93 sierra misfire?

[arren]

hey guys i need your help. i've gotta 93 gmc sierra 2500 with the 350 tbi in it. when im cruising i can feel it lurching a little forward like a misfire feels like. ive tuned it up all new plugs wires cap and rotor fuel filter o2 sensor map sensor and cleaned the egr valve and throttle body. still doing it. then comes the weird part.. at low rpm trying to keep a low speed say 20 in second gear it really bucks back and forth. when it starts this i put the clutch in and it literally idles down to zero rpm putt putts for a second but doesnt die and idles right back up to normal. ive run out of ideas so hopefully someone can throw some suggestions at me. thanks, arren

 

[stimmie78]

almost... and I mean almost... sounds like my little bro's 95... ended up doing intake gaskets. solved everything. it was leaking towards the rear.. he tried fuel pump, filter, cap and rotor, timing a million times... it wasn't until the coolant was noticed that the intake gaskets were changed. But it solved the problem.

 

[mikeindmills]

I've seen the coolant temp sensors go bad in those trucks and make them run pretty wacky(dumping fuel, sputter, misfire, etc.). While you're throwing parts at it, thats a pretty solid guess.

 

[fordman4x492]

my 95 was missing so i did a complete tune up on it (minus the coil) and it still missed then i put the msd street fire coil on it and it fixed that problem real quick. its like 40 bucks for the coil at autozone

 

[JohnnyU]

I've seen the coolant temp sensors go bad in those trucks and make them run pretty wacky(dumping fuel, sputter, misfire, etc.). While you're throwing parts at it, thats a pretty solid guess.

I've seen this too.

Have you changed the fuel filter and checked fuel pressure?

 

[arren]

i forgot to put i did end up having to have a shop take my truck in as part of the 150 dollar emissions waver and they replaced the coolant temp sensor which was keeping it from passing. recently replaced pcv valve and seems like its not doing the idle down thing anymore so thats a plus. ive sprayed carb cleaner around the intake hoping to find an obvious leak but no luck there. when i get up into 3-5000 rpms i can see the needle on my tach actually jumping with this bucking which steers me maybe towards a new coil.

 

[ranger1999 Bob]

if its cool with the mods i can give you three chevy sites to try kinda like this

 

[arren]

that'd be awesome! i've been trying to find a chevy forum like trs but theres nowhere near the info or help anywhere but here. if you've got a couple good ones i'd appreciate it

 

[JohnnyU]

if its cool with the mods i can give you three chevy sites to try kinda like this

I don't know of nay half-way decent Chevy forums anymore. FSC and GMFS are pretty much it, and they suck.

 

[arren]

i think the coil was it. it feels like its runnin a whole lot better and its got more balls now. and for 15 bucks! sweet. its got a little bit of a lurch here and there when im drivin real slow in second gear but im thinkin thats just because its in too high of a gear since its got basically a four speed plus a granny gear so the gears are so far apart and i need to be in first but once i get on the gas a little it goes right away. does that sound like a reasonable explanation?

 

[ranger1999 Bob]

well there is GMFS but they arent as technically good as other forums.. you can try www.chevytalk.com or www.67-72chevytrucks.com.. the latter started out as strictly 67-72 then they have all chevy trucks on there..
If you go there for the 73-87 trucks, im actually one of the moderators there and on all those forums im Old Rusty C10
Hope this helps you

 

[arren]

in case anybody has the same problem.. well the misfire came back and this time i payed attention and noticed that it was only when the truck was warm. so the only thing i could think of that i hadnt tried yet besides intake gaskets was the egr valve. tried cleaning the old one a few weeks back but didnt help. so i went to the local jy and picked up one that seemed in good condition, put it in and there it was. no more hesitation, lurching, or bucking. the truck will drive smooth even at 10mph in second gear.