Is it normal for the 4.9 to read low oil pressure at idle when warm?

I am pretty sure I have asked this and I am pretty sure the answer is yes but I want to double check before nuking another engine. I searched and couldn't find it. So if people with 4.9s using the stock Fiero gage could chime in that would be nice.

As of my ride in this morning (4.9 with Fiero OP sending unit and Fiero gauge)

At warm idle, just under 40. When steady cruising at 45 a couple of hash marks over 40.

At cold start up - 80

[This message has been edited by michfiero (edited 08-11-2010).]

hmmm.... hopefully some others will chime in.

Thanks.

Anyone know of an inexpensive and easy to install aftermarket that I could install inline that would allow me check the gage pod readings against it.

[This message has been edited by Dizzixx (edited 08-11-2010).]

My oil pressure seems to run higher then most other 4.9 owners. 80 cold startup. Warm idle never drops below 55psi. 2-3k rpm ranges from ~60-65. My motor had a fresh rebuild when installed. I use 10w40 also. The 800rpm manual trans idle helps keep it higher also.

Cheap mechanical gauges can be had at harbor freight for a few bucks...
http://www.harborfreight.co...re-tester-92687.html

[This message has been edited by Fieroseverywhere (edited 08-11-2010).]

The engine when hot and at idel will be as low as 12 PSI. If you are using a 86 or 87 Aux gauge package the low oil pressure is set at 15 PSI. If you are using an 88 Aux gauge package the low oil pressure is set at 7 PSI. I am having some of the same problems in my car. If you can get a mechanical gauge I would check it with that.

Jack

quote Originally posted by J Gunsett: The engine when hot and at idel will be as low as 12 PSI. If you are using a 86 or 87 Aux gauge package the low oil pressure is set at 15 PSI. If you are using an 88 Aux gauge package the low oil pressure is set at 7 PSI. I am having some of the same problems in my car. If you can get a mechanical gauge I would check it with that. Jack

what he said - IIRC, there was a link at one time where someone was able to modify the 86/87 gage to trigger at the lower 88 level.

Good infos.

I went and bought a mechanical gauge from harbor freight and the T-adapter to install it. As soon as the car cools down I am going to put it on.

Why do you run 10w40?

If someone can find that link to mod the aux gauge I sure would like to have it.

Jack

If someone could interput this might be it.



I am thinking it has to do with the 100k resistors and that diode but I kinda suck at electrical so who knows.

Edit - Image Linked from: //www.fiero.nl/forum/Forum2/HTML/105838.html

[This message has been edited by Dizzixx (edited 08-11-2010).]

quote Originally posted by Dizzixx: If someone could interput this might be it.

If you increase the 54.9k resistor it will make the light come on at a later time.

As a quick guess, you can change it to 68k, but at the moment I am not sure of the exact oil psi reading that this will turn on the light at.

I could be more specific as to what value it should be at a certain PSI reading if you can tell me what the voltage is on pin 3 (reference to pin 4) in the diagram is. I will need to know 2 reference readings, say voltage at cold idle (and corresponding oil pressure reading) as well as voltage at warm idle (as long as they are at 2 different pressures – also as many decimal places as your meter will read). I can do this myself, but it will have to wait until I get home (and assuming I have time and remember).

edit: of course this also means deciding on at what pressure should the light come on at (I am not sure what the stock 4.9 low oil pressure is - probably in the book someplace).

[This message has been edited by Mickey_Moose (edited 08-12-2010).]

Cool deal I will try and do that.

Also at what psi do I begin to cause damage to my engine?

I took it for the longest drive on this engine yet and I noticed that after going WOT a few times on the freeway and an hour or so of cruising at temp when I did let it idle down at a light it was more like 10psi and if the idle dipped at all it would go as low as 8. I am going to check the oil level, I lost a little messing with the gage. But I would like to know at what point should I worry? and at what point should I shut her down?

or...maybe you can just replace it with a 70k pot and adjust it until the light just goes off...

edit >> just realized that I do not have a mechanical oil pressure gage, so if I was to do the reading myself not all that sure how accurate it would be by just reading off the dash gage...

[This message has been edited by Mickey_Moose (edited 08-12-2010).]

Yeah the dash gage is about +-5 psi off at 40psi and then wayyyyy off at the extremities. For instance at a reading of 80 psi on the dash in truth it is about 60 on the mechanical.

quote Originally posted by Dizzixx: Yeah the dash gage is about +-5 psi off at 40psi and then wayyyyy off at the extremities. For instance at a reading of 80 psi on the dash in truth it is about 60 on the mechanical.

put 15w-40 oil or 20 w 50 in it and the pressure will go up a little bit... over in the caddy forums, people start using 15w 40 after 150k + miles typically, to get better oil pressure. i get 30 psi at warm idle with 10w-30 synth, but my engine is low mileage...

I know at hot idle (such as a stop light) my oil pressure light will flicker on and off. I was told not to worry about it since the oil pressure of the 4.9 usually runs a little low compared to the 2.8. Which sounds just like what J Gunsett was talking about.

Dan

How much of a jump is it to go to 20w 50 or 15w 40?

quote Originally posted by Dizzixx: How much of a jump is it to go to 20w 50 or 15w 40?

About one dollar.

Just go up one grade and see what your differences are. I have never been real happy with 10W30. I have always thought it was sorta thin.

[This message has been edited by josef644 (edited 08-15-2010).]

I meant how much a difference does it make to the engine? Will it cause problems in the winter? etc etc stuff like that. Seeing as at hot idle I get about 8-10psi I was thinking I would go all the way to 20w 50 but I want to know if that will cause other problems.

I would think 15W40 would be better, and it has been real hot here in Texas.

Put in 15w 40, virtually no difference. Maybe 2psi at the bottom end and it seems to pick up faster. So does this mean its the oil pump going? Should I make the jump to 20w 50?

Dizzixx, I tried a new oil pump and it did not help me. And they are not cheap. When I return home I am going to try the 20/50 and see what that does.

Jack

Well thats good getting my exhaust off is a pain. I was going to have to cut it and weld on a flanges to take it out in two pieces to be able to get into the oil pan without dropping the cradle again. What are the temps like in Michigan? What psi are you getting at the moment?

Honestly - I really wouldn't worry about it, mine would cause the oil light to flicker at idle as well (solve that problem when I installed the Firebird dash).

I knew it would flash and never worried about it, but if it does bother you, do the oil gage mod - use the pot method and adjust it so that the flicker just goes off.

The 4.9 is fairly bullet proof and you will probably get a fair amount of use out of it - mine is going on 6 years and the gage would still be flickering today is things were left as they were. I also drive mine fairly hard - taken out valve train (high revving) and had axle issues, even one point where I thought I had seized the engine (stopped due to overheating - temp gage issue and the starter couldn't turn it over, but it worked fine the next day after it cooled off). I have gone through some really cold days during the winter as well - we had set a local cold record this past winter and the 4.9 gave no problems that day, but I use 10W30 - don't see a point in using heavier weight. Maybe one day I will buy a mechanical gage and get a real reading.

Just enjoy...

Cool deal. Having nuked the last one I am a little paranoid. I guess I will just keep an eye on things. I think I will install a pot and mod it to turn the light on at 12 or 15 psi.

Jack did you try the 20w 50?

I used to use 20w50. Worked great in the summer but was a little thick in the winter until the car fully warmed up. Now I just use the 10w40. I didn't really notice a differnce in pressure but I'm still going off the stock gauge so its not super accurate. The engine didn't seem to care much either way.

[This message has been edited by Fieroseverywhere (edited 08-18-2010).]

Yeah the 15w 40 makes a difference. Mostly if you idle above 1k. Below that and it really doest seem to matter the thing only wants to put out 8-10psi. Above that threshold though and it did seem to make a difference the pressure picks up more quickly and it adds a little pressure at WOT not entirely sure thats what you really want, but not so much to worry about only talking like 5-10 psi at the most.

Dizzixx, I am going to put a mechanical gauge on it first just to double check. If the gauge will tell me the truth and I do have a problem then I will try the 20-50 and see what I get. I never had any problems for the last 5 years, then driving to Daytona this spring it just dropped 5 PSI. But I am out on a job at this time but hope to get a few things done on this pressure problem before winter sets in.

Cool deal no problem just let me know if you/when you do. How are you going to do it and what type? I got a mechanical gage from harbor freight for dirt cheap and brass fittings that I was able to put inline with the oil cooler. I have heard others say they put a fitting under the pressure sender and ran a line from there. I think if I did it again or get around to it I would like to do it that way its cleaner and keeps the pressurized line to the gage away from the heat of the exhaust better. 500 miles though and no problems.

I have a 0-60 mechanical gauge. I plan on warming up the engine and once it is up to tempeture I am going to remove the oil senser and screw in the mechanical gauge in the hole and restart the car and watch it for a while. I will let you know what happens.

Jack