'76 AMC Pacer - Tune up help again....

[jim1941]

Began my tune up project by watching a youtube video for the same engine, but a Jeep and probably a few years earlier than '76.  Grateful you guys told me I have electronic ignition not points as in the video.  Adding to my confusion, went to Autozone with my year and model of car and they ordered points, condenser, etc. for me.  Glad I didn't get the parts yet because can still cancel; no return on electrical parts I think.  Anyway, took off my distributer cap and took a photo. Tip of rotor (is it?) is blurred in photo, but looks good. Rotor does not lift off like I'm used to, so left it alone.  Notice underside of cap, the one point toward top has residue on it.  What would cause this?  I cleaned it, reattached.  Car seems to idle smoother now but didn't run it for long.   Jim

[rocketraider]

2 hours ago, jim1941 said:

went to Autozone with my year and model of car and they ordered points, condenser, etc. for me.  Glad I didn't get the parts yet because can still cancel; no return on electrical parts I think.

🙂

 

AZ is my least favorite of the chains. I find their parts monkeys to be the most ignorant of all, even on "modern" vehicles. O'Reilly's is the best chain IMO, or is here anyway. I like two of the nearby NAPAs, the third is about half a step up from AZ.

 

The corrosion on the cap contact is unusual in that it's only on the one. If it cleaned off with no residue it should be ok for a while, but I'd look close at the outside post too. Hit them all with a fine brass brush. Do the wires one at a time if you're not comfortable with firing order.

 

The more you do tuneup work the more comfortable and adept you'll become. People here will have your back.

[Rusty_OToole]

So, you definitely have electronic ignition, appears to be Motorcraft brand which is made by Ford. Follow the wires from the distributor to the ignition module and see what kind it is. AMC changed suppliers around the time your car was made.

Cap and rotor look like new should not need to be changed.

I would put in a new set of spark plugs, and let it go at that.  Unless you have reason to believe there is something wrong.

If you want to spend a little money you could splurge on Bosch platinum spark plugs.  Or, if you prefer, use the original equipment brand. In any case check the plug gap and adjust to factory spec if necessary.

There is a simple test for worn spark plug wires. Go out at night and, with the engine idling, look for sparks jumping from the wires to ground. To make the test extra hard you can mist some water from a spray bottle on them. If you see sparks the wires are bad and need to be replaced.

With electronic ignition the timing does not change, unlike points ignition where it changes as the points wear and needs to be reset if the points are changed. You can check the timing with a timing light but it is probably ok.

[jim1941]

Thanks to you both!  Guidance very needed and appreciated.  I launched this project because the car runs rough; better after warmed up. When I first got the car it was really running rough and a mechanic discovered a very bad harmonic balancer which got replaced. Re; tune up: I took out all the spark plugs one at a time and cleaned them with a brass brush. The one near the A/C compressor was horrible to get out and when I did, noticed the base just below the porcelain was very rusty unlike all the others.  Did someone skip that one?  Anyway, I'll be changing all 6 checking proper gap.    I'd like to figure out how to check and compare firing order with where plugs go on distributer cap, just in case it's wrong.  Jim

[jim1941]

Plugs are fine on cap.  Everything should be so easy.  Jim

[rocketraider]

This should help.

 

 

The AMC 258 cylinders are numbered front to back, with #1 at front nearest the fan.

 

If unfamiliar with replacing plug wires, leave them attached to the old cap. Install the new cap, then attach the plug wires to it ONE AT A TIME, to the same tower they were on the old cap. A strip of masking tape on each wire, marked with the cylinder it goes to, can also help.

 

 

[Frank DuVal]

Hmm, is the one you say next to AC compressor the front plug, i.e. #1 spark plug? I ask because in the diagram Glenn provided it is possible the terminal inside the distributor cap with the corrosion could be #1 , if I assume you tilted the cap toward the engine. If #1 plug was not firing well, being a sort of short circuit that might explain the situation on the terminal. 😉

 

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[rocketraider]

1 hour ago, jim1941 said:

 the car runs rough; better after warmed up. When I first got the car it was really running rough and a mechanic discovered a very bad harmonic balancer which got replaced. Re; tune up: I took out all the spark plugs one at a time and cleaned them with a brass brush. The one near the A/C compressor was horrible to get out and when I did, noticed the base just below the porcelain was very rusty unlike all the others.  Did someone skip that one? 

Rough on cold start then smoothing out makes me think of a few things. 

 

1) a poorly adjusted choke, or the choke vacuum pull-off is weak or failed.

 

With cold engine with aircleaner lid off, set the choke and then look at the carburetor choke flap. Should be FULLY CLOSED or very close to it. If not, choke needs adjustment.

 

Start the engine with lid off and look at the choke flap again. With engine running it should have opened 1/8" to 1/4" or so to allow the engine enough air to run. If not, the vacuum operated choke pull-off is likely bad.

 

2) this is likely an EGR (exhaust gas recirculation) equipped engine. If the EGR valve is not properly seated it will allow exhaust gas to recirculate into the engine and cause cold operation stumble.

 

3) all this emissions control equipment is likely vacuum operated, so any near 50 year old vacuum hose or device is suspect. There should be a vacuum diagram label underhood of your Pacer.

 

The AMC 258 was used for right at 20 years, in cars, trucks and Jeeps. It's a great engine, reliable and torquey, and pretty fuel efficient too. What that means is the Jeep community is very well-versed on these engines and is a good source of information. So if someone tries to tell you it's an oddball because it's in a Pacer, they quite simply don't know what they're talking about. 

 

Fishbowl comparison notwithstanding, I always thought Pacers were pretty cool because it showed AMC was still adventurous and willing to take risks, when the Big Three were sitting on their hands.

[Rusty_OToole]

1 hour ago, jim1941 said:

Thanks to you both!  Guidance very needed and appreciated.  I launched this project because the car runs rough; better after warmed up. When I first got the car it was really running rough and a mechanic discovered a very bad harmonic balancer which got replaced. Re; tune up: I took out all the spark plugs one at a time and cleaned them with a brass brush. The one near the A/C compressor was horrible to get out and when I did, noticed the base just below the porcelain was very rusty unlike all the others.  Did someone skip that one?  Anyway, I'll be changing all 6 checking proper gap.    I'd like to figure out how to check and compare firing order with where plugs go on distributer cap, just in case it's wrong.  Jim

Is the bad plug identical to the others or is it slightly different, possibly even a different make? Because sometimes if a plug is hard to get at the mechanic will just skip it when replacing plugs.

 

You can turn the engine by hand until the timing marks line up. That should point the rotor to #1 spark plug wire. Careful, it is possible that it will be 180 degrees out. You can check this by doing this test while the #1 spark plug is out, if you get a Woosh of air out the plug hole it is coming up on compression, in other words, that is the firing stroke which is what you want.

Now you can check that the wires are all correct according to the diagram provided by Rocketraider above. Sometimes they get mixed up especially #3 and #4. If they do the engine may still run but it will run rough.

[Rusty_OToole]

Jim I think you should put the new spark plugs in, check that the ignition wires are all correct, then if it still won't run right, do a compression test. Only if it passes this test can you do a proper tune up, if you have bad compression you may be able to get it to run better but it will never run right.

 

The key questions are, how is the compression? How is the oil pressure? If you have good compression and good oil pressure you have a good motor.

 

Your AMC six is one of the strongest, most long living motors ever made. But it is now nearly 50 years old. So who knows. On the good side, if it needs a valve job, all parts should be easily available and it is a simple engine to work on.

[jim1941]

Plugs replaced and what an improvement!  Photo showing the set of 6 with that hard to change one at #1.  Question:  the #1 plug wire inside cap connection looks different from all the others (see photo) and the wires are all matching as a set. Is this ok?  

 

Rocketraider advice taken regarding choke test.  First photo cold engine. Second is with engine running and a few moments after starting.  I think all is well.  Should mention, before starting cold engine the choke was open a bit. I touched some side linkage and it quickly snapped shut as seen in first photo.   Jim 

[TerryB]

Ha! Somebody didn’t want to mess with getting to plug #1.  Five champion plugs and one AC.  What are the numbers on the champion and AC?

[jim1941]

A 😄  R44XLS.  The other 5:  RN14YC

[jim1941]

Smiling face a mistake.  A C 

[TerryB]

Do you recall the number on the new plugs you installed?

[TerryB]

From my 1980 Chilton’s Auto Service Manual 

 

[TerryB]

The 14Y plug is a slightly hotter plug than the 12Y.

[Frank DuVal]

Ah, the old "how to set an automatic choke" instructions in this day of EFI. 50 years ago it was second nature to every driver to do it. You need to depress the accelerator pedal a little (1/4 to 1/2 way) then release on a cold engine to set the choke. That is what you accomplished jiggling some levers before your first picture.

 

 

[TerryB]

The owners manual, if it’s still with the car, will include starting instructions for cold and hot conditions.  Like Frank says, never thought the day would come when this is not second nature.

[Rusty_OToole]

Those plugs look rather black. Do they seem oily, gassy or sooty? If they seem oily your engine may be burning oil. If they are gassy or sooty engine is running rich. This is a normal condition when starting from cold with the choke on so if you have been messing around and not driving anywhere, this could be normal. On the other hand the choke could be stuck or something.

[Bloo]

17 minutes ago, TerryB said:

The owners manual, if it’s still with the car, will include starting instructions for cold and hot conditions.  Like Frank says, never thought the day would come when this is not second nature.

 

But think about how long fuel injection has been standard. When were the last of the last US market carbureted cars? 1991?  That's 32 years ago. In the 80s and 90s we were teaching people to not touch the pedal on fuel injected cars.

 

It's still second nature to me to set the choke, but you just can't expect people to know that anymore.

 

[pfloro]

3 hours ago, Bloo said:

When were the last of the last US market carbureted cars? 1991?  That's 32 years ago.

I'm pretty sure that the last American carbureted engine was the Olds 307 V8 which was made through the 1990 model year.

It was used from 1980 and GM didn't see the need (those bean counters...!) to convert it to FI (even throttle body) because it easily met

emission standards.  

 

Paul

 

 

Edited December 19, 2023 by pfloro (see edit history)

[m-mman]

8 hours ago, Bloo said:

But think about how long fuel injection has been standard. When were the last of the last US market carbureted cars? 1991?  That's 32 years ago

And if the carburetor cars lasted 10 years then the American fleet was all FI by the turn of the century. That was 25 years ago.  😲
 

Now to understand why the choke on my Model T is located at the radiator! 😆

[Bloo]

Because you are cranking it.

 

[Frank DuVal]

Just like pulling the rope on a lawnmower, I liked the choke to be right there so I could apply it or not while pulling, pulling....  Now the rope grip is up by the operator position on the handle and no separate choke function or any speed function on some models....😲

 

Oh wait, we were discussing Pacers... 

 

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[EmTee]