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Volvo 5.0gxi-d. tps stalls engine

mallardmasher

New member
5.0gxi-d. this boat got a new long block motor installed. Mechanic gave it back to me with a hesitant idle and hard start. Had to open throttle to keep it running.
It starts immediately every time but stalls after a second or two. I replaced iac,dissy,rotor,pressure regulator,fuel pump, and tps. After playing around with it today I have narrowed it down to the tps sensor. If tps is unplugged it runs at idle perfect on start up. If I plug it in it stalls or catches itself at stall and hesitation idle. Does the tps need to be programmed on a scan tool ? Like the mechanic just did t want to adjust it properly ? Thanks
 
FWIW... I've reengined several boats that I intended to keep. If you have to pay a mechanic to swap old parts, a long block engine replacement is a marginal (at best) way to go. A brand new all up factory crate engine is often only a few thousand more ( and can be done in far less calendar time) and they work and come with a "no finger pointing" warranty. Almost every long block swap I've seen friends do over the last decades, comes with drama.
If an engine "dies before it's time", then a long block may be the way to go. Paying shop rates to swap 10 or 20 yo parts is sketchy. Just my opinion and observation...
 
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FWIW... I've reengined several boats that I intended to keep. If you have to pay a mechanic to swap old parts, a long block engine replacement is a marginal (at best) way to go. A brand new all up factory crate engine is often only a few thousand more ( and can be done in far less calendar time) and they work and come with a "no finger pointing" warranty. Almost every long block swap I've seen friends do over the last decades, comes with drama.
If an engine "dies before it's time", then a long block may be the way to go. Paying shop rates to swap 10 or 20 yo parts is sketchy. Just my opinion and observation...


It already got a new long block. They gave it back to me with hesitant or stalling idle. Can only keep running with throttle open. When back down to idle it will stall or hesitated idle. Unplug tps sensor and it start and idle perfect. Any idea why two new tps sensors both do same thing and idle perfect only when tps unplugged?
 
Obvious question is why is this your problem and not their problem?

I tried to have them look at it. I asked for a scanner tool diagnostic. But they are shady and sent me a video of the fuel pressure drop on gauge when testing high rail. They let engine stall and then pressure dropped from 50 to 35 at stall. Then pressure dropped to zero in blink of an eye. Like they hit the pressure relief on the gauge. I pressure tested myself before and after I brought it to them. So I already know pressure is ok and doesn’t drop to zero until gauge button is pressed. I even tried another fuel pump just to be sure. I think they want to make me buy an oem pump through them and fix whatever tps problem there is to make money. If I have it running at turn key off pressure stays at 50psi. If I have it running and it stalls at idle pressure hits around 35-45 after the stall. I can never mimic it drop to zero until hitting the relief button on gauge.
 
You can check your TPS with a DVOM. should be around .5 volts at idle and go up smoothly to 4.5 volts at WOT. Make sure the base idle screw was not turned on the throttle plate. Look for the stop on the plate you will see marks on the screw it it was turned.......
 
You can check your TPS with a DVOM. should be around .5 volts at idle and go up smoothly to 4.5 volts at WOT. Make sure the base idle screw was not turned on the throttle plate. Look for the stop on the plate you will see marks on the screw it it was turned.......

I did test it. Idle was .75v. Wot was 4.47v. They didn’t turn the screw. I chipped the paint away and tried backing it out to close the plenum more to mimic where the tps wheel idle perfect when I had it off the throttle body. But once I did that I lost my extra air intake and lost the perfect start up and idle. I move screw back down to where it was at factory setting. I did the paper clip jump code reading and get both codes 21 tps voltage high. Code 22 tps voltage low.
It will start and idle perfect with tps unplugged. I can take tps off and move wheel counter clockwise till it stops fire it up and idles perfect. But if I close plenum to match that hand moved wheel position then I lose idle as plenum is closed to much. I e tried three different tps sensors.
 
Does anyone know why engine would start and idle perfect with tps unplugged, but will only start and stall within a second if tps is plugged in. Tried three tps sensors to confirm. Tested volts. .75 at idle. 4.5v at wot.
 
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