Need help: rough engine diagnosis - Taurus Car Club of America : Ford Taurus Forum
Register Home Forums Active Topics Topic Finder Photos Members List Search Today's Posts Mark Forums Read Auto EscrowAuto Loans
TaurusClub.com is the premier Ford Taurus Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools
Old 11-19-2012, 04:13 PM   #1 (permalink)
Junior Member
 
Member Number: 51276
Join Date: Nov 2012
Location: Renton, WA
Chapter: Pacific Northwest
Drives: 1998 Ford Taurus 3.0 OHV
Visit: My Garage
Posts: 9
Trader Score: 0 reviews
Rep Power: 0
jbh425 is an unknown quantity at this point
Default Need help: rough engine diagnosis

I've been trolling the boards and going back and forth with my 1998 3.0 OHC trying to diagnose and fix a misfire. I have new plugs, wires, ignition coil, fuel pump and filter.

Codes read by mechanic
P0305
P0102
P0351
P0174

Symptoms are intermittent misfire/rough idle, worse at idle and under power. Occasionally bucks. I've tried unplugging the MAF, and the car *almost* dies, but then idles back up and continues to run rough.

Next steps?
jbh425 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 11-19-2012, 04:43 PM   #2 (permalink)
Sam
breeves002
 
Sam's Avatar
 
Member Number: 49890
Join Date: Sep 2012
Location: St. Louis, MO
Chapter: Midwest
Drives: 2008 Mercury Sable Premier
Visit: My Garage
Posts: 6,089
Trader Score: 8 reviews
Rep Power: 68
Sam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond repute
Default

Start here: How to Understand and Diagnose Misfires

Sounds like this is pretty complicated.

Let's go through the basics:

- Make sure your wires are routed correctly. There is a diagram on the thread I linked above. Also make sure your wires are just plugged in all the way.

- Make sure your Mass Airflow (MAF) is plugged in. Clean it if you have not already, it may need to be replaced. There are pinpoint test you can do to check. EDIT: After re-reading your post, it looks like this code could be caused from you unplugging your MAF to do tests. So we'll come back to this if we have to.

- Looks like you have a vacuum leak somewhere, you can do a cigar smoke test. Video on that in the linked thread above. Check PCV assembly (hose and valve, location on above thread).

- One thing you can do now: preform a power balance test to make sure only #5 is misfiring. Just remove the wires from the coil and replace one by one. If the idle of the engine does not change, that cylinder is misfiring.
__________________
Sam

2008 Mercury Sable Premier
2012 Kia Soul Base AT 1.6GDI
2004 Acura TSX 2.4
Moved On: 2000 Sable LS Premium Duratec

Last edited by Sam; 11-19-2012 at 04:45 PM.
Sam is online now   Reply With Quote
Old 11-19-2012, 07:11 PM   #3 (permalink)
Crazy Devoted Member
 
Member Number: 10865
Join Date: Dec 2006
Visit: My Garage
Posts: 12,178
Trader Score: 1 reviews
Rep Power: 52
sheila is a glorious beacon of lightsheila is a glorious beacon of light
Default

Check pcv u-shaped hose under the throttle body.
sheila is online now   Reply With Quote
Old 11-19-2012, 08:05 PM   #4 (permalink)
Technical Advisor
 
behlinla's Avatar
 
Member Number: 14275
Join Date: Dec 2007
Location: Wisconsin
Chapter: Midwest
Drives: A blue car
Visit: My Garage
Posts: 7,481
Trader Score: 0 reviews
Rep Power: 79
behlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond repute
Default

P0305 = Cylinder #5 misfire
P0102 = Mass Air Flow (MAF) Circuit Low Input
P0351 = Ignition Coil A Primary/ Secondary Circuit Malfunction
P0174 = System to Lean (Bank 2)

You might have caused the P0102 code by unplugging the MAF if you checked the codes after you did that test.

Check the spark on all cylinders, especially #5. You have a coil A circuit code, which is the coil for cylinders #1 and #5. If you replaced the coil already, you might have gotten a bad one, or you have some other issue with the wires going to the ignition coil (or possible a PCM driver failure). It's important to check for spark to make sure the coil is working properly.

Bank #2 lean is probably related to the misfire on #5.

I would also pull the #5 spark plug and have a look. It's the middle one on the radiator side of the engine.

P.S. Your engine is either OHV or DOHC. Which one?

Last edited by behlinla; 11-19-2012 at 08:11 PM.
behlinla is offline   Reply With Quote
Old 11-19-2012, 08:15 PM   #5 (permalink)
Sam
breeves002
 
Sam's Avatar
 
Member Number: 49890
Join Date: Sep 2012
Location: St. Louis, MO
Chapter: Midwest
Drives: 2008 Mercury Sable Premier
Visit: My Garage
Posts: 6,089
Trader Score: 8 reviews
Rep Power: 68
Sam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond repute
Default

^
He says OHC, but he may have meant OHV... Took me a while to figure out the difference.

P.S. How often do you see that the PCM is actually bad?
__________________
Sam

2008 Mercury Sable Premier
2012 Kia Soul Base AT 1.6GDI
2004 Acura TSX 2.4
Moved On: 2000 Sable LS Premium Duratec
Sam is online now   Reply With Quote
Old 11-19-2012, 08:53 PM   #6 (permalink)
Junior Member
 
Member Number: 51276
Join Date: Nov 2012
Location: Renton, WA
Chapter: Pacific Northwest
Drives: 1998 Ford Taurus 3.0 OHV
Visit: My Garage
Posts: 9
Trader Score: 0 reviews
Rep Power: 0
jbh425 is an unknown quantity at this point
Default

OHV (sorry, sticky fingers)

I cleaned the MAF tonight and the engine is running smoother, but I can still feel a misfire.

I'll try to find a vacuum leak, check the pcv, and check spark on #5 and go from there.

Thank you all for the suggestions so far.
jbh425 is offline   Reply With Quote
Old 11-20-2012, 12:47 AM   #7 (permalink)
Technical Advisor
 
behlinla's Avatar
 
Member Number: 14275
Join Date: Dec 2007
Location: Wisconsin
Chapter: Midwest
Drives: A blue car
Visit: My Garage
Posts: 7,481
Trader Score: 0 reviews
Rep Power: 79
behlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond reputebehlinla has a reputation beyond repute
Default

Quote:
Originally Posted by Breeves002 View Post
P.S. How often do you see that the PCM is actually bad?
Not very often. Somewhere about 1-5% of the time. GM products seem to have a much higher PCM failure rate though.
behlinla is offline   Reply With Quote
Old 11-20-2012, 07:11 AM   #8 (permalink)
Sam
breeves002
 
Sam's Avatar
 
Member Number: 49890
Join Date: Sep 2012
Location: St. Louis, MO
Chapter: Midwest
Drives: 2008 Mercury Sable Premier
Visit: My Garage
Posts: 6,089
Trader Score: 8 reviews
Rep Power: 68
Sam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond reputeSam has a reputation beyond repute
Default

I usually see people replace the PCM when they really don't need to. I read online that 60% of the time the original isn't faulty. Every one is so quick to blame the computer...

I notice in alldata with all of the pinpoint tests, there are a lot that lead to the option "replace PCM". I feel like they are wasting your time with a lot of those tests.
__________________
Sam

2008 Mercury Sable Premier
2012 Kia Soul Base AT 1.6GDI
2004 Acura TSX 2.4
Moved On: 2000 Sable LS Premium Duratec
Sam is online now   Reply With Quote
Old 11-20-2012, 11:53 AM   #9 (permalink)
Crazy Devoted Member
 
Member Number: 10865
Join Date: Dec 2006
Visit: My Garage
Posts: 12,178
Trader Score: 1 reviews
Rep Power: 52
sheila is a glorious beacon of lightsheila is a glorious beacon of light
Default

If you have the Vulcan ohv eng., your pcv is on the rear pass. valve cover. On gen3 Duratec dohc engs., it's under the throttle body.
sheila is online now   Reply With Quote
Old 11-20-2012, 03:01 PM   #10 (permalink)
Junior Member
 
Member Number: 51276
Join Date: Nov 2012
Location: Renton, WA
Chapter: Pacific Northwest
Drives: 1998 Ford Taurus 3.0 OHV
Visit: My Garage
Posts: 9
Trader Score: 0 reviews
Rep Power: 0
jbh425 is an unknown quantity at this point
Default

Used carb cleaner to search for a vacuum leak, but couldn't find anything. I sprayed all around the manifold, hoses, connectors, etc. Nothing caused an idle change.
Checked spark at the ignition coil and everything there looks fine. It is definitely #5 that was missing, but now that the MAF is clean the problem is less noticeable.
I pulled plugs 4, 5 and 6 and 5 looked substantially worse than 4 and 6. Replaced it. When I bought the plugs the O'reilly staff told me that the OEM plugs were platinum, whereas the plugs I currently have are copper. I bought the platinum plugs but decided to replace just the #5 for now (with copper) until the source of the miss has been fixed.
The SEL is on and solid, not flashing anymore. Should I clear the codes now and see what pops up next, or does the computer automatically reset when problems are fixed?
jbh425 is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply


Thread Tools

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 On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 11:03 AM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.3.2