1986 AMC Eagle Wagon cheap rehab

[zeebo76]

Hi, I tried to post just a little while ago and got an error, so I’m trying again.

I’ve got an ‘86 eagle that’s pinging/detonating on normal gas.  Im running 89 octane at the moment and it works BETTER, but it’s still not gone.  I think something’s wrong, but I’m stumped.  When it starts to ping, it’s quiet at light throttle, loud at medium throttle, and goes away entirely at WOT.

Head is freshly machined (replaced head gasket a while back), I’ve tried richening fuel mix on the carb, retarding the timing, and it’s not running hot.  What could be the issue?

EDIT:  I realized that I should give more info.  It’s the 258 I6, has a rebuilt Carter carb, vacuum wiring was totally screwed up when I got it from the PO and I think it’s mostly fixed now. I’ve replaced the ignition control module on the passenger side fender well.  I don’t know when the timing belt/chain was last replaced.

Though the car doesn’t seem to run hot, it DOES change in temp very quickly depending on conditions.  I can move from cool shade to warm sunlight and the temp will rise.

[AMC of Houston]

First, I'd set the carb and timing per the AMC IS-12e service letter and see if that makes any difference.  Next I'd be checking out the knock sensor system per the TSM (sensor, wiring, etc.).

Note my '85 with 200K miles sounds like its pinging, but its really the timing chain rattling on the timing cover!   Its the original chain - I really need to replace it.......

[zeebo76]

I THINK I happened upon the answer last night...  Was doing a little forum searching and read that a machined head without a thicker head gasket to match will increase compression, and can therefore cause pinging on regular gas.  Well...  The PO drove this eagle on a bad head gasket and overheated it very badly, warping the head.  The machine shop managed to machine it straight for me and it runs fine with exception of the pinging...  Which is probably a result of them taking so much material off of the mating surface.  Thoughts?

EDIT:  Thanks for the input, Houston.  This eagle only has 80k original miles, so I doubt it would be the timing chain by this age - but never say never, I suppose.

As for timing and carb, I’ll try to fiddle with those some.  I should really buy a TSM...

[zeebo76]

Just bought a vacuum gauge.  Off the manifold I’m making 20 in. Hg at idle speed...

[Mitch]

First, I'd set the carb and timing per the AMC IS-12e service letter and see if that makes any difference. 

Here is IS-12E...

http://amceaglesden.com/guide/November_1987_-_IS_12E_-_Idle_Speed

[Taylor]

Congratulations on the Eagle.
Have you checked all the vacuum lines?
What about timing? Ignition upgrades?
With the machine work done, have you tried premium fuel? Octane booster?
As for the errors that you were getting. If it happens again can you take a screenshot and send it to me. I’ll see if it can figure out what happens.

[zeebo76]

Mitch:  thanks for the link, that will definitely come in handy here real soon.

Taylor:  I’m in the process of working through all the vacuum lines simply to find leaks.  I’ve had a mechanic go through them to ensure relatively correct routing, but I’m not too sure it’s all correct...  More correct than it was before the mechanic touched it, I’m sure!

I’ve fiddled with timing.  Right now it’s sitting back at 12 BDC, base timing.  Vac advance bumps it to 18-20 right now, possibly more when it’s spinning faster - haven’t had the RPM too high with the timing light hooked up.  Only other things I’ve done related to spark are replace plugs, wires, cap and rotor.

After the machine work done I tried to get it not to ping on regular octane and couldn’t for the life of me - I’m on 89 octane right now, and it only starts to ping when the temp needle climbs over halfway up the gauge.  Pinging gets louder both at higher temps (to be expected) and between 1/4 and 3/4 throttle.  Haven’t tried octane booster.

I’ll shoot you a message if I get another error - thanks!

[Mitch]

when the temp needle climbs over halfway up the gauge. 

That could be a red flag. I've never had an Eagle's temp gauge go any where near the half way point. They usually barely get into the 'normal' range. You may need to flush the cooling system.

[zeebo76]

when the temp needle climbs over halfway up the gauge. 

That could be a red flag. I've never had an Eagle's temp gauge go any where near the half way point. They usually barely get into the 'normal' range. You may need to flush the cooling system.

That’s news to me!  On hot days it can pretty easily reach the upper third of the gauge.  I guess a system flush is on the list, ASAP.

[zeebo76]

I’m going to buy an infrared thermometer.  What temp should I see on the engine at normal operating temp?

[Mitch]

If your thermostat is the proper one and is operating properly the coolant temp should stay real close to 195 degrees.

[zeebo76]

If your thermostat is the proper one and is operating properly the coolant temp should stay real close to 195 degrees.

I let it warm up to where it wanted to stay in the driveway (let it sit, running, for probably 30 mins) and it hovered around 190 like you said.  I took measurements at all coolant hoses - ranged from 160 to 190 depending on location.  However, it does rise quickly under acceleration or in warmer weather...

The fan works properly too, as far as I can tell.  Thermostat is new (installed it probably 500 miles ago) though the car might have overheated since then.  Temp gauge got to 90% once in rush-hour, uphill, in 100 degree weather...  Nothing burst, it just pinged loud enough that the echo of each ping off of the cars beside me actually drowned out any of my own engine noise.

[Mitch]

Did you take the temp on different spots on the rad? A clogged rad will have cool spots. Also ensure the rad is topped up with coolant and doesn't have an air lock.

[zeebo76]

I was going to take the eagle on a little trip today, but I didn’t get the chance.  About an hour in, the car started to buck.  Felt like some kind of issue with the transmission, but it’s not an engine issue....  Some kind of drivetrain problem.  The same thing will happen when I’m coming home, going up my driveway.  It’s angled a good 20 degrees and when I go up, the car tends to kick up into second gear and I get the same feeling.  Like a repeated clunk that feels like a tooth hitting somewhere.  Whole car shakes, and I can hear it a little bit.

UPDATE:  About to drive home now.  Wish me luck!

[zeebo76]

Made it home.  Man, that feels bad...

UPDATE:  Just checked trans fluid.  near full, and it looks to be in good condition.