About Grant Mcleod Expertise ford 7.3 diesel and most ford technical problems excluding, automatic transmissions and air conditioning. I have access to all current technical service bulletins and shop manuals
Experience I have worked in ford dealerships for the last 20 years as a technician, service manager and shop forman, as well as working with ford on solutions to some technical problems
Automotive - Engine Repair/Troubleshooting; '93 Ford Explorer
Expert: Grant Mcleod - 8/26/2004
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Followup To
Question -
Hi Grant,
I would greatly appreciate your repair help with my truck which is a '93 Ford Explorer. I'll provide you with a little history first that may help you in answering my questions.
About 3 weeks ago, I started to have problems with the Explorer. It would run rough and some black smoke was coming out of the exhaust once it arrived at normal operating temp. During this time, the "Check Engine" light would come on and off periodically. As I would accelerate, the engine would run better but at idle, like at a stoplight, it would run really rough. This would happen intermittently over a period of a few days. In fact, one morning, 5 miles into my 12 mile drive to work it ran great but then all of a sudden it started to run rough and emit black smoke again. Then it changed to running rough all the time, either cold or hot to stalling at idle, to not being able to start it now. I have sinced checked, with a meter, the (IAT) Intake Air Temp sensor, the MAF sensor and the Idle Air Control Valve and all appear to have the correct readings for either voltage or resistance. I have a Scan Tool and have checked the DTC and the stored codes are 113, 157 and 158. Code 113 is IAT sensor circuit open, or reads -40F. Code 157 is MAF sensor circuit below minimum voltage. Code 158 is MAF sensor circuit above maximum voltage.
Do you have any recommendations what I should do now? Can a faulty oxygen sensor(s) cause this problem? What about a bad or clogged catalytic converter? What may cause it not to start now?
Thanks in advance for your help. It is greatly appreciated.
Brent H.
Answer -
Hi Brent
Did you go through any large puddles or very heavy rain before this started?
A bad IAT may cause a slight drop in fuel economy but no real change in performance. check the vac line to the map sensor and all vac hoses for leaks. I would suspect a severe vac leak, bad mass air flow or map sensor or low fuel presure
I doubt the O2 sensor is causing your problem.
Hope this helps, Grant
Grant,
Thanks for the reply.
As far as rain goes, we did have a very large rainfall a week or two before this started to happen but if my memory serves me correct, the truck didn't exhibit this behavior soon after the rainfall, it was days later. If the rain is the cause, which components are usually susceptable or affected by water and would cause this engine problem?
What puzzles me is the black smoke. I don't know exactly what could be causing that. I could replace the fuel filter but that doesn't seem like a clogged fuel filter would make it emit black smoke. I will change it anyway. Does black smoke typically indicate an ignition problem?
Where is the MAP sensor located? On the manifold?
Thanks for all your help...again.
Brent
Answer Hi Brent
Black smoke indicates that the engine is getting way to much fuel or running way to rich.
If the air filter gets wet it will collapse on itself and even after it dries it won't pass air and may appear ok. The mass air flow sensor uses two wires a hot wire and a cold wire, the hot wire is a small heating element the computer looks a how much power is needed to maintain a certain temp above the temp of the cold wire and calculates how much air is getting to the engine, then the computer provides the correct amount of fuel. If the hot wire gets wet (just 1 drop of water) the sensor no longer can provide the right info to the computor.
The map sensor is at the passenger side rear of the engine on the firewall or on a bracket above the engine there will be a three wire connector and a vac hose. The map sensor measures manifold absolute presure, this also has a major influence on fuel mixture and can be out of range without setting a code.
Start with a new air filter or just remove the air filter for test purposes. Clear the codes and try to start the engine if it starts and runs great, if not re-scan for codes if mass airflow codes come back check the wirning carefully for signs of a poor connection or corrosion if its ok recheck all vac lines pull the vac linr off the map sensor and look into the vac port on the sensor. Is any grey goo visible? if yes replace the map sensor, if it appears clean reconnect it and replace the mass air flow sensor. as for iat reading -40 this is usually cuased by an open circuit (broken wire) inspect the harness carefully and repair as required.
