Been helping a friend out with his 91 mustang over the last 2 months with many things, and have an engine question for you guys.
It's a 5.0/302 HO; the same thing as our MGM's stock engine with some slightly different parts (cam, heads, headers, intake) tuned for higher rpms. It DOES have a mass airflow sensor.
Since I've seen it, it has always idled rough with an uneven possibly random missfire at idle.
I did a basic tuneup, and with cause. It has 52,000 miles (legitimate: NOT 152,000 miles) but I didn't know the maintenance history. The distributor cap looked a bit burnt up, the plugs and wires were old, one O2 sensor was plumb missing!, and there were some cracked vacuum lines.
I did engine tuneup 101 type stuff. Distributor cap and rotor, plugs, wires, both O2 sensors, pcv valve/grommet/screen, replaced the cracked vacuum lines and the charcoal canister line, which was disintegrating. EGR spacer gaskets, and while it was apart, cleaned the throttle body, and what little I could get to of the IAC, EGR, and intake plenum. Did the fuel filter, air filter. Put seafoam in the gas tank.
And a whole bunch of other stuff too not related to engine performance: coolant system mainly, all the lines, thermostat, and the fan (which was plastic, and about to fly apart).
Darn thing runs just about the same! I thought surely those blatant vacuum leaks, visibly scorched distributor cap, and criminally absent O2 sensor were the cause...
OK, so where next?
thanks!
-Bernard
It's a 5.0/302 HO; the same thing as our MGM's stock engine with some slightly different parts (cam, heads, headers, intake) tuned for higher rpms. It DOES have a mass airflow sensor.
Since I've seen it, it has always idled rough with an uneven possibly random missfire at idle.
I did a basic tuneup, and with cause. It has 52,000 miles (legitimate: NOT 152,000 miles) but I didn't know the maintenance history. The distributor cap looked a bit burnt up, the plugs and wires were old, one O2 sensor was plumb missing!, and there were some cracked vacuum lines.
I did engine tuneup 101 type stuff. Distributor cap and rotor, plugs, wires, both O2 sensors, pcv valve/grommet/screen, replaced the cracked vacuum lines and the charcoal canister line, which was disintegrating. EGR spacer gaskets, and while it was apart, cleaned the throttle body, and what little I could get to of the IAC, EGR, and intake plenum. Did the fuel filter, air filter. Put seafoam in the gas tank.
And a whole bunch of other stuff too not related to engine performance: coolant system mainly, all the lines, thermostat, and the fan (which was plastic, and about to fly apart).
Darn thing runs just about the same! I thought surely those blatant vacuum leaks, visibly scorched distributor cap, and criminally absent O2 sensor were the cause...
OK, so where next?
thanks!
-Bernard
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