2000 Olds Bravada - Runs Rough Until...

[LRAMP]

Upon start up, engine runs rough. No misfires or fuel injection problems. No codes at all. IMPORTANT NOTE. Blower is on high setting, but starts at low speed. As soon as blower reaches high speed, engine smooths out and runs normally. i have poured over the schematics, but have been unable to see a correlation between the engine performance and the blower motor.Can anyone orffer some suggestions?

[Jeff @ Able Auto]

Sounds like you might have a low voltage issue. I would check the charging system on start..see what its output is along with amps draw. If the fan is turned off or disconnected does it run better? It might be a stretch but if the fan is pulling max amps and the alternator is weak it could just not have enough "juice" to run the fuel pum and ignition system up to spec.

[Tim Martin]

In addition to the low voltage possibility, another possibility would be the integrity of the ground circuits.

Strange challenges we get nowadays.

[liljoe]

Does it do it the blower turned off? It might not be related at all, I have seen pressure regulators act like this when they have a leak and let extra fuel into the intake. It the truck has auto air the blower starts slow then ramps up to speed. If it is not, I would check the voltage to the blower and also the voltage drop on the ground circuit as well to see which side of the circuit is causing problems.

[steven kiser]

A bit late on this but I would run a jumper wire from positive post or jump start lug straight to main feed at alternator and see if this eliminates issues. Assuming that the battery lug or stud shows 12 volts and it resolves the issue I would look for a blown fuseable link. The battery may be the culprit as well. Check for voltage at the battery and replace if less than required. There was a ground issue if I recall correctly where cable oxidized (negative) between frame and block. A quick test I use is taking a load tester and hooking it to positive battery and block as ground. If I'm correct in my thinking the load should drop way down leading to a bad cable connection.

[liljoe]

One other thought I had is to turn the switch on and let the blower come up to speed and then start truck and see what happens, I might even use a remote starter button to crank it over just make sure I didn't reset the blower during cranking when that circuit loses its power feed in the crank position.

[steven kiser]

Any news?

[LRAMP]

Allowed blower to come to full high and started. Vehicle runs fine.Now checking out fusible link.Thanks to all for the excellent replies. When I get it fixed, I will share with all.