Multiple Misfire code

[nakodaman]

I have a 1999 Chevy Tahoe LT 4x4 4 door Utility Sport that I recently bought and it was running great when I bought it. I recently took it out on the freeway and it drove great until it got good and warmed up then it died. I assumed it was the Cam sensor so I changed it. Brought it home after a short stay in a shop, all they did was a diagnostic but could not say exactly what was causing it. They also did a compression test on #1 and it had 150 lbs psi but the plug was fouled. they changed it out because it was an NGK. I drove it home and changed the rest of the plugs and started it up and set my diag scanner to record when the light comes on and revved it up to 2000 rpm's and in about 20 minutes it started to misfire and died. In the recorded data i watched the MAP and it jumped from 10 to 30 when it died. I'm not sure where to go from here? I don't want to just change parts until I figure it out!

 

[rockenthebowtie]

When it dies out check for spark at the coil wire that plugs into the distributor disconnect it at the distributor only leave it plugged into the coil then what you can do it place the end of the wire about a 1/8 of an inch off any part of the engine that is grounded like around the lower intake manifold to see if its arching that will let you know if you have spark to the distributor if its good reconnect it back on to distributor then pull off the plug wire at no. Cylinder stick a small screw driver in the plug wire boot so that it has a good secure connection to the terminal in the boot and do the same thing but with the screwdriver metal part about an eighth off an inch off ground if you get no spark then you may just need a distributor cap and rotor. Also want to checl fuel pressure

 

[nakodaman]

One more thing I forgot to mention, all the odd cylinder spark plugs were black and fouled.

 

[nakodaman]

Update
coil still sparking, moved on to no plug and it is firing as well. Next I hooked up my fuel pressure gauge and KO EO pressure 51psi EO 45psi. Assuming new pump is in order?

 

[rockenthebowtie]

Yeup that is low

 

[lesterl]

Could also have a leaky FPR.... If you do a new fuel pump module, stick with OEM (Delco/Delphi)...... You never did say how many miles you had on your rig either.....

 

[nakodaman]

multiple misfire

It has 185,000 miles on it. Is FPR a fuel pump relay? Also money is an issue right now as I am on disability as is my wife but Texas being the caring understanding state that they are has decided to take her SSI away from her because I get $869.00 a month. Needless to say I have to get what I can afford for my Tahoe.

 

[lesterl]

The FPR is Fuel Pressure Regualtor, the vac port on it is aimed towards the drivers side of engine and if the diaphram ruptures it will squirt more fuel on that side....

 

[nakodaman]

That makes perfect sense! Thank you very much, after the weather clears I check that out!

 

[lesterl]

Keep us updated on what you find, the FPR is available as a separate component from the fuel metering body if funds are tight and you dont have $300 to drop on a new MPFI assembly.....

 

[Randy911]

I just posted my experience with this issue, and what fixed it for me. Hope it helps.

http://www.tahoeforum.com/showthread.php?t=531288