Could this be the EGR valve?

[Falcon_LS]

I'm having some detonation/preignition issues with my '01 Grand Marquis, and have yet to pinpoint the issue.

Driving along, there's no detonation, but as soon as the transmission upshifts, there's detonation under light throttle unless I depress the gas further. If I'm going uphill, it happens again at the same throttle position.

The first thing I did was check and clean my MAF sensor, which reads 0.69V (should be in the 0.6V - 0.75V range), but that did not help. If I'm running 91 RON (87 AKI), the issue is much more noticeable. Move up to 95 RON (91 AKI), and it doesn't happen as much, unless you depress the a little further in the same gear. Move up to 98 RON (94 AKI), and the issue disappears completely.

There are no codes stored in the PCM. I'm just wondering if the time has come to replace the EGR valve. It's still on the factory one at almost 293,000 km (183, 125 miles). Thanks!

 

[demarpaint]

It could be the EGR valve, cheap gas, bad gas, or timing, to name a few of the more likely causes.

 

[Falcon_LS]

Thanks, demarpaint.

Timing is controlled by the PCM. The gas is high sulfur, but otherwise pretty good...no one I know with Crown Vic (14 people) is having any issues. Should I take the plunge and just replace the EGR valve?

 

[Trav]

It could be but it could also be the EGR passages are clogged or carbon build up in the combustion chamber.
Problems with the EGR pintle movement itself usually throw a code but the ECM doesn't really monitor EGR flow except for exhaust gas temp.
Have you added a low restriction exhaust?

 

[Falcon_LS]

Thanks, Trav. The exhaust is untouched, and comes with a factory catalytic converter delete as the car is built to run on leaded gas.

The exhaust tips, at least, are clean but I guess I'll have to remove the check the EGR valve. I've made a habit of adding MMO to the gas at each fill up and running Liqui-Moly's fuel system cleaner every 2,000 km.

 

[Falcon_LS]

Worth noting, leaded hasn't been available here since 1995, I'm running on unleaded.

 

[Trav]

Is this car still running on leaded fuel?
With no cats and leaded fuel the O2's must have also been deleted?

 

[Falcon_LS]

Sorry, the car's been running on unleaded since new. There are no oxygen sensors.

 

[Trav]

I would pull the EGR and check those passages, use a piece of old speedometer cable to clean the crud out, make a few little kinks in it the first couple of inches.
You can put one end on a drill and run it at low speed.

 

[punisher]

No need to pull the EGR.

Apply vacuum to EGR while at idle and see if the engine stumbles/dies, if it does, EGR valve/passages are OK.

Never have dealt with that calibration code (leaded with no O2 sensor) but check to see if there is an octane adjust plug you can remove. There might be a calibration update/PCM reprogram available as well to address pinging. Sometimes with age you get carbon deposits that cause pinging.

If you can, pull codes just to see if anything is hiding in memory.

Most pinging problems on those (at least with US calibrations) is MAF (which you checked) and the ignition curve (hence the PCM reflash I suggested).

Checking the MAF voltage at idle really doesn't help you diagnose a condition that occurs at anything other than closed throttle. A MAF that is borderline often reads normal-rich at idle, and goes lean as you increase airflow/engine load. In a perfect world you could hook up a data/scanner, select fuel trims and verify trims go lean at cruise/accel, but since you have no O2 sensors, I just do not know how you would diagnose that with any certainty.

 

[PZR2874]

I would CLEAN the EGR first

Then follow up with a SeaFoam treatment

Then check the plugs


That's just me.

 

[Trav]

Quote:
Apply vacuum to EGR while at idle and see if the engine stumbles/dies, if it does, EGR valve/passages are OK.


It will not indicate a partially blocked system, it doesn't take much flow to cause a stumble or make the engine die at idle.
True its a good enough quick and dirty test to test if the EGR system is functioning but not very accurate at determining the amount of flow restriction if any.
With proper equipment EGR can be commanded at a specific RPM's and RMP drop measured.

Reflash is probably the last thing i would consider at this point. This issue occurred over time or came on all at once, it apparently ran fine with the current programming.
EGR lift off should occur at about 1.6 in-Hg and full open at about 4.5 in-Hg i would check that first.

I wonder how this ECM controls fuel trim? Agreed, the MAF may be playing a roll in this.

 

[Mud]

DPFE controls the EGR valve but since there is no trouble code I lean to carbon deposits and not a faulty DPFE. I can't rush to say to replace the EGR but I've not left an EGR on either of my cars longer than 130K miles or so. When replaced, the OEM EGR had significant carbon deposits, plus it gave me the opportunity (a pain lol) to replace the EGR tube.

I have no idea about the calibration code either, unfortunately. I think the post above is pretty sound advice.

 

[UNC017]

Does that engine management system configuration use knock sensors?

 

[punisher]

Trav, bear with me on my thinking.

Even if there is a restriction in the EGR system, if there is enough flow to stumble/kill an engine at idle, there is enough EGR flow to do the job as far as mitigating pinging etc.

Off topic: I absolutely remember only replacing one EGR valve on a 4.6L in ~11 years as a FoMoCo tech, and it was cracked (by me)due to a crossthreaded upper EGR tube nut. It siezed and crossthreaded while I was attempting to remove the tube (oh what fun).

Now I am not saying the EGR isn't the cause, but it is way down on the list of causes in this case. Even when the EGR ports were clogged to the point of "0" flow, pinging wasn't ever a complaint.

Just an opinion, I could be wrong.

 

[Jim Spahr]

I would definitely try cleaning the EGR valve first before you replace it. Buy an EGR gasket (Fel Pro) and remove and clean the old EGR. Make sure it works while you have it off. Apply vacuum to it /while it is out of the car/ and see if the diaphram opens the pintle and keeps it open while the vacuum is applied. Clean the carbon off the pintle and the passages. Clean the gasket area and the passages on the block. If the EGR tests good, use the new gasket and reinstall it.

Another thing to check is the spark plug wires. They were often a problem on that model Ford engine and were often mistaken for many other problems: transmissions, fuel pump, etc. If you do decide to change the spark plug wires, use only OEM ie Ford replacements, even though they are rather expensive.

 

[Trav]

Are the EGR ports going to both heads? That's where my mind was wandering, you know one side restricted.
The only cars i ever saw with official cat delete were GM's brought into Germany early/mid 80's era, the problem was they left the O2's in and they fouled quickly.
This leaves me wondering how Ford is controlling the fuel trim or are they?

This leads me to wondering about more deposits on one bank than the other because of it.
I don't really have any answers more like only questions.

No offence intended you always have valid points and quality input as i hope i do as working mechanics we tend to wander into deeper waters.
IMO its a good thing to dissect the problem and the answers to find the correct answer, i welcome it and hopefully learn something every day.

 

[mechtech2]

Sure - it could be a faulty EGR system - the symptoms fit .
But high engine heat, hot intake air, or carbon deposits are just as likely.

 

[The_Jeff]

I wonder how much effort Ford put into your specific cat-delete engine tune. If you have no cat you may not have the back pressure to send enough smoke through the EGR system. And Ford may not really care.

Also with fuel octane there's a "sensitivity" that's the difference between Research and Motor octanes, which is surely different between leaded and unleaded. You could have a new problem or your fuel blender just came up with a lousy batch.

GM made turbocharged Typhoons and Syclones for the Mideast market that were designed to run in open loop on leaded fuel. They just lopped the wires off the o2 sensors in place-- talk about half-baked programming!

 

[Colt45ws]

Originally Posted By: Trav

Problems with the EGR pintle movement itself usually throw a code but the ECM doesn't really monitor EGR flow except for exhaust gas temp.

Yes, it does, and No, it does not.
EGR flow is monitored by the DPFE. There is a restrictor in the EGR tube and the DPFE takes a reading on both sides to compare the pressure. Opening the EGR valve results in a pressure drop on the upstream side of the restriction. Then the computer can calculate the flow. EGT is not monitored.