91 Bravada won't start sometimes, cranking OK

[wbchang]

My 1991 Bravada won't start from time to time, sometimes it starts right away on first try, other times if first try failed, it won't start on any tries after that. Let it sit for a while, it will start again. It is not consistent so could not send to garage. The car had a history of "check engine" light on intermittently, the code showed that the TPS (Throttle Position Sensor) may need to be replaced, would this sensor has something to do with the starting problem? Where is the sensor located? I have the picture of the sensor, but could not locate it. Thanks for all your help.

[Chris Stewart]

The TPS is mounted on the fueler throttle, be it on a TBI or CPI injection system. It tells the computer how much power you're asking for and the computer then directs the fuel injection how much fuel to squirt. If the TPS is broken and no signal for power is sent to the computer, the computer thinks the motor is not running and no signal is sent to the fueler. The TPS is typically located on the throttle body near where the throttle cable is attached. It should a 3 wires attached to it. You might also wiggle the wiring connector on it in case it's slipped and lost connection.

[wbchang]

I am still not quit sure where the TPS is? can you share with a photo? Is that easy to replace TPS myself?

[Chris Stewart]

Does you Bravada have a round air cleaner element or square element?

[wbchang]

Originally Posted by Chris Stewart

Does you Bravada have a round air cleaner element or square element?

Round.

[Chris Stewart]

Ok, you have the Throttle Body Injection system...TBI.
On one side of the TBI, the throttle linkage from the gas pedal is connected to an arm. On the opposite side is a black device, the TPS and it's held on with 2 screws and has 3 wires coming from it. By disconnecting the 3 wire connector and the 2 screws holding the TPS on, the tps can be removed and new one installed IF that's what's setting off the trouble code. If one of the wire's is grounding out on top of the motor or behind the firewall or some similiar trouble, 3 new TPS's won't help.
You really need to at least get a repair manual at your local chain type auto parts store or a Factory Service manual at Helmic.com or eBay if you want to enjoy success at repairing Bravada's...then you can help me understand some of this stuff.

[wbchang]

Originally Posted by Chris Stewart

Ok, you have the Throttle Body Injection system...TBI.
On one side of the TBI, the throttle linkage from the gas pedal is connected to an arm. On the opposite side is a black device, the TPS and it's held on with 2 screws and has 3 wires coming from it. By disconnecting the 3 wire connector and the 2 screws holding the TPS on, the tps can be removed and new one installed IF that's what's setting off the trouble code. If one of the wire's is grounding out on top of the motor or behind the firewall or some similiar trouble, 3 new TPS's won't help.
You really need to at least get a repair manual at your local chain type auto parts store or a Factory Service manual at Helmic.com or eBay if you want to enjoy success at repairing Bravada's...then you can help me understand some of this stuff.

Thanks a lot, Chris. Helmic.com looks like a foreign site!?

[Chris Stewart]

Ooopps, make that Helminc.com...they ain't cheap.

[J-Ray]

When you try and start your bravada...does it eventually turn over? Does tapping the gas pedal help? If so, you may have some fuel pressure regulator problems. Pretty common problem with pre-96 4.3l Vortec engine. Check the Jimmy and Blazer boards for more detailed info. If this is the problem (as I speculate it is) get it checked ASAP, otherwise your gas is mixing with your oil, and that will lead to severe engine problems!

Hope this helps...had the same problem with my '94 jimmy...

J-Ray

[Chris Stewart]

J-Ray,
The TBI fueler doesn't spray fuel like the cracked fuel lines inside the intake manifold on a CPI fueler motor you're refering to.