timing

[dracon79]

If the timing is computer controlled and the computer does nothing when the engine is cold (open loop mode) then what controls the timing until the truck warms up and all the electronics kick in?

 

My 88 manche 5speed 4.0L wants to stall when you hit the gas when its cold once it warms up runs like off the lot. Fuel injectors been replaced. Most all sensors been replaced except the map. New plugs, new cap, new wires, burns and uses no oil. I checked the cat looks clean. I can't seem to track it down. Maybe its one of those things with age.

[mvusse]

The computer does not do nothing in open loop mode.

 

In closed loop mode it uses information from all sensors to calculate the supposed optimal amount of fuel to give the engine, how much to advance the timing, etc.

 

In open loop mode, it uses a table with precalculated values to look up what it should need (fuel, timing etc.) for a given throttle position, engine speed and vehicle speed.

 

You do not want to always run in open loop mode, because the values are "on the safe side", which in short form will hurt your wallet from burning way more fuel than you need to.

 

This is a (perhaps overly) simplified explanation, and is in no way meant to be complete.

[maddzz1]

yeah, before the engine warms up the comp uses a pre determined set of specs

[HOrnbrod]

If the timing is computer controlled and the computer does nothing when the engine is cold (open loop mode) then what controls the timing until the truck warms up and all the electronics kick in?

 

My 88 manche 5speed 4.0L wants to stall when you hit the gas when its cold once it warms up runs like off the lot. Fuel injectors been replaced. Most all sensors been replaced except the map. New plugs, new cap, new wires, burns and uses no oil. I checked the cat looks clean. I can't seem to track it down. Maybe its one of those things with age.

 

The O2 sensor has the most to do with the mode shift. Have you checked / replaced that?

[chicofuentes0224]

This is going to sound dumb but I had similar symptons. Couldn't figure out what it was. I changed everything you did and no differnce. Then I put a new cable from the negative terminal on the battery to the block that also had a second wire attatched that bolted on to my inner fender. I cleaned up all three connections real well and problem solved.

[HOrnbrod]

This is going to sound dumb but I had similar symptons. Couldn't figure out what it was. I changed everything you did and no differnce. Then I put a new cable from the negative terminal on the battery to the block that also had a second wire attatched that bolted on to my inner fender. I cleaned up all three connections real well and problem solved.

 

That's not dumb at all. Good low resistance grounding between the battery neg. post, engine block, and body are essential for all electrical circuits to function efficiently, including ignition. But good grounding, bonding, and shielding are probably the most overlooked symptoms when troubleshooting electronics. :eek:

[dracon79]

Yes I did change the o2 sensor. But Ill have to take a look at the negative cable. Thanks for the help hopefully thats it.

[dracon79]

Well replaced the negative cable cleaned the connections and still same issue. I guess ill try the map sensor and since the computer is using preset values and it runs like crap cold Ill replace the computer it must be shot.

[Backdraft]

Clean the throat of your throttle body as well as the butterfly. This happened to me once before, it would stall or try to stall when i gave it gas, but only when cold. Cleaned the TB and problem solved.

 

Mike

[chicofuentes0224]

Well replaced the negative cable cleaned the connections and still same issue. I guess ill try the map sensor and since the computer is using preset values and it runs like crap cold Ill replace the computer it must be shot.

 

Did you get the cable that has a second wire that bolts to the fender? If no try replacing that braided ground line on the back of the engine to the firewall.

[dracon79]

No, I didn't try the smaller wire Ill give that a shot and take off my tb and clean that. Thanks.