i have a code reader and can clear codes. I did have a lean bank 1 and bank 2 problem which wouild have caused the miss but when i replaced the elbow it ended those codes but still missed. I've cleared them but i keep gettting random misfire codes and various cylinder misfire codes.

 

yeah it runs real bad when cold I would assume tha'ts because on a cold engine the misfire is more pronounced because it's a cold engine with "cold" exhaust getting dumped into the cylinder which would IMHO make it twice as hard to fire and not miss. when it gets hot the miss is still there enogh to put up a flashing check engine light when going over a overpass because it stumbles so much. yesif i clear the codes they come back. I will try tocheck out that regulator it's the one right by the dpfe sensor right???

 

on your misfire are you still getting them after you changed the plugs and wires ?

 

Right. The regulator is right in front of the DPFE, should look like a small black canister with a two prong electrical connector and and dual vacuum hook up.

 

yes actually the only reason i changed the plug and wires is because I had one plug get loose and rattle out. so i changed them all. it was not missing at this time. the miss from this came later.

 

right then will try tonight when wife gets home with truck.

 

I also have a 98 expy 4.6 V8 and had the exact same codes that you did. I would get a misfire for 1 &5 as well. Did the same and replaced the coil pack, no luck. I even used an air cleaning gun and sprayed a driveway cleaner all around the plugs with the wires removed, then sucked it out the water and blew it out with compressed air. cleaned the wires as well. this all helped it to run better for a few miles and then the codes came back. after searching several forums with tons of suggestions here is what I did.

I removed the EGR valve and used a small tooth brush to clean out both ports on the valve using the same driveway cleaner, throughly flused with clean water and then blew it out with the trusty air compressor. I performed the same cleaning ritual for the IAC as well. But here is what i believe was the big problem. I removed the throttle body and the base. cleaned the throttle body throughly again with driveway cleaner and a tooth brush and did the same with the throttle body base. i found that the 2 breather ports that the EGR valve uses, one was plugged completely with what looked like a black mushroom cap coming out of it, and the other port was almost completely plugged as well. It took a flat blade screwdriver and some time and throttle body cleaner to finally clear both breather ports. I did the same thing for the port that the EGR valve attaches to. Then used more driveway cleaner and small tooth brush to thoroughly clean out all gunk in the ports. once completed, put all parts back on with new gaskets, they are only about 5.00 total for the gaskets. Used same plugs and wires to make sure it was not the plugs and wires. fired her up and all was good. excellent pickup, power, idling and running smooth and no more codes.

after all was good, I did replace the plugs with Motorcraft and got rid of the autolites since there were alot of people having issues with autolite, bosch and no name plugs. Seems that the expy prefers motorcraft, no idea if this has any true bearing, but worth it to me in the long run since she just got her insides all clean, figured might as well get her some new accessories to go with the new attitude. Changed the plug wires as well.

Hope this helps you out.

Now that i got all that done the speedometer is not working, checked for 5 volts on the VSS plug and got zero volts. Guess it could be the PCM. Does anyone have a schematic of the PCM or a good wiring diagram to trace the wires back to the PCM? not really wanting to shell out 300+ for a new PCM. Does anyone have any other suggestions for this problem.

 

sorry about the wordy post and hijacking it for a different problem. I'll start another thread for my issue.

 

was going to do this this weekend.

 

I went out to the truck this monring to start up and pulled the vaccumm on top of the egr valve and it was pulling vacuum. truck was completely cold and it was about 40 degrees out side. BUT i left it off and drove it and it was still missing. i would think if you pull the vacuum on the egr and it's not working then the port would be closed from exhaust gases and would run smoother without exahust being dumped into the cylinder. I wil lsay it seem to run a tad bit smoother though but still missed. this is a darn headache.

 

Based on the findings on your last post, I think I know what is going on. Granted, I'm troubleshooting from behind a computer, and you'll have to do it under the hood. This will be another wordy post.

Let's review what you've told us so far

I think the last post tells alot. Earlier I asked you to apply a vacuum to the EGR valve with the engine idling (cold) and see how the engine runs in that condition. Since you haven't tried that, the last test does the almost the same thing. If the regulator is porting a vacuum to the EGR valve at idle and the EGR valve is working like you say it is, then EGR is being adminstered to the engine at idle when it is not supposed to be. That explains the P0402 (EGR excessive) code. That code is primarily set, as well as checked at idle operation. During normal operation at idle, the DPFE sees equal pressure on both sides of the orifice, therefore no code. But if the valve is open then the DPFE sees the pressure differential and sets the code.

Now for part 2 of your EGR problem. If you have vacuum present to open the EGR valve at idle, then your engine should die, or at least run like 99% crap! But since you indicated that the engine ran smoother, then I'm going to say again that your ports inside the throttle body are clogged. That explains the EGR insufficient code. That code is primarily set at higher engine RPMS and under load when EGR is needed to cool combustion process to keep nitrogen oxide from forming. The DPFE is looking for a large pressure drop across the orifice, but with the ports plugged, it does not see that large pressure drop, hence the code is set.

Wait a minute, how can the ports be clogged, but I still get an excessive EGT code at idle??? I'm glad you asked that question. The carbon that builds up inside the ports is still porous enough to be able to pull a vacuum through it. Example- You could pull the EGR valve off and start the engine and you would feel a vacuum at the plenum, but nothing near what you would feel if the ports were clear. Since your EGR is valve is being driven open when not needed, there is enough of a vacuum produced to pull the exhuast gas through, and for the DPFE to see the pressure drop. Same thing is true for the EGR insufficient code. There is enough of a vacuum present to pull the EGR in, but not in sufficient quantity that the PCM is hoping for. That is why it usually takes a number of drive cycles before the code is set, since the DPFE may detect a pressure drop which on the edge of its envelope.

All this leads me to my first reply to your original post. Perform the troubleshooting to the EGR system including the regulator as outlined in the posts. I'm pretty sure you'll find something very similiar to what rrumba and myself have described. I know you probably won't totally agree with what I'm saying, but if you don't troubleshoot, it won't go away by itself. If you fix the EGR problem, I think your misfire will go away as well.

Remember, this is based on what you have told us so far, so get in there and let us know what you find!!

Can anyone give me an AMEN!?

 

rrumba

I have a PCM diagram for the VSS. Start a new thread and I'll post it.

 

I took the throttle body off and cleaned the egr ports they were compltely clogged with gunk very hard gunk too. i cleared the codes too. le'ts keep our collective fingers crossed.

 

AMEN!!!!!! Very informative, and yes wordy, but VERY informative post. thanks.

<TABLE class=tborder cellSpacing=1 cellPadding=4 width="100%" align=center border=0><TBODY><TR><TD class=thead colSpan=2></TD></TR><TR title="Post 5351485" vAlign=top><TD class=alt1 align=middle width=125>ToddRG</TD><TD class=alt2>rrumba

I have a PCM diagram for the VSS. Start a new thread and I'll post it.</TD></TR></TBODY></TABLE>
i did it is below. again thanks.

https://www.ford-trucks.com/forums/6...ml#post5354324

 

truck runs even worse before. Check engine light is back on. will be going to autozone to pll the code.