Rough Idle - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

Reply
 
LinkBack Thread Tools Search this Thread
  #1  
Old 05-31-2014
Chris98's Avatar
Member
Thread Starter
iTrader: (3)
 
Join Date: Feb 2010
Location: Thornton, CO
Posts: 705
Rough Idle

This isn't on my truck but on Kyles truck. It's also a 98 with the 4.0l. But he's been having a really rough idle that shakes the whole truck for close to 4 months now. And he keeps throwing parts at it. It's got new spark plugs, wires, IAC, MAF, Intake Gasket, EGR and the downstream O2 Sensor. Now most of that stuff it was throwing codes for. But now it's not throwing any codes any more and the rough idle continues. So I hooked up my scan gauge to it and to mine to compare what the readings on everything were and the Fuel trim on his was way richer than mine.

My readings are:

Bank 1 Long Term - 8.95%
Bank 1 Sensor 1 - 0% - 5.78%
Bank 1 Short Term - 0% - 3.91%
Bank 2 Long Term - 12.5%
Bank 2 Sensor 1 - -3.12% - 0%
Bank 2 Short Term - -2.34% - 2.34%

His readings were:

Bank 1 Long Term - 0%
Bank 1 Sensor 1 - 29.61% - 38.12%
Bank 1 Short Term - 35.94%
Bank 2 Long Term - 0%
Bank 2 Sensor 1 - 32.01%
Bank 2 Short Term - 11.01% - 16.41%

Not really sure where to go from here with it. He's tired of putting money into it and now there's no codes to go off of anymore.

Edit: Forgot to mention that it idles fine when it's in open loop. It's when it goes into closed loop is when it starts to idle really bad.

Last edited by Chris98; 05-31-2014 at 09:45 PM.
Reply With Quote
  #2  
Old 06-01-2014
cheese_man's Avatar
Member
iTrader: (1)
 
Join Date: Nov 2009
Location: arthur
Posts: 2,100
when the engine is warm , remove the EGR vacuum line and check it for vacuum draw

the manifold vacuum to EGR valve switch may be stuck open from coolant deposits
Reply With Quote
  #3  
Old 06-01-2014
RF Veteran
iTrader: (1)
 
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,615
In open loop(choke mode) the Computer doesn't use any feedback from the O2 sensors, it runs engine rich, with higher idle and advanced spark timing.

When engine temp gets up to about 160-180degF the computer will switch to Closed Loop and use the feedback from the UPSTREAM O2 sensors(sensor "1"'s) to adjust fuel/air mix.

Downstream O2 sensors(sensor "2"'s) are only used to test Cat converters, the data from these is compared to the data from the upstream sensors to verify cats are burning off hydrocarbons.

I would swap the new O2 sensor with an upstream sensor then redo the live data scan, and see if that bank is showing better numbers.

Yes, to above post, although a bad EGR vacuum switch would be bad full time not just when engine is warmed up.
But if there is an issue with EGR system adding exhaust gas to intake at idle it would explain the rough idle.
Computer doesn't use EGR system until it is in Closed Loop, so a problem in that system could only show up after warm up.

With the live scan what did the engine temp read?
Should be between 195-220degF(90-104C)
Reply With Quote
  #4  
Old 06-01-2014
Chris98's Avatar
Member
Thread Starter
iTrader: (3)
 
Join Date: Feb 2010
Location: Thornton, CO
Posts: 705
Quote:
Originally Posted by RonD View Post
With the live scan what did the engine temp read?
Should be between 195-220degF(90-104C)
It was around 182 degF. Didn't really get any higher even after driving for 30 minutes with it being close to 90 degf outside.
Reply With Quote
  #5  
Old 07-06-2014
kyle ranger's Avatar
Member
iTrader: (1)
 
Join Date: Mar 2011
Location: westminster,colorado
Posts: 54
Quick update found out it was a bad injector, but also did a compression test and drive side had low like 4 125 psi, 5 125, 6 110. 1 2 and 3 were at 130-140 psi witch is good for 220k on motor. Next step is new head for driver side and replace head gasket on passenger side. New lifters, push rods, rockers and injectors then it be good for another 220k.
Reply With Quote
  #6  
Old 07-06-2014
RF Veteran
iTrader: (1)
 
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,615
I am at 300k on my 4.0l and last time I checked I was at 165 psi average.
test was:
Cold engine
all spark plugs removed
Throttle plate at full open(this also cuts off the fuel injectors)
Battery in good condition

But your numbers are all close to 10% of their average(128psi) so they are fine, the actual numbers are really meaningless since test parameters vary so much

$25 Vacuum gauge can tell you alot about engine condition, good read here: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine

For Chris98: someone has put in a 180degF thermostat, it should be changed to a 192degF thermostat.
People have some odd thoughts about thermostats, pretty much all of them are wrong, lol.
An engine running between 190-220degF has cleaner oil so better lubrication, that's from S.A.E. tests, condensation and blow-by contaminants are burned off better above 190degF.
Fuel economy is better above 190degF and below 220degF.

Running an engine cooler may sound like a good idea, but that's all it is, a sound, it ain't correct, lol.
A 180degF t-stat just shortens the life of an engine.
Reply With Quote
  #7  
Old 07-07-2014
kyle ranger's Avatar
Member
iTrader: (1)
 
Join Date: Mar 2011
Location: westminster,colorado
Posts: 54
Still going to rebuild the top end I'd feel better in the end. Other reasons is the stock heads like to crack and sick of replacing the spark plug every few mouths because of it. Also I am getting a new thermostat, because I have to do a coolant flush with the rebuild.
Reply With Quote
  #8  
Old 07-28-2014
Chris98's Avatar
Member
Thread Starter
iTrader: (3)
 
Join Date: Feb 2010
Location: Thornton, CO
Posts: 705
Thought I would give a little update on this. This weekend we got her running good as new. There were so many things wrong with the truck that I am surprised it even ran at all. First off the timing chain had a 1/4" of play in it, the cam synchronizer had play and was noisy when pulled, #6 full injector was cracked, passenger head cylinder was cracked at the #1 cylinder and starting to crack at the #2 cylinder, driver side head the exhaust valve seats were gone on cylinder #5 and cylinder #6 and was cracked on cylinder #6.

So we installed brand new heads, new timing chain, new lifters, new push rods, new rocker arms, new fuel injectors, new cam synchronizer and all new seals.

Onto the pictures.

Overall picture of the driver side head. Notice the exhaust valves on cylinder 5 and cylinder 6.


Sorry shitty picture, but you can kind of see the crack between the valves on cylinder 6
Name:  20140725_201148_zps9c7e3ebe.jpg
Views: 98
Size:  20.3 KB

Again sorry for the shitty picture, but you can really see the crack between the valves on cylinder 1.
Name:  20140725_201209_zps967eedb5.jpg
Views: 97
Size:  22.0 KB

One Pile of junk.
Name:  20140725_201223_zps1e913ee1.jpg
Views: 110
Size:  93.5 KB

From this angle you can see how much higher the exhaust valves were sitting.
Name:  20140725_201234_zps7e83ac83.jpg
Views: 104
Size:  62.3 KB

Passenger new head installed.
Name:  20140725_201246_zps5438f18c.jpg
Views: 97
Size:  85.7 KB

Picture of new head.
Name:  20140725_201437_zps4068d87f.jpg
Views: 102
Size:  69.2 KB
Name:  20140725_201445_zps22114eb4.jpg
Views: 102
Size:  63.6 KB

Both heads installed.
Name:  20140725_202821_zps778801fc.jpg
Views: 98
Size:  83.5 KB

Starting to look like an engine again.
Name:  20140726_131454_zpsc20de3e5.jpg
Views: 99
Size:  81.2 KB
Name:  20140726_131502_zpse368d996.jpg
Views: 98
Size:  83.0 KB
Reply With Quote
  #9  
Old 07-28-2014
RF Veteran
iTrader: (1)
 
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,615
Thanks for the update

Good work
Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
2003 3.0 Ranger - rough low idle (400 rpm), bogs at 2500K, rough shift, NOW FINE ChargerOnDavins 2.9L & 3.0L V6 Tech 3 03-23-2015 04:25 PM
1995 rough idle/slow return to idle whiskeybreath SOHC - 2.3L & 2.5L Lima Engines 1 11-27-2014 05:06 PM
M5OD rough shift on rough roads, potholes, speed bumps Mike_92 Drivetrain Tech 0 10-28-2013 10:26 PM
1997 Mazda b2300 starting rough, running rough! bonecrusher SOHC - 2.3L & 2.5L Lima Engines 3 03-19-2011 05:04 AM
Rough idle, check engine light SnowGoAK 4.0L OHV & SOHC V6 Tech 6 06-24-2005 04:55 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -6. The time now is 08:52 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.