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Username Post: TBI poor cold performance        (Topic#342958)
wz junk 
Forum Newbie
Posts: 9

Reg: 04-21-10
02-28-17 07:06 AM - Post#2678916    

I did a search and I read a lot here but I have been unable to solve my problem.

I have the complete drivetrain from a 1990 Chevrolet Caprice in my 1954 Chevrolet. I used the 305 engine, 200r, computer, and factory gas tank with the factory fuel pump. I used an aftermarket wiring harness.

Once the engine reaches 185 degrees and goes into closed loop, it runs great and the fuel mileage is great, but when it is cold it will hardly pull itself.

I have a diagnostic tool hooked to the car and I monitor all of the data and it seems like everything is within normal limits. However, I am not knowledgeable in this area.

I have replaced most of the sensors, the egr, and the computer with no change.

I would appreciate some help and I will answer any questions.

John

Chopped 48 Chevy truck (was junk) license plate
1954 Chevy 210

Crew chief #974 1953 Studebaker Bonneville record holder B/BGCC 249.9 MPH


http://purplesagetradingp ost.com/sumner/hooley/hoo...


 




Shepherd 
Contributor
Posts: 812

Loc: Lake George, NY
Reg: 11-11-15
03-01-17 06:50 AM - Post#2679115    
    In response to wz junk

The engine should go to closed loop before 185. How long does it run before it calms down, what does the coolant sensor read when cold, using a scanner? Where is the O2 sensor mounted, has to be close to the engine, closed loop is commanded by the sensor when it is hot enough.



 
wz junk 
Forum Newbie
Posts: 9

Reg: 04-21-10
03-01-17 01:49 PM - Post#2679188    
    In response to Shepherd

Thanks for your interest and help.

I just check the data with the car setting cold in my shop. The water temperature is 59F and the manifold air temperature is 66F. When I start the car both of these rise. The water temperature will go to 185F and this is about what my Autometer temperature gauge reads. The manifold temperature will be slightly higher than the outside air temperature and rise even more when the car sits running at idle.

The o2 sensor is in the right exhaust pipe just about 2 inches back from the factory cast manifold and in the horizontal position towards the outside of the car.

The engine runs fine at idle. It does not smoke or seem to misfire but when it is first started it does idle faster as it should. The problem starts when you drive the car and the engine is not in closed loop. After it is in closed loop it does fine, even when it occasionally cycles between open and closed loop.

John

Chopped 48 Chevy truck (was junk) license plate
1954 Chevy 210

Crew chief #974 1953 Studebaker Bonneville record holder B/BGCC 249.9 MPH


http://purplesagetradingp ost.com/sumner/hooley/hoo...


 
Shepherd 
Contributor
Posts: 812

Loc: Lake George, NY
Reg: 11-11-15
03-01-17 02:18 PM - Post#2679195    
    In response to wz junk

Everything looks good, how long before it goes to close loop. The O2 could just be lazy and slow to go to closed, this would cause the engine to be over rich during the warm up period. Some sensors on the market are not up to par. Can you see the sensor fixed cold voltage?and does it switch voltages up and down say between .200-.700v? Once in closed it should stay there while driving unless you idle for a period or shut it off and restart.



Edited by Shepherd on 03-01-17 02:20 PM. Reason for edit: No reason given.

 
wz junk 
Forum Newbie
Posts: 9

Reg: 04-21-10
03-01-17 02:36 PM - Post#2679196    
    In response to Shepherd

Saturday I plan to drive it a couple of hundred miles and I will try to log some of the data during the day. I am joining a group on a road trip to a drag racing museum.

I have a lifetime of building and driving hot rods but this is my first computer controlled engine in a hot rod. If baffles me that it can run so good when it is at operating temperature and so poor when it is cold. When cold it drives like a carbureted engine that has no accelerator pump and no choke.

thanks again

John

Chopped 48 Chevy truck (was junk) license plate
1954 Chevy 210

Crew chief #974 1953 Studebaker Bonneville record holder B/BGCC 249.9 MPH


http://purplesagetradingp ost.com/sumner/hooley/hoo...


 
wz junk 
Forum Newbie
Posts: 9

Reg: 04-21-10
03-02-17 04:03 PM - Post#2679391    
    In response to wz junk

I had been told that the reluctor in the distributor should produce at least 700 mvolts. I tested the old distributor and it was less than 500. So I replaced the complete distributor with all new not remanufactured parts. I do not think it runs as good now as did, but it is close. It seems to lag a little after it is in closed loop. I checked the new distributor and it is producing slightly more that the minimum 700 mvolts.

I added a can of seafoam to the gas tank just for fun, and I will let it soak some.

I will sleep on it tonight, and start again tomorrow.

John

Chopped 48 Chevy truck (was junk) license plate
1954 Chevy 210

Crew chief #974 1953 Studebaker Bonneville record holder B/BGCC 249.9 MPH


http://purplesagetradingp ost.com/sumner/hooley/hoo...


 
65_Impala 
Very Senior Member
Posts: 3805

Reg: 12-29-02
03-02-17 10:56 PM - Post#2679477    
    In response to wz junk

What is the BLM and INT values doing in closed loop?

What is the EGR valve doing?

It should go into closed loop just over 100*F and not wait until 185*. There certainly shouldn't be that much difference between open and closed loop.



 
wz junk 
Forum Newbie
Posts: 9

Reg: 04-21-10
03-08-17 05:57 AM - Post#2680334    
    In response to 65_Impala

  • 65_Impala Said:
What is the BLM and INT values doing in closed loop?

What is the EGR valve doing?

It should go into closed loop just over 100*F and not wait until 185*. There certainly shouldn't be that much difference between open and closed loop.




INT and BLM are at 128 at start up. Later during driving they fluctuate but it is hard to get data and drive. The car usually goes into closed loop about 145 degrees but yesterday it was nearly 185 before I noticed it in closed loop.

I will try to get more data today.

Thanks,

John


Chopped 48 Chevy truck (was junk) license plate
1954 Chevy 210

Crew chief #974 1953 Studebaker Bonneville record holder B/BGCC 249.9 MPH


http://purplesagetradingp ost.com/sumner/hooley/hoo...


 




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