misfire all cylinders PLEASE HELP!!

[fandmout]

I have a 1997 Jimmy with 4.3 L vortec. There is not much left that I haven’t tried. Plugs, wires, spider module, fuel filter, ignition module, coil, distributor cap and rotor button. Also o-2 sensors (4) , and catalytic converter. The local ace mechanic told me it was the spider module. I changed it out and the light still blinks. He also did a compression test and the motors good. I am left with the egr valve that I haven’t checked. I checked the fuel pressure with a gage, with just the key on it went up to 64 psi., it dropped to 55 psi when running and stayed there. Is this a good reading for the pump? Should I check the EGR before giving up

[95Sierra2500]

Actually those numbers aren't bad for your pump, so I'd say it is okay. When your spider module was replaced, did they replace the poppet nozzles as well? If not you need to go to a dealer and have them clean your injectors with Top Engine Cleaner (this will clean your poppet nozzles as well). If they did replace these poppet nozzles as well, then about the only thing I can think of is the pump, as some of these require higher pressure than others simply due to mass-production variation. My fiancee`'s Jimmy (a 99) has to have more than 65 PSI to start, and about 55-57 PSI to stay running. Other S-trucks, though, can get away with less.

 

Also, double-check your cap and rotor. I replaced the one in her Jimmy with a non-AC part and it failed again within 2 weeks. Replacing it with an AC Delco part made them last for the last 6 months and running strong.

[fandmout]

Actually those numbers aren't bad for your pump, so I'd say it is okay. When your spider module was replaced, did they replace the poppet nozzles as well? If not you need to go to a dealer and have them clean your injectors with Top Engine Cleaner (this will clean your poppet nozzles as well).  If they did replace these poppet nozzles as well, then about the only thing I can think of is the pump, as some of these require higher pressure than others simply due to mass-production variation. My fiancee`'s Jimmy (a 99) has to have more than 65 PSI to start, and about 55-57 PSI to stay running. Other S-trucks, though, can get away with less.

 

Also, double-check your cap and rotor. I replaced the one in her Jimmy with a non-AC part and it failed again within 2 weeks. Replacing it with an AC Delco part made them last for the last 6 months and running strong.

 

<{POST_SNAPBACK}>

 

 

 

I replaced the

whole assembly including new nozzles. Great idea for another cap and rotor. Another thought , can it maybe be a vacuem leak causing this type of problem?

[95Sierra2500]

A vacuum leak CAN cause this problem and is much harder to track down. I would suggest looking over all your vacuum lines and connections.

[sjspor]

Hold the phone here... Okay, you have a flashing misfire, is the car really misfiring??

 

It not, you need to look at what is sensing the misfire, you may be getting a false indication.

 

Hows the car running?

 

Case in Point/ Example, Saturns.. you change the crank position sensor, you have to teach the new sensor to the PCM. Result, P0300, car runs fine though.

[sjspor]

Oh, the EGR, if its hanging open, you will get engine racing, rough running/stalling, if failing closed, or the passages are plug, you will toss a code for that calling the EGR valve.

[fandmout]

It runs real rough. The motor shakes when idling and sputers when driven.

[Tucson_02Silverado]

check the wire harness....especially to the ignition module that triggers the coil...make sure no little critter got hungry or like the insulation for it's nest.

[fandmout]

really great answers, It was the distributor cap! I replaced it with a ac delco and the lights went out in Georgia. Can't thank you people enough for you help.java script:emoticon('')

smilie

[Cranky1]

Also check the little screen that vents the distibutor while you have the distributor cap off. It is at the back on the bottom. This will cause the terminals inside the cap to corrode if it is plugged.

[jhoch]

I have a similar problem like this.

 

I have a 99 Yukon, and it started running rough one night, and gave me a blinking then steady CEL. Sat and read the manual to see what the light meant, by the time I started the truck up again, ran fine.

 

A day later, CEL ceased. Truck ran fine.

 

After some really rough running, and another CEL, I took it to the garage.

 

They read the code as a "random misfire" code

 

Since then, I have replaced the Spark plugs, wire, distributer cap and rotor, and still got a CEL again today.

 

But it runs fine on straight road, and only faulters on hills and slight grades, and then resumes normal operation.

 

a friend of mine said that it might be the vacuum line going to the distributor cap, which is throwing off the timing?

 

Could this be true? Hopefully someone has gone through this and has found the answer because it is REALLY annoying.

 

thanks in advance.

[Norseman]

Sounds like you have deposit build-up on the CSFI poppet valve ball and/or the seat causing the poppet ball to stick open. Either way, this could be causing misfueling and resulting in the miss-fires.

 

Let me know if I may be of any further assistance.