1997 EX XLT 4.0 OHV Man/Man

[nefudd]

My 1997 Explorer XLT manual trans and 1354M transfer case with 185K miles started throwing codes 1130, 1131, 1132, 1150, 1151, and 1152. Ran fair, but rough idle and flat/weak power. Shortly after it would not start. Diagnostics showed no fuel pressure, electrical ok. Installed new OEM brand fuel pump and vehicle started right up. Assumed that pump was not able to maintain pressure which caused lean and rich codes. Now runs ok for 20 miles or so, but then starts misfiring at any engine speed and feels like only 3 cylinders are running. Hold WOT for a few seconds and it feels like all cylinders "kick in" and runs very smooth....for a little while. I cleaned MAF and checked for vacuum leaks with a leak down gauge (none) and disconnected the battery for 5 minutes. Ran great for 25 miles, goes back to symptoms above but no codes present. And is getting worse to the point that I don't trust driving it. Does this sound like a fuel pump/pressure problem?

 

[koda2000]

Fpr?

 

[GregCO]

Yep, put a fuel pressure gauge on it and go for a spin and see if the fuel pressure gets funky when it starts to fall on it's face. Also pull the vacuum line off of the regulator and see if there is fuel in the line.

Greg

 

[nefudd]

Thanks for the input. FPR keeping pressure at a flat 28-30 psi regardless of rpm or throttle opening. Disconnected (and plugged) vacuum line with no change of pressure. Swapped another fpr and pressure now is 33-34 psi at idle, but spikes to about 40 then drop backs to 33-34 when the throttle is whacked open. No change what so ever in run quality with the FPR change. I found an intermittent vacuum leak (flexing of the hose caused vacuum leak which was otherwise fine with engine off) at the brake booster grommet that I have since repaired. Run quality has deteriorated to the point where it only runs on 3-5 cylinders all the time. I am goin to test TPS and do a battery disconnect reset next. It does not seem logical, but I will also purge the return line in the event I accidentally pushed some debris into it when doing the pump swap. But it seems like I would have different issues if return line is plugged (like really high fuel pressure). I am pretty perplexed by this issue. I am a certified Honda, Suzuki, and Bombardier Tech, and am pretty good at diagnostic and repair on my BMW 735i with 520K miles. Honda and Suzuki are PIA with run issues, but this old Ex is really testing me. IF I can figure it out, I can add some interesting tidbits on the issue of 1354M swaps too. Thanks in advance for the help. Dave

 

[nefudd]

Update! I went back to the basics and did a vacuum leakdown test again, this time with engine hot. Surprise! Leaks at base of plenum when hot, but not when cold. I replaced plenum gaskets, and all vacuum lines (since they were all brittle). Bigger surprise! Absolutely no change in how it runs when warm. It runs perfect for the first 30-40 minutes after a computer reset, then gradually starts to misfire on 1, then 2, then 3 or more cylinders and CEL comes on and I get all the same codes (1130, 1131, 1132, 1150, 1151, 1152). Had already installed new spark plugs, so installed new plug wires and a new coil pack also. Still no change. I keep thinking about the whole sequence. It ran fair before fuel pump failed. Had a rough idle and felt sluggish (and would throw a lean code every few hundred miles) but did not misfire. When the fuel pump failed, I assumed the fuel pressure or flow rate was low which was causing lean issue and flat power. When I replaced the fuel pump, I also replaced both upstream o2 sensors (brand x units) as I had no idea how many miles they had run. After pump and o2 sensor install it ran just like before....until....within 25 miles later the POS control trac transfer case started failing and the speed sensor drive quit working (which of course caused the speedo to stop also). It then started the misfire sypmtoms it has now. I had all the parts needed to do a 1354M swap so I did the swap. I assumed the lack of speed sensor input was causing the engine management system to go nuts (it thought the vehicle was not moving) so I expected that the new transfer case and speed sensor would take care of that issue. Wrong! I am pretty frustrated with this and am about to throw in the towel and take it to a Ford technician. But first, could the new brand x upstream o2 sensors be faulty? Anyone have experience with performance and run quality with a known bad o2 sensor? I tossed my old ones away already as I trusted that I would have no use for them again (why keep bad parts around). Thank you. Dave

 

[nefudd]

Still no solution. So far have replaced: fuel pump (2x), MAF, TPS (x2), IAT sensor, Cam position sensor, Crank position sensor, both upstream 02 sensors, FPR, coil pack, plugs & wires, egr solenoid, EGR sensor, upper intake manifold gaskets, all vacuum hoses, CATCON, ECU, IAC valve (x2), fuel filter (x2). It has significantly more power, and idles much smoother, but still will bog, surge, and misfire after it is warm. If I plant the pedal to the floor after it starts misfiring, after 3-5 seconds it will suddenly get full smooth power and drive okay for a while (5 to 20 minutes) then start the issues all over again. CEL comes on only after several of these misfire events and start with P1131, then 1132, then 1151 followed by 1152, then multiple cylinder misfire. Vacuum signal is very stable and in a normal range at idle and cruise. Fuel pressure is like a rock at 32, will jump to 38 or so when throttle is whacked full open, then settles back to 32 psi. Compression tested again is 160 psi +/- 3 on all 6. No apparent vacuum leaks in any if the usual areas. All of these symptoms appeared immediately after fuel pump replacement. Tank is very clean, no debris showed in the "sack" filter on bottom of old pump assy, or from the original fuel filter. Have ran 3 tanks with high dose techron with no effect. Runs great when cold and around town. Symptoms appear after 20-30 minutes of driving and are worse with highway cruising. None of this makes sense to me, especially when under full throttle it will run normally. So it seems like some system that only affects warn run or high vacuum, that also is ignored at full throttle. Anyone know how the purge system works? Or how the EGR system cycles? No EGR codes are ever present unless I disconnect vacuum to the valve, then the code resets itself after just a couple minutes with vacuum re-connected. I am completely stumped, discouraged, and thinking of a ceremonial fire. Any ideas?

 

[nefudd]

More issues, no resolution. Anyone?

The Explorer is still having issues. Actually they are getting worse. I have been driving it and watching sequence of symptoms and codes when it starts misfiring.

Keep in mind that all of the runability issues have appeared since fuel pump replacement (have done it twice and FP measures 30-36 all the time).

It runs smooth and well when cold. Problems arise when it is fully warm (10-20 minutes of driving).

P1131 is the first code, followed soon after by P0130, then P1132, 1151, and 1152. Exhaust pipe very black and wet. Fuel consumption down to 9-10 MPG. I think it is very rich and in an attempt to lean it enough the ECM reaches the lean range limit and throws the 1131 code.

Now I have P1120 (and there is a new TPS adjusted to .91 VDC at idle in place). And the battery light in the instrument cluster is on. Bat voltage at rest is 12.77 (engine off), at idle 14.70, at 3k RPM 14.67.

I have checked the alternator fuse (cleaned and re-seated the fuse), and assume since charge voltage is normal that it is actually charging.

Also, tried running and driving with TPS disconnected.....no change in running or driving. This seems really odd.

Questions:
It looks like the fuel tank pressure sensor is involved in the dash light circuit. If so, can this create this new problem and relate to the others.
Why is there no change with TPS disconnected?
Anyone have a link to a schematic for an early production (mechanical VSS in t-case) 1997 XLT 4.0 OHV with a 5 speed (originally 4405 t-case, now a 1354M)?
Could the old fuel pump before failure be providing low fuel pressure which masked the current symptoms (such as worn injectors spraying too much fuel)?

I cannot figure this thing out. Without a cure it goes up for sale as is and I move on. I like the EX and would really prefer to keep it. Especially now since virtually every sensor and many other parts have been replaced.

Anyone?

 

[delexploder]

I have seen this on one other ohv and it ended up being the rockers and pushrods. They were worn and not allowing the valvetrain to function kicking all the same codes. Its worth pulling a valve cover and looking.

 

[nefudd]

Solution Found!
Amazing what parts suppliers are doing these days. The problem was in the new supposedly Delphi brand o2 sensors. Although they came to me in a box labeled Delphi, they are in fact counterfeit parts. After making a custom harness to connect a multi-channel digital oscilloscope to the Ex, I found that the output signal line from bank 1 o2 sensor would short to ground at higher temp. This caused the ECU to go baseline and think that bank 1 was totally lean and start dumping huge fuel loads. Which would cause bank 2 to read full rich, and the bank 1 o2 sensor to cool and no longer short to ground. By this time the signal from bank 2 would call for leanest fuel trim which would in turn cause bank 2 o2 sensor to then also short to ground causing a side to side switch in lean/rich and lack of switch codes (P1131, P1132, P1151, P1152). This short to ground was also taking the normal 5v signal to ground (less than 1v) for various sensors like the TPS, Fuel tank pressure sensor, DPFR, and others. I cut one of these sensors apart with a dremel and found it contained only what looked like a resistor (it was really burnt looking so was hard to tell). There was an obvious indication of the leads melting and causing the short to ground. Moral of the story? Use OEM, Bosch, or Denso sensors sourced from known suppliers. I guess the silver lining is that now the entire engine management system has been gone through with a fine tooth comb and it runs exceptionally well. And I have learned a great deal about Ford electronics (I will take my BMW system any day over the Ford) and feel I can trust the EX for a long time to come. Thank to all you posters for your input. I can now finish my documentation on the 1354M swap and post it soon. Dave