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87' TBI 350 rough idle and surging in gear

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SquareBody1776

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2004 Jeep Grand Cherokee 4.0l 4wd 6inch long arm kit
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5 Posts
Discussion starter · #1 ·
Howdy,
So I recently bought an 87' GMC SIERRA short box with the 350 TBI and When I start it, it surges bad and trys to die, and then begins to idle better but still not right it sounds like a misfire. when I put it in gear it bogs down and will sometimes stall then the idle comes up a little bit and continues to run rough. This doesn't happen every time however sometimes I can start it and drive it for an hour or more before it does anything. If it helps this truck sat for a few months before I bought, as it didn't run due to a bad positive battery cable. Any thoughts on what it could be are greatly appreciated - Thanks
 
#2 ·
Start with the basics ALWAYS. Especially with a vehicle you just bought and know no history of.

Compression check, vacuum leaks, bads grounds, other poor connections, new fuel filter, clogged up cat converter, clogged air cleaner <mouse nests??, fuel system pressure check, fouled plugs, ratty ignition wires/cap, rotor, wiring/firing order, spark intensity check.
Any codes?

When you have done all that and come back with values such as compression, fuel pump pressure and determined the basics are all sound or rectified we can proceed with further diagnosis.
 
Discussion starter · #3 ·
juanni said:
Start with the basics ALWAYS. Especially with a vehicle you just bought and know no history of.

Compression check, vacuum leaks, bads grounds, other poor connections, new fuel filter, clogged up cat converter, clogged air cleaner <mouse nests??, fuel system pressure check, fouled plugs, ratty ignition wires/cap, rotor, wiring/firing order, spark intensity check.
Any codes?

When you have done all that and come back with values such as compression, fuel pump pressure and determined the basics are all sound or rectified we can proceed with further diagnosis.
Click to expand...
Okay thanks, I'll get all that done and come back with some answers
 
Discussion starter · #4 ·
Okay, so I've done some testing and pulling of parts, and after testing spark air and fuel found that it has the Holley projection that was on its way out but nothing other than that. UNTIL I pulled the passenger side valve cover and found that the number 4 cylinder had a broken rocker stud on the exhaust side and a pulled stud on the intake side, thus the misfire and surging. Thank you for the help and reccomendations.
 
#5 ·
SquareBody1776 said:
UNTIL I pulled the passenger side valve cover and found that the number 4 cylinder had a broken rocker stud on the exhaust side and a pulled stud on the intake side, thus the misfire and surging. Thank you for the help and recommendations.
Click to expand...
I take it the compression test revealed problems with #4.

Glad you found the problem and reported back.
 
#7 ·
Be sure to clean the idle air motor passages in the throttle body as well. They were extremely bad about getting carbon buildup. Make sure you check the pcv passage as well. This is probably not your issue but was a known problem with higher mileage tbi engines
 
#8 ·
Sounds like a good candidate for removing the intake, getting it sonically cleaned, new intake gaskets, fresh tune up, reset timing, etc.

May as well eliminate a lot of unknowns while you are in there. I just put a 5.7 in my S10 and now I have a small puddle of coolant laying on my intake. If I followed my own advice I wouldn't have that problem 🤦
 
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