4.0 engine won't run, severely flooding out

[Racer14B]

I am new to this forum and will greatly appreciate any help I can get here. I bought this non running 02 explorer with the 4.0 sohc, well, it almost ran, ran just enough that I could hear the timing chains slapping around. It ran terribly rich, smelled like raw fuel coming from the tailpipe. So I ended up pulling the engine to fix the timing chain guides. The number 5 spark plug had no gap at all when I took it out, so I pulled the heads off to check everything out. There was not even the slightest scratch, nick, or anything anywhere on any of the pistons, valves, etc, so that spark plug issue is still a mystery. The guy I bought it from had been working on it, it had new O2 sensors, plugs, and wires on it, I am not sure of how competent he is after seeing he had number 4 and 5 wires reversed. Maybe he dropped the spark plug when he put it in and didn't see the tip got bent down? The only issue I could find anywhere in the engine other than the broken main chain tensioner and broken rear cassette was a collapsed lash adjuster on number 5 cylinder, same cylinder with the spark plug mystery. I replaced the bad parts and put the engine back together, the cams are timed correctly, I have absolutely no doubt about it. I made my own tools (I own a machine shop) for the cam alignment procedure. I got the engine back in and guess what, it barely runs, exactly the same as it did before, will only fire if you hold pedal to the floor, spits and sputters a little, then dies. If you then pull the fuel pump fuse it will fire up and smooth out for a second or two until it runs out of fuel. I have a friend that works a Ford dealer try to diagnose it with the Ford IDS scanner. He couldn't find anything abnormal using the scanner. Cam and crank sensors are in sync, injector duty cycle seems correct. MAF, TPS and coolant temp seem to be reading as they should. I put a fuel pressure gauge on it, it is reading around 58 psi after a few cycles of the key, pressure dropped to around 45 as I was cranking, so I replaced the fuel filter, it's still about the same. I ended up pulling the intake back off, there were puddles of fuel around the intake valves that were closed. I disconnected the coil and cranked the engine so I could watch the injectors spray, they are all doing the same thing, which appears to be spraying a huge amount of fuel when they fire, but keep in mind that there was no TPS, etc. connected during this test since the intake was off. I was going to pull the passenger side valve cover to re-check the cam timing on that side, but thought why not see if it will fire up first. I knew that if it did fire it would instantly rev sky high if there was nothing mechanically wrong with the engine, well that's exactly what it does. the injectors are pumping huge amounts of fuel, but with no intake it gets enough air that it instantly revs sky high. (I only let it run for a split second, probably hit 4000 RPM or so. I don't want rods and pistons going through my garage walls! The point of this was to prove that the cam timing is correct, there is no way the engine would rev up that fast if the cam timing was off) I am to the point that I am down right pissed off at this POS. It also has a strobe light effect on the door ajar system, I sprayed all the door latches including the back hatch and glass and gave all of them a few hard slams shut after a day, no change. Also the shift interlock solenoid will not release. I did go through and remove and clean up every ground wire I could find before I tore the intake back off the engine. I am so sick of working on this thing...this will likely be the last Ford that I buy. Anyway, anyone got any ideas on what to do next?

 

[2000StreetRod]

Running rich

A compression test would have been a simple way to determine if there was any valve damage and if the camshafts were timed correctly after replacing the cassettes.

There is a fuel pressure sensor on the fuel rail that is monitored by the PCM. The fuel pump is pulse modulated to maintain a constant fuel pressure to reduce emissions. As I recall 45 psi is about right. There is a fuel pressure regulator in the fuel tank to limit the pressure to around 65 psi.

The PCM determines the injector pulse width based mainly on calculated engine load, engine speed, acceleration/deceleration demand (TPS), engine and air temperature, and cranking vs running. When the engine is cold and cranking pulse widths are increased. With no intake manifold installed there would be no air flow thru the MAF sensor which is the main source for the PCM to calculate load and the TPS output would be bogus.

The engine seemed to be running rich with everything connected. A defective engine coolant temperature sensor can cause a rich condition as can a defective MAF sensor.

 

[Racer14B]

I forgot to mention that I did compression test number 2 and 4 cylinders, both were about 145psi, cold engine cranked for 2 compression strokes. I was told this is a kinda low, but since cylinders have been washed down by all the fuel it might be the reason, plus my guage is very old and I don't know how accurate it is. The engine has a lot of miles on it, but the cylinders all look good, still have crosshatch in them. Important thing is that it is consistent from one bank to the other, verifying that both camshafts are timed the same. I am a firm believer that you don't just throw money at something to try to fix it, you diagnose the problem, then replace the bad parts, I will investigate the tps, coolant sensor, and MAF some more, I know how to test the tps for 5 volt reference signal and output voltage, is there a simple voltage or ohm test I can do with the coolant sensor and MAF? Thanks for the reply.

 

[2000StreetRod]

ECT sensor test

The easiest way to test the engine coolant temperature (ECT) sensor is with an OBD-II scanner (or equivalent) reading the ECT value reported by the PCM. The other method is to refer to the following table.

You can measure the resistance between the GRY/RED and the LT GRN/RED wires at the sensor connector.

A better test is to measure the resistance at the PCM connector since that also checks the wiring to and from the sensor:
PCM C175C Pin 46 ECT Input (LT GRN/RED)
PCM C175C Pin 17 Sensor Return (GRY/RED)

 

[Racer14B]

Thanks for the info! I put the intake back on, did a quick ohm check of coolant temp sensor, looked like it was really close. I do have a cheap OBD2 scanner which I have always just used for reading codes. I guess I forgot that it will show a limited amount of live data. My scanner is showing accurate temps of coolant and intake air, with engine not being cranked over TPS is 19.2% and MAF is 0 with throttle closed in idle position While cranking with WOT the TPS is 92.4% and MAF is .4 lb/hr, rpm registers at 200. I have no idea what the the TPS values are supposed to be, but the 19.2% seems high for idle position. I did a quick check on my Dodge Stratus for comparison, it is 11.2% at idle position.

 

[2000StreetRod]

measured values

A TPS reading of 19.2% at closed throttle is correct. The reference supply is 5.0 volts and the closed throttle output is about 1.0 volts so 1.0/5.0 = 20%. 92.4% for WOT is also about right.

My 90 LMAF sensor MAF Ad Counts are about 100 at 200 rpm or about 0.4 lbs/min. Are you sure that your mass is in lbs/hr instead of lbs/min?

 

[Racer14B]

the MAF reading is lbs/min, not lbs./hr . Should any of the O2 sensors be showing voltage readings on the scanner? My scanner shows 0 volts on both of the O2 sensor readings that it can do. At this point it is evident that the coolant temp and TPS are reading correctly. I just can't believe this thing won't run. The best I can get it to do is to run about 30 seconds. I pull the fuel pump fuse and crank it with WOT to get it cleared out, I crank it about six different times, it still continues to try to run a little bit each time cause there is so much residual fuel, then put the fuse back in, it will then barely start, and then I immediately go to WOT after it starts, the RPMs come up to 2500 or so before it begins to stumble and die. Only way to get it started again is to pull the fuse and go through the procedure again. It acts like the intake is plugged solid and can't get any air through it. I took the air filter out for now, it was a little dirty, the intake hose is still clamped on everything like it should be, just no filter in the housing. Anyway, thanks again for the reply, I am at a loss with this thing.

 

[2000StreetRod]

closed loop

I think the PCM ignores the O2 sensors (and doesn't report their values) until it switches from open loop at engine start to closed loop after the sensors have had time to heat up. My PCM takes about 20 seconds after engine start to switch from open to closed loop.

It does seem to me that your AFR is rich which is not a common condition. Your TPS, MAF sensor, IAT and ECT readings are reasonable. The fuel pressure is not excessive and you've observed the injectors pulsing on and off. I assume fuel did not leak thru the injectors when switched off. What color are the injectors - maybe a previous mod was to install high-flow injectors.

Another possibility is fuel getting sucked into the intake manifold. There is a fuel pressure sensor on the fuel rail that has a vacuum hose attached.

I suggest disconnecting the hose and checking for fuel in it. There might be fuel flowing thru the pressure sensor to the vacuum hose. If there is no fuel in the hose plug it and then switch the ignition to run to see if fuel squirts out of the sensor vacuum port.

If fuel is not leaking into the manifold from some source then the problem must be that the injector flow is excessive or the air flow is insufficient.

 

[Racer14B]

It has red injectors, I did visually check the injectors for leaking when I had the intake off after I cycled the key a few times, and while cranking the spray pattern was consistent between all injectors. the fuel pressure is not bleeding off. I had the vacuum line off the fuel rail the other day when I had the intake off, I did a close inspection of all the vacuum lines, no signs of any fuel in any of them. I can have the intake off in about 15 minutes, I may pull it back off this evening, maybe the stupid thing has a nest stuffed way up in it, it has to be something stupid that is wrong.

 

[Racer14B]

I didn't pull the intake back off yet, I made another observation worth noting, when I turn the key to the run position all of the gauges move to maximum readings for a second or two, then return normal. However it does not do this every time. Is it possible that my whole problem here could be broken wires or a bad connection somewhere? I am having to keep the battery disconnected when I am not working on it due to the damn door ajar sensor problem, I don't want to waste time trying to fix that till I can get it to run, but now I am starting to wonder if this may all be related to the same problem.

 

[Racer14B]

Well, I finally figured it out....after nearly two weeks of cussing, throwing tools, and 4 year oldish temper tantrums! I pulled the EGR pipe off from the intake and cranked it, fired right up for 20 seconds or so, exhaust gas was spewing out the EGR pipe. Are you f'ing kidding me!, I say to myself. So I crawl underneath and loosen up the Y pipe, and it fires up and runs great. Yes, the damn exhaust is plugged, freakin thing couldn't breathe. That is why it fired up so great without the intake on, it was exhausting through the disconnected EGR pipe. Anyway, now that I know it runs I am gonna let it sit for a week or so. Huge thanks to 2000StreetRod for the help with trying to diagnose it!

 

[2000StreetRod]

Congratulations!

I'm glad that you determined the source of the problem. When I was a kid some other pranksters would jam a rag or potato into the tailpipe of vehicles parked on the street causing similar symptoms.

 

[Scottnyo]

I want to thank you for this post I also started with both timing chains to be replaced and I have about 10 -12 days in this and many were sleepless and probly $2000 doig it all myself and I actually pulled the motor out a second time to check both chains and again all by myself !!!!! But this morning I read this post and figured why not pull the exhaust and as you said pedal to the floor and wake up the neighbor hood to open headers and it’s figured out of course I have 3 converters on my 03 explorer xlt 4x4 to clean out since North Carolina doesn’t do emissions testing on older vehicles anymore and let’s hope they don’t go back to it !!!!! Anyway thanks to the both of you my nightmare is over !!!!! Thank you very much for your story and thank you Explorer forum for being here so we all can keep repairing our vehicles !!!!! Scott