1991 TBI 350 Blazer: Fuel, Ignition, or Tranny problem???

[smier]

Hey guys, I've got a 91 Blazer with a TBI 350 with 143k miles. The issue I'm having is it starts and runs fine until it gets really good and warmed up( about 10 minutes into my commute) then it starts to seem to lose some power, stays in OD until I really get on it, and sometimes when I'm in traffic and I go to move forward and left off the throttle it will almost stall, and on occasion it will stall when feathering the throttle. It only does this in gear, and will almost always do it when backing up to parallel park. So far I've replaced plugs and wires, cap and rotor, and a new o2 sensor. Fuel pump was replaced 2 years ago. I checked for codes and it's not throwing any codes other than the normal 12... Drove it with the scanner plugged in and it goes into closed loop as it should according to the manual... I'm kinda wondering if I've got a faulty ignition module, or if the tranny is acting up an just bogging it down??? I'm grabbing at straws at this point, Help!!!!

 

[THUNDERUSONE]

My 91 Burb was doing the exact same behavior. I replaced the fan clutch and ran some lucas fuel treatment through it and it has improved about 70%. I have also replaced the same items as you have. I hope someone has the answer on this one. I have 183K on mine. I wonder if a lobe is going down on the cam or valve springs just worn completely out. Mine does not burn a drop of oil....so I feel relatively good about the cylinders. I need to do a leak down on it when I get a chance to see what if anything mechanical is going on.

 

[79rustyk10]

is the coil over heateted?

 

[smier]

I forgot to mention that I had the transmission serviced over a year ago, new screen etc... No apparent problems according to the transmission shop. Mine doesn't burn or leak a drop of oil either! I just put $2000 worth of body work into it, itsbeen such a great truck, cheaper than buying another used one!!! This is really the only complaint I have with it. I did run some seafoam in the tank a couple of weeks ago, it did help a little...

 

[smier]

Probably wouldn't hurt to change the coil as well, as far as I know it's the original, I have a new ignition control module I had bought for my 86 TPI camaro, I'm assuming they're the same?

 

[smier]

Tinkered with it a bit tonight before dark. I discovered it will actually do it in park or neutral as well, after it's warmed up if I just feather the throttle and let off it starts to starve for fuel, for a half a second then picks back up... Won't do it when cold because the idles still up since it hasn't warmed up yet... Not sure what to do next. Check idle settings, throttle position sensor??? I have never checked the timing either...

 

[bronc3buster842001]

Have you checked the fuel filter.

 

[smier]

Yes I have replaced the fuel filter, actually twice.

 

[bronc3buster842001]

The ignition module you bought for your Camaro will work if it had the small cap dizzy.

 

[nm4x4]

Does it still have the catalytic converter? I changed a lot of parts only to find out it was clogging and causing to much back pressure.

 

[runamok151]

check the fuel pump? mine started doing what you described before it totally went

 

[smier]

Hmmm the converter, the truck does get that stinky rotten egg smell when it starts to stutter. I hadn't even thought about checking that.

 

[smier]

I've been doing a lot of searches and I found a few mentions about coolant temperature sensors and faulty thermostats causing similar issues, I never thought about it but my engine temp never gets above the 150 to 160 degree range.... Any thoughts???

 

[nm4x4]

I cut out my Cat and it ran like new. It is tagged in a non emission county so I just replaced it with a straight pipe. If I ever need to get it inspected I will replace the Cat then.