Question about Chevrolet Corvette

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My 69 Vette with a base engine has a vacuum problem. I have replaced the check valve and relay valve. With the engine warm and running at speeds of 40 mph or more the wiper door will rise and then the head lamps. They do not go down until I start the engine when cold the next morning. The vaccum tests low at idle around 10 lbs. Any Ideas???

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Ignition timing, cam grind of a performance cam shaft, can lower engine vacuum at idle, also check for a bad diaphragm or vacuum storage container in the system, some of the old vettes had a vacuum storage container to store vacuum because of the solid lifter motors and the cam grind they were noted for having low vacuum , so GM would use often a container that almost looked just like a 1 lb. coffee can painted black and put in in-line in the vacuum system to store vacuum so when you suddenly accelerated the headlight doors would not slam shut, it would provide enough lag time in the vacuum loss, that the storage would recover.... hope this helps...

Posted on Sep 05, 2009

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Posted on Jan 02, 2017

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Engine idle very lumpy and wanting to stall on gear down shift. Sometimes poor on starting until fuel gets through then car runs well but very smelly.


SYMPTOM 1: ROUGH IDLE IN THE COLD

The engine will not idle smoothly, or it stalls during idle when the engine is cold. When the engine is cold and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine, or at least it runs more smoothly.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace accelerator pump or replace the carburetor.
  2. There may be a vacuum leak.
    The Fix: Check and replace the vacuum lines as required.
  3. There may be some type of ignition problem.
    The Fix: Check and replace the distributor cap, rotor, ignition wires, and spark plugs.
  4. The ignition timing may be set wrong.
    The Fix: Adjust the ignition timing.
  5. There may be a fault in the computerized engine control system.
    The Fix: Check engine control systems with a scan tool. Test the circuits and repair or replace components as required.
  1. The EGR valve may be bad.
    The Fix: Replace the EGR valve.
  2. The engine may have mechanical problems.
    The Fix: Check the compression to determine the engine's condition.
  3. Idle speed is set incorrectly.
    The Fix: Set idle speed to the car's original settings.
  4. The fuel injectors may be dirty.
    The Fix: Clean or replace the fuel injectors.

SYMPTOM 2: ROUGH IDLE WITH WARM ENGINE

The engine will not idle smoothly, or it stalls during idle when the engine is warm. When the engine is warm or hot and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace accelerator pump or replace the carburetor.
  2. There may be a vacuum leak.
    The Fix: Check and replace vacuum lines as required.
  3. The fuel pressure regulator may be operating at too low a pressure.
    The Fix: Check the fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (This is not really a do-it-yourself kind of job.)
  4. Idle speed set incorrectly.
    The Fix: Set idle speed to specs.
  5. There may be some type of ignition problem.
    The Fix: Check and replace distributor cap, rotor, ignition wires and spark plugs.
  6. There may be a fault in the computerized engine control system.
    The Fix: Check engine control systems with a scan tool. Test circuits and repair or replace components as required. (This is not really a do-it-yourself kind of job.)
  7. The EGR valve may be bad.
    The Fix: Replace EGR valve.
  1. The engine may have mechanical problems.
    The Fix: Check compression to determine engine condition.
  2. The fuel injectors may be dirty.
    The Fix: Clean or replace fuel injectors.

SYMPTOM 3: FAST IDLING

The engine idles too fast. After the engine has run long enough to become warm, the idle speed does not come down to normal. You really notice it when you come to a stop and must have to push ******* the brake pedal to keep the car from moving.
Possible causes:
  1. If you have a carburetor, you may have a bad accelerator pump or power circuit.
    The Fix: Replace the accelerator pump or replace the carburetor.
  2. The engine may be overheating.
    The Fix: Check and repair the cooling system.
  3. The fuel pressure regulator may be operating at too low a pressure.
    The Fix: Check fuel pressure with a fuel pressure gauge. Replace fuel pressure regulator. (This is not really a do-it-yourself kind of job.)
  1. The ignition timing may be set wrong.
    The Fix: Adjust the ignition timing.
  2. There may be some type of ignition problem.
    The Fix: Check and replace the distributor cap, rotor, ignition wires and spark plugs.
  3. There may be a fault in the computerized engine control system.
    The Fix: Check the engine control systems with a scan tool. Test the circuits and repair or replace the components as required.
  4. There may be a vacuum leak.
    The Fix: Check and replace vacuum lines as required.
  5. You have a bad idle speed control unit.
    The Fix: Replace the idle speed control unit.
  6. The alternator may not be working properly.
    The Fix: Replace the alternator.

SYMPTOM 4: STALLING UPON STOPPING

Car stalls when stopped quickly. You are driving along and everything is just fine ... until you let off the gas pedal and apply the brakes. The engine starts shaking and may even stall. Not a good thing to happen because you lose power steering when the engine dies and could risk an accident.
Possible causes:
  1. There may be a serious vacuum leak.
    The Fix: Check and replace the vacuum lines as required.
  2. There may be a fault in the computerized engine control system.
    The Fix: Check the engine control systems with a scan tool. Test the circuits and repair or replace the components as required. (This is not really a do-it-yourself kind of job.)
  3. Broken linkage.
    The Fix: Repair or replace the linkage as required.
Idling issues can be very frustrating, but with some patient troubleshooting, you'll have a real chance at figuring it out. Remember to always check your engine idle with the air conditioning and defroster turned off, as both of these systems are designed to change the idle when they are on due to the air conditioning system's demands on the engine.

Aug 25, 2017 | Cars & Trucks

1 Answer

We replaced the thermostat in ford f150 but heater still blows cold air


another expert named:
telemachus
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First, if the engine seems to take forever to warm up, you may have a stuck (open) thermostat. Replacing the thermostat would help get your engine to warm up quickly and maintain the proper running temperature of about 180 deg F. This would solve your heater woes.

However, if the engine warms up normally but the heater just doesn't seem to put out, check the heater inlet valve. This valve is usually next to the firewall on the engine side and is activated by cable(s) or vacuum lines. It is common to find that the valve cables have frozen, the cable ends have broken off, or the vacuum lines are disconnected or broken. Another common problem on vacuum run valves is that the vacuum diaphragm that operates the valve has failed. The diaphragm won't "hold a vacuum" meaning that it leaks and won't operate the heater valve.

If all that seems to work okay. The heater core could be getting warm coolant through it but the underdash heater air handler box has a movable door inside that is not in the requested position. These doors are operated by cables or vacuum lines---so same checkout as above.

Jan 31, 2011 | Ford F-150 Cars & Trucks

2 Answers

I have very little heat, how do I fix the problem?


you may need a new thermostat if its stuck open or the heater core is plugged up and needs replaced or flushed.

Jan 29, 2011 | Saturn SL1 Cars & Trucks

1 Answer

Engine stalls, when stopped. Engine can be warm or cold when this happens. Could it be fuel filter or pump?


first thing to do is check for vacuum leaks. grap a can of spray carb cleaner and spray hose connections and elbows while the engine is running. the idle speed will change when you hit a leak with the spray. also clean the IAC valve. Idle air control valve. This device controls the idle speed. then clean or replace the PCV valve. The EGR valve will cause problems like this if it is clogged with deposits.

Nov 27, 2010 | 1998 Ford Escort

1 Answer

Engine light came on in my dodge caravan sxt 3.3L 6cyl. Code P0404. It seems to be running fine, how do I check the EGR valve myself? Any advice would be greatly appreciated.


To check the egr yourself you will need a hand held vacuum pump. To perform the test start the van and let it warm-up, then remove the top vacuum hose from egr valve and attach hand vacuum pump to egr valve. Apply about 5 in-hg vacuum to the egr valve. With the engine at idle speed and vacuum applyed the engine idle speed will drop or stall. If not then the egr valve is faulty and will need to be replaced. If the engine didi change idle speed and or stalled the egr valve is good. Hope this will help you.

May 17, 2010 | Cars & Trucks

1 Answer

After start up,{about 10-mins.] the engine bogs out, No throttle.


i have a 1990 vette doing the exact same thing. i have checked; fuel pressure, replaced fuel filter, checked spark, checked engine vacuum and i still cant seem to get the car to run once it's up to temp. any help on this would be great.

Dec 19, 2009 | 1990 Chevrolet Corvette

1 Answer

1990 Deville 4.5 litre v-8 vacuum present from vacuum line to egr selenoid but no vacuum from egr selenoid to egr valve the car runs fine when cold but runs poorly when warmed to operating temperature.


You will not see any vacuum from the egr solenoid until the engine has reached normal operating temperature and certain other driving conditions have been reached (like throttle position and road speed). If the engine runs rough when warmed up, check the CTS (coolant Temp sensor) when hot and cold and if no fault shows there, start checking input sensors for engine and cam position, engine timing, RPM etc. If the EGR valve was leaking, it is only adding air to the exhaust stream and usually, manually opening the valve and blowing out the seat with compressed air should fix the issue. This can also be an issue with clogged injectors. When the engine is cold, fuel enrichment supplies more then normal fuel amounts to encourage even running. When the engine warms up (normal operating temperature), fuel enrichment mode is turned off. If your injectors are clogged (even if only slightly) fuel starvation will cause rough running. Fuel enrichment overcomes the starvation of clogged injectors. Try adding a propriety injector cleaner to your fuel tank and watch for an improvement. If you do see an improvement, have your injectors cleaned and tested professionally. If you locate any other issues with engine sensors, replace them and ensure the new components are adjusted correctly if required..

Dec 12, 2009 | 1990 Cadillac Deville

2 Answers

Jaguar xj6 4.0 1990. showing fault code fuel 14, fail 14. what does this code mean ?


2 airflow sensor out of operating range 3 coolant temp sensor out of operating range 4 oxy sensor indicates full rich 5 throttle potentiometer/airflow sensor... (low throttle pot signal with high airflow sensor signal) 6 throttle pot/airflow sensor...... (high throttle pot signal with low airflow sensor signal) 7 throttle pot...idle fuel adjustment failure(idle speed??) 8 intake air temp sensor...open or shorted circuit to sensor 11 Throttle pot at idle: Throttle pot idle trim out of normal range 12 Airflow meter: MAF signal out of range 14 Coolant thermistor: Resistance out of range or static during engine warm up 16 Air thermistor: Resistance out of range 17 Throttle pot: Out of range 18 Throttle pot/Airflow: Low throttle pot signal at high airflow 19 Throttle pot/Airflow: High throttle pot signal at low airflow 22 Fuel pump drive: ECU output to fuel pump relay 23 Fuel supply: Engine running too rich 24 Ignition Drive: ECU output to ignition Amp 26 Air leak: Engine running too lean 29 ECU self check 33 Injector Drive: ECU output to injectors 34 Injector: Looks for Injector dribble 37 EGR Drive: ECU output to EGR switching valve 39 EGR check sensor: EGR not working (normally pipe blocked) 44 Lambda (O2) sensor: Poor mixture control rich or weak (or misfire) 46 Idle speed Control valve: ECU output to Coil AB 47 Idle speed Control valve: ECU output to Coil CD 48 Idle Speed Control Valve: Stepper motor grossly out of position 66 Air pump: ECU output to air pump relay 68 Road speed sensor: Seen speed < 5km/h at high engine airflow 69 Drive/Neutral switch: Seen cranking in "D" or high airflow in "N" 89 Purge Valve drive: ECU output to purge valve
this is all I could find

Nov 09, 2009 | 1990 Jaguar XJ6

1 Answer

1990 vette runs rought after warming up.


bad vacuum lines or need replacement fuel filter could even be a leaky line faulty fuel sending unit or check air filter ..start there first

Aug 25, 2009 | 1990 Chevrolet Corvette

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