My 03 MCS threw this code over the weekend, P1109.

68 mile drive. About 50 miles in to the drive a little surging around 3000rpm stalled at a light started up fine and drove fine. 10 miles later some surging, heel-toed around a corner to keep from stalling, pulled over and died, throws code P1109. started it up revs hit 1500-2000 rpm drops and dies, won't keep idle. Check belt, plugs tensioner all good, Start up and it idles but doesn't sound right (can't explain the sound, hollow). turn off the engine give it a minute, start up again and it idles fine, revs fine, sounds fine. Drive 8 miles to my destination and park.

4 hours later, time to go.

On the way home about 45 miles into the drive. Surging, almost stalling, stalling, can't keep idle, throttle response disappears then surges, feathering the throttle at stop lights to keep from stalling.

Pull over, doesn't idle, dies, try to start and revs hit 1500-2000 rpm drops and dies, won't keep idle.

Wait for tow truck, waiting 15-20 mins, Start up engine and idles, turn off engine, try to start up again to get it on the flat bed and have to feather the throttle to keep it running.

At the shop 30 mins later. Car starts up and idles. I rev it up to 3500-4000 rpm, revs drop and stalls, try to start up again, revs hit 1500-2000 rpm drops and dies.

BTW, I was driving normal. +/-5mph of speed limit. No hard accelerating.

It's at the shop now and seems to be running ok for them with no fix, but I am hoping they can get it to throw the code. I know the shop it's at will have it running perfectly once again but I thought I'd post up here since this doesn't seem to be a frequent code that is talked about. So, if you have dealt with this problem and have the fix, post up.

the Bentley repair manual says
P1109 Manifold Air Pressure too High in Deceleration

I can't seem to find more than 2 posts about the code on here. the only fix I have seen is the MAP sensor and then the TMAP sensor. In this situation the car was throwing a SES+DSC. Mine is only throwing a p1109+SES

Any ideas?

 

Please report the freeze frame data associated with the error.

When all is well during deceleration and the throttle plate is closed the vacuum will be very strong (the engine is in negative torque - the drive wheels are turning the motor and not the other way around)

The engine will also be in fuel cutoff as well. The ECU is expecting a high vacuum based on the throttle opening and RPM values.

The map sensor can be checked by applying vacuum from a hand pump and monitoring the voltage from the sensor with a volt meter or scan tool. The voltage will be low for a strong vacuum and high for no vacuum.

A significant vacuum leak will be seen by the MAP and more fuel will be added to cure the lean condition resulting in the RPM flare ups you have been seeing!

 

did u ever find out the problem with the code p1109? having the same problem

 

I thought I updated this, but I guess I didn't. I'll try to find the receipts.

 

My 05 MCS is throwing the p1109 code as well. No other codes shown. It seems to come and go. May go a couple of days and the ses light will be out then all of a sudden, usually while cruising the car will start to feel like it is fuel starved and surge a bit. This sometimes results in stalling when car is at idle. But leave it sit and start back up and the idle is fine and no ses light. Very random. But the p1109 code is all i have to go by.

If your issue was solved please post what the fix was in your case.

As was said there are very few threads on this particular code and it may become a good resource for those with future related issues.

Thanks

 

Just checked my receipts: MAP Sensor replaced. Sorry for the late update

 

I replaced both the map and the tmap and my problem/ engine code are all gone.