Hello,

In the process of searching for the issue that's causing my 1992 Sovereign to stumble on deceleration, surge and (rarely) stall when coming to a stop, I'm looking back into the ignition system.

I've replaced the spark plugs, wires, and distributor cap and rotor. Up to now, I hadn't thought about the coil.

I'm getting resistance readings of 1.5 ohms between the positive and negative terminals (primary) and 7,710 ohms between the negative and output (secondary)

My service manual says the primary resistance should be 0.5 ohms (+/- 10%) and the secondary, 6000 ohms (+/- 10%)

Would the readings I'm getting from my original coil be bad enough to cause issues? Should I follow the book and just replace it?

Thanks,
Nick

 

Nick,

Are your resistance measurements done with the coil wires connected or disconnected? Let me know and if I get a chance I'll measure the coil on our '93.

Another thing you should check is your transmission fluid. Low fluid has been associated with bogging and stalling when coming to a stop or slowing to make a turn. There's at TSB on it. Check the fluid hot after a good drive and parked on a level surface. With the engine running and your foot on the brake pedal, move the gear selector from Park through all the gears, pausing a few seconds in each gear for the fluid to fully pressurize in each gear. Return the lever to Park, and with the engine still running, check the fluid level on the dipstick. It should be exactly on the HOT line. If it is much below (or above), that could be contributing to the symptoms you describe.

Cheers,

Don

 

Thanks Don,

The coil wires were disconnected when testing the resistance, and I've verified my transmission fluid level and it's spot on after a nice long drive.

I should mention that I disconnected and plugged the EGR vacuum line and my stumbling on deceleration is almost completely gone. However, I still have a high idle. When coming to, and after a stop, in gear, my RPMs are sometimes at 1,000 which requires a lot of braking force.

I have adjusted my base idle speed the best I can with my PDU but the bypass is fully closed and still a bit high. I have already adjusted the throttle plate.

I'm thinking maybe I have two issues, EGR and an air leak.

I was having stumbling issues ever since I replaced the factory original EGR valve. I have gone through two OEM dealer EGR valves and swapped the Vacuum Solenoid thinking maybe it was sticking... One EGR valve was so bad the car wouldn't idle with it installed. I've used a new gasket with each new EGR valve.

At least I have some leads to follow.

Thanks,
Nick

 

Nick,

I don't know if any of this may be helpful, but gimenofm is having similar troubles and I just posted a download of all the possible causes I could think of:

https://www.jaguarforums.com/forum/x...t-fire-155730/


Cheers,

Don

 

Thanks Again, Don

I ended up getting a new coil and with the Output of the EGR solenoid plugged (EGR disabled, essentially) the engine is running very, very smoothly.

Now I have the issue of high idle. At stoplights I'm pushing 1100 RPMs and after my last drive I could smell the brakes were being worked hard.

I've had the TB off and cleaned a few times since I owned the car. The mating surfaces weren't perfect, however. I plan on disassembling the whole thing today and readjusting it.

I plan on using a fine scotch brite pad on the surfaces then using a very slight application of oxygen sensor-safe RTV just to smooth the surface out.

I've adjusted the throttle plate a few times before. I will double check it again, maybe narrowing the gap very slightly from spec, then resetting the TPS with my PDU, then doing the base idle adjustment. I figure I can always make up for the smaller gap with the IACV bypass a little if I have to. (Currently the bypass is fully closed, and my base idle is too fast) I have tried checking for intake leaks all over with various means (spray, propane, etc) and have found nothing.

Then I need to figure out what's wrong with the EGR system...

Thanks.
Nick

 

Nick,

Please keep us informed!

Cheers,

Don

 

Okay. So I have some results.

I removed the throttle body, cleaned and reset the gap to .002", cleaned all the mating surfaces with Scotch-Brite. I applied a very small and thin application of RTV to the throttle body, the spacer plate and the trumpet, and reinstalled everything.

I used my PDU to adjust the throttle position sensor, the base idle speed, the MAF idle speed mixture correction (I'm getting a almost perfect 2.55v average O2 Sensor Feedback Voltage at Idle, after the adjustment), and disconnected the battery to reset the ECM.

At stop lights, in Drive, fully warmed, I'm getting engine speeds of 900-1100 RPMs. This is causing a bit of a fight with the brakes when slowing, especially when the car downshifts to 1st gear just before stopping.

If I put the car in Neutral when I'm stopped and the idle is high, engine speed will climb to about 1200-1300 RPMs and hold steady for a second or two, then it starts to drop, sometimes down to 600-800, where it should be.

Other times, the RPMs will drop correctly when coming to a stop.

I have a feeling this is because the Idle Speed "baseline" hasn't been set yet. The AJ6 EMS manual says you need to allow the car to idle from cold to operating temp, then drive for 50 yards above 3mph.

Perhaps the values haven't been stored yet since I've been disconnecting the battery a lot, and replaced the battery last week.

I can confirm the stumbling IS due to the EGR system. The engine doesn't skip a single time after all this work has been done UNTIL I reconnect the EGR vacuum hose. Immediately, when coming to the first stop, the car begins to stumble when the RPMs drop through 1200 to idle.

I'm wondering, though, if the EGR stumble is caused, now, by my high idle in gear. EGR operation is in effect, in gear, above 1100 RPM. With my high idle in gear lingering around that speed, maybe the EGR is commanded on when it really shouldn't be.

We'll see. I'm going to try and relearn the idle baseline by following the procedure and see where we're at then.

Nick