Truck will not cold start in the cold.

[jaystcb]

In the afternoon (85deg) I can walk out to the truck, Cold start it up and drive away. But in the morning... (40deg) That's another story. I have to do 1 of 2 things. 1) keep starting it and letting it die untell it's worm enough to stay running on it's own. Or 2) start it and feather the gas untell it's worm enough to stay running on it's own. I just noticed this problem started happening after I removed the ultimate chip (sytychip v10).
Another thing I noticed. This morning. I drove for about 5 miles @ 30mph. If I ease the gas pedal down to the floor. It has alot of power. But if I punch it. It boggs untell i let off the pedal.

Any ideas???

 

[sy#2716]

Re: Truck will not cold start in the cold.

Could be alot of different things. One thing i would check is to make sure you have the right map sensor in. 2 Bar GM instead of the 3 bar that is normally changed with Chip upgrades.

 

[sytyguy]

Re: Truck will not cold start in the cold.

Did the problem arise out of nowhere or has it been there and just got worse as the weather got colder? When was the last tune-up? Verified vacuum lines are healthy with no vac leaks? What fuel pressure are you running at idle with the vac line off the FPR and plugged? Does a shot of starting fluid instantly make it fire when it otherwise would not? Have you verified that the timing is set at 0 deg BTDC at idle with the EST connector unplugged? Got a datamaster or Tunerpro scan of the truck running?

Sorry for all the questions, but we need more info. If I called my doctor and said my knee hurts, he's gonna ask me a lot of questions too. Just trying to narrow down the possible culprit, because (as Pope said) it could be A LOT of things.

 

[TY162]

Re: Truck will not cold start in the cold.

In the afternoon (85deg) I can walk out to the truck, Cold start it up and drive away. But in the morning... (40deg) That's another story. I have to do 1 of 2 things. 1) keep starting it and letting it die untell it's worm enough to stay running on it's own. Or 2) start it and feather the gas untell it's worm enough to stay running on it's own. I just noticed this problem started happening after I removed the ultimate chip (sytychip v10).
Another thing I noticed. This morning. I drove for about 5 miles @ 30mph. If I ease the gas pedal down to the floor. It has alot of power. But if I punch it. It boggs untell i let off the pedal.

Any ideas???

My quick guess for the cold start (and just a guess) is IAC (idle air control valve)

 

[Big Mike]

Re: Truck will not cold start in the cold.

What chip are you running?

 

[jaystcb]

Re: Truck will not cold start in the cold.

Basic syty tune up about two weeks ago (because of simular problem that I think just got worse over time).
Cap, rotor, wires, plugs, modual, coil, oil change, timing 0 TDC and of course all vaccume lines. I'm running stock 30 injectors. Stock turbo with the intake ported and a 20g wheel. Syty chip v10 @ t1-15.
I'll check the 3 bar map sensor and the IAC.

 

[sytyguy]

Re: Truck will not cold start in the cold.

Basic syty tune up about two weeks ago (because of simular problem that I think just got worse over time).
Cap, rotor, wires, plugs, modual, coil, oil change, timing 0 TDC and of course all vaccume lines. I'm running stock 30 injectors. Stock turbo with the intake ported and a 20g wheel. Syty chip v10 @ t1-15.
I'll check the 3 bar map sensor and the IAC.

Also, check fuel pressure too and see if starting fluid helps. Trying to determine if it's 100% fuel related or not.

 

[TYTILIDIE]

Re: Truck will not cold start in the cold.

If you have Datamaster, hook it up and turn the key on and see what your engine temp is at. When the CTS goes out it will cause this issue and does NOT have to throw a code. Ours said 135* on a 40* day before the engine was even started.

 

[jaystcb]

Re: Truck will not cold start in the cold.

Update: I reinstalled the chip and found a couple bad terminals on the cable going from the controller to the chip. Also found a vaccume leak on the main hose from the intake manifold to the T by the distributor. Fuel pressure is good ( 0 @ ign off, 48 @ ign acc, 42 ign on, steddy 48 ign off. Now the Truck starts cold and stays running. Has a random studder, almost feels like fuel cut. It is just going to have to sit untel I can get another multimeter to check the map sensor and another cable for DM.

Have a good weekend

 

[jaystcb]

Re: Truck will not cold start in the cold.

... UPDATE.
so far the problem with not starting and staying running when it is cold is fixed when i put the correct 3 bar map sensor back in with the syty chip.
also.the problem with the motor bogging at rapid pedal depress is fixed when i found the vacuume leak from one of the hoses.
NOW at idle it has a studder every once in a while. feels like a miss or fuel cut. FP is good. I ckecked the O2 sensor with an air/fuel gauge. the O2 sensor is good. the truck is running on the lean side. I think it is the 3 bar map sensor. when i ran the map test. i got 5 volts to the sensor from the power wire.but im only reading 1.6 volts out of the sensor at 0 vacuume (Green wire). the vacuume voltage does drop as i add vacuume pressure. but not very much. (.8 volts at 20 vacuume). i still need to ckeck the IAC and the CTS. DM is still down.

 

[jaystcb]

Re: Truck will not cold start in the cold.

IAC & CTS ARE GOOD. I tried 2 new 3bar map sensors and ... Nothing. I removed the ultimate Gage, chip and the 3-bar map sensor, And the problem (feels like a miss or fuel cut, surging) went away. Right now the truck is running good. I Should get new DM cable by Monday.

Thank you guys for all the input.

Jay's T.C.B.

 

[midnightbluS10]

Re: Truck will not cold start in the cold.

IAC & CTS ARE GOOD. I tried 2 new 3bar map sensors and ... Nothing. I removed the ultimate Gage, chip and the 3-bar map sensor, And the problem (feels like a miss or fuel cut, surging) went away. Right now the truck is running good. I Should get new DM cable by Monday.

Thank you guys for all the input.

Jay's T.C.B.

Great job! Getting the truck to run good stock is the key. :tup: