Technical Brakes and missfire

[RicardoS]

For the breaks:
I had a problem that when i pressed the pedal it woul brake but slowly drop to the floor and when i released the pedal the left front caliper stay stuck for about 5 seconds. Went to bleed that caliper and had almost no oil flow. With the bleeder open the pedal would stay very hard. Replaced the hose and fixed that. Now after bleeding all brakes i dont have the pedal dropping slowly but i also dont have braking force. The pedal goesto the floor and the weels wont lock up.
Could it by a master cylinder problem?

For the missfire:
Car as a 1.2 engine with a 1.1 ecu and spi assembly. The car has trouble idling missfires from 1500 to 3000 rpm and if i press the clucth while driving the rpm drops and stalls. Did the same when it had a 1.1 engine. Ive changed the plugs coils and leeds and lambda. Ive already cleaned the throtle body and one thing i noticed is that having the idle valve connected or disconnected make no diference on the idle. Could it by a bad idle valve?

 

[bugsymike]

For the breaks:
I had a problem that when i pressed the pedal it woul brake but slowly drop to the floor and when i released the pedal the left front caliper stay stuck for about 5 seconds. Went to bleed that caliper and had almost no oil flow. With the bleeder open the pedal would stay very hard. Replaced the hose and fixed that. Now after bleeding all brakes i dont have the pedal dropping slowly but i also dont have braking force. The pedal goesto the floor and the weels wont lock up.
Could it by a master cylinder problem?

Does sound like a brake master cylinder.
Two things , if you hit the brake pedal fast does it feel like some sort of brake , but worse if you press it normally, if so it can be the seals in the master cylinder feeling their age, so new cylinder safest option.
Second thing to try is fill reservoir to brim, open brake pipes at master cylinder and keep topping fluid until no air bubbles come out only clean fluid and retighten pipes.
If that works and you get a brake pedal it confirms suspect master cylinder.
You can also do that test using a pressure bleeding system , but not a vacuum type or basic old school bleeding as will only make it worse.

Only guessing about misfire but I would have a good look for an air/vacuum leak, some have had brake servo rusted through causing massive air leak, if you pull vacuum pipe off servo and block with your finger, see if engine improves?

 

[RicardoS]

Does sound like a brake master cylinder.
Two things , if you hit the brake pedal fast does it feel like some sort of brake , but worse if you press it normally, if so it can be the seals in the master cylinder feeling their age, so new cylinder safest option.
Second thing to try is fill reservoir to brim, open brake pipes at master cylinder and keep topping fluid until no air bubbles come out only clean fluid and retighten pipes.
If that works and you get a brake pedal it confirms suspect master cylinder.
You can also do that test using a pressure bleeding system , but not a vacuum type or basic old school bleeding as will only make it worse.

Only guessing about misfire but I would have a good look for an air/vacuum leak, some have had brake servo rusted through causing massive air leak, if you pull vacuum pipe off servo and block with your finger, see if engine improves?

Sorry for the late reply. I havent had time to mess with the car since i posted.
Today i replaced the master cylinder and booster and the problem is weird now. Went for a drive and some times it brakes as normal with little pedal travel and some times brakes as before with the pedal almost to the floor.

The missfire also is worse now as the car stall every time. It idles with a noticible missfire and either driving or ideling the rpm drops to low. Pressing the clutch for to long to shift it stalls reving at idle it stalls. Blocking the vaccum pipe has no effect on the stall

 

[bugsymike]

Sorry for the late reply. I havent had time to mess with the car since i posted.
Today i replaced the master cylinder and booster and the problem is weird now. Went for a drive and some times it brakes as normal with little pedal travel and some times brakes as before with the pedal almost to the floor.

The missfire also is worse now as the car stall every time. It idles with a noticible missfire and either driving or ideling the rpm drops to low. Pressing the clutch for to long to shift it stalls reving at idle it stalls. Blocking the vaccum pipe has no effect on the stall

Were the replacement brake servo and master cylinders new?
It does sound like to separate problems then if blanking the vacuum pipe to servo had no affect on the misfire.
Re the poor running and the idle valve disconnected makes no difference, does sound like something not set up correctly.

 

[RicardoS]

Both are new.
Looking at the state os the 1.1 engine i know the maintenance was not something the previous owner did.
It had silicone on the core plugs mismatched sparkplugs leaking oil everywere etc.
The only thing on the 1.2 that was on the 1.1 is the ecu, spi assembly, fuel pump and the evap.
Spark plugs, coil packs, leeds, temp sensors, lambda and map are new.
For the evap i already unplug it from the throtle body and made no difference. The only thing that makes a diference is if i unplug the map sensor it will hold idle with no problem.

 

[348azeus]

For the brakes you must be losing hydraulic pressure check the rear wheel cylinders for leakage and also the rear compensator. You may also find that the flexi hoses are breaking down.
If you have a misfire and you have changed all those items you can check the earth connections to the engine and to the body , try spraying brake cleaner over the inlet manifold to see if there is a leak because sometimes they can crack otherwise may well have a dry joint or some other problem with the ECU itself.

 

[Frank Folker]

what do you unplug at MAP sensor to make it run normal? Vacuum hose or electrical connector? If it runs normally with unplugged MAP connector but runs bad with it plugged in then it is likely the problem. New sensor can be faulty, try a known good used one or another new sensor.

Unplugging idle valve should make a difference, not immediately but when conditions change as the ECU won't be able to compensate idle airflow. For example, if you unplugged it while idling a warm engine, next time you start it cold it will run on very low rpm, possibly stalling until it warms up a bit. If you unplug it while idling a cold engine, when it warms up the idle will be too high (1000-1200).

Check rear brake shoes. Some low quality shoes can have too small teeth on the self-adjusting mechanism, allowing the spring to retract them more than it should and when you press the brake pedal next time, you have to press it very deep to push them back out against the drum.

Also check if rear brake cylinders leak and if both pistons freely move (push brake shoes left-right a bit). If they leak, maybe they're bad or maybe the compensator valve failed. It's sort of a one-way valve that normally retains some slight pressure on the wheel cylinder (1 bar or less) even after you release brake pedal to keep the rubber piston seals pressed against the bore.

 

[RicardoS]

what do you unplug at MAP sensor to make it run normal? Vacuum hose or electrical connector? If it runs normally with unplugged MAP connector but runs bad with it plugged in then it is likely the problem. New sensor can be faulty, try a known good used one or another new sensor.

Unplugging idle valve should make a difference, not immediately but when conditions change as the ECU won't be able to compensate idle airflow. For example, if you unplugged it while idling a warm engine, next time you start it cold it will run on very low rpm, possibly stalling until it warms up a bit. If you unplug it while idling a cold engine, when it warms up the idle will be too high (1000-1200).

Check rear brake shoes. Some low quality shoes can have too small teeth on the self-adjusting mechanism, allowing the spring to retract them more than it should and when you press the brake pedal next time, you have to press it very deep to push them back out against the drum.

Also check if rear brake cylinders leak and if both pistons freely move (push brake shoes left-right a bit). If they leak, maybe they're bad or maybe the compensator valve failed. It's sort of a one-way valve that normally retains some slight pressure on the wheel cylinder (1 bar or less) even after you release brake pedal to keep the rubber piston seals pressed against the bore.

I unplug the eletrical connector. What changes is it will idle and wont stall but still missfires does the same with the new and old map sensor. Im going to unplug the idle valve again as i thought the change was instantaneous.

The rear break shoes, cylinder and compensator are new as old ones were leaking. It might be the small teeth how do i check that?

On the brakes the only thing that is not new are the front calippers rear rubber lines and the hard lines.

 

[blu73]

I unplug the eletrical connector. What changes is it will idle and wont stall but still missfires does the same with the new and old map sensor. Im going to unplug the idle valve again as i thought the change was instantaneous.

The rear break shoes, cylinder and compensator are new as old ones were leaking. It might be the small teeth how do i check that?

On the brakes the only thing that is not new are the front calippers rear rubber lines and the hard lines.

The brake thing, that could be the flexi lines are failing internally, I'd carefully inspect all the hard lines and replace any flexi hoses you haven't yet, bleed and try again. Did you adjust the rear shoes out when your replaced them too?

engine wise, we must remember the idle control valve cannot cause a misfire so even if it is not working thats not the cause of the misfire, it would either idle all over the place, or high or just stall. The map sensor could totally cause a misfire but i doubt its that if you changed it - do check the vac line for any damage though. No-one has said crank sensor yet... pretty common fault really, I've changed loads of cranks sensors in my time. They usually start with a slight misfire, then constantly misfire and eventually no running at all.

Does it have the engine management light on? permanently? only when misfiring? not at all? Highly recommend getting the cables if you havent and plan to keep it or have other pre OBD fiats. But i ask about how it acts cause a dodgy crank sensor will usually only log a misfire in the ecu and only have he light on when its happening - it will only go on permanently if the completely fails and goes open circuit and say that sensor isnt working, until then it will just flicker