1990 Q45 ENGINE STALLS WHEN sudden BRAKING OR WHEN ENGINE IS COLD

[slshearer]

I started to experience the engine stalling if it was cold and the brakes were applied some what harder than normal when the car stopped, the engine would stall, engine starts up immediately and engine runs smooth. Appreciate your input!

[maxnix]

A little recent maintenance history, please. We are not very good clairvoyants.

Is your battery strapped down well? Meet OEM specifications? All connections tight and not corroded?
Modified by maxnix at 8:56 PM 2/7/2007

[CrimsonQ]

Hows the trans fluid?Had same issue on a friends car (g50)fluid level was low.

Im not positive their related, but it did solve the issue for us. IIRC there is a post somewhere here from someone else with the same story. something with the tc being starved

[slshearer]

I recently changed the complete engine, all the maintenance items, water hoses, emission hoses, spark plugs, were installed within 4000 miles, car only stalls when braking when engine is cold or an emergency stop when engine is hot, the engine will lose revs and the engine will try and recover by reving up to prevent the stalling when warm, there is 1 wire which goes to the timing cam on the front of the engine which does not have the clip as th eplastic clip cracked where the metal clip held it on, I have checked this and it appears to be tight, it is located near the mass air flo sensor. engine runs great and this is the only real problem I have been experiencing, The battery is tight and properly grounded, I will check the transmission fluid, I did when the engine was installed but I can check again,

Thanks for your helpstewart

[elwesso]

my Q does the exact same thing (it did it tonite). there is nothing wrong with my Q.. When its really cold out like this you HAVE to let it warm up!!!!!!!!!!!!!

[slshearer]

Well before I changed my motor it never stalled, although before the change I could smell gas when it was cold, I think your car is pretty built up compared to my stock motor, I don't mind warming up the engine but I don't like it if in an emergency it would stall like it will even when warm, Thanks for the input from everyone!

[CrimsonQ]

my Q does the exact same thing (it did it tonite). there is nothing wrong with my Q.. When its really cold out like this you HAVE to let it warm up!!!!!!!!!!!!!

soo youre saying you didnt warm it sir? tsk tsk...

[ScottJackson]

Check for vacuum leaks (spray some carb cleaner in little squirts around the hoses and intake... if idle changes you have found the leak). Also clean the throttle body with the same aerosol can if it's really dirty.

[KwoodTheOne]

my Q does the exact same thing (it did it tonite). there is nothing wrong with my Q.. When its really cold out like this you HAVE to let it warm up!!!!!!!!!!!!!

I have the same problem it does it very rarely seems like its when i hit the brakes as well, when its not fully warmed up!!! I was thinking it was that increasing humm im beginning to hear (fuel pump)

[Q_SHIP]

Check for vacuum leaks (spray some carb cleaner in little squirts around the hoses and intake... if idle changes you have found the leak). Also clean the throttle body with the same aerosol can if it's really dirty.

X2

[slshearer]

I will try this and see if I can find any leaks, my engine runs fine and very smooth, I use Mobil 1 synthetic and normally only warm my car up for about 1/2 minute, I will advise if I find anything else.Thank you to everyone for your input, I appreciate the tipsThanks Stewart

[Q451990]

It might be worth taking a look at your brake booster vacuum hose and check valve. Someone here had a similar issue with a QX4 and replacing the check valve fixed it. Apparently hard braking was pushing a blast of unexpected air into the intake (not metered by MAF or controlled by ECU) and causing the issue. I've never heard of one failing on a Q, but at 15 years old, anything is fair game.

Heath

[ScottJackson]

yep, that's pretty much the same as a vacuum leak (the brake booster thing). One other place the booster can leak (although I've not seen it specifically from this spot on a Q) is where the rod goes into the brake booster from the brake pedal. A little squirt of carb cleaner up in there will sometimes show a leak and it often won't leak until the pedal is pushed in, in which case you'll probably be able to hear the faint air noise if you're up under there.