another rough idle

B

build 557

Member
Ok so my truck is stock, except for MSD ignition and distributer, put on about 6months ago. recently serviced new plugs, filters and 19lb injectors. run 98 octane here in Aus, and timing set to 16.

So at idle it has a little miss, then did a trip on the freeway and after about an hour i started losing power and rpm to the point i needed to pull over. Let it cool down and when restarted still rough idle but had power again, drove another 20mins home.

Thought i might have a blown head gasket, as my heater box let go the day before, truck didnt overheat but did lose alot of water, have now bypassed the heater box.

Truck does not have water in the oil, no longer losing water and the head gasket comes up ok when running a die test, and compression ranges 153-159 on all cyclinders, though the second plug was fouled.

Fuel pressure check comes up good, and pluggin a scan tool in shows that my short term fuel trim is sitting around 23% and spiking up to 33%

both me and mechanic are a little at a lost, so any help would be appreciated, also test on oxygen sensor comes back good as well
 
What plugs are you running. 16* is pretty far advanced for a stock truck - try dialing that back. May also have a clogged injector.
 
I'm running Bosch Irridium plugs, and always use 98 octane been running it at 16 for six months now since I put the plugs in and the MSD gear on
 
How are you measuring the fuel trims? I'd clear the KAM, and then watch what the trims do and make sure the O2 is switching at idle. I'd also pull the plugs and check the distributor gear if you recently installed one.


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I think what's most confusing is why you have one fouled spark plug and aren't trying to figure out why that is. It's like there's an X on a map marking buried treasure and you're going around looking for the rest of the alphabet. ;)
 
build 557 said:
I'm running Bosch Irridium plugs, and always use 98 octane been running it at 16 for six months now since I put the plugs in and the MSD gear on
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These trucks run a lot better on copper plugs - ignition systems aren't designed for iridium plugs.

What MSD gear? If it's not a stock type cast iron gear you're gonna chew up the cam gear.
 
I would definitely change to a copper Motorcraft plug. Also, check the plug wire on the fouled plug.

I installed an MSD ignition box in my 1993 GMC truck, this was in 1999, MSD recommended the use of "copper plugs only" with their ignition components.
 
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so just a little update, i ended up having one completly stuffed injector and two others that were average at best. Engine has survived the loss of water luckily, just coincidence that it happened at the same time maybe.

What i do need to know is whats a good tool i can get from summit to change out the fuel filter, as the cars here use different lines and i've been to three different mechanics, none of which have a tool that will fit, i still have the factory style filter up in the chasis rail.
 
build 557 said:
so just a little update, i ended up having one completly stuffed injector and two others that were average at best. Engine has survived the loss of water luckily, just coincidence that it happened at the same time maybe.

What i do need to know is whats a good tool i can get from summit to change out the fuel filter, as the cars here use different lines and i've been to three different mechanics, none of which have a tool that will fit, i still have the factory style filter up in the chasis rail.
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These:
http://www.lislecorp.com/divisions/products/?product=207&division=1&category=28

Used with this:
http://www.lislecorp.com/divisions/products/?product=624&division=1&category=28
 
You forgot to add the laundry list of foul language and brute force to that list of tools. I don't think Summit sell that but, if you need a list of words I can provide that.
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Once the tool is bottomed, the connection is broken and it should come apart with a tug.... Lol unless you crinkled up the basket, then you're totally hosed...
 
IVSVS said:
Once the tool is bottomed, the connection is broken and it should come apart with a tug.... Lol unless you crinkled up the basket, then you're totally hosed...
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In theory and then the fuel comes spurting out all over you. Good stuff right there!!! I got so tired of disconnecting those damn things and dropping tanks due to burning up 190 Walbros ....... this is what I ended up with. And FYI, you can get those baskets in the HELP section at your local parts store. PITA to replace but, I've used them after using the tools I specified above.
 
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