random & #5 missfire 99 burb

I seem to get these codes every so often.Vehicle has 166k miles and codes appeared.Vehicle runs fine now,checked codes with scanner and then cleared them.I have owned vehicle since 2003.Plugs ,cap and rotor were changed at 130k.At 141k,got #5 missfire,so I pulled the plug checked the gap and put plug in #3 hole.At 154k,I decided to remove ignition module,clean the back side ,install new dielectic silicone and reinstall.I had no problems for 25k miles.A new fuel pump and in Dec 2011 a new fuel filter was installed.There is only two common occurances that I have noticed.When it is excessively damp out,the code appears and just after I have fueled up and headed on the highway.I have read about worn distributor drive gears.Would this not put a cam to crank correllation code?How much back lash is acceptable for the drive gear?This is what I am looking at,but without a correllation code,I am questioning that solution.I am also wondering if my ignition module could be at fault due to age, temperature breakdown and that I don't believe there is a specific code for ignition module failure . I am excluding the fuel injectors because I think they would give a code much faster.My ignition wires haven't been changed,but I'm not convinced they may be the culprit. With the mileage that is on the vehicle,would an intake manifold gasket leak be an issue?It has never been done since I owned it and don't think it was done by previous owner.Sorry for the long sad story,but this vehicle has been great other than this issue.Help would be greatly appreciated.
Chuck's

How much back lash is acceptable for the drive gear?

Zero, nada, zip & none

at this age and mileage the ICM and distributor should be replaced . the ICM made today by WELLS is far more reliable and works better than the 1999 oem designed one in your vehicle today. auto zone has wells module testers that can check this out. cost for a new one is about 45.oo.

any arcing in the distributor high voltage system causes the ICM to get damaged. also as you know lack of thermal compound and insuring a secure fastening to the distributor for heat conduction. those ICM do get hot. the distributors usually go at your mileage.no play is allowed .

if the ICM is defective measure the plug wires resistance and insure the wires are routed correctly and have no cracks ..............

j cAT any recommendations on type or brand of replacement distributors. I value your opinion. I maybe facing the same issue.

Chris

j cAT any recommendations on type or brand of replacement distributors. I value your opinion. I maybe facing the same issue.

Chris

I would get the advance auto or auto zone lifetime warrantee distributors @150.00 ea.

the ac delco has a one year warrantee cost is 370.00....

then you always have the scrap yard for a possible good find .

if the distributor has over 170,ooomi on this engine good chance the distributor is worn and moving around too much. it always begins with random missfires that over time get worse. might take 25-50,ooomi to get really bad. wait too long it will damage the converters plus your MPG drops.

Did some work on my suburban today and pulled the distributor cap off to check the distirbutor drive gear backlash.There was some movement,I'm guessing about 2- 4 degrees of rotation.I am guessing that the drive gear is made of a softer material than what is on the cam shaft.The gear will probably get changed later this spring.

Chuck's

Did some work on my suburban today and pulled the distributor cap off to check the distirbutor drive gear backlash.There was some movement,I'm guessing about 2- 4 degrees of rotation.I am guessing that the drive gear is made of a softer material than what is on the cam shaft.The gear will probably get changed later this spring.

Chuck's

replace the distributor . these vehicles at this age have bearing issues as well. do the complete job not half.

Thanks for the additional info.
Chuck's

Check out this distributor on ebay. Richporter with lifetike warranty.

http://www.ebay.com/itm/1996-2002-Chevrolet-Trucks-5-0-5-7-V8-NEW-Distributor-/250905258307?hash=item3a6b1e6943&item=250905258307&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr

Spent last weekend troubleshooting the miss fire.Changed plug wire,coil wire and cap.After each part was swapped,I road tested the unit.Every time the same result.#5 & random miss fire.I then pulled the distributor to check the drive gear wear.Didn't seem to be lots,but there was some wear.Had some difficulty to put distrbutor back in because the oil pump drive moved.Finally reset the distributor in place and took the unit for a drive.I drove the same as before and no # 5 or random missfire.I didn't have a scanner to check my timing initially,but I think that I did change the timing somewhat which eliminated the miss fire.I am glad that the light doesn't come on.Just want to pass on the findings that I experienced.Thanks.
chuck's

Spent last weekend troubleshooting the miss fire.Changed plug wire,coil wire and cap.After each part was swapped,I road tested the unit.Every time the same result.#5 & random miss fire.I then pulled the distributor to check the drive gear wear.Didn't seem to be lots,but there was some wear.Had some difficulty to put distrbutor back in because the oil pump drive moved.Finally reset the distributor in place and took the unit for a drive.I drove the same as before and no # 5 or random missfire.I didn't have a scanner to check my timing initially,but I think that I did change the timing somewhat which eliminated the miss fire.I am glad that the light doesn't come on.Just want to pass on the findings that I experienced.Thanks.
chuck's

my guess is the distributor is worn as it gets worse this will return. when it does get new distributor

Last weekend I got a scanner to check the cam retard on the distributor.I found the value to be at -5 degrees.I reset the retard to 1 degree.I had then taken the vehicle on a trip on the highway and found that it seemed to respond and preform better.The position of the distributor was no where near its starting point when I first pulled the distributor out.I am guessing that wear on components was the cause of my miss fire and that an adjustment of the distributor was all that was needed.Thanks for the help and hope this info will be helpfull to othe members.
chuck's

Last weekend I got a scanner to check the cam retard on the distributor.I found the value to be at -5 degrees.I reset the retard to 1 degree.I had then taken the vehicle on a trip on the highway and found that it seemed to respond and preform better.The position of the distributor was no where near its starting point when I first pulled the distributor out.I am guessing that wear on components was the cause of my miss fire and that an adjustment of the distributor was all that was needed.Thanks for the help and hope this info will be helpfull to othe members.
chuck's

this is common where the timing is off because of wear. you adjusting this will work for some period of time until it will no longer be proper for the entire engine rpm range.

thanks for the update. good luck