engine hunting for idle

[99iowa4x4ranger]

i have a 1994 reg cab 2.3 5 speed ranger, and truck sometimes will buck a slight bit, not too noticeable, but if i am coming to slow down and pop it into neutral, the truck will surge/hunt and go up and down in rpm, until i get to about 20 mph, and then it will smooth out and run fine, i have no tach, so im unsure of the rpm spike, and also it seems like it idles kinda high, i know it should when its cold, but its like that all the time. the truck did buck some upon acceleration, so i removed and cleaned the MAF and throttle body, and that has gone away, but the surging is still there. the CEL is on, not when i first start it up, but will come on shortly after running. and i will check that tomorrow with my dads scanner, i do not have the obd1 cables for mine. Just looking for some clues, or if this has happened to anyone else. i will update tomorrow when i check out the codes.

Thanks in advance

 

[99iowa4x4ranger]

well, scanner not working properly, going to do the old fashion blink test tomorrow if i can. anyone have any ideas? seafoam through brake booster today, and new fuel filter. no change. i know my icm was messed up at one time, and has been finicky lately, but that shouldnt control the idle and such

 

[Mazda]

Does it do this just sitting and in idle ?

Do you turn the steering wheel at all before it starts to stumble.?

Here are a few things to check:

Check that you have vacuum to the EGR.

Check that both hoses are connected to the DPFE and are not cracked or broken at all.

Check the hard line that goes from under the throttle body to the cannister.

If you hit turn the wheel at all it could be the 'power steering switch'.

Bryan

 

[99iowa4x4ranger]

it does not do it while just idling, just idles high, and no to when the steering wheel is turned. it stays the same. i cannot check the engine codes for some reason, the CEL will come on after approx 30 sec. or running, and everytime you shut it off, it does the same, but its never on when starting the truck. what is the DPFE? the hose to the egr is on, but it doesnt seem like it has much vacuum going to it, it will not suck my finger, or you cannot hear a hissing. the hard line looks good..

 

[Mark_88]

You won't feel much vacuum with your fingers usually at idle...but it will suck in smoke or a piece of paper (use a large piece so it doesn't actually get sucked in...)...

If you haven't already done so, try spraying the intake area with brake cleaner or something similar...if you hear the idle go up when you do this then you have a vac leak...

The DPFE is the control switch for the EGR...someone just posted an excellent video explaining the relationship of the EGR and the DPFE...and I think it was in this section...maybe a couple of posts down...but if you search YouTube for Wells products you should find a whole whack of them...very good to watch for someone like me who has never actually worked on a FI engine...

 

[Mazda]

The DPFE is bolted on the firewall. You will see 2 hoses that go down to the EGR pipe to the exhaust manifold. Check to make sure these hoses are connected both on the EGR pipe and the DPFE.

Check out this site to see what it looks like, also tells you how to fix certain codes:

http://easyautodiagnostics.com/ford_egr_test/ford_egr_valve_1.php

Bryan

 

[dmassey]

well, scanner not working properly, going to do the old fashion blink test tomorrow if i can. anyone have any ideas? seafoam through brake booster today, and new fuel filter. no change. i know my icm was messed up at one time, and has been finicky lately, but that shouldnt control the idle and such

The icm or DIS module as Ford calls it can contol idle since it turns the SPOUT (SPark OUTput) circuit on and off. When my DIS messed up, it would drop the idle (CEL would come on), then it would work properly (CEL would go off) and the idle would come back up to normal. If you're close to an Auto Zone or Advance Auto, give them a call to see if they can check the DIS for you. If they can, take it off and let thim check it. The easiest way that I have found to get them off is to take the serpentine belt off the compressor pulley, take the compressor loose and pull it as far forward as you can and secure it in place with a coat hanger or other stout wire. When I've got the DIS off, I clean the back off with a rag and some 400 grit sandpaper and the mounting surface the same way to be sure I have a good ground and good heat dissipation as either can cause it to malfunction.