Hello,

For years I've been dealing with an EGR issue on my '92 Sovereign. Shortly after I bought the car, I got a FF code for the EGR temp sensor. The EGR valve was shot, not holding vacuum, and I replaced it with a Jaguar OE valve.

After installing the new valve, the engine would always stumble while decelerating in drive or reverse when at operating temp, only when the RPM dropped from at least ~1200RPM to idle at closed throttle. (Almost as if the EGR was sticking open) I've replaced the EGR valve with another new Jaguar genuine unit, replaced the vacuum solenoid, etc. I've gone through the intake and ignition and fuel system. I've tested the EGR solenoid with a vacuum gauge, and when the RPMs drop below the EGR cutoff speed, vacuum is released quickly and sharply, as it should. To this day, I cannot explain the stumbling.

So my solution was to disconnect the EGR hose and plug the port on the solenoid. Which, of course, sets off the FF for the EGR temp sensor after a few drive cycles.

I thought I'd be smart, and I wired in a resistor (equal to an approximate value the EGR temp sensor should be reading when EGR is active) to the sensor connector. Now the light stays off, but if I let the car idle for any more than about 7 minutes or so, the FF code comes back. The ECM must be smart enough to realize that the sensor is detecting "EGR flow" while the solenoid is commanded OFF.

So now my idea is to use a relay, triggered by the same signal the ECM uses to command the EGR solenoid ON. The relay would close and provide the proper resistance to the EGR temp sensor connector, tricking it into thinking there is EGR flow. When the EGR solenoid is commanded OFF, the relay would open and the ECM would no longer see that resistance.

Any thoughts on the feasibility of this idea? Maybe there's a better way?

Nick

 

Why not just make a threaded plate in the EGR location and install the temp sensor.
It should get exhaust gas all the time and tell the ECM it is getting hot gasses flowing on it??

bob

 

Thanks Bob. That's actually pretty much the problem I have now, though. I'm faking the hot exhaust gases by using resistors. The problem is that the ECM knows that there shouldn't be hot exhaust gasses when the car is in Park or Neutral, when the coolant temperature is below 140*F or outside the EGR envelope.



Now looking at this chart makes me wonder... If engine speed *and* MAF voltage determine the EGR envelope, and I've already confirmed that EGR doesn't run under ~1200RPM (just as it should be), perhaps my stumbling problem is in the MAF?

Maybe, just maybe, my MAF is faulty and giving too high a voltage reading to the ECM under this particular situation (deceleration, closed throttle) when maybe the EGR shouldn't be commanded on then at all. I mean the stumbling is happening at speeds of under 20mph! I can't imaging EGR should be operating at that low a speed.

I think I should take a look at my MAF voltages today and see where I'm at. Maybe I won't have to rig this up at all?

Thanks,
Nick

 

Hi Nick,

Just a few random thoughts:

Have you followed the flow charts in the AJ6 Engine Management System Diagnostic Guide? If not, you can download the manual at the link below courtesy of Gus and his jagrepair.com website:

http://www.jagrepair.com/images/Auto...stem%20S91.pdf

I don't recall the fault code for the EGR temp sensor but I think the manual gives the correct resistance for the sensor at various temperatures.

Edit: I was typing this up as you and Bob were posting - obviously you have the manual.

Have you cleaned the carbon from the EGR port on the underside of the throttle body?

Cheers,

Don

 

Hi Don,

I still, for the life of me, haven't been able to figure out how to access the EGR port on the manifold. The last time I tried to gain access, it appeared I would've had to remove the oil filter to get to the bolts. Also, I am unable to loosen the fitting on the EGR transfer tube, there just doesn't seem to be enough room to get a wrench in there... Any secrets?

Wouldnt carbon only serve to prevent the flow of EGR gasses, which (with the stumbling) I know are making it to the intake?

Also, there isn't any kind of vacuum restrictor or something of that nature that should be on the EGR vacuum line,
right?

Thanks,
Nick

 

My car stumbled till I cleaned out the egr port.

The bolts will come out without removing the oil filter but they have to be loosened simultaneously and when all released, egr port assembly will drop out, although it will still be attached to the egr pipe - best to undo that fitting first.
In a pinch you can always do a partial clean out from above through the IACV housing which is directly above.

HTH

Larry

 

Nick,

It definitely isn't easy. Try soaking the pipe nut and the two hex screws with penetrating oil for a couple of days before you make your next attempt. Larry is right that you want to loosen the big nut on the pipe first, and he's also right that a partial cleaning from above is better than nothing, but you really want to also clean the smaller port on the left that comes from the carbon canister purge valve. Just in case they help, the photos of the port on our '93 are at this link:

Throttle Body & EGR Port


Cheers,

Don

 

Thanks Larry, if it's fixed the stumbling in your case, I'll give it a go and hope for the same with mine (:

And thank you for the pictures, Don, hopefully I can sort this out once and for all. I will take your advice and soak them all with PB blaster. Maybe my crowfoot wrench set will come in handy for this job.

I'll post some pictures of what I find

Thank you,
Nick

 

Nick,

Memory/nostalgia ain't what it used to be

I just reviewed my own thread about doing the EGR port/TB cleanout and I was mistaken about the bolt sequence thing - the correct procedure for the removal is in this thread :

https://www.jaguarforums.com/forum/x...leanup-109079/

cheers

Larry

 

The dirty Intake once I removed the throttle body.
The dirty EGR adapter.
More of the adapter


Cleaned the best I could.
The slit in the accordion hose. Most of the slit rests on the top surface of the Intake trumpet, so I don't think air is coming in through the ENTIRE slit, but for sure there's excess air getting in from it.


Okay, thanks to everyone's help, I got the EGR adapter removed after about 2 or 3 hours. The nut on the transfer tube would NOT budge. I was actually spinning the male coupler which connects the EGR adapter and the transfer tube. I had almost no clearance due to my '92 having a filler tube which is in the way. Also, I removed the oil filter as well. I found I was missing one short screw for the EGR adapter, but found I had one lying around (that I probably picked up off the garage floor...)

So I unbolted the EGR adapter then actually unscrewed it from the transfer tube. Once it was free I was able to remove the male coupler from the transfer tube.

The EGR adapter was pretty bad, but not as bad as I was expecting. Pictures are attached. I did find the inside of the manifold was VERY oily and cruddy. I did try to clean it as best I could. I also removed 4 of the 6 plastic intake runners and cleaned them out (they were also cruddy).

My throttle body was slightly dirty with only a thin film of oily residue. MAF was very clean. I did have to clean some yellow/milky goo from the PCV hoses.

My main discovery was a pretty bad slit in the accordion tube that connects the Intake elbow to the throttle body trumpet. A new one is on its way. I've never noticed it before, but the last 3 or 4 times I've had the Intake plumbing apart, I never really examined under the seating surface of the large clamp (which is where the slit is.)

I did put everything back together, readjust the base idle and reconnect the EGR vacuum hose. I did have a stumblimg
as I've had before, but it didn't seem as bad. I'm hoping I can eliminate it completely with the new Intake hose and one last reset of the throttle plate gap and base idle speed.

I'll post back when I get the new Intake hose installed.