Just a few questions. Ihave changed the plugs, wires, cap, coil, and rotor. Still no help. I checked the fuel pressure and it never went below 52 while revving the engine. It seems like the miss gets worse when the vehicle warms up. It is there at idle, mild acceleration and hard acceleration.What else can be causing this? What about the IAC or EGR? I am going nuts. What is the best way to check for a vacuum leak and is there any way to determine if it is the intake gasket.Thanks for the help.

Brian

 

I would start by cleaning the EGR valve and the MAF sensor. Both can contribute to a misfire as can a large vacuum leak.

If cleaning the EGR valve and the MAF sensor do not do the trick, have a read through this rather lengthy post:

The dreaded PO300 CAUTION LONG POST AND GETTIN LONGER

Many, many things are discussed there, but I do not believe that gator ever followed up on the results...

 

I cleaned the MAF and that didn't seem to help. I will try the EGR tomorrow and let you know. Thanks!!

 

I was having the same problems and after I cleaned the EGR, they disappeared! Lot's of carbon deposits in there! Hopefully that's the problem, and good luck!

 

Here is a hint. While you have the EGR valve off, attempt to start the motor. If it actually fires, be ready to shut it off relatively quickly. What this will accomplish is to clear the EGR supply tube of any carbon debris that may have been loose inside the flex tube from the exhaust manifold to the intake manifold.

Also, there is an EGR gasket available that incorporates a screen into the inlet side of the EGR valve. This greatly reduces the likelihood of carbon deposits hanging up the valve.

 

When I cleaned my EGR a couple weekends ago, I plugged the intake manifold port to get rid of the vacuum leak that will make the engine race. I was able to let the engine run for somewhere between 5-10 seconds, including a couple revs up to around 1,500 rpms, with no worries about the engine rpms taking off on me.
I also figured it also helped by preventing the intake vacuum from sucking in any debris coming out of the exhaust side of the EGR port.

 

I cleaned the egr and no help!! I also pulled the map sensor just to check and it looked ok. I know I shouldn't have but I couldn't resist spraying a little starting fluid around the intake to see if the engine would rev. No signs of a leak. I was able to get a friends scanner and save some real time data at an idle. I have no clue what I am looking at but I can forward the file to someone if they think it might help. Thanks for all the help!!!!!

Brian

 

Still no luck!! I pulled the intake and hoped I would find a vacuum leak or leaky gasket but I didn't. When I started it still had a severe miss. I also tried disconnecting the O2 sensors and it didn't help the problem. I only let it run for a few minutes though! I decided to pull all of the new plugs again and they were all black. Only about 100 miles on them. Any ideas??? The miss is at idle all through acceleration. I don't know what else to do!! Please help!!!!!

 

Do you have an exhaust leak? Sound like something is making it run rich.

Could you post a few lines of the info?

 

ABSLT TPS(%) 0.4
ENGINE SPD(RPM) 601
CALC LOAD(%) 2.7
MAF(LB/M) 0.65
MAP("HG) 10.3
COOLANT(øF) 199
IAT(øF) 106
IGN ADV(DEG) 15.0
ST FTRM1(%) 2.3
LT FTRM1(%) 14.1
ST FTRM2(%) -1.6
LT FTRM2(%) 0.0
VEH SPEED(MPH) 0
FUEL SYS1 CLSD
FUEL SYS2 CLSD
O2S11(V) 0.205
ST FTRM11(%) 0.8
O2S13(V) 0.795
O2S21(V) 0.405
ST FTRM21(%) -3.1
PTO STATUS Disen
OBD2 STAT CA

I don't think I have and exhaust leak but I will check when I get home today. Thanks for all the help!!!