Q45 Engine Stall When Going Complete Full Braking

[94 Q45]

Hi, I have a 94 Q45 and now I notice the engine will stall if I brake too fast, I think this only happen when I press the brake all the way down to a complete stop in speed of more than 30 MHP. Does anyone experienced this and what is the problem? I just bought the car not long ago and I don't know any maintainence history, I cleaned the MAF sensor which helps to improve the idle speed, but it is still not as stable as I would like. Thank you for your input and help.

[maxnix]

I just bought the car not long ago and I don't know any maintainence history.

Well, if you ar ethe history, then have you replaced all fluids with fresh? Replaced all the under pleunum hoses, KS and harness? Ohmed the injectors and railflushed them, or at least used BG44K? Cleaned the plenum and lower intake runners, EGR and IAC valves and TB?

When one buys acar in the dark, it is up to that owner to return it as close as possible to as new OEM condition. Too much deferred maintenance means multiple system failures are possible making diagnosis very difficult in person, let alone via text on the internet.

You might start with a power balance test with a Consult and record engine behavior at idle and a couple of other higher rpms.

[96Qowner]

It might also be as simple as your transmission fluid level. If the fluid is low, the torque converter can lock up and stall the motor, when coming to a stop.

[Q45tech]

Dirty or improperly set IAC...............................ir some electrical connectors.

[94 Q45]

Hi, Thanks for the suggestion, I did some TB and EGR and MAF sensor cleaning, fluds, spark plug and air filter change after I got the car, but I did not clean the IAC and I don't even know where the IAC is on this car. Does anybody know how to clean the IAC? It seems this weird situation happen after I changed both valve cover gasket. Maybe I accidentally mess up some electrical stuff while I was putting back the valve covers. I am not sure if the ATF level is correct because everytime I check, the level changes. Thanks for the input.

[Jesda]

This happened on my first Q. Second owner figured out that it was caused by an overfilled transmission.

[Q45denver]

You could also swap out the MAF with another one and see if that corrects it.

[94 Q45]

Hi, Thanks all for the response, I think I was caused by low ATF level, I added some ATF and it is ok now. BTW, how many quart of ATF should I add if I am doing a drain and refill? The owner's manual indicates the capacity for ATF is 10 quarts. Also, I am planning using seafoam to clean the engin, does anybody know where can I find a best vaccum hose to ingest the seafoam? PCV valve or brake booster vaccum line? Thanks for the reply.

[Q451990]

It's best to measure what comes out and put that much back in on a transmission drain and refill - assuming your level was correct to begin with. I think it's about 4 quarts... to some extent it depends on how long you let it sit there and dribble.

I'm a little skeptical of the Seafoam treatment. I know Wes has done it before, so he may have some insight. I would think the brake booster hose would be the easiest one to remove... If not taking out the EGR temp sensor might work if you don't have too much carbon there gumming up the works.

Good luck!

Heath