I just picked up a 90 ext cab V6 with 153K on it, it seems to have a cold start issue going on.
takes forever to start when cold, 15-20seconds, when it does catch, it seems boggy, sputtery, until it runs for a few mins, runs strong, just doggy at the start.
but once it is warmed up it starts quick and normal. driving is ok, maybe some small power loss but nothing major.

No idea what is going on, just bought plugs, wires, cap, rotor, o2

any ideas?

 

Run a search on the cold start injector timing switch for the V6. Those are the symptoms of one going out, in need of cleaning, or a bad connection. Refer to the FSM stickied on the main forum page for testing.

 

Quick update, before work this morning I changed out the o2/plugs/wires/cap/rotor/pcv/gromet/air filter to K&N
Also had swapped out the airflow sensor.

Got another coil/ignitor but it is from a 94 and the two plugs are diffrent, but I do have that wiring harness that has the right plugs, I would just have to solder the conector to the coil/ignitor

The truck runs great now, but it still won't start up good when it's cold.
But perfect when warm.

I am going to go thru the cold start stuff, the sensor,timming switch, injector. and also the fuses.

Anyone have any other ideas?

 

Trust me....if you only have problems starting when the engine's cold, the timing switch is your problem. Or the cold start injector itself, but less likely so.

 

I looked for a diagram of the switch and didn't see one.

 

http://personal.utulsa.edu/~nathan-b...ne/97colds.pdf

This is a view if you are looking at the sensor cluster (on the back of the manifold, close to the firewall, and under the back of the plenum) from the firewall towards the front of the motor. So, if you were looking from the opposite.....from the front towards the rear....the timing switch is the second from the left on the cluster. Should be a black connector.

 

Incidentally, a good way to test it.....to narrow down if the sensor's the problem or you have a bad connection....is to take a single wire, hook it to one of the terminals in the harness (one will be the ground....not sure which...but, only the ground side will cold start the engine) and hook the other end to the neg. terminal of the battery. Then, when the motor is cold, try to start it. If it will fire, the sensor is the problem. I've had good luck with just cleaning off the build up. You may not if the sensor is actually bad. If the motor still won't start, then there is a problem in the wiring harness to the ECU or at the ECU connection. OR! There's a problem with the injector. Cross that bridge if you come to it.