# oil pressure and reverse help



## james.j.smith (Sep 20, 2010)

I was our plowing with my 1991 for f-250 with a 351 for the first time. I purchased this truck a couple months back. When I pun the truck in reverse the oil pressure would drop off and the truck would stall if the pressure didn’t go up any. I eventually found the sweet spot and the truck wouldn’t stall that much. After about 10 hours of running the truck the pressure would go down sporadically when going in drive however it would just momentarily drop and then come right back. Now I can’t simulate any of this, I drove the truck last night about 35 miles with no issues. Has anyone else had this issue? I think I need to change the oil, I put some 10W-30 (1.5qts) over the past couple weeks. My neighbor thinks I should put some 10W50 in it with a oil treatment for high mile trucks.

thanks for your help


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## Milwaukee (Dec 28, 2007)

NO 10w50 you would kill that engine NO anything engine oil treatment they FALSE to me. Normal 10W30 is ok until it low oil pressure at hot idle.

Get real oil gauge tester and verify what hot oil psi at idle. http://images.auctionworks.com/hi/60/59874/engine_oil_pressure_tester.jpg

Reverse stall You have vacuum leak somewhere and IAC sensor could be stick. Worth to pull off and clean.


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## james.j.smith (Sep 20, 2010)

thanks for the reply, what is the IAC sensor:?


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## Milwaukee (Dec 28, 2007)

james.j.smith;1195145 said:


> thanks for the reply, what is the IAC sensor:?


http://www.2carpros.com/articles/how-idle-air-control-valve-works


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## hydro_37 (Sep 10, 2006)

dont trust the factory guage
wont kill the engine to run 10W50...will just make it harder to start when it is cold
a fresh oil change will do the engine good too


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## james.j.smith (Sep 20, 2010)

going to do the oild change next week been want to get it done the past couple weeks. does anyone know where tha IAC sensor is located?


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## Milwaukee (Dec 28, 2007)

Do you see IAC like this?
http://www.supermotors.org/getfile/266545/fullsize/6 Remove IAC Plug.JPG


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## Dr Who (Dec 16, 2010)

Castrol motor oil, been good to me realy good to me....

might sound stupid, but make sure your battery is not getting pulled over into the hood in reverse, I had a wagoneer that did the same thing only forward, but not all the time. took me a year and one transmission to figure it out (727 tourqflight don't like to be neutral droped...)

also you may have a broke motor mount and its pinching a wire....


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## mrv8outboard (Dec 29, 2009)

Fuel injected correct? This is going to sound funny but check the transmission fluid. I had a 1993 Bronco 5.8 do the stall when shifted into reverse. It ended up being low transmission fluid. The uneven inertia from varying fluid level in the torque converter was teasing the computer that when shifted into reverse it would the rpm's exceed the PID limit and would then compensate to lower them back to with in the PID limits just as the load would start to reapply as the transmission completed the shift cycle.


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## Dr Who (Dec 16, 2010)

mrv8outboard;1195985 said:


> Fuel injected correct? This is going to sound funny but check the transmission fluid. I had a 1993 Bronco 5.8 do the stall when shifted into reverse. It ended up being low transmission fluid. The uneven inertia from varying fluid level in the torque converter was teasing the computer that when shifted into reverse it would the rpm's exceed the PID limit and would then compensate to lower them back to with in the PID limits just as the load would start to reapply as the transmission completed the shift cycle.


now that is complicated sounding....

but is very logical and likely....


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## james.j.smith (Sep 20, 2010)

I checked the trans fluid last week and if anything it looked a little high I,m going to recheck it this weekend. I'm debating on getting the fluid and filter changed. the reason I'm debateing it is I have recently had a trans line break and alot if not all the fluid was drained while fixing it.

milwaukee, I do have that setup should i take it out and clean it or just replace it. I've been looking for a vacuum leak since I think the truck is a little rough at idle?

The thing that is wierd is that it hasn't stalled since the other night plowing, no stalls and the LO pressure gage has been steady.


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## james.j.smith (Sep 20, 2010)

I just looked at the price of a new IAC valve and I think I'm going to test it and clean it. what have you used to clean them? I was thinking carb or throttlebody cleaner.


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## linckeil (Sep 18, 2007)

does your truck have the automatic overdrive (e40d)? if so, the filter is known to drop into the pan and stalls the truck when put into reverse. you need to remove the trans pan to check. 

either way it's a good opportunity to change the trans filter and fluid.


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## linckeil (Sep 18, 2007)

and you can buy a clip for like $10 that prevents the filter from ever dropping again. i think its called a "stay-put" clip.


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## james.j.smith (Sep 20, 2010)

Well I tested the IAC and there was no movement of the valve when i turned the key on. So I replaced the valve. I also had the oil changed with 10W40 oil last week. the oil pressure haven't moved and the Op test of the truck with the new valve went well. I've place it in 4X4 after the truck has warmed up and (know on Wood and cross fingures) the truck hasn't stalled. Well see what happens during the next storm.

thanks again for all your help.


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## james.j.smith (Sep 20, 2010)

I'm going to get the trans filter and oil changed when i get paid again.


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