High Idle, Running Hot = Running Lean?
04-08-2006, 01:44 AM
#1
Lazer Beam Shooter
Rennlist Member
Rennlist Member
Thread Starter
High Idle, Running Hot = Running Lean?
Ok the 951 is acting funky lately. It idles really high (2000rpms+). I had to adjust the idle screw a bit to stop it from jumping up to 3000rpms.
That is the first problem.
The second problem is the car will run abnormally hot. I dont know if turbos are supposed to run hotter than N/as, but both N/as ive owned usually linger around the mid line on the temperature gauge. The 951 climbs more toward the hot side.
I think this could be because it could be running lean. The spark plugs have a light brown crust on them which I believe would mean its running lean. Thats my guess.
Could this be caused by a vacuum leak. What should I check for first?
That is the first problem.
The second problem is the car will run abnormally hot. I dont know if turbos are supposed to run hotter than N/as, but both N/as ive owned usually linger around the mid line on the temperature gauge. The 951 climbs more toward the hot side.
I think this could be because it could be running lean. The spark plugs have a light brown crust on them which I believe would mean its running lean. Thats my guess.
Could this be caused by a vacuum leak. What should I check for first?
04-08-2006, 04:59 PM
#2
Three Wheelin'
I would start by checking for vacuum leaks. Look at ALL of the vacuum lines and all of the hoses that are hidden beneath the intake manifold. Pull the fuel rail and install new injector O-Rings. O-Rings kits are like $4.00 each at your dealer. You will need 4 kits.
If the plugs are light brown to orange, than you should be OK. An easy way to figure out if the engine is running lean is to back probe the O2 sensor with a Digital Volt Meter. Set the meter to read the 2 volt DC scale, put the positive lead into the connector, ground the negative lead, and start the engine. As the O2 sensor heats up the meter should start to display a voltage. You are looking for a display that varies across about 0.50 volts. If the display does not vary, the O2 sensor could be bad.
Another way to test the O2 sensor is to start the engine, let it come up to temperature, and then disconnect the sensor. You should see a change in engine RPM.
As for the high idle, you need to put a jumper between pins B and C of the diagnostic connector, connect a dwell/tach to the coil, start the engine and the use the idle adjustment on the throttle body to set the idle to 840 +- 50 RPM. NOTE: Do not turn the mechanical stop screw! If you mess with the stop screw you MUST remove the throttle body and reset the mechanical stop.
As for running hot, 951s can have problems here. Make sure the coolant is at the proper level (between the MIN and MAX marks on the expansion tank when the engine is HOT), make sure the system is properly bled, make sure the cooling fans operate normally, and make sure there is no road debris or other trash blocking the radiator and/or the A/C condensor.
If the plugs are light brown to orange, than you should be OK. An easy way to figure out if the engine is running lean is to back probe the O2 sensor with a Digital Volt Meter. Set the meter to read the 2 volt DC scale, put the positive lead into the connector, ground the negative lead, and start the engine. As the O2 sensor heats up the meter should start to display a voltage. You are looking for a display that varies across about 0.50 volts. If the display does not vary, the O2 sensor could be bad.
Another way to test the O2 sensor is to start the engine, let it come up to temperature, and then disconnect the sensor. You should see a change in engine RPM.
As for the high idle, you need to put a jumper between pins B and C of the diagnostic connector, connect a dwell/tach to the coil, start the engine and the use the idle adjustment on the throttle body to set the idle to 840 +- 50 RPM. NOTE: Do not turn the mechanical stop screw! If you mess with the stop screw you MUST remove the throttle body and reset the mechanical stop.
As for running hot, 951s can have problems here. Make sure the coolant is at the proper level (between the MIN and MAX marks on the expansion tank when the engine is HOT), make sure the system is properly bled, make sure the cooling fans operate normally, and make sure there is no road debris or other trash blocking the radiator and/or the A/C condensor.
04-08-2006, 09:32 PM
#3
Lazer Beam Shooter
Rennlist Member
Rennlist Member
Thread Starter
Charolette thanks for the input!!! 
It has a new 02 Sensor with one of those narrowband A/F gauges (garbage I know). It says it runs rich to stoich under full throttle, but off of throttle it says its running more toward lean.
The car runs so hot that it burns off the oil! Ive had to put like 3+ quarts in within 1 week. When I pull the dipstick, the top of the stick is so hot that it burns my hand. You can see oil smoking off of the dipstick too.
I have the venturi delete, I'll install that and see what happens!
It has a new 02 Sensor with one of those narrowband A/F gauges (garbage I know). It says it runs rich to stoich under full throttle, but off of throttle it says its running more toward lean.
The car runs so hot that it burns off the oil! Ive had to put like 3+ quarts in within 1 week. When I pull the dipstick, the top of the stick is so hot that it burns my hand. You can see oil smoking off of the dipstick too.
I have the venturi delete, I'll install that and see what happens!
04-09-2006, 12:17 PM
#4
Three Wheelin'
Rock:
I've been through some of these same problems with both of my NAs and my 951, and there are several things that can cause over heating. Finding the source (or sources) of the problem is going to take some time and effort.
My first NA started overheating under acceleration due to a head gasket leak. My second NA overheated because of a radiator leak, and my 951 overheated because of a bad fan switch and an internal flow restirction.
To start off with, it is imperative that the coolant be at the proper level, and that there is absoultely NO, ZERO, NADA, ZILCH air in the system. Make sure the heater works properly. The heater should put out heat with little or no temperature change when the engine is either idling or at speed. If the vent temp drops when you come to a stop light, chances are there is air in the cooling system. This can also be caused by a loose/slipping timing belt, bad water pump, or crud build up in the heater core.
This may sound way off base, but CLEAN YOUR GROUNDS!!!. Dirty/loose ground points can have an affect on things like the O2 sensor, DME Temp Sensor II, as well as the in-dash temp gage. If the O2 and DME Temp Sensor are not working properly, the DME cannot maintain the proper fuel/air mixture.
Speaking of fuel, make sure you are running at least a mid-grade fuel, and if possible, run some premium.
Make sure the cooling fans are running properly.
Check all of the hoses. When the engine is running and up to temperature the hoses should be firm, but not so firm that you cannot squeeze them. If the hoses are REAL firm, you could have a head gasket leak. Look for signs of cracking, or dry rot. Make sure the hose clamps are tight. Be sure to check the turbo cooling pump and associated plumbing for leakage. Same thing goes for the expansion tank cap. If this puppy isn't holding pressure, the engine will over heat and you will loose coolant.
Keep a very close eye on the coolant level. Check the level when the engine is hot and the car is parked on a level surface. Put a piece of black electrical tape on the expansion tank to mark the coolant level. Check the level EVERY TIME your drive the car.
If you go through all of this and are still having problems, drain the coolant and remove the thermostat. Get a new on and install it. HINT: I drilled 4 1/8" holes in the flange area of the T-Stat. These holes make it a lot easier to drain, fill, and bleed the cooling system. These holes also provide just a tad more flow during intitial engine warm up.
If you have to drain the cooling system, I would highly recommend using a chemical flush. I like the stuff from Prestone. They make two "flavors," and I prefer the one that you run for like 6 hours of driving time over the 10 minute quickie flush.
Post some pictures of the spark plugs so I can see what is going on.
I've been through some of these same problems with both of my NAs and my 951, and there are several things that can cause over heating. Finding the source (or sources) of the problem is going to take some time and effort.
My first NA started overheating under acceleration due to a head gasket leak. My second NA overheated because of a radiator leak, and my 951 overheated because of a bad fan switch and an internal flow restirction.
To start off with, it is imperative that the coolant be at the proper level, and that there is absoultely NO, ZERO, NADA, ZILCH air in the system. Make sure the heater works properly. The heater should put out heat with little or no temperature change when the engine is either idling or at speed. If the vent temp drops when you come to a stop light, chances are there is air in the cooling system. This can also be caused by a loose/slipping timing belt, bad water pump, or crud build up in the heater core.
This may sound way off base, but CLEAN YOUR GROUNDS!!!. Dirty/loose ground points can have an affect on things like the O2 sensor, DME Temp Sensor II, as well as the in-dash temp gage. If the O2 and DME Temp Sensor are not working properly, the DME cannot maintain the proper fuel/air mixture.
Speaking of fuel, make sure you are running at least a mid-grade fuel, and if possible, run some premium.
Make sure the cooling fans are running properly.
Check all of the hoses. When the engine is running and up to temperature the hoses should be firm, but not so firm that you cannot squeeze them. If the hoses are REAL firm, you could have a head gasket leak. Look for signs of cracking, or dry rot. Make sure the hose clamps are tight. Be sure to check the turbo cooling pump and associated plumbing for leakage. Same thing goes for the expansion tank cap. If this puppy isn't holding pressure, the engine will over heat and you will loose coolant.
Keep a very close eye on the coolant level. Check the level when the engine is hot and the car is parked on a level surface. Put a piece of black electrical tape on the expansion tank to mark the coolant level. Check the level EVERY TIME your drive the car.
If you go through all of this and are still having problems, drain the coolant and remove the thermostat. Get a new on and install it. HINT: I drilled 4 1/8" holes in the flange area of the T-Stat. These holes make it a lot easier to drain, fill, and bleed the cooling system. These holes also provide just a tad more flow during intitial engine warm up.
If you have to drain the cooling system, I would highly recommend using a chemical flush. I like the stuff from Prestone. They make two "flavors," and I prefer the one that you run for like 6 hours of driving time over the 10 minute quickie flush.
Post some pictures of the spark plugs so I can see what is going on.
