, since it is easy to go looking for complicated problems without checking your plugs, etc. first. And 99% of the time it is something really basic that is wrong.
Good luck, I'm sure you'll have it figured out soon.
If you want to take your rex to a shop, find a competent rotary mechanic who is recommended by other rexers in your area.
I'm no pro like some of the guys here, but I'll throw out a few suggestions based on the experience I've had with mine.
No offense, I'm sure you've already done this, but have you changed your fuel filter? If it was bad, it would cause the exact problems you described. It would run fine after sitting for a while, then after driving for a few minutes it would stall. Then it wouldn't start at all. After a while, it would start up, but run badly. The next day it would again run fine for a bit.
This happened to me once, I got stuck out in the middle of nowhere in the middle of the night, and now I always carry a spare in the car.
It is located on the driver's side rear of the car, and is very very easy to change, check the thread "what fuel filter should I buy" for instructions.
Other than that, I guess check your fuel pump. There is an easy volume-test procedure described in the Haynes manual. Just pull off the main fuel line from the carb, and stick it in a container with volume markings. It should pump out about 1.2-1.5 litres or so in one minute I believe. There is also a one-way valve on your fuel return line between your carb and the firewall. I'm told this can become clogged, you can check it by removing it and blowing air through.
What about your ignition system? Going up a hill in 4th gear is a high load condition where problems would first start to appear. Have you replaced your plugs, cap&rotor, wires, coils, and checked your distributor for correct operation? Is your timing set properly? All of this stuff is really easy to do.
I guess my advice is to make sure all the easy stuff is ok, since it is easy to go looking for complicated problems without checking your plugs, etc. first. And 99% of the time it is something really basic that is wrong.
Good luck, I'm sure you'll have it figured out soon.
09-27-01, 08:44 AM
#3
Round&Round not Up&Down
Join Date: Aug 2001
Location: West Bloomfield, MI
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When you change your filter....see if its really dirty. If it is, you can pull the drain plug on the tank, hopefull it's not full of fuel, and drain all that junk out. If you don't mind wasting a half gallon of gas, pour some down the filler neck for a good flushing of the tank.
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