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Poor idle, NO power

Discussion in 'Stock 2002 - 2005 Explorers' started by JW, April 22, 2017.

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    1. JW

      JW Third Gen Collector Elite Explorer

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      2003 4.6L has a bad idle and barely enough power to crawl down the street.

      - Fuel pressure is 65 PSI
      - Tested several injectors and got 12-14 ohms
      - Tested several coils and got resistance across the terminals of about 0.5 ohms
      - Tested the TPS and it seems to be fine
      - Tested the MAF based on a thread from 2000StreetRod. The specs don't match, but the existing MAF is comparable to a remanufactured replacement. MAF has been cleaned.
      - Plugs are brand new NGK iridium and show a light gray color.
      - No apparent vacuum leaks. Manifold bolts are tight.

      History: the long block in the truck is new. I replaced it because the old one exhibited the issues I'm seeing now, and I also had bad oil pressure on an aftermarket gauge. Carryover items from the old engine include a Trick Flow intake manifold and throttle body. The combo ran great for about four months prior to drastically losing power. Power output gets worse as the engine reaches operating temp. No overheating. EGR is not currently connected (needs to be modified, as the tube interferes with the upper plenum on the Trick Flow), so I do get a code for that. Feels like it's misfiring but no misfires are being recorded. If I slowly open/close the throttle, it will continue to run, albeit poorly. If I get on and off it fast, it'll rise up and then stall. When I experienced the original issue, it had run great up until it didn't; the loss of power was very sudden.

      I have codes for the EGR, of course, and also saw some from when I disconnected an injector and a coil to try and trigger a misfire code (which it didn't, oddly enough). I also had codes for primary and secondary fuel pump circuits, which I'm trying to replicate (I started it without the fuel pump relay once, so that may have been the cause). I cleared the codes and am letting it idle now to see what comes up.

      Additional testing - in park, throttle completely to the floor, I can't get over 1500 RPM.
       
      Last edited: April 22, 2017
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    3. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      I had a similar problem on my V6 when the common ground wire for the injectors on one bank was open. It was difficult to find because the PCM assumed that the O2 sensor on that bank had failed and used the O2 sensor on the good bank. I suggest making sure fuel is getting to both banks and the injectors on both banks are pulsing.
       
    4. JW

      JW Third Gen Collector Elite Explorer

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      Sorry, not sure how to go about doing that. I know about the screwdriver trick to listen for injector pulses, but today I can't even get the truck to run long enough to do that. It's slowly deteriorating. And still no codes. I've considered the possibility of plugged cats but can't figure out how that could happen suddenly.

      Would a bad pump or filter still allow proper fuel pressure, but not enough flow to properly feed the engine?
       
    5. JW

      JW Third Gen Collector Elite Explorer

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      Update...

      Replaced the fuel filter, because I had one and in 178K miles, it hadn't been done. No change.

      Currently, the down pipes to the upstream cats are disconnected, and it runs great but won't idle. I'm going to remove the (brand new) IAC and clean it when it cools off.
       
    6. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Before it wouldn't run above 1,500 rpm. Now you state it runs great but won't idle. To me that's quite a change. Was it because of replacing the fuel filter or disconnecting the down pipes? A bad IAC valve won't result in no power - just poor idle control. Engine idle is degraded when there are only exhaust manifolds connected.
       
    7. JW

      JW Third Gen Collector Elite Explorer

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      I tested after the filter replacement and had no change at all. With the down pipes disconnected, it runs really smooth but struggles to hold idle speed. I figured that could be the IAC or that it needs a tune (new engine has different cams in it, but nothing radical). Hearing that disconnected exhaust may result in poor idle adds to the possibilities there. It revs freely now, where before it felt like something was choking the life out of it.
       
    8. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Apparently there is an exhaust restriction. I suggest a visual inspection of the tailpipe (and tip if there is one) for dents or collapsed bends. Also check for something stuck in the tailpipe that could block airflow. Since the downpipes are disconnected from the exhaust manifolds you might try blowing air thru the exhaust system. You might be able to adapt a leaf blower.
       
      Last edited: April 24, 2017
    9. JW

      JW Third Gen Collector Elite Explorer

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      That's a good idea. We'll rig something up for that.
       
    10. JW

      JW Third Gen Collector Elite Explorer

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      OK, apparently it's not the exhaust. It's still way down on power. Idle is sometimes better but still not drivable. What else should I be looking for? I'm about ready to put the stock TB and manifold back on, as it was the last change (albeit three months before the issues started).
       
    11. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      There are a lot of possibilities and I don't know your actual configuration. Are you using the stock MAF sensor or did you install a higher flow unit? Since the engine will now idle did you try listening for injector pulsing? I've had luck on my engine using a length of flexible hose with one end near an injector and the other near my ear. You posted that the engine loses power as the operating temperature increases. Do you have any way to determine if the AFR is lean or rich? Is there black smoke exiting the exhaust pipe? Have you performed a compression test? Have you examined the condition of the new plugs since they were installed? According to my 2003 wiring diagrams the cylinder head temperature sensor provides data to the PCM that passes the data to the instrument cluster microprocessor. Do the instrument cluster engine temperature readings seem reasonable?
       
    12. JW

      JW Third Gen Collector Elite Explorer

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      Current, complete configuration is below.

      Are you using the stock MAF sensor or did you install a higher flow unit?
      Stock

      Since the engine will now idle did you try listening for injector pulsing? I've had luck on my engine using a length of flexible hose with one end near an injector and the other near my ear.
      Not yet but I will

      You posted that the engine loses power as the operating temperature increases. Do you have any way to determine if the AFR is lean or rich? Is there black smoke exiting the exhaust pipe?
      No black smoke. Exhaust smells as it should. I don't believe I have a way to check AFR (I don't have a separate gauge or wideband O2s; my OBD scanner has some logging capabilities but I haven't messed with it yet).

      Have you performed a compression test?
      Not specifically, as this engine/config is exhibiting the same issue as the previous one.

      Have you examined the condition of the new plugs since they were installed?
      Not all of them, but the ones I have looked at are light gray and dry (I've examined at least one from each bank).

      According to my 2003 wiring diagrams the cylinder head temperature sensor provides data to the PCM that passes the data to the instrument cluster microprocessor. Do the instrument cluster engine temperature readings seem reasonable?
      Yes; no signs of overheating at all, though I suppose if I pushed it harder (and it's running really lean), it would probably overheat.

      Short Block:
      Block - Stock Romeo aluminum, 0.020" over
      Crank - Stock Romeo 6 bolt
      Main bearings - Clevite
      Main bolts - ARP
      Side bolts - ARP
      Rods - MMR I-beam/ARP bolts
      Rod bearings - Clevite
      Pistons - Manley/MMR
      Rings - Total Seal
      Oil pump - Hurricane (MMR)
      Front main seal - Fel-Pro stock replacement
      Rear main seal -MMR billet housing

      Long Block:
      Heads - PI, MMR Stage 2 ported
      Head bolts - Fel-Pro stock replacement
      Head gaskets - Fel-Pro stock replacement
      Camshafts - Comp XE262H
      Valves - Stock
      Springs - Manley
      Rockers - Stock
      Lash adjusters - Stock
      Cam sprockets - Melling
      Cam timing - Straight up, matched side to side
      Crank sprocket - Stock
      Timing chains, guides, tensioners - Cloyes stock replacement
      Reluctor wheel - MMR billet

      Top End/Ancillary:
      Intake manifold - Trick Flow Street Burner
      Throttle body - Trick Flow 75mm
      Injectors - Stock 19 lb/hr
      Ignition - Stock
      Spark Plugs - NGK Iridium 7164, 0.056" gap
      Air intake - K&N cone, custom intake tube
      MAF - Stock
      Exhaust manifolds - JBA headers
      Exhaust system - Stock
      Fan - Ford Thunderbird OEM Electric, Flex-A-Lite controller
      Water pump - MMR Performance
      Pulleys - Steeda underdrive, stock alternator pulley
       
    13. JW

      JW Third Gen Collector Elite Explorer

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      If I understand the throttle position sensor test properly, I should see 5 volts in, and from 1 to 5 volts out depending on throttle position, with a pretty linear progression as the throttle is opened. Is that correct?
       
    14. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Yes, although the range will probably only be from about 1 volt to about 4.7 volts.
       
    15. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      My point on the engine temperature displayed on the instrument cluster was not about overheating. The PCM varies the AFR based on the engine temperature - rich for a cold engine and normal for a warm engine. If the gauge shows cool when the engine is cold started and normal when the engine has had time to warm up then the engine temperature is probably not an issue.
       
    16. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      As I recall, Ford enabled the rev limiter in Park and Neutral around 2001. I think the limit is 3,000 rpm but that is well above the 1,500 at WOT that you experienced according to your first post.

      Since you have a custom engine configuration I suggest a compression test of at least one cylinder in each bank. That will build confidence in camshaft timing, valve functionality and head gasket integrity. Make sure the throttle plate is wide open for the test.

      Some tuners encourage a custom tune when the throttle body diameter is changed significantly. However, it is my opinion that your loss of power is not attributable to the increased throttle body diameter.

      I'm not familiar with your camshaft specifications but if the changes are mild compared to stock the idle would be slightly uneven but acceptable.

      In my opinion the stock 4.6L alternator output capability is marginal. I think it is only 100 amps. If you have an underdrive crank pulley and a stock alternator pulley then the available output will be decreased. What is the start up draw of the T-bird electric cooling fan motor? Does the Flex-A-Lite controller provide a soft start? I suggest monitoring the battery voltage when the fan starts rotating. If the voltage drops excessively the PCM and the ignition voltage may be adversely impacted. This could be an explanation of why the engine loses power when the engine is warm and the fan starts running.
       
    17. JW

      JW Third Gen Collector Elite Explorer

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      Thanks for continuing to check in. Let me fill in some gaps.

      - The fan and underdrive pulleys have been in for close to five years. The controller does seem to have a soft start, though I don't know offhand what the current draw of the fan is (I followed JoshMcMadMac's install thread and used the same parts). I don't see a voltage drop when the fan engages.
      - Alternator and battery are six months old.
      - Intake and throttle body are about nine months old. I had a really good three month run with the combo installed.
      - The power output issue is exactly the same as it was with the old engine, which leads me to believe something that carried over is the culprit. All of the electronics transferred over - sensors, injectors, coils - as well as the rails, upgraded intake and throttle body, everything beyond the new long block. Idle is more erratic, but that could simply be the camshafts being thrown into the mix.
      - The power loss was immediate and drastic. It mimicked the performance/behavior of the original engine when it lost oil pressure, and I had signs of bad oil pressure with the previous engine after it lost power, which is why I went in the direction I did (and built an engine I would have built within a couple of years anyway).

      I'll do a compression check this weekend. I did get to see the front of the engine before the cover went on, and the cams/timing gear all seem to be correct, but a compression check will rule that and many other things out. I also have a new Motorcraft TPS on the way, as what I've read suggests a bad one can cause a whole host of issues. The current one *tested* good, but it's a cheap experiment.
       
    18. boominXplorer

      boominXplorer Elite Ranger Elite Explorer

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      I'm thinking the MAF is reading off. Do you have a scanner to bring up the stft and ltft (fuel trims)
       
    19. Turdle

      Turdle I bake stuff Staff Member Moderator Elite Explorer

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      If you have a vacuum gauge, I would suggest checking idle vacuum.

      If the gauge is not steady post a video of it with audio please.
       
    20. JW

      JW Third Gen Collector Elite Explorer

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      My scanner does do long and short term fuel trims. But I don't know what they mean. I can post what I'm seeing, though.

      I did put in a different (non-Motorcraft, FWIW) MAF and got no change as a result. That went back to the store.

      I need to get a vacuum gauge as well.
       
      Last edited: May 2, 2017
    21. JW

      JW Third Gen Collector Elite Explorer

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      Update: She's home.

      Since completing the engine install, I've only made two changes - I tweaked the idle adjustment screw on the TrickFlow throttle body, and I replaced one vacuum line (no apparent splits or anything, but the very end of it was starting to go). That's it.

      Idle is rock solid. Vacuum is a little low at idle (14-15) but perks right up above 1000 RPM. It struggles a bit over 2500 RPM or so, but I suspect that's a tuning issue (it's probably leaning out). I ran graphs for the upstream O2 sensors and short term fuel trims but don't really know what I'm looking at. The O2s varied between 0 and 1 volt and the fuel trims were between roughly -5 and +5%. Again, I have no idea what any of that means.

      Current plan is to wait for my SCT iTSX to arrive from Unleashed Tuning and get that uploaded. Then we'll see how it goes.
       
    22. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      A different throttle body should not make a significant change in AFR at 2,500 rpm. The MAF sensor measures the higher air flow (if any) and the PCM compensates. The AFR might be lean above 5,000 if there is enough increase in air flow to peg the MAF sensor.

      The PCM cycles the AFR between slightly rich and slightly lean from optimum. This is reflected in the short term fuel trims (STFTs). The pre-cat O2 sensors should cycle between about 0.2 and 0.8 volts. The long term fuel trims (LTFTs) should be fairly constant at less than + or - 5%.

      It is desirable to have reliable performance before loading a tune.
       
    23. JW

      JW Third Gen Collector Elite Explorer

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      OK, did some more testing. Performance seems to be inversely proportional to throttle position. At part throttle, it works as expected. But anything more than about half open and it goes nowhere. Lots of intake noise but no power. Long term fuel trims are generally around 7-9% with spikes into the 10-12% range (steady at 7 or so at idle, and consistently higher on bank 1 vs bank 2 by about 0.5%). Short term is jumpy between -2 and 4 at idle. Idle RPM is around 800.
       
    24. 2000StreetRod

      2000StreetRod Staff Member Moderator Elite Explorer

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      Fuel trims at idle are not very useful because there is very little load on the engine. 0.5% LTFT difference between banks is inconsequential. As I recall the PCM will adjust the LTFTs to keep the STFTs within + or - 30%. Is the vehicle drivable? If so, I suggest turning off the O/D and driving at a constant 1,800 rpm or so and check the fuel trims. It may take two people in the vehicle to do it safely. If the LTFTs are greater than +5% then the engine is running lean. Does your engine have a crankcase breather that vents to the atmosphere? If so, then unmetered air (not measured by MAF sensor) can indirectly enter the intake system resulting in a lean condition. I noticed that you live in California. Autos produced to be sold in CA frequently have lower than standard flow fuel injectors to meet the stricter CA anti-pollution requirements. If your PCM is programmed for 19 lb/hr injectors and you have 13 lb/hr injectors the engine will run lean - especially after mashing the accelerator (tip in) or under load.
       
    25. JW

      JW Third Gen Collector Elite Explorer

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      It is drivable, and I discovered last night that my OBD app will log to a CSV file any parameter the PCM will output. I'm about to go take it out for a bit, so the test criteria is very helpful. I'll post the test results when I get back.

      I believe it has the 19 lb/hr injectors (orange).

      No breather to atmosphere. I have the PCV connected to the Trick Flow intake with a rubber hose, and the driver's side vent is connected to the intake tube the same as stock. PCV isn't stuck.
       
    26. JW

      JW Third Gen Collector Elite Explorer

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      Last edited: May 10, 2017

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