How to Tune for Fuel Economy

[donnyeagle]

I hear ya on the Festiva. I'm no into owning allot of cars. That's why I want to get this one working. I really like the challenge. I like tweaking. It just seems like I have done allot of the things suggested with no improvement. I do want to try the ECM system and see what happens. Not sure what I have to have hooked up for it to work. I know I have to undo the bypass and hookup the stepper motor. What else do I need to have hooked up?

[carnuck]

The first "modification" I do to every AMC I have ever owned is change the ignition coil to match a late '70s Mopar. (NAPA number IC12 or IC12SB the cheaper version) and do away with the horseshoe connector that left me stranded several times. It makes nearly double the spark of the stock coil, which was designed for points systems. You need hotter spark to jump a lean gap on the plugs.

[donnyeagle]

Did the Mopar coil help your fuel economy?

[eagle87]

for fuel economy i would recommend bosch fusion spark plugs 4508 or platinum +4 4428, as well as replacing the tired fuel pump, and coil (stock coil), what condition is the pcv valve in? and fuel and air filters? and re connecting the ecm would be recommended, what exactly do you have left in your engine compartment for the electronics? does the stepper motor operate when power is applied when the carb was rebuilt?( also are the idle/milture screws set to factory spec), what is the ignition timing set to? also if you reconnect the ecm it must be reset using the correct amc proceedure due to the knock sensor, if you reconnect the ecm i would recommend a new oxygen sensor as well, also using royal purple engine oil i found helped mileage some

[greymarooneightytwo]

As someone who just ordered the Motorcraft 2150 and an HEI distributor... I don't like hearing everyone talk about having to reconnect the ECM, I was planning on permanently bypassing it.

[eagle87]

i have 5 eagles and a concord with the ecm connected, once tuned exactly (there very sensitive) it is possible to get upwards of 25 + mpg hwy

[carnuck]

As someone who just ordered the Motorcraft 2150 and an HEI distributor... I don't like hearing everyone talk about having to reconnect the ECM, I was planning on permanently bypassing it.

The ECM isn't on my list of things to have. Mind you my end game plan is EFI from a Cherokee

[eagle87]

carnuk, did you know there is, or atleast was a direct retrofit kit from chrysler for the 4.2 L jeep engine (ie amc engine)?

[carnuck]

The Chrysler HO EFI conversion kit? No longer available, but a '91 to '95 XJ setup is pretty easy to convert into the Eagle, especially if you are doing the head swap anyways. I have a J10 with 4.0L/AW4 and we converted my Spirit of the Eagle to 4.2L/AW4/NP242. He plans to switch to EFI later, but the 4.2L gets 20 mpg already with the non-feedback BBD I modified on it.

The best part about that kit was the MPFI intake designed for the 4.2L head that clears the brake booster. I plan on an Astrovan Hydroboost to cure that issue.

[eagle87]

would the kit we are talking about be the 1st one listed here from summit racing?

http://www.summitracing.com/search/department/air-fuel-delivery/part-type/fuel-injection-systems/make/jeep

[donnyeagle]

I just had a strange thing happen. I filled up and topped off after a 110 mile mostly 55 mph run, about 20% hilly. I got 25 mpg, Sweet. I'll keep you posted. I think it may be as a result of an adjustment to the metering rod piston position. I loosened the small flat head screw on the pump counter shaft, light pushed down on the metering rod assembly while lightly pressing down on the tab near the flat head screw and then I tightened the flat head screw. It seems to be running better now. Time will tell.

It amazes me that so much un-burned gas is being wasted on so many of these engines. How can an engine run so rich and still run decent? Strange.

Also on the PCV valve. I have been experimenting. I tried hooking up 2 PCV valves (some say it works better on and older 258). So far this has lead to increased oil usage, difficult tuning and an erratic idle. I think it is bleeding to much air with two. I switched back to the correct setup with 1 PCV valve from the front opening on the valve cover with the evaporator tank teed in and an open connection from the rear opening on the valve cover to the air cleaner. It seems to run best this way. This engine doesn't seem to have a big blowby problem.

Thanks for all of the posts!!!!!! Hopefully it will help allot of our fellow nesters.

[carnuck]

It's available again? Cool, but $till too expen$ive though. EPA put it on hold in '05 I was told.

[donnyeagle]

Here's an interesting idea. According to info I have been reading if the coolant temp switch is unplugged the ECM does not operate. Would that be EASIER than the bypass. Also a dashboard switch could be connected to the coolant temp switch connector and then you could turn the computer off or on when ever you want to. Hmmmm, might be fun.

[greymarooneightytwo]

That sounds brilliant...

[ammachine390]

Here's an interesting idea. According to info I have been reading if the coolant temp switch is unplugged the ECM does not operate. Would that be EASIER than the bypass. Also a dashboard switch could be connected to the coolant temp switch connector and then you could turn the computer off or on when ever you want to. Hmmmm, might be fun.

Don't think it would work right. Computer may not go into closed loop until the coolant is warmed up, but I believe that it always controls the ignition timing. And if the coolant is reading cold all the time, timing will be retarded giving poor economy.