Weird Misfire

[Foxone]

Ok, I've read through the threads, and I cant find anyhting similiar to my situation.

My '99 3.8 has started misfiring. This misfire is very intermittent, I'll be driving along, and I can feel it shudder, then the light comes on. Code has said 304,302 and 300.

Ive replaced plugs (Motocraft platinum) new wires, new Accel super coil.

Rechecked all plugs for cracks,gap etc.
New EGR valve.
Seafoamed
New PCV valve
Checked for vacum leaks.

I replaced the camshaft position sensor assembly a couple weeks prior, but I didnt have any misfiring, does not seem like it would show up later.

Im guessing the fact that is isnt happening all the time leads me to believe something loose or ??

Now where to look?

MAP sensor?

 

[Aeroman]

Can also be fuel related blockage, when did you last change the fuel filter?
Also check your fuel pressure, could be signs of a failing Fuel pressure regulator.

Check all ignition wiring for corrosion or damage also the injector harness
(especially related to #2,4 cyls). Can you get a misfire at idle speed & do you have access to a noid light set?

Aeroman.

 

[Foxone]

I actually got one at idle today waiting for a light, I didnt feel it, but the light came on. Then afterward one at speed. It seems like it needs to warm up for it to happen also.

No noid set. What should I look for on the harness? just screwed up wiring? I did hold a dowel to the running engine and listened to each injector, they also sounded the same.I have never changed the fuel filter, and Im pretty sure the last guy didnt either.

 

[Aeroman]

I think your description points more to fuel restriction. First thing I would do is change the fuel filter for $10 you might cure this immediately. Ford injectors are reliable, rare to fail especially an intermittent. However electrical connections can corrode, check all plugs on the ignition/injector harness for good connection/ corrosion.
Do you have a scan tool to monitor RPM's?

 

[wmburns]

Use the cam sensor alignment tool

Did you use the correct tool to align the cam shaft position sensor? The key to understanding this problem is the Random misfire P0300 DTC. Should focus on causes that affect multiple systems or the entire engine.

A bad cam sensor can cause P0300 DTC's. Since the sensor has recently been replaced, I am going to go out on a limb and say that the correct tool was not used. The cam sensor is out of alignment thus giving the symptoms of a bad cam sensor.

>>>
P0300 - Random Misfire

The random misfire DTC indicates multiple cylinders are misfiring or the PCM cannot identify which cylinder is misfiring.

Camshaft position sensor (CMP)
Low fuel: less than 1/8 tank
Stuck open EGR valve
Blocked EGR passages

One or more EGR passages may be blocked or partially blocked. If this is the case the Misfire Detection Monitor will indicate the EGR port to check for possible blockage.

 

[Foxone]

You just reminded me of something. While changing the thermostat, I cracked the sensor itself on top of the camshaft position sensor, it was bent a bit, so I JB welded in place, think maybe something is screwed up there?

Also, today I changed the fuel filter, now Im getting these codes

0411
1314
0300

At least I feel like im getitng somewhere.

 

[Aeroman]

If you have a Cam position sensor problem (CMP sensor) usually you get a p034X if there is a problem with the sensor or timing. Did you loosen the synchroniser unit ? if not & you only replaced the sensor (the plastic part with the electrical connector) you don't need to time the synchro drive unit. Otherwise you will need the alignment tool to hold the worm gear shaft in the correct position while you install the synchro housing with the engine set on #1 cyl set to TDC on the firing stroke. You need to engage the synchro at the correct angle to ensure Fuel Injector timing is correct. You cannot just rotate the synchro drive unit into the same position, the drive shaft has to be orientated correctly to the cam position.

 

[wmburns]

Ford TSB on cam alignment

Ok, I am confused. Did you REPLACE the cam sensor or did you crack it and repair with JB weld?

There are several Ford TSB's that state outright that the alignment of the cam sensor is critical and can not be done correctly without the alignment tool. Further the symptoms of a misaligned cam sensor has a close relatation to your symptoms.

Soooo what am I missing because it sure seams to me that you have a good possible solution to your problem.

>>>excerpts from Ford TSB
Technical Service Bulletins » All Technical Service Bulletins » Engine Controls - Engine Surge/Rolling Idle/DTC's Set » Service Procedure Notes


Service Procedure

If you suspect that a vehicle (engine) may have had the synchronizer assembly (Figure 3) installed incorrectly, check the vehicle history to see if related service has been performed. If you determine that the synchronizer could have been installed incorrectly, use the following procedure with WDS to verify correct installation (Figure 5).

NOTE CORRECT CAMSHAFT POSITION SYNCHRONIZER ASSEMBLY INSTALLATION IS CRITICAL. AN INCORRECTLY INSTALLED SYNCHRONIZER CAN CAUSE HARD TO DIAGNOSE DRIVEABILITY CONDITIONS AND POSSIBLE SERIOUS ENGINE DAMAGE.

Reasons for incorrect installation are:

^ Not setting the # 1 cylinder on Top Dead Center (TDC) of the compression stroke

^ Use of the incorrect camshaft synchronizer tool for installation

^ Incorrect alignment of the synchronizer tool

 

[Foxone]

I replaced the whole assembly, then later cracked the plastic sensor. So would installing it without the tool cause such intermittent misfire? Wouldnt it happen pretty regular? I basically pulled the old one, and lined the new one up exactly the same and installed it.

As far as the other codes, I pulled the air pump out and it was totally rusted and corroded, and the round part on the bottom was full of water. So a new pump is in order, as well as an alignment tool if I can find one. Anyone know where I can get one?

 

[wmburns]

1999 3.8 cam tool OTC-6470

It would have been nice to know that you pulled the air pump. That explains the DTC codes associated with the air injection system. I was thinking there was a problem with my references or the wrong codes were posted.

I am not sure how to make it anymore clear that the alignment of the cam sensor is CRITICAL. Excerpts from the actual Ford TSB have been supplied. The TSB also states that the symptoms can be slightly different and DIFFICULT to diagnose.

OBTW, what is the 1st item mentioned under the DTC for "random misfire"?

If you are happy with re-installing the cam sensor by "eye ball", so be it.

Ford 303-630 OTC-6470

Ford Rotunda Cam Synchronizer
Amazon.com: OTC 6470 Ford Cam Sensor Sync Tool: Automotive

Or your local autoparts store.

 

[Foxone]

Well the 411 and 1414 codes showed up after I replaced the fuel filter, so those are new. So I went ahead and pulled the pump. I am looking for a tool now to redo the cam sensor. So hopefully that will cure the 300 code.

 

[Aeroman]

I replaced the whole assembly, then later cracked the plastic sensor. So would installing it without the tool cause such intermittent misfire? Wouldnt it happen pretty regular? I basically pulled the old one, and lined the new one up exactly the same and installed it.

As far as the other codes, I pulled the air pump out and it was totally rusted and corroded, and the round part on the bottom was full of water. So a new pump is in order, as well as an alignment tool if I can find one. Anyone know where I can get one?

If you replaced the whole assembly.... easiest way is to get the alignment tool, you will then need to find cyl #1 TDC on the compression stroke & at that stage re-engage the synchroniser assy at the correct angle. There are instructions as to the correct angle with the alignment tool I believe.

What the CMP sensor does is confirms the power stroke cycle of engine rotation so that fuel injection will be timed correctly & not fired into the intakes on the exhaust stroke..

Good luck!

 

[Foxone]

Thanks all, I ordered a tool today.And I went ahead and picked up a new sensor since the other was cracked, hopefully Ill be flyin down the road soon.

 

[Foxone]

Well, I got the tool today set the #1 cylinder to TDC, popped the tool on, it was perfect, reinforcing my belief that you can pop out the old and put the new one in the same. I replaced the actual sensor, Im gonna drive it tomorow. I will be moving on to injectors if its still not fixed.

 

[m1903man]

I am getting the same issue with my '94. Tell me if this sounds about like your car: Normally there are no issues in acceleration, deceleration, or just foot to the floor WOT. The issue always seems to be when I am at about 60 to 70mph. It feels like a split second loss of all power in the vehicle.

This issue started when I swapped the AODE out for a T5. Everything reads good on the car and the only codes are tranny related (I didn't change the computer to a manual computer).

I see that the post was from a few months back, so I am wondering if you found a solution.