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New ECU still runs rough

RADIOACTIVE_TOOL_SHED___

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1993 Ford explorer xlt
Alright guys i have replaced alot of parts on my explorer in Hope's that it would have a better idle I have had it smoke checked for vacuum leaks I have had the fuel pressure checked all was good I have never had a CEL my CEL light bulb illuminates on start up I have replaced the maf sensor IAC valve plugs and wires computer nothing has seemed to really help it I have a new motor craft throttle position sensor on the way hoping that will fix my issue oh and I replaced the coolant temperature sensor for the ECU basically what the truck does is when I first start it up the idle will surge slightly then once it's warm it's have a slightly rough idle would bad 02 sensors cause this?
 


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RADIOACTIVE_TOOL_SHED___

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1993 Ford explorer xlt
Alright guys i have replaced alot of parts on my explorer in Hope's that it would have a better idle I have had it smoke checked for vacuum leaks I have had the fuel pressure checked all was good I have never had a CEL my CEL light bulb illuminates on start up I have replaced the maf sensor IAC valve plugs and wires computer nothing has seemed to really help it I have a new motor craft throttle position sensor on the way hoping that will fix my issue oh and I replaced the coolant temperature sensor for the ECU basically what the truck does is when I first start it up the idle will surge slightly then once it's warm it's have a slightly rough idle would bad 02 sensors cause this?
Alright guys i have replaced alot of parts on my explorer in Hope's that it would have a better idle I have had it smoke checked for vacuum leaks I have had the fuel pressure checked all was good I have never had a CEL my CEL light bulb illuminates on start up I have replaced the maf sensor IAC valve plugs and wires computer nothing has seemed to really help it I have a new motor craft throttle position sensor on the way hoping that will fix my issue oh and I replaced the coolant temperature sensor for the ECU basically what the truck does is when I first start it up the idle will surge slightly then once it's warm it's have a slightly rough idle would bad 02 sensors cause this?
Forgot to mention no stored codes, compression is in good spec as well again the only time it runs rough or surges is at idle goes down the road perfectly it never stalls either or acts like its gonna die
 




ChildIdenticant

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Have you measured fuel pressure? Have you measured vacuum? You noted trans fluid was entering vac line, did you change your modulator?
 




Roadrunner777

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When cold, the engine runs off of a pre-programmed calibration in the ECU. At some point as it warms up, it changes over to a sensor feedback scheme, which does, in fact, involve the O2 sensors. So, to the question, could bad 02 sensors cause this, the answer is yes, they could.

Is it the most likely issue? Well, I like what you have done so far with chasing down the more probable causes. You changed out the MAF which would have been one of my first thoughts. I assume you got a new MAF? Junkyard MAF's can have issues. I bought a used MAF from someone on Ebay and it looked nice and clean but it was actually bad. Just saying, if you bought a used MAF you shouldn't rule it out yet. I liked the idea of the IAC, easy to change and not very expensive, same issue with used ones though.

You have ruled out fuel pressure. Did the readings follow the profile, that is, did the pressure drop slightly when you reved the engine? I'm trying to decide if the fuel pressure regulator is in play.

You have ruled out vacuum leaks. That's good, that's a tough one.

You replaced the plugs. Were the old ones uniformly similar in wear and color? I like your thinking on this, could be weak spark. So, that puts the coil and ignition control module on the table.

I think somewhere along the line I would get the ECU on a bench and check for bad capacitors. That's a freebie to check without actually replacing an expensive part on a chance.

Or O2 sensors. They are not particularly expensive, it's more the work of replacing them.

Assuming you replaced all the parts you did with new parts, and assuming the fuel pressure followed the profile, I would do the following:
1) Check the ECU for bad capacitors
2) Replace the O2 sensors
3) Replace the ignition control module
4) Replace the coil

It's too bad you don't have codes to rule some of this out without buying a bunch of parts. But, I do like the ECU bad capacitors for this... there was been a rash of bad capacitors reported here lately and they will eventually fail with age. Good Luck!
 




RADIOACTIVE_TOOL_SHED___

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1993 Ford explorer xlt
Forgot to mention no stored codes, compression is in good spec as well again the only time it runs rough or surges is at idle goes down the road perfectly it never stalls either or acts like its gonna die
Also cleaned throttle Body and changed the air filter along with the fuel pump and fuel filter
Have you measured fuel pressure? Have you measured vacuum? You noted trans fluid was entering vac line, did you change your modulator?
Yes vacuum system was checked when I had the transmission rebuilt compression has been checked along with fuel pressure
 




RADIOACTIVE_TOOL_SHED___

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1993 Ford explorer xlt
When cold, the engine runs off of a pre-programmed calibration in the ECU. At some point as it warms up, it changes over to a sensor feedback scheme, which does, in fact, involve the O2 sensors. So, to the question, could bad 02 sensors cause this, the answer is yes, they could.

Is it the most likely issue? Well, I like what you have done so far with chasing down the more probable causes. You changed out the MAF which would have been one of my first thoughts. I assume you got a new MAF? Junkyard MAF's can have issues. I bought a used MAF from someone on Ebay and it looked nice and clean but it was actually bad. Just saying, if you bought a used MAF you shouldn't rule it out yet. I liked the idea of the IAC, easy to change and not very expensive, same issue with used ones though.

You have ruled out fuel pressure. Did the readings follow the profile, that is, did the pressure drop slightly when you reved the engine? I'm trying to decide if the fuel pressure regulator is in play.

You have ruled out vacuum leaks. That's good, that's a tough one.

You replaced the plugs. Were the old ones uniformly similar in wear and color? I like your thinking on this, could be weak spark. So, that puts the coil and ignition control module on the table.

I think somewhere along the line I would get the ECU on a bench and check for bad capacitors. That's a freebie to check without actually replacing an expensive part on a chance.

Or O2 sensors. They are not particularly expensive, it's more the work of replacing them.

Assuming you replaced all the parts you did with new parts, and assuming the fuel pressure followed the profile, I would do the following:
1) Check the ECU for bad capacitors
2) Replace the O2 sensors
3) Replace the ignition control module
4) Replace the coil

It's too bad you don't have codes to rule some of this out without buying a bunch of parts. But, I do like the ECU bad capacitors for this... there was been a rash of bad capacitors reported here lately and they will eventually fail with age. Good Luck!
I had the fuel pressure tested at a shop that I trust along with compression and I the vacuum system my capacitors wer actually leaking it didn't make much of a difference when I replaced the ECU tho the plugs are all wearing about the same, I may order up a new maf sensor I got it from the junkyard everything else has been brand new motor craft parts that ive used gonna try a new throttle position sensor First if that doesn't work 02 sensors if it's still doing it coil pack and ICM If I can't fix it with all of that I could possibly have a ground issue with the ecu somewhere?
 




RADIOACTIVE_TOOL_SHED___

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Alright guys i have replaced alot of parts on my explorer in Hope's that it would have a better idle I have had it smoke checked for vacuum leaks I have had the fuel pressure checked all was good I have never had a CEL my CEL light bulb illuminates on start up I have replaced the maf sensor IAC valve plugs and wires computer nothing has seemed to really help it I have a new motor craft throttle position sensor on the way hoping that will fix my issue oh and I replaced the coolant temperature sensor for the ECU basically what the truck does is when I first start it up the idle will surge slightly then once it's warm it's have a slightly rough idle would bad 02 sensors cause this?
UPDATE I replaced the throttle position sensor a minute ago with a new motor craft one still runs rough thinking I'm gonna replace the maf and 02 sensors with some new motor craft units
 




fastpakr

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Stop replacing parts.

Clearly there's a root cause here, and throwing parts at it is just draining your wallet. So take a breath, and don't order -any- more parts until you know you're replacing a bad one.

Honestly, what you're describing still sounds like a vacuum leak to me. Even if you've tested it once, I'd go back and very thoroughly check that. And consider checking the torque on all the intake manifold bolts.
 




RADIOACTIVE_TOOL_SHED___

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Stop replacing parts.

Clearly there's a root cause here, and throwing parts at it is just draining your wallet. So take a breath, and don't order -any- more parts until you know you're replacing a bad one.

Honestly, what you're describing still sounds like a vacuum leak to me. Even if you've tested it once, I'd go back and very thoroughly check that. And consider checking the torque on all the intake manifold bolts.
I retortorqed the intake manifold bolts back to spec I have no codes or anything I checked for vacuum leaks for months and then I finally gave up and had a shop check it with a smoke machine it's driving me crazy and if it actually was a sensor seems like it would throw a check engine light cause if you unhook say the maf for example the CEL will illuminate the shop told me I shouldn't be worried the way it's running I want it to run like new tho lol even if it's got 340k miles
 




fastpakr

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What do you get for manifold vacuum?
 








92exp4x4

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Fuel injectors? Could they be weak, leaking, or loaded with crud? Perhaps if they are not shutting off completely and leaking a bit, or have a bad spray pattern. However, I would think the feedback system would indicate a rich condition and the system should set a code at that point. I dunno man, you seem to have checked almost everything.
 




Gadget X

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One thing you could try would be to run the tank almost empty, then pour a bottle of GOOD fuel injector cleaner in and put about a half-tank of top-tier 93 octane gas in it. Drive it like you stole it for a few miles, and see if that clears it up any. You could also "seafoam" it. They have one now that you spray into the intake with a special tube, so you don't have to pour it into a vacuum line, and I got good results from that. Mine just hit the half-million mile mark, and I do both of those things at least annually.
 




RADIOACTIVE_TOOL_SHED___

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One thing you could try would be to run the tank almost empty, then pour a bottle of GOOD fuel injector cleaner in and put about a half-tank of top-tier 93 octane gas in it. Drive it like you stole it for a few miles, and see if that clears it up any. You could also "seafoam" it. They have one now that you spray into the intake with a special tube, so you don't have to pour it into a vacuum line, and I got good results from that. Mine just hit the half-million mile mark, and I do both of those things at least annually.
Im currently running a bottle of injector cleaner in the tank will try seafoam next I found some paperwork that came with it in 2005 it was taken to a ford dealer for this problem they professionaly cleaned the injectors and replaced the ECU, very strange to me that it's never thrown any codes really starting to wonder if something seriously is wrong with it since I'm assuming the dealer could never get it fixed, it was parked in 2007 until I got it I'll try seafoam and if that doesn't do it I'm going to just replace all the vacuum lines and hope for the best even tho I had the vacuum system smoke checked,
 




92exp4x4

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What about eliminating all vacuum systems other than those that need to be for running the engine? There is no vacuum advance on these, so I think you could get some rubber plugs and seal off the manifold vacuum tree and test it. If you drive the vehicle, you would need to have the vacuum brake booster and trans modulator hooked up, but it may tell a lot about your issue doing this.

A smoke test won't show a bad diaphragm in the brake booster, or a bad trans modulator unless the tech looks specifically for those things. I'm more inclined to use a vacuum pump and a gauge to test individual systems, but that takes time. Most shops are flat rate. They want a solution as fast as possible or they don't want to mess with it.
 




RADIOACTIVE_TOOL_SHED___

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What about eliminating all vacuum systems other than those that need to be for running the engine? There is no vacuum advance on these, so I think you could get some rubber plugs and seal off the manifold vacuum tree and test it. If you drive the vehicle, you would need to have the vacuum brake booster and trans modulator hooked up, but it may tell a lot about your issue doing this.

A smoke test won't show a bad diaphragm in the brake booster, or a bad trans modulator unless the tech looks specifically for those things. I'm more inclined to use a vacuum pump and a gauge to test individual systems, but that takes time. Most shops are flat rate. They want a solution as fast as possible or they don't want to mess with it. I have not thought about the brake booster, ik the modulater on the Trans is good just had it replaced when the transmission was rebuilt, oh yeah one more thing I've thought about dose anyone happen to know what the valve looking thing on the drivers side of the engine it has some kind of line attaching to it cose to to the radiator wonder if that thing affects the idle
 




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