Changed Alternator, then the cap/rotor/wires and now runs rough

[RonK]

Just purchased a 1975 280z w 111k mi, driven 200-500mi a year past 10yrs. Drove it over 300-400mi w no problems. My mechanic(good friend of mine) checked it out for overall condition and determined alternator was putting out only 12amps (explains why battery is bad).

I replaced alternator with a Bosch unit he provided me, started and ran engine for couple of minutes to make it was all good...no problems

Replaced distributor cap, rotor & wires and now runs like crap (like timing is off or not firing on all cylinders). Checked and doubled checked wire order. Plugs are getting spark. Even tried putting old cap, rotor & wires back on but no difference. (btw, this is "transistor", not contact points ignition)

Rotated distributor as far to each direction allowable but no better, just slower when retarded and faster when advanced but still running like

My mechanic put the new plugs in to make sure that wasn't the problem but still running like crap and apparently continues to foul the plugs (hence, no lack of fuel). He tried working with the timing but no success. He checked the air gap on the one part (sorry, dont have manuel with me) located under the rotor. He's stumped at this point with limited amount of time he has been able to devote to it.

Wondering if the additional amps (50 vs 12) fried something? (Is it pretty obvious how much of a mechanical rookie I am yet?) here I thought I would have something simple to work on, if need be...Crap, first simple thing I do, like change the alternator, cap, rotor and wires, and now it's screwed up and off the road!

Signed, "Help The Rookie"

P.S., my mechanic is now thinking the distributor may be bad???

[disepyon]

Look back at the order of the spark plug wires. Doesnt hurt to recheck simple things like this to make certain its right. I remembered mixing up two of them and it took me about an hour to figure out i had mine in the wrong spot.

Im not sure what the 280z distributors look like, but if they have a rotor head, perhaps you took it off and put it on backwards, if its even possible to fit the wrong way. Their grooved a certain way to fit specifically one way but some people may mistake it and force it on the wrong way.

Im not sure if these cars have a maf, i think they do. Check that, make sure the inside is clean or see if the sensor is working properly. I have a 240z so thats why im not certain what the 280z has.

What did you gap the plugs at?

Try to think back on what exactly you took off or unplugged and recheck it all, even things that do not relate to what you replaced, but for some reason you might had taken it off to get to the things you needed to replace.

Sorry if im not much help, hopefully somebody with knowledge will chime in soon.

[slowride]

first make sure you're at tdc check firing order 1-5-3-6-2-4. i did the same thing the other day

the worst mechanic in the world is the one that thinks he always right. good luck

[Gary in NJ]

Make sure that the #1 wire is lined-up with the vertical index mark on the side of the cap. It's CCW from there.

[madkaw]

So after replacing the alternator did you check voltage-not amps-voltage at the battery while it's running. Low voltage will exhibit your symptoms. Don't take for granted that a new alternator works right, I have gotten bad ones right out of the box. OR, the alternator was not the problem all along. Plus I am not sure about your statement about putting out 50 amps-did he really measure amperage? 50 amps is a TON of amps. Did you have your battery load tested? Bad batteries cause numerous issues that show up in other areas. Start back with the basics and don't assume anything

[SteveJ]

Conventional wisdom (meaning a lot of people have said/typed this, though I have no empirical way of discerning the truth) says to replace the voltage regulator with the alternator. A bad VR can prevent your alternator from getting the excitation it needs to have an output.

[Zed Head]

Re disepyon's suggestion about plug order - the engine will run with the plugs installed in the right order but wrong rotation direction. Maybe your mechanic assumed clockwise instead of counterclockwise. I've done it. Very confusing, especially since the engine will start and run.

[PastorMike]

So after replacing the alternator did you check voltage-not amps-voltage at the battery while it's running. Low voltage will exhibit your symptoms. Don't take for granted that a new alternator works right, I have gotten bad ones right out of the box. OR, the alternator was not the problem all along. Plus I am not sure about your statement about putting out 50 amps-did he really measure amperage? 50 amps is a TON of amps. Did you have your battery load tested? Bad batteries cause numerous issues that show up in other areas. Start back with the basics and don't assume anything

Well said Madkaw! Everyone, print this and put it in with your famous quotes.

[RonK]

Thank You, Everyone!

I am going to print this thread and take it to my mechanic and see if the two of us can isolate this problem. My goal is to learn how to do this stuff myself and with the support I'm receiving so far, I feel very encouraged....Thanks, Again!

[RonK]

Yeah, I found out (contary to the old Chevy caps) the cap goes on only one way (my mechanic friend educated me - it's "Indexed")....same goes for the rotor.

maf: don't know but will check it out

plugs: have to check what the new ones were set at (mechanic did them after I gave up and took the car in), but this whole problem started before I ever got to the point of changing the plugs (remember, it was running fine with old plugs and all BEFORE I changed the cap & rotor .... I was attempting to do one thing at a time so I could know if one step caused a problem..got too impatient and went 1) Alternator and 2) cap AND rotor.. then the problems began. Tried the new wires after that, then tried messing with the timing, then took to the shop

Only other items removed were the wires/condensor on the alternator, but all were restored to original spot.

Thanks, disepyon

[RonK]

So after replacing the alternator did you check voltage-not amps-voltage at the battery while it's running. Low voltage will exhibit your symptoms. Don't take for granted that a new alternator works right, I have gotten bad ones right out of the box. OR, the alternator was not the problem all along. Plus I am not sure about your statement about putting out 50 amps-did he really measure amperage? 50 amps is a TON of amps. Did you have your battery load tested? Bad batteries cause numerous issues that show up in other areas. Start back with the basics and don't assume anything

Did not check voltage at battery (not that I know how at this point), but will check it out. The battery was new...the low output from the alternator was suspected as being the reason for the bad battery.

[RonK]

Thank You, Everyone!

I am going to print this thread and take it to my mechanic and see if the two of us can isolate this problem. My goal is to learn how to do this stuff myself and with the support I'm receiving so far, I feel very encouraged....Thanks, Again!

Update.... my mechanic thought maybe the distributor may be bad ... We swaped w reman'd distributor and made no difference. He is now wondering if the timing has jumped. Going to pull the over and check it out :-\