Rough as guts Cold Starts, 26lt/100km (1 Viewer)

[Brayden3223]

Howdy Guys, got an issue that i cant quite put my finger on

got a 1997 1FZ in Australia (So No Cats ETC) 495xxxkms Top end rebuild 25xxx ago, Petrol/LPG

Its been running super rich lately, getting about 26LT/100km and extremely poor when it first starts in the morning.
At first the idle will seem fine but roughly right before it gets to running Temp the Idle will fluctuate between 200-400RPM
It Always Seems to have a very light consistent Misfire feeling when idling
I DO NOT use LPG and plan to have it removed

So Far i Have Replaced Fuel Pump, Fuel Filter, Air Filter, Spark Plugs, Spark Leads, Ignition Coil, Coolant Temp Sensor And Cleaned the IAC and MAF
Could It be Timing or Injectors? Or Maybe Sensor related
I dont believe its a Vacuum leak as ive sprayed down every visible hose with Carby Cleaner to no Avail

Any Advice would be much appreciated

 

[Brayden3223]

Just a thought to whether a leaking brake booster or vacuum line on the booster could cause a poor idle as I have also noticed my brakes getting progressively softer

 

[robnicko]

a leak in the brake booster and or the hose leading to the booster will cause issues with idle stability, brake feel and the light misfire you mention as that would be unmetered air entering the intake

if replacing the brake booster hose doesnt fix the issue then you may need to look at either the booster itself or the one way valve that the hose connects to at the booster.

 

[mudgudgeon]

Could still be sucking in air somewhere. I had a rough idle, and sprayed carby cleaner around to find leaks. Didn't indicate a leak anywhere.
I replaced all hoses, and found many of them cracked, rock hard, and loose on spigots

Replace all rubber hoses on the engine.
Replace O-ring on your oil fill cap
Replace the grommet for PCV hose on the valve cover
Replace valve cover gasket
Replace spark plug tube gaskets
Replace the main intake hose, or tightly wrap the main intake hose with PVC duct tape to see if sealing all the tiny cracks helps

All can suck in unmetered air and cause idle issues.

 

[Brayden3223]

a leak in the brake booster and or the hose leading to the booster will cause issues with idle stability, brake feel and the light misfire you mention as that would be unmetered air entering the intake

if replacing the brake booster hose doesnt fix the issue then you may need to look at either the booster itself or the one way valve that the hose connects to at the booster.

I did find a crack in a booster line going to the intake manifold and replaced that making no difference at all

Could still be sucking in air somewhere. I had a rough idle, and sprayed carby cleaner around to find leaks. Didn't indicate a leak anywhere.
I replaced all hoses, and found many of them cracked, rock hard, and loose on spigots

Replace all rubber hoses on the engine.
Replace O-ring on your oil fill cap
Replace the grommet for PCV hose on the valve cover
Replace valve cover gasket
Replace spark plug tube gaskets
Replace the main intake hose, or tightly wrap the main intake hose with PVC duct tape to see if sealing all the tiny cracks helps

All can suck in unmetered air and cause idle issues.

ill start replacing all the hoses when i have the time to but i did find a crack in a hose to the brake booster, i already replaced the Oil cap, THe Valve cover gasket, Spark plug gasket. the intake hose is a good idea as it had LPG added so it has a weak point in the intake hose in case it ever backfires, do you know the size of the intake hose and whether silicone hose will suffice?

 

[mudgudgeon]

I did find a crack in a booster line going to the intake manifold and replaced that making no difference at all

ill start replacing all the hoses when i have the time to but i did find a crack in a hose to the brake booster, i already replaced the Oil cap, THe Valve cover gasket, Spark plug gasket. the intake hose is a good idea as it had LPG added so it has a weak point in the intake hose in case it ever backfires, do you know the size of the intake hose and whether silicone hose will suffice?

No sure on the size. The OEM intake hose is still available new.
Not super pricey through Partsouq.com

 

[robnicko]

try crimping the vacuum hose that goes to the booster so the booster is taken out of the equation.
If the idle comes good then your booster has problems internally which probably explains the brake feel getting softer as well

 

[Brayden3223]

try crimping the vacuum hose that goes to the booster so the booster is taken out of the equation.
If the idle comes good then your booster has problems internally which probably explains the brake feel getting softer as well

The braking issue has been fixed, have checked over multiple times and can’t find anymore vacuum leaks

Over the week the idle has actually gotten worse, when it’s cold the car will try to stall the entire time, the only way to keep it running is to press down on the throttle even when braking, when it’s at running temp it won’t try to stall but the idle constantly jumps between 550-700rpm

Any more ideas?

 

[Brayden3223]

The braking issue has been fixed, have checked over multiple times and can’t find anymore vacuum leaks

Over the week the idle has actually gotten worse, when it’s cold the car will try to stall the entire time, the only way to keep it running is to press down on the throttle even when braking, when it’s at running temp it won’t try to stall but the idle constantly jumps between 550-700rpm

Any more ideas?

I am wondering whether it is sensor related, could it be signs of a failing Maf?

 

[western flyer]

I did not see you report it (apologies if otherwise), but did you check the actual brake booster (not just the hose) for leaks? The booster needs to hold vacuum.

 

[Brayden3223]

I did not see you report it (apologies if otherwise), but did you check the actual brake booster (not just the hose) for leaks? The booster needs to hold vacuum.

yeah the brake booster has no leaks at all and holds vacuum fine

 

[Brayden3223]

update: just had a 5 hour drive, idle has gotten worse, can see heaps of vibrations under the hood at 2000rpm. if car is cold it wants to stall and it feels like the brakes arent taking any vacuum, seems to be brake fine when warm. lacks a large amount of power, had to go 4low in 1st gear to make it up a not so steep gravel hill where others could get up in 4High in second no problem. when in 4low after giving it a bit of right foot i also noticed the idle would drop to about 400rpm.