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Oil or idle?

1997 ford f150 4.2 105,000. When fully warmed,and come to complete stop, idle drops, watch oil pressure indicator drop, bring up idle, oil pressure comes up too. Being would have to pull engine to clean sump- Have done the kerosene added to oil before changes to clean any goo, oil now runs clean, and replaced the IAC valve. Just do not have money to throw at this. Goes down highway fine, runs fine cold. Being the truck is a stick, stop and go traffic has become a nightmare of epic proportions. taken to shop, where it idled all day with no problem. Have lost ability to go to work. please help.

I’d run an oil pressure test with an external gauge to verify if the problem is really related to lower than normal oil pressure or whether it’s a shaky oil pressure sending unit.
What kind of pressure readings? (Both idle and off-idle)

If the problem is really related to sludge then cleaning methods such as kerosene may or may not work. Sometimes the oil pump pickup screen will develop coked (burnt basically) oil on it and it simply will not clean off short of removing it and doing it by hand.

That brings up a few points.
One is that if the oil pressure is iffy because of a coked screen then this means the rest of the engine has suffered a bit.
Two is if the engine idle drops excessively low the oil pressure may drop lower than its normal idle reading.
Three is why would a shop allow an engine to idle all day long? That seems a bit misguided to me.

External gauge was used, with the idle all day. Sending unit was replaced-sorry, I forgot, this has been months. Had to shop numerous times,was told pressure fine, but they couldn’t find problem.To clean the screen engine must be pulled to get to pan. But, would this only show up when engine is hot? Or only when fully stopped? If I go through large puddle, problem stops. As to your “two” that is the problem-is it oil related? or is it idle related? got one error code which cleared itself, that was IAC, which has been replaced. The only problems i have had with this engine have been throttle related. Have always done maintenance on time, oil changes before the 5000 mile mark, usually 3000. Have not been able to work because of this, job too far with major traffic. Doing stop and go would stress out a gymnast, only 2 feet for needed simultaneous three pedals. Just don’t have money to throw at this. Driving down highway, or any roadway, you would think truck is fine, until you have to stop. If truck does stall, takes a few minutes to start back up. Cranks, but will not turn right over. the idea of having to slam on brakes makes for a scary scenario. Am at wits end.

It just sounds like the truck is trying to stall. When the idle drops the oil pressure will drop so I’m thinking that oil pressure may not be your issue at all.

Find your EGR valve and pull the vacuum line from the top of it. Stick something like a golf tee into the vacuum line and put a vacuum cap on the EGR connection. Drive around that way for a while to see whether your at idle problem doesn’t go away.

This will set an error code, and you should not leave it like this as you will likely end up with some pinging which will not be good for the engine. So I’m just suggesting that you try this to see whether the EGR is hanging open.

Report back.

What is the oil pressure reading with the external guage at idle? And what is the motor rpm at idle also measured via an external guage?

If the oil pressure is 5 lbs or higher at idle you should be ok.

If the motor is idling at 600 rpm or lower, the idle is the problem. Low idle speed would reduce the oil pressure below specs and put the motor at higher risk for stalling out.

Has the throttle body been cleaned?
Also make sure the PCV valve and passages are clear.

what is a vacuum cap?
so, just to make sure I understand, if the problem goes away, then is bad EGR. And if I get error code, then is not EGR.

I do not have external gauge for measuring idle. When had in shop, they idled it all day, and it did not exhibit symptoms. It must be driven and be completely up to temperature for the problem to happen. it does not happen when engine is cold. Shop did external pressure test for oil, that was not the problem. At least under just idling condition.

Or, is it just to test EGR, and will set error code no matter what?

I have this same year F150 and same engine (4.2, 6cyl). I agree with cigroller to eliminate the EGR first. The other quick test you can do is pull the vacumn hose off the top of the EGR and with the truck running, connect a piece of vacumn hose to the top and apply a vacumn. The truck should start to idle rough and may stall. Report back afterwards. Out of curiousity, does the engine sound OK ? No bearing knock ??

what passages?

wouldn’t I get Check engine light for EGR? Light does not come on.

You should get a CEL for an EGR problem. But we’re just trying to figure out if it could be something in the EGR system and it’s easy (real easy) to check. When the idle drops down (600-800rpm), does the engine still sound OK ?

All I was saying about a vacuum cap is to cap off the port on the EGR when you disconnect the vacuum line. It doesn’t matter what you do it with, but you can buy little rubber caps for vacuum lines at an auto parts store.

If the EGR valve is ending up open at all during idle then the engine will run poorly - like it has a vacuum leak. You can easily have relatively minor issues that will not set an error code. In fact you can test/check every part of the EGR system, have it all be within specs and still have a problem. (As far as the Ford EGR system goes I know this for sure from first hand experience).

Disconnecting the EGR will set an error code no matter what. It will probably take 100 miles or so, though that will vary.

If the EGR is a problem this method only might tell you. Its still possible for the EGR valve to hang open a bit even without the vacuum line on it. If it comes to that you can remove the valve and temporarily install a blocking plate for it.

If you find that any of that helps then - NO - it doesn’t mean that you need a new EGR valve. The EGR valve is only one part of the whole EGR system. The system involves the lines that move the exhaust gas around, a DPFE sensor, EVR solenoid, and the EGR valve itself. If you don’t want to blow a lot of $$ on guesses then you evaluate the whole system. And before replacing an EGR you can always just try cleaning it.

Here’s one source of info on checking out the system: The web is covered with them.

for ebk087, truck sounds fine, slight tap, but it always did that. It has idled rough since brand new. This problem used to only happen after highway driving, (about 45 mins to work) then when would come off highway and have to stop at light. Could drive around town doing errands all day and would be fine. the problem now happens as soon as up to temperature, no need for highway, but when moving is fine, no hesitation on acceleration. Maybe stupid question, but, with pulling vacuum hose off top of EGR, do you mean to rig a connection to a real vacuum cleaner? Run said cleaner?

Were you reading that other April Fool’s post or something? No - there is no vacuum cleaner involved.

Engines create vacuum. The vacuum power they create is often used to run stuff. Your EGR valve is vacuum actuated.

There a little electric motor (EVR solenoid) that has a vacuum line on it from the engine. There’s another vacuum line that runs from there to the top of the EGR valve. When the conditions are right, the engine’s computer tells that little electric motor to activate and let engine vacuum go through to the EGR valve. That’s what opens up the valve.

If the spring on your EGR valve is weak, and/or there is a lot of carbon gunking it up, and/or the EVR solenoid is not sealing off the engine’s vacuum when its not supposed to be open then your EGR valve can end up being stuck open. This will cause the engine to stumble. Listen - I mentioned it b/c its meant to be a very simple thing. Your EGR valve looks like a little flying saucer with a small tube stuck on top of it ( Pull off the little tube - plug it up, along with where it connected. Drive the truck. Report back.

ekbo did mention you manually applying some vacuum to the valve while the truck idles. You could do this with a little piece of tube and your mouth - you just suck in a bit - not inhaling! But the question of whether or not your valve opens is completely irrelevant to your current problem.

Pull the vacumn hose off the top of the EGR. Then get a small piece of automotive vacumn hose at an auto parts store - they sell it by the foot (same type that was there on the EGR). Then connect it to where the hose you just took off was (on the EGR). Apply a vacumn to it. If you don’t have a vacumn gauge, you can do it yourself by creating a vacumn (sucking on it) - not accurate but should do. The truck idle should stumble and possibly stall. The link that cigroller has below explains the EGR system really well and how to test it. Don’t get overwhelmed - it’s very easy to test the entire system on that engine.

Does the truck STALL?? Or are you just worried about low idle oil pressure?? Because that’s NORMAL…

thanks for your patience with me cigroller. thanks for the link, it’s for ford! OMG! This will take a while, testing all these things.

It has, and then won’t start right back up.It cranks, won’t turn over for 5-10 minutes. The concern is to eliminate the need to raise the idle every time I stop. To fix what causes the idle to drop. I think is dangerous to have to put truck in neutral, then left foot brake(left is clutch, i stop FAST), right foot to raise idle, at every traffic light, once truck is warm.