jwillman

Started last week on one drive and has happened a couple of time each drive over the last two days.

While driving at speed the car suddenly surges/ jerks pretty hard leaning towards violent (scared the hell out of me the first time).

At first I thought the engine was shutting off momentarily as it felt like a very abrupt hesitation but I am seeing no decrease in RPM or in speed, no warning lights etc. I also thought it might be the transmission seizing as it is that pronounced but seems to shift/ run fine between events.

Today it almost sounded like the jerk was a very short rev up but again so quickly that I see nothing on the gauges.

I have no clue where to even begin, fueling issue, distributor/ electrical, drive train.

Anyone have something similar happen and fixed this before?

jwillman

update, last two days I have not had the issue,

Think the issue is related to a water leak at the blower housing. We have had a wet summer here and looking at the passenger side I found some water under the carpet.

Blower comes out this weekend for a reseal. My new guess is a water related electrical issue.

AirtekHVAC

Might do you good to pull loose the CE and clean/deoxit....mine was rusted out from years of water getting in there. Could be water bridging relay points....might have a little corrosion?

Good luck.

Mrmerlin

To do a blower box reseal ,
disconnect the battery,
remove the wood covers over the CE panel and the parcel tray.
disconnect the ground wires above the CE panel.
remove the bolts holding the top of the CE panel to the brackets,
remove the red power supply wire wires at the top of the CE panel;
tilt the panel down and then remove the two CE panel supports,
get a towel and place it over the CE panel ,
Remove the 2 screws that hold the blower motor to the lower portion of the blower box assembly.
Note these screws are under the cowl cover, one screw is inside the blower duct.

Then remove the 3rd blower motor screw from the underside of the blower box inside the car.

Remove the blower electrical connector and a vacuum line if fitted, under the cowl,

remove the blower box nuts then carefully pry the blower box downwards
the lower portion will drop down along with a lot of dirt and leaves,
make sure the towel is covering the CE panel to keep this dirt from getting into the panel.

The blower motor will now come through the same opening so you dont have to remove the lower windshield cowl cover or hood.
I suggest to use 3M strip caulk to replace the old factory caulk,
about 3 strips deep should do.
scrape off the old stuff first,
Vacuum out the firewall well as it will be open, and do the same for the blower duct under the hood.
Swap in a new fresh air/ cabin air pod in the blower box.
Deoxit spray the back of the CE panel. clean the grounds and the power wire connections

Fogey1

"...driving at speed..."
On the throttle, steady state or trailing throttle? Ignition cutout on #1 will scare you, #2 is disconcerting, #3 you might not notice.

Merlin's advice is good. Water on relays is not your friend.

jwillman

I actually had the blower and blower box out last year when I pulled the dash for a recover.

I did use 3M strip caulk but only went one strip deep

I needed to pull the blower box again anyway as I had to rig the old one to the recirculate position as the old valves are NLA and the later models require a different blower box mount which I bought during 928 INTL 50% off sale last December. Still have allot of the strip caulk left so will go three deep per your recommendation.

Did not De-oxit it last time either and have a can now so time to clean up the CE panel as well.

Thanks Stan for the in depth reply and expert advice - as always!!

jwillman

So today leaving work the car starts but barely runs. Giving it gas it runs at 1500 rpm and abruptly drops to 200 and sounds like its running on 1 cylinder and then abruptly surges back up again.

Thought I was going to have to call a tow truck but it settled down. heading up the road it surges violently a couple of times and I coast into a parking lot where it again runs normally.

Set out again and all seems fine till I use the turn signal to change lanes at wham the abrupt decrease once. The rest of the trip home it surges every time I use the turn signal. Not with emergency flashers or head lights but when I use the turn signal.

What the hell?

vze2jshn

Even before you take out blower make sure leaves or other debris is not blocking the drain in the firewall area.

ltoolio

Are your turn signals actually functioning when you flip the switch? Maybe a short in the wiring?

jwillman

Got home yesterday and confirmed turn signals are working and when I started car that cycling the turn signal caused the engine cut out.

I pulled the CE panel last night and gave it a healthy coating of Deoxit.

I also looked at the wiring diagram and realized the front right turn signal shared a ground point with the ignition system. I pulled that ground point and treated with deoxit.

Once back together car started right up and the surging idle issue seems gone as well as the engine surging when turn signal is engaged.

Drove the car to the monthly Austin 928 lunch and all seems fine. Fingers crossed!

jwillman

Crap, spoke too soon. Went out to the store later today and again got the surge when using the left turn signal and now I have a right rear bulb out.

I will be replacing all 4 turn signal bulbs tomorrow and looking at bulb sockets.

I also noticed an appreciable relay click when turning on the left side blinker that I don't get on the right side. Don't know if I have a relay issue or that a function of the power draw also causing the engine to surge. Thoughts?

Mrmerlin

when you do the CE panel refresh ,
make sure to remove every relay and inspect it.
I have found that water leaking can fill a relay

jwillman

Thanks Stan. Did the CE panel Friday night. All relays pulled. CE panel pulled out completely. All fuses pulled and used deoxit on all including car side A-Z connectors.

jwillman

Update.

Have all turn signal lights working. Turned out to be a bad connection with the fuse holder. Once fixed I have turn signals all corners and 4 way flasher.

I still have the engine surge when using the turn signal. Does not happen when using the 4 way flasher. Happens at idle and at speed. Really struggling with where the connection is between the turn signals and what I am guessing is the ignition system.

I tested all other pod switches and 4 way flasher and nothing else causes the condition.

Any and all ideas welcome.

vze2jshn

Check wires at WUR.