Replace intake manifold now check engine light on

HMM, it has been awhile since ive worked on that toyota motor. Check for vacuum leaks on hoses and the intake manifold. Check egr system for a dirty pintle leaving the egr stuck open. It will cause bad acceleration and idle quality. A properly closed egr cannot be blown through to the opposite port. Check for a clean throttle plate, if it is not, clean it. If it is a fuel injected engine check for bad fuel injector o rings for wear, if they leak they cause fuel burning and idle problems.

What engine ? vacuum leak intake runner control , possibly ! Is the check engine light on ? Ford Windstar P0171 P0174 Upper Intake Manifold Gasket Replacement

The automatic tranny relies on vacuum pressure from intake manifold to signal when to shift. As the engine RPM increases, there's a proportional increase in intake manifold vacuum pressure. When vacuum pressure reaches a certain point, that signals the tranny to shift up to the next gear. When this vacuum hose has a crack or loose connection, it sends the wrong signal as to when to shift because vacuum pressure is dropping as air enters through the leak source, which the tranny interprets as a need to shift down to a lower gear. Replace all the vacuum hoses and see if this solves the problem. Look at the tranny and identify any air hose connected to it. These are vacuum hoses that you should replace, which usually there's only 1 or two connected to the air intake manifold.

Most common problem is a failed mass airflow sensor. Remove sensor and carefully inspect the sensor for debris building up on the diode. Another possibility is the egr valve may be partially stuck open. The upper intake manifold is made of plastic. The egr gases enter the intake just behind the throttle body inside the plastic intake. It is pretty common for the hot exhaust gases to burn through the plastic and possibly cause coolant to enter combustion chambers. A restricted catalytic convertor from previous engine misfires will accelerate this due to exhaust gases having no place to escape.

BAD spark! check plugs wires and coil packs. the wires are a real pain to replace because of the location of the coil packs between the intake manifold and firewall.

change the plug wires they may be bad. or you may have a bad coil

The upper intake gaskets may be leaking. They are made of plastic and metal and will leak air. Do not remove the cover on very top of manifold when changing.

I'd check for vacuum leaks next. use a spray can of intake or brake cleaner. spray around vacuum lines, manifold gaskets etc. if the rpm increases you found a leak.

Ok, there are many issues here that you will need to inspect. I recommend changing the fuel filter and pump as well. this will fix the hesitation. the intake and exhaust manifold gaskets will need to be replaced as well. this will stop the backfiring.

I also recommend checking and running a teat on the PCV valve and inspect the PCV hose as well. it could have a leak or a small crack on it.

Check the air filter and change if needed. this will help with acceleration issues as well. Next, i would run a check on all plugs and the complete wire set as well. change if needed.

Inspect the injectors for leaks and lose wires. make sure they are in good condition. replace any injectors that isn't firing properly.

Ok, there are some sensors that you will need to check as well. i will list them below.

SENSOR CHECK LIST--

1. Check the O2 sensors for worn wires.
2. Check the MAFS(Mas Air Flow Sensors) Check for Damaged, Loose, or Faulty Mass Air Flow Sensor or Circuit.
3. Check the Air Cleaner Temperature Sensor. this sensor could be damaged ro have loose wires. check accordingly.
4. Check the Throttle Position Sensor. this device could be connected wrong or it may be faulty as well. replace if needed.

Be sure and inspect all the above and repair any problem spot you ruin across during your inspection.

Please rate and god bless:)

check for a vacuum leak,you could possibly hear a whistle under the hood,or you can spray starter fluid near the intake manifold where the suspect leak could be and if the engine accelerates it has an vacuum leak,try the simple things first,can also be a clogged PCV valve,it is in the valve cover somewhere and it will have a rather large rubber hose going to the intake manifold