97 5.0 issues

[lugnut1009]

New member, first post. I’ve tried searching for this extensively before posting my own thread.

Ok, I just purchased a 1997 EB 5.0 AWD w/ 156k miles that had a miss. Thinking I could fix it easily but I’m at a loss. Also I am using AutoEnginuity software to look at all of my OBD2 info.

The explorer is mostly stock but I found that the cats have been removed. Everything else is completely stock. The previous owner did a lot of stuff and sold it because he couldn’t get the miss fixed. I did a compression test yesterday, all cylinders were 150-160 psig, verified the proper autolite plugs, plug gap, wires were routed to the right spot on the new coils. By the way he already replaced both coils, all plugs, wires, MAF sensor, injectors, and 1 (bank 2 upstream) O2 sensor.

The engine runs horrible, low erratic RPMs, almost no power, in closed or open loop. All of my STFT and LTFT are really high, O2 readings are high, which if I understand correctly indicated a lean condition and adding fuel. And the O2 graphs are cycling up and down and not flat lined so they’re working. But when I pulled the plugs they were nearly dripping with gas and sooted up. What is going on here??

 

[Mbrooks420]

What are the codes? Still have the front 2 cats?

These motors like Motorcraft plugs. I wouldn’t run anything else.

 

[lugnut1009]

All the cats are gone, replaced with straight pipe to the muffler. They did reinstall all of the O2 sensors though.

As for codes, about the only thing I’m getting right now is system readiness not completed. I cleared the codes prematurely not realizing I’d have a hard time completing the driving cycles to make current codes come back.

 

[Mbrooks420]

You’ll need the front cats or an aftermarket tune for it to ever run correctly. You cannot simply remove the cats.

 

[lugnut1009]

Not even in open loop at initial startup? I thought the 2nd set of O2’s were only measuring the efficiency of the cats. I wouldn’t have removed them, but I got it this way.

Also I’ve checked the EGR valve, it’s operating properly, and purchased a new IAC valve, waiting on the throttle body mounting gasket before I put all that back on.

 

[Pete Deering]

Not even in open loop at initial startup? I thought the 2nd set of O2’s were only measuring the efficiency of the cats. I wouldn’t have removed them, but I got it this way.

Also I’ve checked the EGR valve, it’s operating properly, and purchased a new IAC valve, waiting on the throttle body mounting gasket before I put all that back on.

I think you solve your own problem. Because the cats are removed, you have 0 % efficiency of the cats , and no input to the computer for the rear O2 sensors. the O2 sensor control the fuel trim.

 

[410Fortune]

Have you checked fuel pressure?

 

[lugnut1009]

Have you checked fuel pressure?

Yep, fuel pressure is a constant 40 psig

 

[lugnut1009]

Going to get a new throttle body gasket today, get it all back together, and datalog the O2 readings along with the short and long term fuel trims. Will report findings this evening.

** also going to get a set of the 18mm spark plug non-foulers to fool the secondary O2’s.

 

[lugnut1009]

Was able to get it all back together, only able to install one of the non-foulers on the B2S2 due to the B1S1 being too close to the transmission I won't be able to screw it back in with that 1/2" extra height on it.

Anyway, see the attached screen shots of the error codes and the other readings I got.

I tried driving it up the road and it has ZERO power! All indications to the ECU is it is extremely lean, right? But I know it is as rich as it can be and still stay running. Fuel is dripping off of the plugs when I take them out. O2 readings were in the 0.3-0.5 v and fuel trims were in the +25-55% on STFT and LTFT

 

[lugnut1009]

Should have gotten a screenshot of the O2 readings with it running, not sure why I didn't. So the above screenshots were with the engine off.

 

[lugnut1009]

Well this is interesting… I found a mustang site and a guy had the same problem. Although this one is heavily modified, they say if the mixture is extremely rich the O2’s will read it as lean. Check it out: Mustang rich-lean

 

[CDW6212R]

Based on what has been posted so far, I wonder what condition are the front O2 sensors, the cam synchronizer and sensor, plus the balancer. I'd also check the plug wire positions again, and again later if the problem remains. The front O2's are critical, the rear pair are trivial, the CMP is a big deal, and the balancer can be slipped on the rubber ring, and not properly located any more.

Keep checking everything you have, and the wet plugs are highly likely bad(but usable until you find the issue).

 

[lugnut1009]

Thanks. I think my next step is to try to clear everything out to a blank slate, because I have no clue what was done before I got it. I plan to disconnect the battery and drain the capacitors so when I power it back up I’ll be back to the factory default fuel tables. Then maybe run it in open loop with MAF or something critical unplugged so it won’t go into closed loop. And make sure the firing and injectors are working properly. I’ll also clean my primary O2 sensors before starting it. Then when running in open loop i should be able to monitor O2 levels, IAT, ECT, and TPS sensor for any issues.

I know one thing, when I do find the solution, I’ll be sure to post it here. I don’t know how many threads I’ve read with similar issues and they never come back and finish the thread with what the fix was.

 

[1998Exp]

The complete loss of power sounds like a mechanical issue. Someone already suggested a possible slip of the tone ring on the harmonic balance. This can be checked with a simple timing light. Also, does anyone know if a one-tooth jump of the timing chain would still make a correct compression?

 

[lugnut1009]

I’ve also thought about failed lifters or something mechanical on the intake side. I think that’s going to be my next plan of attack, remove the valve covers and inspect all of the valve train I can.

Today I installed a new O2 sensor on B1S1 and no change, maybe worse. I also tried cleaning the other sensors, not sure it helped much. Also if anyone else is wondering, the green O2 sensors are upstream and blue is downstream. B1S1 looks to be oscillating correctly and B1S1 seems to be doing only half of B2S1.

I did reset the ECU which zeroed out the fuel trims, I ran it with the MAF disconnected so it stayed in open loop but STFTs still kept increasing all the way to 28% while LTFTs stayed at 0. I can give it an unmetered air (pull large vacuum line) and it runs a lot better. Baffles me…

 

[1998Exp]

I’ve also thought about failed lifters or something mechanical on the intake side. I think that’s going to be my next plan of attack, remove the valve covers and inspect all of the valve train I can.

Today I installed a new O2 sensor on B1S1 and no change, maybe worse. I also tried cleaning the other sensors, not sure it helped much. Also if anyone else is wondering, the green O2 sensors are upstream and blue is downstream. B1S1 looks to be oscillating correctly and B1S1 seems to be doing only half of B2S1.

I did reset the ECU which zeroed out the fuel trims, I ran it with the MAF disconnected so it stayed in open loop but STFTs still kept increasing all the way to 28% while LTFTs stayed at 0. I can give it an unmetered air (pull large vacuum line) and it runs a lot better. Baffles me…

A stuck lifter would make noise that you can hear from ten feet away - not to mention that the affected cylinder would have low compression. Before tearing into anything I would check for separated tone ring on the harmonic balancer. I am looking at one as I am writing this and can see that the double-wide gap is centered at about 25deg BTC. If you see it more than a few degrees away from that spot, you found the problem.

 

[lugnut1009]

Thank you I'll look at that as soon as I get home this evening.

I didn't think about the noise a stuck lifter would make. IF the tone ring is in place correctly, I guess I'll still remove the intake and open the valve covers just to know everything is good. Who knows, I may find a rocker arm broken off or come loose in there. The engine sounds quiet as far as valve train noise, but at this point if I don't look at it I'll be wondering about it until I do.

 

[SuperGordo]

Have you Checked for vacuum leaks under and around the plenum? I recently purchased a 5.0 EX and have also been working on it extensively. Previous owners hacked up and jerry rigged all kinds of vacuum "solutions". The PCV was barely hanging in place because the grommet was so old and hard. Plenum gasket was original even though it was clear that the plenum had been removed before. All kinds of little things were amiss. That said if your previous owners cut off the cats, then ask yourself what else did they do? Or what didn't they do??
I always suggest to look for all the small stupid stuff before you look for the big stuff.
Even without the cats the upstream o2 sensors are doing the fuel management, the downstreams monitor the cats. So the lack of cats guarantees a check engine light, but your truck should still run. Check the vacuum lines. Probably check the injectors.

 

[lugnut1009]

Yep that’s one reason I want to pull the intake. I have no clue what they did or didn’t do. They could have left rags stuffed in the intake manifold for all I know. But it pulls great vacuum and I haven’t found anything really hacked up aside from the cats being removed.