02 Mazda Tribute will not go faster than 30mph??
 

This is my wifes car. it started a few weeks ago with the engine light coming on and found by running the codes that it was a misfire on #4 cylinder.
replaced the spark plugs and added injecter cleaner to the gas.
Car ran fine for a week then the weather changed and got colder around here and the Tribute started to have issues with going faster that 30mph.
Today I found that the EGR valve was broken, I replaced it as well as the vacuum line that comes off the top of the valve due to dry rot.
Test drove it and it still would not go past 30mph. going by others here I started looking for other vacuum leaks and found that the short rubber line from the manifold to the steal line going down to the transmission was pinched and had holes.
Replaced that hose and still the car would not go past 35mph. I seeking some help with this due to the engine runs fine, checked the throttle body and it works fine. It is just when it is in gear that it does not want to go past 35mph.

Any advise would be greatly appreciated. Thanks

Remove the catalytic converters then go for a drive. These are common for blocked cats.

Some reasons why your cat could fail:

Engine Tune-up
A number of problems could occur to the catalytic converter as a result of an engine that is out of tune. Any time that an engine is operating outside of proper specifications; your converter suffers unnecessary wear and damage, as well as your engine. The damage is often the result of an incorrect fuel/air mixture, incorrect timing, or misfiring plugs. Any of these conditions could lead to catalytic converter failure or worse.

Excess Fuel Entering Exhaust
The fuel that powers your vehicle is meant to burn IN THE COMBUSTION CHAMBER ONLY. Any fuel that leaves the combustion chamber unburned will enter the exhaust system and “light off” when it reaches the converter. This can “superheat” the converter to temperatures far above normal operating conditions and cause a CONVERTER MELTDOWN.
This is an example of a converter meltdown. The converter was super-heated due to a raw fuel condition in the exhaust flow. The excess unburned fuel ignited when it struck the hot ceramic catalyst and drove the temperature far above the normal operating condition of the converter. The ceramic catalyst is unable to withstand the extremely high temperature and begins to melt. The ceramic collapses and the converter is destroyed. The melted ceramic may block the exhaust flow and cause additional damage to the engine. A converter glowing red-hot or evidence of heat discoloration confirms this situation. The too-rich condition that led to this converter melt down could be the result of a number of malfunctions including faulty oxygen sensor, an incorrect fuel mixture, worn spark plugs or plug wires, a faulty check valve, incorrect ignition timing, sticking float, faulty fuel injectors or other ignition malfunctions.

Oil or Antifreeze Entering Exhaust.
Oil or Antifreeze entering the exhaust system can block the air passages by creating heavy carbon soot that coats the ceramic catalyst. These heavy Carbon Deposits create two problems. First, the carbon deposits prevent the catalytic converter from reducing harmful emission in the exhaust flow. And second, the carbon deposits clog the pores in the ceramic catalyst and block exhaust flow, increasing backpressure and causing heat and exhaust to back up into the engine compartment. Your engine may actually draw burnt exhaust gasses back into the combustion chamber and dilute the efficiency of the next burn cycle. The result is a loss of power and overheated engine components. Possible causes are worn piston rings, faulty valve seals, failed gaskets or warped engine components.

Deteriorated Spark Plug & Spark Plug Wires.
Spark plugs that don't fire or misfire cause unburned fuel to enter the exhaust system. The unburned fuel ignites inside the converter and could result in a partial or complete melt down of the ceramic catalyst. Spark plugs and spark plug wires should be checked regularly and replaced if damaged or if wires are worn or cracked.

Oxygen Sensor Not Functioning Properly.
An oxygen sensor failure can lead to incorrect readings of exhaust gasses. The faulty sensor can cause a too rich or too lean condition. Too rich and the catalyst can melt down. Too lean and the converter is unable to convert the hydrocarbons into safe elements and may not pass a state inspection.

To expand on this watch these videos:



I would run lacquer thinner thru it to see if that helps (not paint thinner).

I would also re-set the ecu by disconnecting the negative terminal on the battery followed by a few brake applications, wait 10 minutes before re-installing negative terminal followed by letting enging idle for 5-10 minutes before driving withouit flooring it!

What would cause the EGR valve to blow out? Would that be the back pressure from the cat?

Don't know what would cause the EGR to "Blow Out", however, the crap from it could have re-entered the engine and back to catalytic.

Depends on which cat is clogged. Normally these days, there is one or 2 pre-cats (4 cyl or 6 cyl) before the EGR valve and 1 or 2 main cats after the EGR.
The pre-cats are monitored with the O2 sensors, the main rear ones are not.

Your car is old. Do the lacquer thinner right away and re-set the ecu as i suggested ASAP!

Constipated cats are a PITA!

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