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Over-rich TBI nearly solved...

2K views 4 replies 4 participants last post by  sbchevfreak 
#1 ·
The engine is a '93 350 TBI, complete with its 700R4 from a Buick Roadmaster, now in my '57 Chevy Suburban. The truck has just spent the (rainy) winter parked outside, and I have only driven it about 100 miles this spring so far. This engine has been in my truck for about 8000 miles, so I know the set-up can work very well!
A few days ago, the engine started running not quite as smooth as it always had, for a couple of days. Then it developped an over-rich situation, I could not drive it, had to floor the throttle to start it, big black smoke, but no check-engine-light... After doing a search here (once again, thank you, Hot Rodders.com!), I unplugged the coolant temp sensor, and the over-rich situation was solved; I will have to buy a new sensor, easy.
Problem is that the engine went back to running not quite as smooth as it should, it even sometimes dies in gear with the A/C on.
The check-engine-light is now on (normal, because I had unplugged the temp sensor) but not always! I tried to see if there are any codes with a paper clip, but I may have an issue with my ALDL connector, I do not even get the 12 code I should get.
Any suggestions to make my engine run smooth again?
 
#2 ·
As I umderstand it, when you unplugged the cts the engine went into a default mode since it no longer can tell the coolant temperature. It still thinks the coolant is cold so you are basically driving around with your choke on.

When you replace the CTS and plug it back in your problem should be solved from what I have read.

John
 
#3 ·
I think with the CTS unplugged the ecm thinks its 256 or more degrees. That throws the fuel leaner and may affect timing too. Once you get a new sensor installed it should go back to running right.
 
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