4.0L having problems!
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From: Bowling Green USA
4.0L having problems!
I just swapped a 4.0L from a 93 aerostar into my BII. so I figured you guy's might be able to help. the motor is doing some wiered crap!
it runs good about 50% of the time with only a small knock under load. the other 50% of the time it bogges down and starts to jump around hard. I mean HARD! it poped my hood going down the road! I have had the EDIS sensor, coilpack, crankcase position sensor checked, and I even took it to get the computer checker thing put on the system. they said the sensors were good?????? mechanicly I have replaced all push rods 6 rockerarms, checked the timing gears, chain and tnesioner, and when the timing cover was off I even reached into the oil pan and wiggled the first two rods to see if they had any play. I can't find any thing wrong with this motor and it still runs funny any of ya'll had this problem? I would like any sugestions because the only other thing I know to do is take the heads off and inspect the valves.
sorry about the long post
it runs good about 50% of the time with only a small knock under load. the other 50% of the time it bogges down and starts to jump around hard. I mean HARD! it poped my hood going down the road! I have had the EDIS sensor, coilpack, crankcase position sensor checked, and I even took it to get the computer checker thing put on the system. they said the sensors were good?????? mechanicly I have replaced all push rods 6 rockerarms, checked the timing gears, chain and tnesioner, and when the timing cover was off I even reached into the oil pan and wiggled the first two rods to see if they had any play. I can't find any thing wrong with this motor and it still runs funny any of ya'll had this problem? I would like any sugestions because the only other thing I know to do is take the heads off and inspect the valves.
sorry about the long post
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4.0L having problems!
Swaps like these are often accompanied by a host of gremlins. Either an intermittent fuel problem or electrical system malfunction could elicit the rather violent behavior described.
Rather than removing the cylinder heads, first check your fuel pressure regulator to see if the vacuum line is in good condition, seated properly and vacuum is present when the engine is suddenly accelerated. If you pull the vacuum line and fuel is present in the line, the diaphram is bad and the regulator should be replaced.
The "small knock" under load could be as simple as a bad spark plug wires or a failing coil pack. Coil packs rarely fail but the 4.0l engines are sensitive to failing plug wires, so a replacement would be in order if in doubt. (You will find extensive posts on this site regarding both these issues).
Hope this at least gets you pointed in the right direction. Post back with your findings.
Rather than removing the cylinder heads, first check your fuel pressure regulator to see if the vacuum line is in good condition, seated properly and vacuum is present when the engine is suddenly accelerated. If you pull the vacuum line and fuel is present in the line, the diaphram is bad and the regulator should be replaced.
The "small knock" under load could be as simple as a bad spark plug wires or a failing coil pack. Coil packs rarely fail but the 4.0l engines are sensitive to failing plug wires, so a replacement would be in order if in doubt. (You will find extensive posts on this site regarding both these issues).
Hope this at least gets you pointed in the right direction. Post back with your findings.
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From: Bowling Green USA
4.0L having problems!
I pulled the vacume line on the regulator and pluged the intake end but not the line end. there was no fuel in the line but with the line just hangin' there their was no change in idle? should that have happened? also I unpluged the "idle air control"(I think thats what it is called) and the motor calmed down alot! it still stumbles but it doesn't jump like it did before. should that have happened? I'm thinking that the thing I unpluged might have just been agrivating the miss or hesitation. am I correct in thinking this?
Postmaster
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4.0L having problems!
There will be no appreciable vacuum in the line at idle, only when the throttle is opened quickly or during de-acceleration. A dry line and no change at idle are good signs the regulator is operating properly.
The idle air control valve on the other hand is suspicious as the engine should normally idle very rough and lumpy when it is unplugged. Try removing the idle air control valve and spraying it with choke cleaner. There is a very small regulator pin controlling s the amount of air admitted to the throttle body. Frequently it gums up and causes the pin to stick in either the open or closed position. This can occur while driving and can also elicit the symptoms you described earlier.
The idle air control valve on the other hand is suspicious as the engine should normally idle very rough and lumpy when it is unplugged. Try removing the idle air control valve and spraying it with choke cleaner. There is a very small regulator pin controlling s the amount of air admitted to the throttle body. Frequently it gums up and causes the pin to stick in either the open or closed position. This can occur while driving and can also elicit the symptoms you described earlier.
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From: Toronto Canada
4.0L having problems!
Hi Aerocolorade:
After reading this document,[http://www.grubinski.com/grubinski/20.pdf], page 2. I am confused about the vacuum condition at the pressure regulator vacuum line when in idle. I always think that there is 'high/appreciable' vacuum at the line at idle because the throttle plate is close and causing vacuum to suck the diaphgram. When the throttle plate is opened, vacuum at the line will be little/reduced because some vacuum got transferred/distributed to the air box. It is kind of like the pressure regulator vacuum got bleeded off to the atmosphere. The document is for Toyota. Maybe aerostar is differnet. Thanks.
After reading this document,[http://www.grubinski.com/grubinski/20.pdf], page 2. I am confused about the vacuum condition at the pressure regulator vacuum line when in idle. I always think that there is 'high/appreciable' vacuum at the line at idle because the throttle plate is close and causing vacuum to suck the diaphgram. When the throttle plate is opened, vacuum at the line will be little/reduced because some vacuum got transferred/distributed to the air box. It is kind of like the pressure regulator vacuum got bleeded off to the atmosphere. The document is for Toyota. Maybe aerostar is differnet. Thanks.
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4.0L having problems!
dtong_ck:
You are partially correct, however the confusion lies in the "kind" of vacuum referred to. Vacuum orginating directly from the manifold works like your description. However, most EFI engines use what is called a ported vacuum source, which operates almost opposite what you would think. Ported vacuum (vacuum only present when the engine is just off idle) is normally used to control many of the various assistive devices found on newer engines. I may be mistaken here as I have no references, but I believe the fuel pressure regulator is operated from the ported vacuum source and thus, there would be no vacuum at steady idle, only when the engine moves off idle.
Sorry for the confusion.
You are partially correct, however the confusion lies in the "kind" of vacuum referred to. Vacuum orginating directly from the manifold works like your description. However, most EFI engines use what is called a ported vacuum source, which operates almost opposite what you would think. Ported vacuum (vacuum only present when the engine is just off idle) is normally used to control many of the various assistive devices found on newer engines. I may be mistaken here as I have no references, but I believe the fuel pressure regulator is operated from the ported vacuum source and thus, there would be no vacuum at steady idle, only when the engine moves off idle.
Sorry for the confusion.
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From: PNW
4.0L having problems!
[updated:LAST EDITED ON 16-Dec-02 AT 03:59 PM (EST)]Measuring vacuum in the climate control system (which comes off the octopus at the rear of the intake manifold, as does the fuel pressure regulator vacuum line), I got about 20 inches at idle, which is pretty high, when I was doing some troubleshooting. The fuel pressure regulator needs to be exposed to manifold vacuum. It uses manifold vacuum as a reference so that a constant pressure drop is maintained across the injector.
Regarding the funny running motor, are you sure you have the spark plugs hooked up right? In other words, the correct wire from the coil pack is going to the correct plug?
Regarding the funny running motor, are you sure you have the spark plugs hooked up right? In other words, the correct wire from the coil pack is going to the correct plug?
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From: Bowling Green USA
4.0L having problems!
yes the plugs are hooked up right. I double checked.
someting is majorly wrong here! the truck is now idleing high, and the tach is landing on 7000 when I turn off the truck. when I say idleing high I mean like 2000. I think their is probably a corralation but I just don't know what would cause this?
someting is majorly wrong here! the truck is now idleing high, and the tach is landing on 7000 when I turn off the truck. when I say idleing high I mean like 2000. I think their is probably a corralation but I just don't know what would cause this?
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From: PNW
4.0L having problems!
Regarding the idle, make sure there are no vacuum leaks. Also, what is your idle speed when the IAC is unplugged? It should be around 6-700 rpm. You can adjust it with the set screw on the thottle with the IAC unplugged to get it to the right level. What kind of tach are you using (aftermarket or OEM)? Have you verified that the engine speed is indeed running 2000 rpm? The reason I ask this is that some tachs will read 2 times the rpms because the spark plugs fire once every revolution, as opposed to the more normal (used to be anyway) once every two revolutions. I run into this problem when I have to go through the emissions test. Their tach reads twice the actual rpm because it counts the number of times the spark plugs are fired.
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From: Bowling Green USA
4.0L having problems!
when the IAC is unplugged it runs at 6-700 rpm's but it is deffinatly running at 2000. you can hear the motor running at a higer rpm. also why would the tach flop to 7000 instead of going to 0? I checked the vacume lines and all are ok, no cracks crap like that. I also cleaned the IAC with carb cleaner and no change.
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From: PNW
4.0L having problems!
OK, sounds like your calibrated ear agrees with the tach, so the tach reading is believable. It appears as though the IAC is getting voltage when it shouldn't. There are a couple things that I can think of that could cause this. On some Fords, there is a power steering pressure switch that closes under high pressure (such as when turning the steering wheel for parking) and this kicks in the IAC so the engine speed won't drop. There is also a similar situation when the AC is on, due to the increased load of the compressor. If either the AC switch or power steering pressure switch is stuck closed, then this could be the source of the problem. There could also be a short.
I'll dig into the wiring diagrams and see if there is anything I can think of that would cause the tach to go to 7000.
By the way, have you driven with the IAC unplugged and if so, how does it run?
I'll dig into the wiring diagrams and see if there is anything I can think of that would cause the tach to go to 7000.
By the way, have you driven with the IAC unplugged and if so, how does it run?
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From: Bowling Green USA
4.0L having problems!
with the IAC unpluged it runs rough but more consistant to 6-700 but it still hesitates. I unpluged the MAF and pluged in the IAC and it doesn't hesitate but it wants to die when it is at an idle. should it do this without the MAF unpluged? the only thing else I can come up with is a bad computer.
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From: PNW
4.0L having problems!
[updated:LAST EDITED ON 20-Dec-02 AT 03:19 PM (EST)] When I've had the MAF unplugged, I've never noticed any difference in the way the engine ran, other than the check engine light came on. Have you noticed any difference in the way the engine runs when it's cold vs. when it's fully warmed up? Also, maybe a compression check is in order. Or, if you have the tool, do a leakdown check. That should give you some idea of the condition of the engine.
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From: Bowling Green USA
4.0L having problems!
ok this is what it is doing:
when you start it, it runs rough and will die a couple of times.
once it will run on its own it has a very eardic idle. any where between 700-1200rpms
when it is running at 700 it jumps realy hard! so hard it will pop the hood.
when it is running at 1200 it couldn't run better other then the constant tapping and high idle.
the motor rattles when you first start it but then when it is under load it has a tick or knock but when I put a screwdriver to the oilpan, and valvecover I hear nothing.
this is all I have done:
replaced all pushrods and 6 rockerarms
had the crank position sensor, coil pack, and EDIS checked.
put in new plugs and wires
had auto zone check the sensors(only ones that came up bad were the O2 and a bunch of trnsmision sensors but the motor came from a auto and I'm using a mitsu 5spd so that souldn't matter. I also put in a new O2.)
checked the timing gears, chain and tensioner. all ok
while I had the cover off I checked the first two rods and they seemed tight so I'm assuming the others are ok.
also as above I pulled the vacume on the fuel pressure regulator and it seemed to be in good shape.
when you start it, it runs rough and will die a couple of times.
once it will run on its own it has a very eardic idle. any where between 700-1200rpms
when it is running at 700 it jumps realy hard! so hard it will pop the hood.
when it is running at 1200 it couldn't run better other then the constant tapping and high idle.
the motor rattles when you first start it but then when it is under load it has a tick or knock but when I put a screwdriver to the oilpan, and valvecover I hear nothing.
this is all I have done:
replaced all pushrods and 6 rockerarms
had the crank position sensor, coil pack, and EDIS checked.
put in new plugs and wires
had auto zone check the sensors(only ones that came up bad were the O2 and a bunch of trnsmision sensors but the motor came from a auto and I'm using a mitsu 5spd so that souldn't matter. I also put in a new O2.)
checked the timing gears, chain and tensioner. all ok
while I had the cover off I checked the first two rods and they seemed tight so I'm assuming the others are ok.
also as above I pulled the vacume on the fuel pressure regulator and it seemed to be in good shape.
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