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1993 Ford E-150 Malfunction - Engine
Question: Hi guys
I own a 1993 e150 with a 5.0 engine and 80, 000 miles.On my back from Fla.doing about 75 mph going up a slight incline the van started to vibrate a lot, would not maintain steady mph, temp started to rise to 3/4 reading. If I let off the gas and accelerate again it runs ok for a while and it starts again.
I brought it to a trans shop and they told me the overdrive converter and overdrive clutch was not working correctly. Since this happens when o-d is working I had the unit rebuilt and a new converter installed but the problem is still there.It feels like a few cylinders are not working, so I pulled the plugs and found the insulators white and blistered. I checked fuel pressure and it is good, and I was able to brake rev it and the problem came in fuel pressure stayed the same. I hooked up a snap-on scanner and it will only read codes no data, no codes found. I put on a vac gauge and it reads ok but no more brake revving, it strains it too much. I think it is a ctc-converter problem but can't figure out why it comes and goes. Any input is greatly appricated. Thank you
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Technican: Hi,
I beleive it could be your catalytic converter. Here are several tests to confirm a bad converter.
The first and easiest test is to hit the converter with a rubber mallet and listen for internal noise. If the substrate is overheated and breaking up, it will rattle and can clog itself going down the road. If it only efects one bank, it could cause the shaking and also intermittant problems that relieve when the vehicle is decelerated.
Another test you can make is with an infrared temperature gun. Let the engine run at about 2500RPM for 2 minutes after the engine is warm and take the exhausst pipe temperature before and after the cat. At the rear of the cat should be about 10-20% warmer than the front of the cat if all is well. If the temp difference is greater, the cat is being killed due to excess fuel (tuneup or rich condition) If the temp difference is less than 10%, then the cat is already dead and needs to be replaced.
Hope this helps,
Owner: I replaced the cat 2 weeks ago thinking it would solve the problem but it did'nt.
On my snap-on scanner it asked what trans do I have,
Automatic overdrive or electrictronic overdrive. I have AOD and the scanner will not give data, how ever if I choose electic overdrive I get data.I cant get a answer if the data is correct or not.
While looking at the data while brake-reving hard about 3/4 gas the data indicates OPEN loop and release the gas it goes back to closed loop. I don't know if i'm going in the right direction or not.
Technican: I believe the data is most likely right now that you are getting some. It is normal to go into open loop on hard acceleration. Use the scanner to watch oxygen sensor data when the problem is occurring. It should be around .7-.9 volts (700-900 millivolts) when under load and in open loop.
If the oxygen sensor is reading properly, then your fule supply is fine. Check for strong spark at the spark plugs, it should jump 1/2 inch with a strong blue spark and a nice "click". If this is OK, check the timing for irregular changes when under load.
If the oxygen sensor is reading low, then double check your fuel pressure, if OK, watch the sensors for something odd. Pay particular attention to the throttle position sensor, the MAP sensor and the coolant temperature sensor. Check for strong spark as detailed above.
Sounds like we have a tough one!
Owner: Hi
If I remember correctly the computer takes care of running the engine after it warms up such as setting the advance, pulse width, and so on according to the throttle position, closed loop operation. If this goes to open loop the car runs on a fixed parameter.I need 3 things for closed loop, preset computer time, temp sensor reading, and o2 sensor reading. I changed the sensors and they read the same as the old ones.I would think the computer in closed loop would do a better job of running the car than open loop on acceleration. Also it goes to open loop just crusing at 30 mph or above.I found this today driving around, but the trouble didn't occur.I think my next step is a Ford dealer.
Any thoughts?
Technican: Hi,
The computer should not go into open loop on normal cruising, only on hard acceration. The computer stategy is to go into open loop on hard acceration, using assumed fuel requirements, adding or subracting the learned fuel trim values from closed loop operation and then adjusting the mixture to the rich side. This is to give the extra power that is gained from a 12:1 ratio instead of the closed loop 14.7:1 ratio. Under proper operation, it should stay in closed loop as long as the temperature is in the operating range, the o2 sensors are cycling, the engine has been running long enough and the TPS is not over about 3.5 volts.
I recommend watching the TPS, CTS and o2 sensors and loop status to determine what is going on. Watch o2 first. On hard acceleration, they should peg over .7 volts...with your new sensors, I would expect over .9 volts. Watch what the o2s are doing under normal driving when the van is going to open loop. If they are doing something crazy, the computer is set to ignore irrational readings (or the motor could flood itself or stall from lack of fuel) If that looks fine, watch TPS, (should be steady when the throttle is steady, should move when the throttle is moved) and CTS. (Should read 190*-220* and stay steady within 30* from cruise to stop and go) Again, if all looks well, and the computer is shifting into open loop on normal driving then the compputer is failing in the logic portion. Time for a replacement.
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