Possible Valve Timing Problems????

[jmitchell38925]

I recently rebuilt my 5.0 HO in my 1986 mustang. Since that time it has never run quite right.....very small backfires from time to time and running a little bit rich. Have tried everything i know and basically totally replaced the ignition system . still having probs though....here is a list of symptoms

- at around 1500 rpm with load on engine i have bad shake
- if i remove vaccuum advance to set timing it will sometimes go dead, when it does this right after it dies there is a huge gasp of air through my intake...like there was a built up suction that was finally released
- only code i am pulling says system is rich
- VERY sluggish acceleration, notice small backfires when i come off clutch...
- small amount of smoke noticable after sitting at idle for a while then revving engine


I am at my wits end on this...still seems to be something in the timing...i lined up the keeper pins on my camshaft and crankshaft so they were facing towards each other. any help would be appreciated thanks.

 

[jrichker]

What code?

Code 41 or 91 - O2 indicates system lean. Look for a vacuum leak or failing O2 sensor.
The computer sees a lean mixture signal coming from the O2 sensors and tries to compensate by adding more fuel.

The following is a Quote from Charles O. Probst, Ford fuel Injection & Electronic Engine control:
"When the mixture is lean, the exhaust gas has oxygen, about the same amount as the ambient air. So the sensor will generate less than 400 Millivolts. Remember lean = less voltage.

When the mixture is rich, there's less oxygen in the exhaust than in the ambient air , so voltage is generated between the two sides of the tip. The voltage is greater than 600 millivolts. Remember rich = more voltage.

Here's a tip: the newer the sensor, the more the voltage changes, swinging from as low as 0.1 volt to as much as 0.9 volt. As an oxygen sensor ages, the voltage changes get smaller and slower - the voltage change lags behind the change in exhaust gas oxygen.

Because the oxygen sensor generates its own voltage, never apply voltage and never measure resistance of the sensor circuit. To measure voltage signals, use an analog voltmeter with a high input impedance, at least 10 megohms. Remember, a digital voltmeter will average a changing voltage." End Quote

Measuring the O2 sensor voltage at the computer will give you a good idea of how well they are working. You'll have to pull the passenger side kick panel off to gain access to the computer connector. Remove the plastic wiring cover to get to the back side of the wiring. Use a safety pin or paper clip to probe the connections from the rear. The computer pins are 29 (LH O2 with a dark green/pink wire) and 43 (RH O2 with a dark blue/pink wire). Use the ground next to the computer to ground the voltmeter.

Most of the common multimeters have a resistance scale. Be sure the O2 sensors are disconnected and measure the resistance from the O2 sensor body harness to the pins on the computer.

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter. Do not attempt to measure the resistance of the O2 sensors, it may damage them

The O2 sensor ground (orange wire with a ring terminal on it) is in the wiring harness for the fuel injection wiring. I grounded mine to one of the intake manifold bolts

 

[jmitchell38925]

The code i am pulling is 92

 

[jmitchell38925]

I tried relocating my O2 ground to my manifold bolt for better connection. Now i am pulling thses codes...they seem unrelated to O2 sensor but here they are:

- 67
- 18
- 22
on key on enging off .... did not test key on engine running agian since theses codes are probably gonna affect the readings anyway

 

[jmitchell38925]

Finally!

i think i got it worked out....on a whim i decided to take my ignition module in and have it tested....it was brand new so i hadn't thought to do it before...well the module failed horribly, in fact only one function passed lol, so now i have replaced it and the car seems to be doing much better, ty for the help