1995 Sierra running rich Help!

[1995sierraz71]

Hi, new member here. Ive been on this site countless times, researching many problems in the past and its been of great help! But I have two problems that are about to drive me completely crazy. My 95 K1500 has always had a problem where if you press the clutch in to coast, the idle will hang for a few seconds and then come back down. Ive replaced the IAC and checked all vacuum lines. I swapped from a 305 to a 350 about 5 months ago and it still has the problem. I swapped the engine out of a 1988 c2500 and transferred most parts to it from the 305, minus the knock sensor, same hanging idle. Since the swap, it has been running rich, soot in the tailpipe and a strong gas smell from exhaust. In the morning, the motor likes to bog down occasionally, like its flooding.This mostly goes away when it warms up. Most of the time the truck idles rough, not too bad, but a little shake. The mileage dropped too. I have replaced: MAP sensor, IAC, TPS, CTS, EGR (used), plugs, wires. O2 was replaced by PO about 20k ago, along with fuel filter. Im at a loss, this is my DD and Im on a highschooler budget and need my truck. Any help would be appreciated!

 

[Crash]

Did you swap the TBI from the 305?
Did you change to a 350 chip?

 

[1995sierraz71]

Thanks for the reply. I have not swapped ECMs or put a 350 chip in it. Of course its darn near impossible to find a 1995 donor truck with a five speed and 350. Would this make it run rich? I don't want/ need a performance chip, stock is good for me. Where can I get a stock chip? Dealer? Could you give me a ballpark estimate in price?

 

[1995sierraz71]

An yes I swapped the 305 tbi to 350 and put the 350 injectors into that

 

[Crash]

Don't know where you would find a stock chip and I can't in good continence recommend jet chips, so here...
http://www.ebay.com/itm/TOWMASTER-C...Parts_Accessories&vxp=mtr&hash=item1e50ff39b4

 

[someotherguy]

Of course its darn near impossible to find a 1995 donor truck with a five speed and 350.

Look in base model 8 lug C2500's, work truck type vehicles. I've seen more than a few. Even had one given to a friend for free (in exchange for a little labor.) Yeah it's tough to find that exact combo for a one-year vehicle, but at least they are out there and you might luck into a boneyard that has some fleet vehicles.

By the way, that momentary hanging idle is a characteristic of many manual trans-equipped GMT400's. Not 100% sure which ones do it but I've seen it complained about more than once, and explained away by people that have more inside knowledge than I do. Something to do with either helping smooth shifts or meet some stupid paperwork emissions requirement.

Richard

 

[Crash]

By the way, that momentary hanging idle is a characteristic of many manual trans-equipped GMT400's. Not 100% sure which ones do it but I've seen it complained about more than once, and explained away by people that have more inside knowledge than I do. Something to do with either helping smooth shifts or meet some stupid paperwork emissions requirement.

Richard

Mine does it too.

 

[1995sierraz71]

That chip is a little pricey for my budget right now, but im gonna have to do it someday. And its great to know that the idle is pretty normal, I would have drove myself crazy trying to figure it out. I will see if I can find any 95 5spd. 350 3/4 tons as well, but theyre not to common around here.

 

[someotherguy]

Just on the off chance, check the MAP sensor vacuum connection at the rear of the TBI. Maybe it got knocked loose, or the boot for it is cracked/hardened and not sealing well.

Richard

 

[1995sierraz71]

Just on the off chance, check the MAP sensor vacuum connection at the rear of the TBI. Maybe it got knocked loose, or the boot for it is cracked/hardened and not sealing well.

Richard

I have checked vacuum lines and replaced this one and several others. forgot to mention that.