94 k1500 5.7 rough idle

[vipergtrdj]

So i have searched and I can't seem to figure out what steps to take next, I am hoping someone has suggestions that I can try. I am pretty mechanical when it comes to vehicles, but I haven't had the chance to work on any pre 2000 vehicles (American that is). I was in the import scene for awhile (good gas mileage haha) but now into the American vehicles.

First short story of the history of the truck - I picked up this truck back in June 2011, and it ran great. I had to go 200miles from my house to get it, but the price was right and it was exactly what I was looking for. It made the 200mile drive absolutely beautiful, it was probably around 250miles after the side trips I took.

New Parts include

• Inner and outter fenders
• Cab corners, bed sides and wheel covers
• New Exhaust (new cats, xpipe, mufflers, headers)
• 180 degree T-Stat
• Throttle body spacer
• Air Filter
• Fuel pump, sending unit, fuel lines except for vent line
• Spark plugs, wires, cap & rotor

Last week I put it all back together. I then hooked up all the grounds and made sure i did not miss anything. All seemed fine, so I started her up. Seemed to idle ok, but when moving her around the property she would miss and had a hard time going. So I was assuming just needed a tune-up, no idea when the last one was done. So I had some plugs, and wires from an 87 3/4ton chevy 5.7, and according to the parts store they would work with my K1500. I also picked up a new cap & rotor from the parts store for my K1500. I followed the Haynes book on firing order, and replaced all the parts. I went to start her up and she was missing even harder, and it was more noticable at an idle.

The only thing I can think of is either, I messed up on gapping a plug (my gauge is pretty warn), or it could be due to the vent line which is rusted off. I believe the vent line had been rusted off when I purchased the truck, but it drove 200miles prior to all this work. Where does that vent line go and do I need it connected to the sending unit or can I leave it open ? Is capping it a resolution without causing and damage in the future to the engine? It looks to be 1/4" line, can I just use 1/4" rubber hose to connect it for now ?

Any help is greatly appreciated! I have attacked a picture of her below - not the best looking yet but thanks to Hurricane Irene I had to rush to put all the pieces together to get her ready for winter. Next year will be finishing body work and paint. Pictures were taken with an Iphone so sry for quality (one picture is dark as it was getting dark out, and it is rattle-canned black for temporary. I did not want to waste the good paint with no climate controlled garage to spray it in)

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[TruckinAin4Sissies]

You mentioned " Fuel pump, sending unit, fuel lines except for vent line" (if you hadn't already) I'd replace the Fuel Filter.

 

[vipergtrdj]

Sorry, Fuel filter is new as well. I redid the entire fuel system - the only thing I left out is the vent line from the sending unit to the charcoal canister (evap system).

Also all the body panels were replaced due to 160k miles in New England, and rust loves to eat metal lol

BTW Truckin - nice rides

 

[Southern Pride]

Well if it got worse when you put on the wires from another vehicle and plugs then that should be a red flag I would do it over...Also is it not throwing any codes? No CEL light?

 

[vipergtrdj]

Correct - No codes, no CEL. I am going to check the gaps tonight (I bought a new gap gauge). It did the similar thing before the new plugs and all that, just not as noticable. It was still bad but I could not notice it at an idle, now I notice it at an idle, it drove the same tho, like crap and has a hard time moving without missing.

It does feel like a vacuum leak - so after I check the plugs I am going to see about capping that vent line that goes from the gas tank to the canister.

 

[badazzbulldog]

did the issue start after the tb spacer?

 

[badazzbulldog]

also saw new england in your post where ya located?

 

[vipergtrdj]

also saw new england in your post where ya located?

I'm located in Southern, VT (Brattleboro), and the issue did not start after the TB spacer, I did the TB Spacer before I replaced all the body panels and I did the new lines. After I put the TB Spacer in it still idled fine, then after that I pulled the battery for about a month so I could do the panels, and while I had the bed off I did the exhaust, brake lines, gas lines, etc. Also had to replace leaf spring mounts, rear shocks, and shackle mounts. Then last week I put it all back together with the idle problem happening.

I attached a picture of the truck when I picked it up for $800 - the previous owner sold the hood, the back does have wooden sides, and was used for scrapping metal, so it had some weight in the back. I pulled out around 200-300lbs of metal. Sorry picture is small , my cellphone took small pictures then.

 

[badazzbulldog]

check all your grounds to engine also could be a coil issue i had that happen on my 88 i had,it quit on me one morning and when it started back up it was running real rough and a friend brought down a coil we swapped it and it smoothed right out

 

[vipergtrdj]

ok I will check all the grounds again, I ran all new wires and grounds that were connected to the inner fenders and frame since the bed was off. I also started a build thread -> http://www.gmt400.com/forum/showthr...-K1500-5.7-build&p=101601&posted=1#post101601

Also - how do I test if its a coil issue? and how hard is it to replace ? (coil is different from distributor i am assuming?)