Low oil pressure and slight stumble at idle

[Old 94 Turquoise]

Okay wanted to see some other people’s input on a problem I’m having with my 1994 1500 350Tbi . When I first start the truck up the oil pressure is about 40 but then after it warms up and I’m idling in drive , the pressure goes down to about 10 or almost touching the red. Also my rpms go down to about 300 then sometimes the engine will stumble and drop to about the first dash mark and just for half a second and then go back up to 250-300. If I put in in nuetral or park it’s about 500 . So under load it idles low. It runs good when I’m driving . Could it be oil sending unit?? As for the low idle problem maybe clean the IAC?? Just want to see what you guys think.

The picture is when I first start the truck up.

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[Supercharged111]

What's your warm pressure at 500-600 RPM? My TBI 350 only showed like 20psi at a warm idle, maybe 30 warm cruise and 40 cold like you. Ran perfectly that way the 8 years that I owned it.

 

[Old 94 Turquoise]

What's your warm pressure at 500-600 RPM? My TBI 350 only showed like 20psi at a warm idle, maybe 30 warm cruise and 40 cold like you. Ran perfectly that way the 8 years that I owned it.

It’s about 10-15psi warm idle in park . Then when I shift to drive it drops down to almost the red mark. then cruising on freeway it’s like, 30 psi. It just seems low to me .

 

[Old 94 Turquoise]

Also my truck doesn’t warm up all the way. I think the thermostat isn’t closing. I think I just need to replace it and see what that does.

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[Supercharged111]

My TBI truck did the same thing running cold, thermostat it was. Try hooking up a diagnostic gauge to really see what your pressure is.

 

[Old 94 Turquoise]

My TBI truck did the same thing running cold, thermostat it was. Try hooking up a diagnostic gauge to really see what your pressure is.

Like an obd1 scanner? I thought those were only for codes? Or are you talking about like a mechanical pressure gauge? The gauge could also be off , it is a 25 year old gauge. it never gets past 40psi even when flooring.

 

[Supercharged111]

Yeah, mechanical gauge to troubleshoot, not to permanently install. That or just keep driving it if you don't hear lifters ticking.

 

[Old 94 Turquoise]

No lifters tickings. I just wanted to see if it was normal or not.

 

[Old 94 Turquoise]

Here my pressure at idle warm at a stop light

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[Supercharged111]

Do you have a more straight on pic? That angle may make it look like it's reading lower than actual.