HI! I HAVE A 87 CARAVELLE I JUST BOUGHT IT YESTERDAY CHEAP! MY PROBLEM IS THE MOTOR HAS A MIS I THOUGHT IT JUST NEEDED A TUNEUP SO I PUT CAP PLUGS AND WIRES BUT NO DIFFERANCE WHEN I PUT IT IN REVIRCE IT SHAKES SO BAD I HAVE TO TAKE IT OUT OF GEAR. IT DOESNT MIS AS BAD OUT OF GEAR BUT STILL MISSES. REAL BAD MILAGE WILL A MAP SENSOR MAKE THIS HAPPEN.
First you need to find what cylinders are misfiring.
Getting a manual and finding out the firing order would help. If two wires are crossed it can cause this kind of problem.
If the firing order is correct, then look over all of the vacuum hoses to make sure none of them are cracked or disconnected. A bad vacuum leak will cause a bad cylinder miss.
A faulty intake manifold gasket, carburetor base gasket can cause a cylinder miss. Spraying around these areas with carburetor cleaner will help locate the miss. When the bad gasket is located the engine will smoothen out.
An EGR valve stuck open can cause a bad cylinder misfire. Put your fingers under the EGR valve and see if the valve is pushed up to the top of the valve (open). Disconnect the vacuum hose to the EGR valve to make sure the vacuum is not applied all the time.
If all of these suggestions check out, then a compression test of each cylinder is needed. If compression is low on one or more cylinders then this will also cause a bad engine misfire. Burned valves or a bad head gasket can cause cylinder misfires.
Try these suggestions and get back to us with the results.
when i sprayed starting fluid around the bottom of the throttlebody right under the cable the motor wants to shut down .IM .thinking its a gasket under the throttle body. what do u think? Unplugged the map sensor and it wanted to stop also i pulled the hose off the EGR valve no suction what does this mean?
when i sprayed starting fluid around the bottom of the throttle body right under the cable the motor wants to shut down .IM .thinking its a gasket under the throttle body. what do u think? Unplugged the map sensor and it wanted to stop also i pulled the hose off the EGR valve no suction what does this mean?
When you spray around the throttle body it should have raised the idle or made the idle smoother. If you over sprayed the throttle body will suck in the fumes from the top also. Spray is short bursts at the base of the throttle body, if the idle rises or the idle smooths out the change the base gasket. Remember this may not be your only problem.
When you unplug the MAP sensor it tells the computer that you are at wide open throttle and dumps fuel in. If you didn't plug up the vacuum hose then you also had a vacuum leak. The problem doesn't appear to be related to the map sensor.
When the car idles you don't want vacuum at the EGR valve. The EGR valve recycles some of the exhaust gasses into the intake manifold to lower cylinder temperatures. If the EGR valve opens at idle it is a big vacuum leak which will give you a rough idle. Move the valve with your fingers to make sure the valve is not stuck or in a slightly open position.
Try the other suggestions I told you about and get back to me.
when i raise the idle it almost goes away but u can still hear a slight miss i think it is a vacuum leak or sensor.i can hear it in the exhaust coming out of the tail pipe .checked all hoses plugs are fine no dead cylinder. All plugs are burning white when i took the air cleaner off the big hose going into the valve cover was split so I replaced it. it doesn't shake as bad but still has a miss .i no it should smooth out but it seems to choke it off even with small sprays but only on one side of the throttle body.it has new cap and wires and also plugs no smoke starts rite up I'm just looking for something else to try. THANKS FOR THE HELP
Try spraying around the intake manifold gasket area. See if the idle changes. If it does change then it would probably be an intake manifold gasket.
It still could be a throttle body base gasket. You just have to keep looking.
If you could get someone to check the car out with a scanner it would be a big help.
Some times in rare cases the vacuum brake booster leaks. Remove the vacuum line to the booster and plug it and see if the idle changes.
Remove all the vacuum hoses one at a time at the engine and plug them up to see if the engine changes. It's got to be somewhere.
There has been service bulletins on a rough idle on this car. It mentions the EGR valve. Canister purge problems are mentioned when the days are about 90 degrees. Check these out they could be in the area of the problem.
Keep us posted.