1991 Ford E150, 351W, 5.8L, e4od, purchased 2.5 years ago odometer reading 56k(must be 156), I have put 7k miles on, all in town not on the freeway once due to issues.
Since purchase there has been an intermittent issue with the engine surging, this happens when I am driving in first gear, it will rev up regardless of my foot on the accelerator and stay there, very disturbing. To stop it I have to quickly depress and release the accelerator pedal or manage to get to the side of the road and turn engine off. This only happens in hot weather, intermittently. So far I have seen a multitude of mechanics, mobile and shop. So far I have..done full tune-up, replaced all filters, replaced the egr, cleaned the throttle body, replaced the tps, replaced the fuel sending sensor, the idle air control valve,the accelerator spring twice, the accelerator cable, the 02 sensor, the voltage regulator, all battery cables..Any suggestions?

 

If you leave it in gear, how fast does it rev up to or how many MPH in first will it go? Trying to get an idea of just how far it is revving op. Does the gas peddle go down some when it revs up?

 

The gas pedal does not seem to move. It revs up to varying degrees..bu what would be anywhere from 25 to 40 mph. It is significant. Only in hot weather, especially if I am driving after a period of idling, like sitting in traffic or going thru a driv-thru. One of the problems is the mechanics act as if I am not aware of how a vehicle accelerates. One that had just “fixed” it, when I pointed out it was doing it at that moment said “take your foot off the gas”…..my foot was not on the peddle. I am just at the end of my rope. I also have an intermittent transmission problem that seems to stump every mechanic that looks at it.☹️

 

Idk if my earlier response posted, if it did sorry for double response. It revs up to what would be equivalent to anywhere from 25 to 40 mph. It tends to do it more often after idling, like in traffic or going through a drive thru line. The pedal does not seem to move, but if I depress the pedal quickly and release it will go back to normal rpms.

 

you have changed just about every part except the PCM... I was thinking that if the gas peddle went down then there was a long shot you could have a problem with the cruise control. If the gas peddle is not moving then that rules out the cruise control which is the only control besides your foot that open the throttle plates.

If the throttle plates are not opening then the only other part I can think of that could give the engine more intake air is the IAC and you said that you replaced that. The IAC is controlled by the PCM..

The high rev, it is similar in rpm's to starting the engine on a very cold morning? I was having trouble with my engine idle and after changing the Air Charge Temperature Sensor, that solved my problem. The ACT senses the intake manifold air temperature and the PCM adjusts the fuel/air ratio accordingly.

I guess you have checked to see if there are any codes?

 

No codes last I checked, I could try again. When it revs it can be much higher than the amount on cold morning start. Since this only happens when it is hot outside would the Air Charge Temp sensor be possible? I am just sick at this point. The amount I have spent uselessly is overwhelming. I live in the van so I don’t have any choice and every time one of these mechanics works on it, it is another stay at a motel at 100 a night tacked onto the double charge for parts and the outrageously padded labor fees. I have spent over 3,000 on this one issue and still have the issue of 5 mpg and a transmission that intermittently slams into 2nd and has psychotic overdrive ideas. I just give up!

 

I understand ow you feel as far as frustration. I have a couple of issues with my van that is keeping me from traveling very far from home and I haven't been able to solve them yet. Hang in there!

The Air Charge Temp sensor and the Engine Coolant Temp sensor both send information to the PCM. The PCM uses the information from both of those sensors to adjust the fuel ratio. In my experience the ECT can cause bad fuel mileage if it is giving a false reading to the PCM but I have never had the ECT to cause very high idle. If the ECT is bad the PCM may think the engine temperature is still cold and keep the system in open loop causing the engine to run rich...

There are folks her eon the forum that are way much better then i am with these controls and hopeful one will stop by soon..

As to the ACT sensor, it screws into the intake manifold on the left side and is fairly easy to get to. At least on the 5.0.. i am going to make a guess here and say when the engine is idling, it seems like the intake air temperature might become a little warmer due to lower air flow through it. When you depress the peddle quickly you would get a rush of cooler through the intake momentarily but i don't know if the sensor would react that quickly.

If you have a multi meter then you can test both the ECT and ACT with a ohm meter. They both have the same values at different temperatures.
If you have a cooler or fridge you can put the sensors in there to cool them down and take a reading. i put mine in the toaster oven to get the higher reading.



the 5.0 and 5.8 are very similar but I can only say for sure on the 5.0..
to get to the ACT you have to remove the engine cover and you will find it on the left side just behind the distributor. Here is a pic of mine with the connector off. Take it out, test it, and if its good then put it back. If you have a lot of stuff in your van then getting the engine cover off will be a job.. I find it is much easier to unbolt my passenger seat from the seat base and then i have a lot of room to remove the cover instead of fighting with it to get it up and between the seats. My seats have 4 nuts that hold it to the base.

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Here is a pic of the old and new one..It just screws in so depending on your ability you could do it yourself... I did!


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The ECT is right near the thermostat and looks very similar to the ACT.

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Again though these sensors provide information to the PCM. The PCMs are also known to go bad. There are 3 capacitors inside the PCM that are known to go bad. There are a few good videos in repairing them if you are willing to try your hand at it. Changing out the PCM is also a job you can do yourself if need be.

 

Ty,I will check those, I appreciate your input. I agree it seems like a sensor would not react quickly to a burst on the accelerator. It is like something gets stuck and a quick stomp puts it back where it should be. And for it to not do it for months and then very hot weather comes and it starts up again. It is hard to sell something that surges and shifts like crap intermittently, so I am trapped in this pos **** box. When you say pcm, is that the same as the ecm?

 

Yes and no. They are both computers that control the engine and are often used interchangeably but I believe to be proper the ECM Engine Control Module controls the engine only while the PCM Powertrain Control Module controls the engine management as well as the transmission and in newer cars other controls.. Technically My 88 van has a ECM while maybe if you have a E4OD transmission in your 91, the you would technically have a PCM because the E4OD transmission and your engine is controlled by the same computer. That's my understanding. You will also see ECU Engine Control Unit used in place of ECM.

Yours is located under the heater plenum box on the passenger side. It is under the lower plastic cover.

Did it act exactly the same after you replaced the IAC?

As to testing the sensors, if you have them both out at the same time then check them both at the same temperatures, they should read very close to the same ohms..

 

BTW do you know what transmission you have in the van? The E4OD is controlled by the PCM and you will have a overdrive cancel switch I believe on the end of the gear shifter or on the dash. I think it is on the dash on your van.


If you can find the high idle problem then it may solve your transmission issue.

 

Yes it is E4od. The overdrive switch is broken. I have been looking for one for forever, my year the6 are dash mounted not on the arm. I just now ordered on for a 91 Bronco, the switch looks exactly the same except it out s to the dash with screws instead of tension clips. I am assuming they are functionally interchangeable, fingers crossed. I am going to fix that and replace the mlps and fix the antilock system before going any further on the transmission. I have had multiple diagnosis on that issue, from you need a new fan clutch and torque converter, to..it must be a sensor, to…you need a new transmission to..no way to tell until you fix the overdrive button and antilock brakes..no two mechanics have had the same answer…I don’t want to spend 4,000 on a transmission until I can get some kind of consensus..but I am really getting discouraged, I have not left the same 2 mile radius except to go to doctor, 5 miles away,in 2.5 years..very discouraged.

 

Mark Kovalsky is our transmission specialist here at FTE and knows these transmissions. I would start another thread dedicated to your transmission issue and get his advice how to proceed.

I believe it was Mark that said that the overdrive switch is nothing more then a normally open momentary switch like a door bell button! Th lighted switch lets you know the position on or off. But if you want the factory look then you need Ford part #E9UZ-7G550-B
https://www.ebay.ie/itm/224599937823...EAAOSwwK1hNpLo

I have been thinking about your idle problem. Do you know if any of the mechanics have messed with the factory adjusted idle screw? That is a big no no if you are just replacing the IAC or cleaning it and the throttle body. If it has been messed with then you have to go back through a factory set procedure. I have read how to do it but not ever done it.
I mentioned the ACT and ECT and both of those sensors will affect fuel mileage as well as idle but i am not sure they will cause your extreme high idle. You should check them anyway. A bad O2 sensor can also affect fuel mileage and not always throw a code. I changed my O2 sensor purely for maintenance and couldn't believe how much better the engine ran..

Normally if the throttle place is not moving and causing the high idle then it is most likely in the IAC, TPS, or PCM. What brand TPS did you buy? Many of the after market ones are notorious for being bad. Also I am not sure abut your 91 but my 88 TPS has no calibration adjustment and my manual says adjustment is not needed. I believe on the F series and most cars, you have an adjustment on the TPS and it has to be set to a certain value at idle and WOT. If it is not calibrated correctly then the
PCM might think that you have the peddle depressed and then engine needs more fuel. Again though my 88 does not need that done.

The PCM can be removed and you can open the cover and look for any burnt spots on the circuit board or corrosion around the legs on the capacitors or swollen capacitors. Its not uncommon to have issues with the capacitors at 31 years old. If you inspect it and find something that looks bad and are not comfortable repairing it yourself the talk to someone at a electronics shop and ask how much they would charge to replace the capacitors for you. Shouldn't take an hour.. If you can still find a electronics repair shop..

There are ways to test the IAC but I will have to look that up.. does it ever start up with the very high idle or does it only happen after the engine is warmed up?