new engine troubles

[larsen101]

so i put a new long block in my 87 ranger and now im getting worse mpg than the old one. i get anywhere from 10-16 if lucky it was 18-22. my question is what might be some things that would cause this to happen? timing, plugs, wires, cap ect... any help would be great.

 

[177CIOfPureLove]

Breaking in new motors is never easy on MPG. Your going to have to live with it the first hundred to thousand miles as you break her in. Think about new piston rings in fresh cylinders, there not seated or wore in, same with the rest of the motor. Once they are, you will be better off that before. And if not, I would start looking at other things. But I can practically promise you its not the case.

 

[rusty70f100]

Recheck your timing. 10 degrees BTDC, with the SPOUT unplugged. Be sure to plug the SPOUT connector back in when you're done.

 

[larsen101]

ok ill recheck the timing thanks

 

[larsen101]

also what should be the normal idle rpm, i seem to be around 1200 on start up and then maybe goes down to 1100 or 1000.

the other thing is when i start it up cold its at 1400 and then i have to tap on the gas and then idles down. not to sure about that

 

[rusty70f100]

There should be a sticker up by the hood latch somewhere that says the idle speed.

It is normal for a cold engine to idle higher. They have for years, only now it's automatically controlled by the computer. The engine needs to be fully warmed up before you check the idle speed.

IIRC, normal should be 800 to 850, depending on if you have an automatic or manual transmission.

 

[larsen101]

i have a manual, how would i adjust this? timing or is there a different way?

 

[rusty70f100]

No. Do not adjust the timing.

There should be a stop screw on the throttle body. Don't adjust it too far or it will start to stick. Also make sure the engine is fully warmed up.

I'm sure there's a better procedure for setting the idle but I haven't found it. I always just turned the stop screw until it is at the specified RPM when warm.

 

[jhammel85]

Don't mess with that screw unless the IAC is unplugged. The screw on the throttle body is for setting the TPS baseline. The EEC controls idle but the TPS is involved as well..

Here's how to set the idle (at least what has worked for me):

- Get the truck up to normal operating temp, shut it off and unplug the IAC. Restart the engine (might have to press the pedal to give it a little air to start)

- Run it at 2000-2500 rpm for 20-30 seconds. Let off the pedal and adjust the idle speed to 750 RPM since you are running a stickshift.

- Shut the truck off and plug the IAC back in, disconnect the batter for 15 mins or so. Once restarted, all should be well...

Good luck!

 

[larsen101]

ok cool i will do that and let you know how it goes. thanks