'03 GT fresh rebuild, engine severely cutting out on hard acceleration

Bowtierebel

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Hey guys. First post after a long time of reading and searching forums. I have what I think is a strange problem. I've read and searched, but is cannot find the exact information to help me, so I'm hoping that someone can help me. This will probably be a long post so that I can describe what I have going on and what I've done to try and resolve it. Ok, I recently finished installing the fresh rebuilt engine. I used most all of the stock parts like injectors, COPs, ect. Of course I had to replace the intake manifold though. The problem is that when sitting still and flooring the gas the engine falls on its face as its it is misfiring terribly. If I start to roll and hit the gas to about 3/4, if seems to accelerate ok. There are no codes or pending codes. I have removed and checked every part including the COPs, injectors, IAC, MAF, EGR, DPFE, EGR sensor, TPS, FP REGULATOR sensor, I have checked them electrically, physically for voltage, pressure/vacuum using a gauge. I checked vacuum line/hoses and sprayed around checking for leaks. I double checked the fuel rail pressure with external guage and it shows 42-47psi at idle and when bumping throttle. I have factory service manuals I'm also using. I do have a bad ABS module that I am planning on sending out to bosch0004 to repair. I have really done due diligence trying to track down what's going on. I used my scanner to watch live data and see some that confuses me. The IAC does make the howling sound sometimes, but it's clean. Some of the data is as follows. TPS shows 18-22% at idle, about 20% engine load, fuel pressure reads from 37-57psi depending on what I'm doing driving. It did spike up to 90psi once on the graph. The timing at idle is from 18-28° and actually drops down to 10° or so during normal acceleration. It has gone up to 38° while driving. No pinging. Idle rpms float about 725-750 in park and drop to 490-550 in drive. It's as if the ECM is having a hard time getting the values correct. I've forgotten any values just ask. I probably have them. After spending hours checking, testing, troubleshooting I was I sitting in the car and noticed that the traction control off switch will not light up at all. I know it's a momentary switch and I checked it out to see if it was closing when pressed and it is. I began to think that maybe the bad ABS module may be causing the ECM to not work correctly causing the weird timing, along with the other values. It's as if the traction control system is causing the engine management system to cut out the cylinders when I floor the gas and only when I floor it from a stop. I've tried to find more onto on how this could be happening, but so far I'm having a hard time find much. I did find an awesome post about actually how the system works. This really made me wonder if the bad ABS module was causing this. I have not checked into the instrument cluster yet as so far I don't know what all I'd need to do. I do know the ABS module is getting power and the ground cuicuits are good. I also checked the resistance on the pins at the ABS module plug and it checked good. I know this is a long post, but I need help and hopefully once I figure this out, it may help someone else. Thanks.
 
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wmburns

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I double checked the fuel rail pressure with external guage and it shows 42-47psi at idle and when bumping throttle.
The fuel pressure seems too high at idle. Are you sure that the fuel rail pressure sensor (FRPS) intake vacuum reference line is connected and leak free? If the intake vacuum reference line is disconnected at idle the fuel pressure should jump to about 40 PSI as measured by an external gauge. Verify that when the intake vacuum reference line is re-connected the external fuel gauge drops down to about 32 PSI. This will verify that the fuel pressure is being intake vacuum referenced.
 

Bowtierebel

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The fuel pressure seems too high at idle. Are you sure that the fuel rail pressure sensor (FRPS) intake vacuum reference line is connected and leak free? If the intake vacuum reference line is disconnected at idle the fuel pressure should jump to about 40 PSI as measured by an external gauge. Verify that when the intake vacuum reference line is re-connected the external fuel gauge drops down to about 32 PSI. This will verify that the fuel pressure is being intake vacuum referenced.
I agree. That is one of the questions I have. BTW, the ABS module is off the car, for what it's worth. Ok, here is what I found. The battery had been disconnected overnight. I connected and started the car with the external fuel pressure gauge connected. Upon starting, the FP read 30-32psi and the car sounded much smoother. I removed the vac tube from FP regulator sensor n pressure increased to 40-42psi, reconnected n dropped to 26psi briefly n back up to 30-32psi. OBD reads about 10psi higher @ 39-42 while gauge reads 30-32psi. Idle speed fluctuates from 679-726 RPMS in park @ NO temp. Spark advance reads on OBD @ 18-25° at idle, Rev slightly to 1800 or so quickly n it drops to 5-8° until engine goes back to idle. Engine blowing a lot of white smoke on Rev up, but only bout 20 miles or so on it. MAF reads 0.01 lbs/'s at idle n goes up to 0.10 lbs/s on the Rev up. Now after warm up n these checks, the fuel pressure has increased to 38-42psi on gauge. Pulled vac hose off of FP sensor again n went up the 10psi or so to bout 52psi n back down to 40-42psi when reconnected. When the ECM was relearning after battery reconnect, it sounded smoother too. Also, I thought I saw the Intake air temp go blue on my scanner n read 328° for a split second, but I had just glanced at it n when I looked back it was back to 88°.
 

wmburns

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MAF reads 0.01 lbs/'s at idle n goes up to 0.10 lbs/s on the Rev up.
Your MAF readings seem very low to me. My 2000 GT reads about 0.8 at idle.

My Ford service manual states the hot idle MAF is 0.6-0.9 volts

MAF V 88 0 .6-.9 .8-1.2 1.4-1.9 DCV

What are the long term fuel trim (LTFT) values at stable idle? What are the LTFT values under load? IF the MAF under reporting we should expect that the LTFT is positive and large.
 

Bowtierebel

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Ok, the reading I was giving for the MAF was lbs/s from the scanner. Cold and warm idle shows 0.01 lbs/s and goes up to 0.03 lbs/s under load. LTFT bank 1 is 4.7%, bank 2 is 3.9% at idle. LTFT under load bank 1 is 2.3% and bank 2 is 1.6%. Of course fuel pressure shows high on scanner, but Guage is at 38-40psi. Oh, MAF volts at idle is .76 volts. Rev up to 2800 rpms n goes to 1.6 volts.
 

wmburns

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The LTFT's look reasonable. I still think your numbers being reported are off by a decimal point.

What have you done to rule out ignition break down (or spark blow out) under load? Might be handy to monitor LTFM and STFT as load is applied to see IF there's a fuel delivery problem at throttle change? What we are trying to find out is IF the misfire is being caused by a lack of fuel or a break down of spark.

What have you done to double check that the O2 sensors are "switching" in a reasonable manner?

The reference to white smoke bothers me.

Re-reading the opening post, YES the traction control system could cause it to fall on it's face. Traction control works by pulling timing. This would severally limit power production. Also seems like you could graph timing and RPM and see that. Also seems reasonable there's a PID for traction control active.
 

Bowtierebel

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I agree, it would seem that what I am reporting is off, but I promise I wrote exactly what the scanner is showing. I am using a foxwell NT-510 with loaded Ford software, only because I am waiting on my launch to get here. As for checking for proper spark, ect. I replaced COP boots, made sure spark plug wells are clean, checked COPs n injectors electrically n listened for proper sound in each, unplugged each individually listening to the engine and with a stethoscope. As far as spark blow out or break down, I was gonna do a cylinder balance test, but I have to wait till my Launch gets here. I certainly am not a super tech, so much of this I'm learning. It just seems that the parameters are wacky like 28° timing at idle, but it drops to 8-10° when driving. It's like it's backwards, but I'm watching it do it. Oh, what about the white smoke bothers you? If a cylinder balance test is the way to check what you mentioned earlier, I have to wait. Can I do anything else in the meantime?
 

Bowtierebel

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BTW, although it acting like the traction control is pulling power, I did see the scanner show that the traction control was off at last scan, but it sure is acting like it's not. Also the TC switch won't light up at all either. This is why I was wondering if the bad ABS module could be causing any of this since the circuit goes through the switch to the instrument cluster to ABS, which is off the car right now. The switch does pass power when pressed.
 

wmburns

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BTW, although it acting like the traction control is pulling power, I did see the scanner show that the traction control was off at last scan, but it sure is acting like it's not. Also the TC switch won't light up at all either. This is why I was wondering if the bad ABS module could be causing any of this since the circuit goes through the switch to the instrument cluster to ABS, which is off the car right now. The switch does pass power when pressed.
NOTE, traction control requires working ABS. Sooooo it should be expected that Traction controlled breaking is in-op IF ABS has an outstanding DTC. It's part of failure effects mode management.

Regarding the scanner. Don't confuse a "requested enable/disable mode" with an actual operation mode. For example one PID is likely what the switch setting is which is different than an operational mode when wheel slip is actively being detected.

What have you done to rule out a clogged exhaust system (or cat)?
 
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Bowtierebel

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NOTE, traction control requires working ABS. Sooooo it should be expected that Traction controlled breaking is in-op IF ABS has an outstanding DTC. It's part of failure effects mode management.

Regarding the scanner. Don't confuse a "requested enable/disable mode" with an actual operation mode. For example one PID is likely what the switch setting is which is different than an operational mode when wheel slip is actively being detected.
NOTE, traction control requires working ABS. Sooooo it should be expected that Traction controlled breaking is in-op IF ABS has an outstanding DTC. It's part of failure effects mode management.

Regarding the scanner. Don't confuse a "requested enable/disable mode" with an actual operation mode. For example one PID is likely what the switch setting is which is different than an operational mode when wheel slip is actively being detected.

What have you done to rule out a clogged exhaust system (or cat)?

What have you done to rule out a clogged exhaust system (or cat)?

I understand. I certainly may not have been interpreting what I was seeing correctly as far as the traction control on or off goes. I'm learning how to use this diagnostic information better. I've worked on vehicles most of my life, but now I'm getting deeper this side of things. That is why I ordered the Launch scanner. Well as far as the cats and exhaust go, all of the exhaust is brand new, except I did use the 2 original front cats. It's just the 2 front cats and pipes with 2 series 10 Flowmaster type mufflers. The white smoke doesn't smell like coolant really. I can't say for sure what I was actually looking at when I saw the traction control "off" on the scanner. What confuses me the most is the backwards timing, wacky EMC readings. I did notice the fuel pump showing that it was turning on and off with the car running and the pump showed to be running at 115% when on and down to 85% when it turned off. Of course this flipped back and forth very quickly. I didn't know a fuel pump could run at 115% at any time, let alone actually turn off and on. Then again it makes me question what's going on in the ECM.
 

wmburns

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The fuel pump in a return-less fuel system is driven by the fuel pump driver module (FPDM). The FPDM uses a pulsed DC on and off signal with a variable duty cycle. The duty cycle is varied in order to get the the correct fuel pressure in response to changing engine requirements. This is a similar system that is used to control power output on many modern PCM driven cars. The same thing is done for the O2 heaters and CV vent solenoid and many others. If looking at the voltage wave form on an O-scope you would see a square wave where the ratio of the on verses off time equaled the duty cycle.
 

Bowtierebel

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OK, thank you. Learned more. Well, at this point, what do you suggest I do? Wait for the Launch scanner to get here and do a power balance? Also, I ordered a coolant system pressure test kit. I've been meaning to get one for years and now I want to test to make sure I don't have a leaking head gasket or intake gasket/oring type seal. In the meantime I am sending out my ABS module to be repaired also. I really appreciate your help!
 

Bowtierebel

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BTW, I left the external fuel pressure gauge hooked up this afternoon while I was gone out with the wife. I just looked at it and it has leaked down to about 5 psi standing. when I left it was up well over 30psi. is this normal?
 

wmburns

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BTW, I left the external fuel pressure gauge hooked up this afternoon while I was gone out with the wife. I just looked at it and it has leaked down to about 5 psi standing. when I left it was up well over 30psi. is this normal?
No! The fuel system is supposed to maintain fuel pressure between starts. Possible leak down sources include:
  • Leaking fuel injectors. If a fuel injector problem is suspected consider InjectorRX.com.
  • leaking FRPS or fuel pressure regulator.
  • Leaking fuel pump check valve
  • leaking flexible fuel line between the fuel pump and gas tank hat.
 

Bowtierebel

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No! The fuel system is supposed to maintain fuel pressure between starts. Possible leak down sources include:
  • Leaking fuel injectors. If a fuel injector problem is suspected consider InjectorRX.com.
  • leaking FRPS or fuel pressure regulator.
  • Leaking fuel pump check valve
  • leaking flexible fuel line between the fuel pump and gas tank hat.
I've been doing some digging and checking to see if I may have overlooked something when checking the COPs and injectors. I checked the injectors and they all are showing the same resistance of 3.4 ohms or so. I found online, after looking at several sites and finding corresponding info, that these Bosch #280-150-561 injectors are high impedance and looks like they should be reading higher ohms somewhere around 12-15 ohms. I am not sure how they are working at all if the ohms are so low, but I'm not sure I'm seeing the correct range ohms. Maybe this is why I have white looking smoke coming out of my exhaust? IDK. I can't remember the COPs ohms for sure right now, but if you can tell me what I'm looking for, I can check them. I'm not sure how the injectors could be leaking down internally and still work well enough to leave the car at least driveable and not throw any codes. I haven't smelled and gas or seen any fuel around the injectors or fuel pressure sensor on the rail, so I think the injectors are leaking into the cylinders. One more thing I noticed is that since the white smoke has started, when the engine starts, I hear a metallic sound as if it may have fuel laying in the cylinders causing a hydro lock sound. It only lasts for a split second and of course it smokes like crazy. More so on the driver side. It's the kind of sound that makes you cringe. I also pulled all of the plugs and used a bore scope to look down into the cylinders. The plugs look good, slightly gray with a slight film of oily residue of the very outside edge around the ground. A couple had a very slight carbon layer around there too. This is a new rebuild with maybe 20 miles or so on it and a good bit of idle time. The cylinders looked good. I could see the cross hatch. the top of the pistons looks pretty good. Some dark with visible lighter in the area that the injector sprays, best I could tell. Still need help. I was going to check the items you listed above to find the fuel leakage, but got side tracked with the injector checking. Maybe this is why my timing is wacky.
 

wmburns

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Let me give you a couple of "food for thought" items.

Leaking fuel injectors: Don't confuse the electrical verses mechanical operation of the fuel injectors. It's quite possible for a fuel injector to work perfectly electrically but not seal mechanically. When doing a major motor project I always send the injectors for cleaning and flow testing before reusing them. I have had great luck with InjectorRX.com

Do you recall what the long term fuel trim (LTFM) values were? Generally speaking anything less than plus or minus 5 is considered good. As I recall your reported numbers were very good. Anytime the LTFT numbers are low this means in general that the fuel injectors are delivering the correct amount of fuel and the PCM is not having to make "adjustments".

Regarding the hydro-lock question. There really isn't much fuel in the system between starts. Certainly not enough to hydro-lock a motor. IMO any fluid in the cylinders is more likely to be coolant. As a reminder. If there's excessive fuel in the motor, what color is the exhaust? Black. If there's coolant in the motor, what color is the exhaust? White.

If there's coolant getting into this motor, EXPECT this to also decrease the service life of the cats.
 

Bowtierebel

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Well, I have been using the Foxwell NT-510 so far with the Ford software, but it's very annoying because it keeps freezing up and I have to restart the dang thing. I will be so glad when my Launch gets here and I can look at the graphs and even print or email the information. I am planning on sending out my injectors for service too. The biggest thing I've ran into checking the injectors is I do not know the correct ohms range they should be at. They all check as if they are low resistance coils, but the info online says they are high resistance coils and should be reading much higher. What is the resistance range each component should be in? I'd like to know this before I send them out because if they are too low, then I just need to buy new ones. When the engine was running I was able to hear all of them clicking and the COPs too. I don't know what I should be looking for on the resistance for either the injectors or the COPs. In all of the threads I've seen online they just say how to test them, but not what they should be reading. Can you tell me what resistance I need to be looking for on these two components please? In the meantime, I guess I'll have to wait until I get them back from being serviced and until in receive my new scanner to really continue. Then I can see what everything is doing and give much better information to you. BTW, when trying to check things physically without being able to do a power balance, I rechecked my spark plug gaps and they are all at .052-.054. I'm having to use a cheap gap gauge so it isn't as accurate, but as least they areally within the .052-.056 range. Honestly, I need to learn more about what everything means when looking at my scanner and how it corresponds to vehicle diagnostics.
 

Bowtierebel

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Ok, I wanted to give an update. The hurricane that came through here set me back working on the car. I have the the car running about as good as it's going to with the stock tune. Here is what all I did. I tested and replaced several of the parts that I either should have replaced with the rebuild or checked questionably. I sent out the ABS module to be repaired by Matt at Cheap ABS. He did a fine job. Traction control works fine now. I sent out the injectors to Injector RX to be cleaned and flow tested. I found that my IAC valve was sticking, replaced. The awful noise I mentioned that sounded like the crank was going to burst out of the block was simply the torque converter nuts were not tight, tightened and ordered new ones. I only used Motorcraft parts. I replaced the belt tension pulley and idler pulley because they were worn and making noise. Fuel pressure does not leak down now. It will hold indefinitely. The white smoke was unburnt fuel coming out of the exhaust. I replaced the COPs mainly because all but one were original and I felt that they may have been breaking down under load. I did a coolant system pressure test and all was good. It held 14 psi for an hour. I also did a cylinder compression test after I did a power balance test and saw cylinder #1 was not contributing. I could hear the miss too. I did this compression test after I did all of this other work and still had a misfire on cylinder #1. This time the PCM threw a code immediately as misfire detected within first 1000 RPMS and misfire on cylinder #1. It ended up that a piece of trash got into the injector and stopped it up. I'm not sure where the trash came from because I had just had them cleaned, but I was able to use the injector cleaning kit I have to cycle the injector solenoid and spray cleaner through it as I cycled the solenoid several times. At first the injector wouldn't even "click". After all of this the car is running very smooth compared to before. No misses or codes after a few miles of driving. I still see a couple things that don't look quite right, but the car needs to be tuned to the new larger cams and the head work. I am not going to worry about any readings that seems off until I get the car tuned. This car is an automatic transmission, stock gears and it's a convertible, so it's a bit heavier, but I was able to lay down 80 ft of rubber from a stop in drive and it sounded like it may have chirped second, but the car has 10 series mufflers on it so I am not sure of that. I know this is a long post, but hopefully this may help someone else. I also want to thank you WMBURNS for your help! Now I need to decide on shocks and struts and if I'm going to turbo it or supercharge it!
 

wmburns

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Thanks for the update. It sounds like you have been very busy and have learned a ton.

Did you find the InjectorRX.com report interesting? Is it possible there may have been debris in the line that got carried inside the injector? Otherwise it appears they didn't do good work for you.

Loose torque converter bolts. How did you track that down and were you able to figure out how it happened? Good work.

At one point in time I has two Mustangs. A 2003 GT Convertible automatic and 2000 GT coupe manual. I thought the 2003 was quick until I got the 2000. The combination of lighter car weight and lower transmission parasitic loss does make a difference. I never found my 2003 able lay down any real rubber. So in that regard yours must be making more HP than mine ever did.

I just finished putting a new clutch in the 2000 GT. On the test drive it's also picked up a new fairly hard miss. Runs like poo. So I will have the ODB2 scanner out going through mode 6 misfire data myself.
 
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Bowtierebel

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Well, as far as the injector and Injector RX, I can't swear that there wasn't something in the fuel rail that made its way into the injector, but I was very careful when I removed them for each individual bag they were in and took care when installing each of them. I will say that whatever it was caused the internal plunger to stick and it wouldn't even click until I cycled power to it off and on while spraying through it. As far as finding that the torque converter nuts were the cause of the noise, I have a lift in my shop so I raised the car and put it in gear at idle and pulled the Ebrake just enough to keep the wheels slow so it would clank intermittently. I was somewhat nervous to do this without help. Then I rolled under the car on my creeper and just listened until I located the area that the noise was coming from. The engine sounded too good and the torque converter is new. I had a bear if a time tightening the nuts when I installed it because I didn't know FORD had made a provision to access the nuts easily. Wouldn't you know there is a nice big hole in the block just to access those nuts on the drivers side below the head. When I used a pry bar to see if the converter had any play between it and the flexplate from underneath, it didn't move a bit. When I began to tighten the nuts, they were not tight at all. I was able to lay down a good bit of rubber, but I have to say that it isn't a posi rear end, so it was only one black mark. My friend that runs the machine shop and actually has an '02 GT, swears that after he tunes it, it'll be 400-450 HP. Sounds high to me, but he's been doing this for more than 40yrs. I honestly don't know what cams he installed yet or the extent he worked the heads, but he spent more time on the heads than all of the rest of the engine. Upgraded springs, valves, cut the valves somehow more than just a 3 angle job, ect. He's been racing most of that time and knows all kinds of HP tricks. He said he can work the heads to equal many high performance ones out of the box. I need to get the specs on the cams and what all he did do so it will help me if I go on and boost it. Since my bottom end is actually stock and really only the top end was upgraded, if I'm getting that kind of HP I don't think I'll boost it because I don't want to break it. I didn't complain about how he built it because we help each other out and you can't beat free.