Stumbling down the road
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Stumbling down the road
I am new to this forum so I hope that you can help me. I have a 91 Aerostar AWD with a 4.0, about 2 months ago it started to stumble when you give it gas. I have changed the plugs and wires, fuel filter, cleaned mass air sensor. Once you get up to speed then it seems to do ok. If there is anybody that can help me out with this problem that would be great.
Post Fiend
Joined: Apr 2005
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From: Washington state
welcome luddachris
,
please read codes and post to Aero forum....needed to diagnosis
many auto parts stores will read for free....call ahead
or DIY click
,please read codes and post to Aero forum....needed to diagnosis
many auto parts stores will read for free....call ahead
or DIY click
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If the o2 sensor was bad would it not throw the check engine light on or something? The check engine light comes on when you start it, but then goes off. This old van is the best car that I have ever owned, these things are awesome. I am having a mechanic come over to my house and put a code reader on it as well as a scope to see if I can narrow it down a little. I thank you all for your great advise and help.
Last edited by Luddachris; Nov 29, 2006 at 11:30 AM.
Post Fiend
Joined: Apr 2005
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From: Washington state
failing contaminated O2 sensor will not always cause a stored code on pre '96 OBD1 systems
take a look at the O2 signal while in closed loop...should show voltage swing 2>3 times per second 0.5v > 5v on OBD1 sys...
most common failure is slow response time which does not show up except on most advanced engine analyzers....
far more cost effective to replace O2's every 50k>100k...savings in fuel costs more than pay for sensor...easier than changing 1 spark plug
many failure codes will not set CEL
take a look at the O2 signal while in closed loop...should show voltage swing 2>3 times per second 0.5v > 5v on OBD1 sys...
most common failure is slow response time which does not show up except on most advanced engine analyzers....
far more cost effective to replace O2's every 50k>100k...savings in fuel costs more than pay for sensor...easier than changing 1 spark plug
many failure codes will not set CEL
Posting Guru
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From: charlotte nc
Just an idea to remember. Aeros are known for excessive heat under the hood which over time can dry out electrical wires and vacum lines. A good inspection is in order which may show an obvious problem.
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A visual inspection was done and found no problem spots, vacume test was done by the mechanic and I was told that it is all within normal specs. He thought that it was probably the coil pac and I am asking you guys if that is your opinion as well. Thank you for your time on this quest for knowledge.
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A visual inspection was done and found no problem spots, vacume test was done by the mechanic and I was told that it is all within normal specs. He thought that it was probably the coil pac and I am asking you guys if that is your opinion as well. This problem only happens under load, once you get up to speed it does just fine staying at speed. Thank you for your time on this quest for knowledge.
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Originally Posted by Luddachris
Once you get up to speed then it seems to do ok.
With the engine warmed up and idling, disconnect the MAF sensor. If the sensor is working properly, the engine will immediately idle roughly and may even die.
As mentioned previously, the O2 sensor would be the next logical suspect. It tends to die a very slow death without eliciting any error codes. A bad sensor will keep the engine in a rich, cold start mode. As a result, once the engine is warm, there is an incorrect fuel-to-air ratio and the engine runs poorly with resultant poor mileage as well.
A third possibility would the ECT (Engine Coolant Temperature) sensor. A very simple device that sends a variable signal to the EEC (electronic engine control - aka 'computer brain'). A bad ECT has the same effect as a bad O2 sensor, the engine is warmed up but the EEC is never notified. This is easy to replace and cheap as well. There are two temperature sensors. One, with a single wire, feeds data to the dashboard gauge. The ECT sensor has two wires at the the connector. ECT prices vary wildly, so check around before purchasing.
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Well I changed the o2 sensor today and it did make a differance however it is still sputtering on exceleration. One thing that I did notice is that now when I punch it pretty much is unoticeable. I checked the MAF sensor as well appears that it is working as well wanted to die when unpluged. I still have the ECT to change, other then that is there anything else that you guys think might be the cause of this problem.
Post Fiend
Joined: Apr 2005
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From: Washington state
since the stumble problem only shows up on acceleration....i would check the TPS, throttle position sensor...it's a variable resistor mounted on throttle body shaft....
difficult to test for intermittent spot on resistive strip....best to replace...low cost and easy to get to
http://fordfuelinjection.com/?p=10
http://fordfuelinjection.com/index.php?p=30
disconnect - neg. batt. lead for 5 minutes after each sensor change to reset KAM in ECU....takes 5>20 miles for ECU to relearn driver style parameters
difficult to test for intermittent spot on resistive strip....best to replace...low cost and easy to get to
http://fordfuelinjection.com/?p=10
http://fordfuelinjection.com/index.php?p=30
disconnect - neg. batt. lead for 5 minutes after each sensor change to reset KAM in ECU....takes 5>20 miles for ECU to relearn driver style parameters
Last edited by 96_4wdr; Dec 3, 2006 at 10:35 AM.