Volvo 5.0 gxi Stalls at idle. Hard start.

Joined
Nov 17, 2007
Messages
21
That noise is probably to be expected. That’s just the IAC doing it’s job of trying to control and counter what’s going on with the engine trying to stall.
So what rpm is it actually idling at when it’s all as normal and on the verge of cutting out and what rpm does it idle at when the tps is unplugged?
600-615 is when it wants to stall.
600 purrs perfect with tps unplugged.
I picked up a test gauge and going to check fuel pressure high and low today after work. This has got me stumped as it runs perfect once I have throttle open to around 700-800 rpm in neutral.
 

stresspoint

Cadet
Joined
Sep 19, 2022
Messages
23
? ,did your mechanic set the timing and base idle with a scan tool after assembly ,
if he did not i would suggest getting it set up properly before continuing to operate the motor.
 
Joined
Nov 17, 2007
Messages
21
Which Gxi is the motor? A, C, D, 270 ...etc
I’m not sure ? 270 I believe.
? ,did your mechanic set the timing and base idle with a scan tool after assembly ,
if he did not i would suggest getting it set up properly before continuing to operate the motor.
I would think they did. They are the go to place around here for fixing boats and building race boats.
 

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Joined
Nov 17, 2007
Messages
21
I did fuel pressure test today and looked good. Low side 10psi. High side 50psi.
Had a hard time getting it to idle on start up. It either stalls right after start up or will barely catch itself and idle with slight hesitation. Starts and idles excellent when I unplug tps sensor.
 

alldodge

Supreme Mariner
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Mar 8, 2009
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I need motor serial number or something like Gxi-270-G, Gxi-J to narrow it down

If it does have the flat dizzy cap, then verify it is positioned correctly. The motor is not timed used base timing mode unless it has the EST dizzy

To check timing, motor needs to be at TDC on number 1 cylinder
If it does have the flat cap which is HVS ignition, the dizzy can be moved ever so slightly one direction or the other. The base would be scribed marked, then it moved about 1 or 2 degrees. Locked down and see if it runs better. If it does good, if not turn back where it was and go other direction. If neither works better then return to original


HVS Distributor Timing.jpg
 
Joined
Nov 17, 2007
Messages
21
I need motor serial number or something like Gxi-270-G, Gxi-J to narrow it down

If it does have the flat dizzy cap, then verify it is positioned correctly. The motor is not timed used base timing mode unless it has the EST dizzy

To check timing, motor needs to be at TDC on number 1 cylinder
If it does have the flat cap which is HVS ignition, the dizzy can be moved ever so slightly one direction or the other. The base would be scribed marked, then it moved about 1 or 2 degrees. Locked down and see if it runs better. If it does good, if not turn back where it was and go other direction. If neither works better then return to original


View attachment 370631
Thanks for your help. I’ll have to look around the engine for a serial number. All I saw was the engine family number on plaque by alternator and belts brace thing.
It does have the flat top dizzy. Someone earlier posted how they crap out and should be replaced. I pulled old dizzy and rotor off. They didn’t look bad, just had the normal spark/weld look at tips. I put the new one on exactly how the old one sat. Is there a mark to show when #1 is top dead center ? I didn’t notice and was just extra careful to just set new rotor down exactly how old one was. Is there a specific reason the old and the new tps sensors both cause great start/idle when unplugged ? Thanks again for your help
 

alldodge

Supreme Mariner
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Mar 8, 2009
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Yes the caps have been a problem so its good to rule it out. It didn't change anything so keep it as a spare because they can go out without warning

Read thru the post a couple times and I'm always missing something so bare with me. I'm figuring this is a "new to you" boat. Being a new to you the dizzy may or may not have been moved. Replacing parts without knowing what is actually going on can cause more issues. Some if not all the parts you removed may have been good or marginal. The ones replaced may be good or marginal, just nature of the beast so to speak

Need to get some info on what the ECM is actually seeing. Can get some voltage readings on the IAC, TPS and MAP but using a scanner is much easier and better. Right now were guessing because there is no readings. Same goes with the dizzy positioning, it may or may not be in the correct position.

Being able to unplug the TPS and it runs better may be a a sensor, vacuum leak but can also be a fuel pressure issue. Have you checked fuel pressure? Low 8 psi +/- 4, and high 50 to 60 psi
 
Joined
Nov 17, 2007
Messages
21
Yes the caps have been a problem so its good to rule it out. It didn't change anything so keep it as a spare because they can go out without warning

Read thru the post a couple times and I'm always missing something so bare with me. I'm figuring this is a "new to you" boat. Being a new to you the dizzy may or may not have been moved. Replacing parts without knowing what is actually going on can cause more issues. Some if not all the parts you removed may have been good or marginal. The ones replaced may be good or marginal, just nature of the beast so to speak

Need to get some info on what the ECM is actually seeing. Can get some voltage readings on the IAC, TPS and MAP but using a scanner is much easier and better. Right now were guessing because there is no readings. Same goes with the dizzy positioning, it may or may not be in the correct position.

Being able to unplug the TPS and it runs better may be a a sensor, vacuum leak but can also be a fuel pressure issue. Have you checked fuel pressure? Low 8 psi +/- 4, and high 50 to 60 psi
It got a new long block month ago. When I got it back it took 5 tries to get it started. Idle sounded low and hesitant. Drove it back to my slip from mechanics. Shut it off and restarted it, was same 4-5 times to start. I mean it starts right up every time but after a second it stalls or catches itself and keeps a hesitation idle. I called mechanic and they told me to use the neutral alittle throttle to start it. I said “efi never had to throttle before, just turn key and go”.
Without a carb I’m lost on this engine. So I tried the easy fixes with iac,tps,dissy ect. I did fuel pressure test today. It was good. 10psi on low. 50psi on the high.
I miss my old boat with simple carb. If I start it with some throttle and immediatey back down into idle it will hesitate and stall. If I start it with throttle and rev it alittle then back down onto idle it will idle but I can still see it wants to hesitate. It runs and sounds great through all rpms except idle. It doesn’t matter if engine is cold or warm I get the same stall every time when starting with no throttle. Mechanic said they will come to my slip to take a look at it. I truly think it needs a tweak on the scanner tool now that I replaced the simple obvious stuff with no results. Wouldn’t a vacuum leak cause me to idle higher vs low stall ?
 

alldodge

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Does the 50 psi stay there while running?

From this post your mechanics most likely know how to remove/replace a motor, but don't know how to setup a modern motor.

If it was mine I would disconnect spark and fuel to the motor. Do this by pulling fuel pump and coil connectors. Remove the dizzy cap and bump the starter over until number 1 cylinder comes around (but not past) TDC. Install a piston stop bolt in cylinder 1 and bring the cylinder up until piston contacts bolt.

Mark damper and rotate motor by hand clockwise (facing motor) until piston contacts stop bolt. Mark damper location, then measure distance between the 2 marks. The middle between the 2 marks when crank is rotated back clockwise (facing motor) is TDC on number 1 cylinder.

Remove stop bolt and rotate around to TDC no 1. Rotate dizzy so its at the notch shown in post 26 pic.
 

alldodge

Supreme Mariner
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Messages
37,046
Could also say this could be done by removing the port valve cover and watching the rockers
 
Joined
Nov 17, 2007
Messages
21
Does the 50 psi stay there while running?

From this post your mechanics most likely know how to remove/replace a motor, but don't know how to setup a modern motor.

If it was mine I would disconnect spark and fuel to the motor. Do this by pulling fuel pump and coil connectors. Remove the dizzy cap and bump the starter over until number 1 cylinder comes around (but not past) TDC. Install a piston stop bolt in cylinder 1 and bring the cylinder up until piston contacts bolt.

Mark damper and rotate motor by hand clockwise (facing motor) until piston contacts stop bolt. Mark damper location, then measure distance between the 2 marks. The middle between the 2 marks when crank is rotated back clockwise (facing motor) is TDC on number 1 cylinder.

Remove stop bolt and rotate around to TDC no 1. Rotate dizzy so its at the notch shown in post 26 pic.
It kind of jumps from 50 to 58 while running. Then stays at 50 when shut engine off. I don’t have a stop bolt. Could I just use a socket wrench on alternator or pulley to move cylinder 1 to tdc? And see what they lined rotor up on. I agree with you I don’t think they set it up right after replacing long block. which is kind of weird because they build awesome race engines for everyone around here.
 
Joined
Nov 17, 2007
Messages
21
I need motor serial number or something like Gxi-270-G, Gxi-J to narrow it down

If it does have the flat dizzy cap, then verify it is positioned correctly. The motor is not timed used base timing mode unless it has the EST dizzy

To check timing, motor needs to be at TDC on number 1 cylinder
If it does have the flat cap which is HVS ignition, the dizzy can be moved ever so slightly one direction or the other. The base would be scribed marked, then it moved about 1 or 2 degrees. Locked down and see if it runs better. If it does good, if not turn back where it was and go other direction. If neither works better then return to original


View attachment 370631
I went to mess with it today after work but forgot the smaller torx bit for rotor. I did find the engine plaque. It is the gxi-d model.
I wanted to try and loosen dizzy and move it a degree in each direction to see if helps with idle. I see a white marker line down outer shaft of dizzy so I can use that as a reference or possibly just make a new mark for reference. Do I loosen the bolt on top of engine next to dizzy to slightly move it. Or is there another fastner under the rotor. I planned on just turning it a tiny bit and secure it,start it and see if idle improves. If not slightly the other way and see if it improves. If no result I’ll just set it back at original spot and get a real mechanic to take a look. Thanks.
 

alldodge

Supreme Mariner
Joined
Mar 8, 2009
Messages
37,046
The Gxi-D shows 2 vacuum hoses
1 goes the the fuel rail damper, small hose
The other I think would go to the valve cover PVC. If either are leaking it can cause issues with idle
 

QBhoy

Admiral
Joined
Mar 10, 2016
Messages
6,575
Sure sounds like your IAC is trying to control and counter another issue. Is it possible that the throttle position at idle has been messed with previously to counter another, previous or underlying issue ? Have you had a look into the throttle body to check what that’s actually doing for position at idle ?
Tell us more about the details around the engine replacement. Were some parts used from the previous engine to complete and commission the new engine ? Manifolds, intake, injection gear and ecu? Was the previous engine an identical gxi of the same size, running gear and era ?
Are you using the proper spec plugs (itr4a15 spec) ? Need to be either the ac delco 41-993 or the ngk preferably.
 
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