I think I broke my car :/
03-23-19, 07:28 PM
#1
Junior Member
Thread Starter
I think I broke my car :/
I could really use some help right now, I think I managed to break my variable resistor (like everything else I touch) trying to set the idle speed and mixture for the hundredth time now, trying to hunt down a 2k and 3k rpm surge. Checked and set the TPS, unplugged the vac and vent solenoids, set the idle speed...but I also wanted to set the variable resistor to its center/neutral position. Wasn't sure where it was at so gave it a couple 180* turns and heard a gentle pop and the engine just started sounding like it was running lean and wanted to die. Plugged in the solenoids and it was better, but revved it and it dipped below idle and died. Turning the screw for the variable resistor didn't change anything. Checked resistance and A-C was 3.6k ohms and B-C was 1.5k ohms, with about 0.05k ohm difference when turning the screw. So I think I broke it or it was already broken.
If this is the case, would anyone have a good spare and be able to ship it asap?
If this is the case, would anyone have a good spare and be able to ship it asap?
03-26-19, 06:58 PM
#3
Junior Member
Thread Starter
Currently trying to find a DIY potentiometer to rig up and see if it will work, but don't know if it uses a 12v source or standard 5v source. Can't find any online so kinda SOL for now, and I know these 1st gens are pretty much DIY for anything. Mazda should really start a resto shop for RX-7's.
03-26-19, 08:36 PM
#4
ancient wizard...
The stumble/surge you have at 2k-3k is being caused by something else. The variable resistor is only there to (slightly) adjust base idle quality. It is VERY rare this will need adjusting if at all at any point in car's life.
1st thing you should do on this car-if you haven't done it already- is change the fuel filter AND clean out screen in fuel inlet pipe on fuel pump. Tap the filter over top of paper towels and look closely at what comes out.What comes out will tell you what direction you're going next.
Recommend you stop adjusting things looking for a fix,it is all too easy to get throttle,idle adjustments out of whack causing more issues. Look thru all tune up basics..air and fuel filters,condition of dist cap and wires and plugs,the correct ones. If you can't verify the age of ignition parts,replace them,not going to break the bank. Correct set of NGK wires is $15.
Don't fool around trying to rig up something aftermarket for the resistor,you do not want to screw up ecu experimenting. Look thru 1st gen classifieds for a variable resistor or place a want to buy ad in classifieds for one. If you find one-just bolt it in place-don't mess with it. There's a reason the adjust screw is encapsulated in wax/plastic-to keep people from playing with it unnecessarily.
1st thing you should do on this car-if you haven't done it already- is change the fuel filter AND clean out screen in fuel inlet pipe on fuel pump. Tap the filter over top of paper towels and look closely at what comes out.What comes out will tell you what direction you're going next.
Recommend you stop adjusting things looking for a fix,it is all too easy to get throttle,idle adjustments out of whack causing more issues. Look thru all tune up basics..air and fuel filters,condition of dist cap and wires and plugs,the correct ones. If you can't verify the age of ignition parts,replace them,not going to break the bank. Correct set of NGK wires is $15.
Don't fool around trying to rig up something aftermarket for the resistor,you do not want to screw up ecu experimenting. Look thru 1st gen classifieds for a variable resistor or place a want to buy ad in classifieds for one. If you find one-just bolt it in place-don't mess with it. There's a reason the adjust screw is encapsulated in wax/plastic-to keep people from playing with it unnecessarily.
03-31-19, 01:40 AM
#5
Junior Member
Thread Starter
The stumble/surge you have at 2k-3k is being caused by something else. The variable resistor is only there to (slightly) adjust base idle quality. It is VERY rare this will need adjusting if at all at any point in car's life.
1st thing you should do on this car-if you haven't done it already- is change the fuel filter AND clean out screen in fuel inlet pipe on fuel pump. Tap the filter over top of paper towels and look closely at what comes out.What comes out will tell you what direction you're going next.
Recommend you stop adjusting things looking for a fix,it is all too easy to get throttle,idle adjustments out of whack causing more issues. Look thru all tune up basics..air and fuel filters,condition of dist cap and wires and plugs,the correct ones. If you can't verify the age of ignition parts,replace them,not going to break the bank. Correct set of NGK wires is $15.
Don't fool around trying to rig up something aftermarket for the resistor,you do not want to screw up ecu experimenting. Look thru 1st gen classifieds for a variable resistor or place a want to buy ad in classifieds for one. If you find one-just bolt it in place-don't mess with it. There's a reason the adjust screw is encapsulated in wax/plastic-to keep people from playing with it unnecessarily.
1st thing you should do on this car-if you haven't done it already- is change the fuel filter AND clean out screen in fuel inlet pipe on fuel pump. Tap the filter over top of paper towels and look closely at what comes out.What comes out will tell you what direction you're going next.
Recommend you stop adjusting things looking for a fix,it is all too easy to get throttle,idle adjustments out of whack causing more issues. Look thru all tune up basics..air and fuel filters,condition of dist cap and wires and plugs,the correct ones. If you can't verify the age of ignition parts,replace them,not going to break the bank. Correct set of NGK wires is $15.
Don't fool around trying to rig up something aftermarket for the resistor,you do not want to screw up ecu experimenting. Look thru 1st gen classifieds for a variable resistor or place a want to buy ad in classifieds for one. If you find one-just bolt it in place-don't mess with it. There's a reason the adjust screw is encapsulated in wax/plastic-to keep people from playing with it unnecessarily.
The main thing now is like I said, I think I broke the variable resistor trying to get it to idle right first and wanted to make sure that that is the case. I was also going to replace all the vacuum lines next too, but that'll have to hold until I can get a replacement or find something that works. I did find a decent deal on a newer Fiesta ST (thanks to being a mech at the dealer
) so I may actually end up selling this one off. I already have a project Mustang (that is awaiting a roller 302) and this poor 250k RX-7 is turning into another one, unfortunately.
03-31-19, 08:38 AM
#6
First off, the 1st gen RX-7 in not mostly forgotten. There is still a huge cult following surrounding them and people have parts for them. I may even have the variable resistor you need. I have a horde of RX-7 parts in my basement that I'm currently cataloging. Post a want to buy ad in the 1st gen parts section as someone has one for sure.
Don't waste time installing universal parts on the car as it may only make matters worse. Have you checked for vacuum leaks? Were you back probing the connector to get your resistance values? Front probing can create pin fit issues and destroy the pins in a connector. The throttle shaft bushings can wear, causing a vacuum leak and slight stumbling. The throttle body should be removed and cleaned and the injectors should also be sent out to be cleaned and flow tested. Definitely replace the cap and rotor and replace any questionable vacuum lines. Keep us posted on what you find.
Don't waste time installing universal parts on the car as it may only make matters worse. Have you checked for vacuum leaks? Were you back probing the connector to get your resistance values? Front probing can create pin fit issues and destroy the pins in a connector. The throttle shaft bushings can wear, causing a vacuum leak and slight stumbling. The throttle body should be removed and cleaned and the injectors should also be sent out to be cleaned and flow tested. Definitely replace the cap and rotor and replace any questionable vacuum lines. Keep us posted on what you find.
03-31-19, 11:54 AM
#7
ancient wizard...
Op,once you get your replacement variable resistor(i'm sure you'll be able to source one) installed and get car running "normal" again,look at distributor more closely. The statement you made about gashes in a couple of terminals in dist cap would make me want to check to see if dist shaft is bent.
It also reminds me of a driveability problem i had with a 1st gen a while ago,it was not an SE,but distributor is basically the same for FBs. I was chasing a similar problem as what you describe and went thru fuel system to where all was known good and was no better. Electrically,ignition system was solid. Could not duplicate this problem without actually driving car and it was worse in lower gears. Eventually,playing with timing light and checking base timing,mechanical advance,vacuum advance separately and together,leading and trailing both,i noticed something different with spark curve with vacuum advance disconnected. I plugged vac hose to vac advance and drove car. It wasn't as responsive at low rpm as you'd imagine without vac advance but that 2k-3k rpm weirdness was gone.
I tested both advance pods and they both held vacuum,took off cap/rotor/shield and watched both leading/trailing pick up coil plates as i slowly applied vacuum. Neither moved initially with small amount of vacuum,as more applied,they would move but not smoothly.
Pulled distributor and completely disassembled it and found the bearing plate both pickups mount on was very notchy,not smooth at all. Further inspection showed the grease that lubricated ball bearings had dried up into little hard ramps in front of ball bearings that the plates rotate on.
Washing the bearing plate in a parts washer and using carb cleaner a pick and wire brush til all old grease was removed,the bearing plate turned much easier. Using an acid brush i pushed in as much cam lube as possible around the bearings and worked plate back and forth at which point it was very smooth and wiped off any excess with qtip and paper towels.
Cam grease will not be known to many of you here as you're too young,lol. It was used on vehicles before electronic ignition was developed and all cars had points and condensers and some cars had more than one set of points,musclecars had dualpoint distributors and early rotarys had several sets of points in their distributors. Cam grease is different than other types of grease in that it is sticky so won't be flung off parts it's put on and won't thin out when exposed to heat. I do not know where you can buy it nowadays,search online to start.i guess. I'm working with a large tube i've had since the 70s so there's a clue to how old i am.
Distributors had cam lobes on shaft-as many lobes as cylinders-and each set of points had a phenolic rubbing block that rubbed against cam lobes as distributor shaft turned,cam lube or grease kept these rubbing blocks from wearing out pematurely which changed the dwell and timing as they wore,which is why electronic ignition is better,no parts to wear and change ignition timing and emissions.
I did same to dist shaft and advance weights and plate they ride on and reassembled and installed and checked and set timing. I ended up with a couple more degrees of full mechanical advance and vacuum advance came on earlier and more linear. Driving the car,the engine felt stronger everywhere,especially at low rpms and the hesitation was gone.
If you've never had your distributor out and apart to service it ,you may be missing out on a few hp(and better fuel economy) that our cars didn't have enough of in 1st place.
It also reminds me of a driveability problem i had with a 1st gen a while ago,it was not an SE,but distributor is basically the same for FBs. I was chasing a similar problem as what you describe and went thru fuel system to where all was known good and was no better. Electrically,ignition system was solid. Could not duplicate this problem without actually driving car and it was worse in lower gears. Eventually,playing with timing light and checking base timing,mechanical advance,vacuum advance separately and together,leading and trailing both,i noticed something different with spark curve with vacuum advance disconnected. I plugged vac hose to vac advance and drove car. It wasn't as responsive at low rpm as you'd imagine without vac advance but that 2k-3k rpm weirdness was gone.
I tested both advance pods and they both held vacuum,took off cap/rotor/shield and watched both leading/trailing pick up coil plates as i slowly applied vacuum. Neither moved initially with small amount of vacuum,as more applied,they would move but not smoothly.
Pulled distributor and completely disassembled it and found the bearing plate both pickups mount on was very notchy,not smooth at all. Further inspection showed the grease that lubricated ball bearings had dried up into little hard ramps in front of ball bearings that the plates rotate on.
Washing the bearing plate in a parts washer and using carb cleaner a pick and wire brush til all old grease was removed,the bearing plate turned much easier. Using an acid brush i pushed in as much cam lube as possible around the bearings and worked plate back and forth at which point it was very smooth and wiped off any excess with qtip and paper towels.
Cam grease will not be known to many of you here as you're too young,lol. It was used on vehicles before electronic ignition was developed and all cars had points and condensers and some cars had more than one set of points,musclecars had dualpoint distributors and early rotarys had several sets of points in their distributors. Cam grease is different than other types of grease in that it is sticky so won't be flung off parts it's put on and won't thin out when exposed to heat. I do not know where you can buy it nowadays,search online to start.i guess. I'm working with a large tube i've had since the 70s so there's a clue to how old i am.
Distributors had cam lobes on shaft-as many lobes as cylinders-and each set of points had a phenolic rubbing block that rubbed against cam lobes as distributor shaft turned,cam lube or grease kept these rubbing blocks from wearing out pematurely which changed the dwell and timing as they wore,which is why electronic ignition is better,no parts to wear and change ignition timing and emissions.
I did same to dist shaft and advance weights and plate they ride on and reassembled and installed and checked and set timing. I ended up with a couple more degrees of full mechanical advance and vacuum advance came on earlier and more linear. Driving the car,the engine felt stronger everywhere,especially at low rpms and the hesitation was gone.
If you've never had your distributor out and apart to service it ,you may be missing out on a few hp(and better fuel economy) that our cars didn't have enough of in 1st place.
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03-31-19, 09:23 PM
#8
Junior Member
Thread Starter
First off, the 1st gen RX-7 in not mostly forgotten. There is still a huge cult following surrounding them and people have parts for them. I may even have the variable resistor you need. I have a horde of RX-7 parts in my basement that I'm currently cataloging. Post a want to buy ad in the 1st gen parts section as someone has one for sure.
Don't waste time installing universal parts on the car as it may only make matters worse. Have you checked for vacuum leaks? Were you back probing the connector to get your resistance values? Front probing can create pin fit issues and destroy the pins in a connector. The throttle shaft bushings can wear, causing a vacuum leak and slight stumbling. The throttle body should be removed and cleaned and the injectors should also be sent out to be cleaned and flow tested. Definitely replace the cap and rotor and replace any questionable vacuum lines. Keep us posted on what you find.
Don't waste time installing universal parts on the car as it may only make matters worse. Have you checked for vacuum leaks? Were you back probing the connector to get your resistance values? Front probing can create pin fit issues and destroy the pins in a connector. The throttle shaft bushings can wear, causing a vacuum leak and slight stumbling. The throttle body should be removed and cleaned and the injectors should also be sent out to be cleaned and flow tested. Definitely replace the cap and rotor and replace any questionable vacuum lines. Keep us posted on what you find.
Op,once you get your replacement variable resistor(i'm sure you'll be able to source one) installed and get car running "normal" again,look at distributor more closely. The statement you made about gashes in a couple of terminals in dist cap would make me want to check to see if dist shaft is bent.
It also reminds me of a driveability problem i had with a 1st gen a while ago,it was not an SE,but distributor is basically the same for FBs. I was chasing a similar problem as what you describe and went thru fuel system to where all was known good and was no better. Electrically,ignition system was solid. Could not duplicate this problem without actually driving car and it was worse in lower gears. Eventually,playing with timing light and checking base timing,mechanical advance,vacuum advance separately and together,leading and trailing both,i noticed something different with spark curve with vacuum advance disconnected. I plugged vac hose to vac advance and drove car. It wasn't as responsive at low rpm as you'd imagine without vac advance but that 2k-3k rpm weirdness was gone.
I tested both advance pods and they both held vacuum,took off cap/rotor/shield and watched both leading/trailing pick up coil plates as i slowly applied vacuum. Neither moved initially with small amount of vacuum,as more applied,they would move but not smoothly.
Pulled distributor and completely disassembled it and found the bearing plate both pickups mount on was very notchy,not smooth at all. Further inspection showed the grease that lubricated ball bearings had dried up into little hard ramps in front of ball bearings that the plates rotate on.
Washing the bearing plate in a parts washer and using carb cleaner a pick and wire brush til all old grease was removed,the bearing plate turned much easier. Using an acid brush i pushed in as much cam lube as possible around the bearings and worked plate back and forth at which point it was very smooth and wiped off any excess with qtip and paper towels.
Cam grease will not be known to many of you here as you're too young,lol. It was used on vehicles before electronic ignition was developed and all cars had points and condensers and some cars had more than one set of points,musclecars had dualpoint distributors and early rotarys had several sets of points in their distributors. Cam grease is different than other types of grease in that it is sticky so won't be flung off parts it's put on and won't thin out when exposed to heat. I do not know where you can buy it nowadays,search online to start.i guess. I'm working with a large tube i've had since the 70s so there's a clue to how old i am.
Distributors had cam lobes on shaft-as many lobes as cylinders-and each set of points had a phenolic rubbing block that rubbed against cam lobes as distributor shaft turned,cam lube or grease kept these rubbing blocks from wearing out pematurely which changed the dwell and timing as they wore,which is why electronic ignition is better,no parts to wear and change ignition timing and emissions.
I did same to dist shaft and advance weights and plate they ride on and reassembled and installed and checked and set timing. I ended up with a couple more degrees of full mechanical advance and vacuum advance came on earlier and more linear. Driving the car,the engine felt stronger everywhere,especially at low rpms and the hesitation was gone.
If you've never had your distributor out and apart to service it ,you may be missing out on a few hp(and better fuel economy) that our cars didn't have enough of in 1st place.
It also reminds me of a driveability problem i had with a 1st gen a while ago,it was not an SE,but distributor is basically the same for FBs. I was chasing a similar problem as what you describe and went thru fuel system to where all was known good and was no better. Electrically,ignition system was solid. Could not duplicate this problem without actually driving car and it was worse in lower gears. Eventually,playing with timing light and checking base timing,mechanical advance,vacuum advance separately and together,leading and trailing both,i noticed something different with spark curve with vacuum advance disconnected. I plugged vac hose to vac advance and drove car. It wasn't as responsive at low rpm as you'd imagine without vac advance but that 2k-3k rpm weirdness was gone.
I tested both advance pods and they both held vacuum,took off cap/rotor/shield and watched both leading/trailing pick up coil plates as i slowly applied vacuum. Neither moved initially with small amount of vacuum,as more applied,they would move but not smoothly.
Pulled distributor and completely disassembled it and found the bearing plate both pickups mount on was very notchy,not smooth at all. Further inspection showed the grease that lubricated ball bearings had dried up into little hard ramps in front of ball bearings that the plates rotate on.
Washing the bearing plate in a parts washer and using carb cleaner a pick and wire brush til all old grease was removed,the bearing plate turned much easier. Using an acid brush i pushed in as much cam lube as possible around the bearings and worked plate back and forth at which point it was very smooth and wiped off any excess with qtip and paper towels.
Cam grease will not be known to many of you here as you're too young,lol. It was used on vehicles before electronic ignition was developed and all cars had points and condensers and some cars had more than one set of points,musclecars had dualpoint distributors and early rotarys had several sets of points in their distributors. Cam grease is different than other types of grease in that it is sticky so won't be flung off parts it's put on and won't thin out when exposed to heat. I do not know where you can buy it nowadays,search online to start.i guess. I'm working with a large tube i've had since the 70s so there's a clue to how old i am.
Distributors had cam lobes on shaft-as many lobes as cylinders-and each set of points had a phenolic rubbing block that rubbed against cam lobes as distributor shaft turned,cam lube or grease kept these rubbing blocks from wearing out pematurely which changed the dwell and timing as they wore,which is why electronic ignition is better,no parts to wear and change ignition timing and emissions.
I did same to dist shaft and advance weights and plate they ride on and reassembled and installed and checked and set timing. I ended up with a couple more degrees of full mechanical advance and vacuum advance came on earlier and more linear. Driving the car,the engine felt stronger everywhere,especially at low rpms and the hesitation was gone.
If you've never had your distributor out and apart to service it ,you may be missing out on a few hp(and better fuel economy) that our cars didn't have enough of in 1st place.
May end up keeping it though, just need some reliable transportation at the moment.
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