[SafariJeepXJ]

The rest of the system seems pretty fool proof, but you never know. I believe it should throw a code if its inop. ...

Yeah, unless it's failing in-spec right? so false reading instead of inop, but there's no real way to test that.

OK, I will assume EGR is probably good.

LTFT numbers were good yesterday, we'll give it a couple more days and see if the code comes back. I'll also run the fuel pressure test while driving and see what happens and take note of LTFT/STFT and fuel pressure numbers while pinging. See how that looks, and if good get the FPR that Mad Porter suggested in the other thread from Summit.

I need to see if Torque can record data so I can watch fuel trim and give you accurate numbers later, instead of from memory. I'm sure there's a way.

 

[Lead Head]

4. Tested MAF sensor. 11.99 volts power, both ground test with the same, and signal voltage fluctuates from 1.4 to around 2.5 with throttle applied. Not sure I applied WOT, but there was a voltage fluctuation so my understanding is that means it's good.

Voltage fluctuation doesn't mean it's working correctly. On a WOT run up to about 4,000 RPM, you should see the MAF voltage well above 4 volts. I would suspect an issue with the MAF, if the fuel pressure holds at 39-40 PSI @ WOT and its still running lean enough to set codes.

A quick test is to unplug the MAF and see how it runs. If it runs better with the MAF unplugged - it's probably faulty.

 

[SafariJeepXJ]

Voltage fluctuation doesn't mean it's working correctly. On a WOT run up to about 4,000 RPM, you should see the MAF voltage well above 4 volts. I would suspect an issue with the MAF, if the fuel pressure holds at 39-40 PSI @ WOT and its still running lean enough to set codes.

A quick test is to unplug the MAF and see how it runs. If it runs better with the MAF unplugged - it's probably faulty.

Thanks all for the input.

Fuel pressure does say at 39-40 on WOT or under load. I drove a good distance and through the whole trip it never dropped below 32, and it climbing hills and with a fair bit of throttle it was always 39 if not 40.

I have been driving for a few days with no CEL so it looks like the new O2 sensors took care of that. I still do not understand that, given that if the O2 sensor was telling the ECU that the system was lean when it wasn't, then the effect would be running rich. However we know it's not running rich because pining and plugs are white. So strange.

But that could point to the bad MAF as well - two faulty sensors combining wrong information to come up with "it's lean" when it's not, and now it thinks it's right but it's still wrong because bad MAF info.

When I pull the MAF sensor while idling, it drops RPM for about 5 seconds and then it levels out. Today I just made a trip to the parts store. Left it connected on the way there, disconnected on the way back. It's hard to say but it seemed a little bit more peppy with it disconnected. Still got some pinging but maybe not as bad? The hills But it might be worth the replacement. Ugh, those things are annoying not cheap...

So I will swap the MAF and I think also buy the adjustable FPR. Then if that doesn't work we can always say it should have...

Sound like a plan?

 

[The Mad Porter]

Engine has been refreshed?

OEM replacement pieces?
Stock cam and timing set?

I have seen instances where cam timing was advanced 8 degrees from true straight up, which all efi engines are, creating excessively high cylinder pressure.
I've had a number of core EFI engines come back with the H535cp flat top pistons.

Just to be sure I would run a cranking PSI test to rule it out. Should crank at < 155 psi at or near sea level.



S

 

[SafariJeepXJ]

Engine has been refreshed?

OEM replacement pieces?
Stock cam and timing set?

I have seen instances where cam timing was advanced 8 degrees from true straight up, which all efi engines are, creating excessively high cylinder pressure.
I've had a number of core EFI engines come back with the H535cp flat top pistons.

Just to be sure I would run a cranking PSI test to rule it out. Should crank at < 155 psi at or near sea level.



S

Cranking PSI test = compression test, yes?

Cam was not touched. #5 piston burnt up rings and side of piston so I replaced all 8 pistons, rehoned all cylinders, and replaced rod and main bearings. Also installed new timing set - chain and gears - which appeared to be identical to the one removed. Reused lifters and push rods in their original locations.

Pistons were stock spec Speed Pro pistons and rings were stock spec Speed Pro/Federal Mogul rings. Pistons were identical top to the ones removed (oval dish in center).

I did all the work except for pressing the wrist pins into the pistons. Reused original rods.

Also, Mad Porter, I was just looking in more detail at that FPR you suggested from Summit in the other thread. Says the range is 35 psi to 70 psi, but standard pressure (without vacuum) should be 32 psi, right? will 35 be too high? Should I look for a different one?

 

[The Mad Porter]

Cranking PSI test = compression test, yes?

Cam was not touched. #5 piston burnt up rings and side of piston so I replaced all 8 pistons, rehoned all cylinders, and replaced rod and main bearings. Also installed new timing set - chain and gears - which appeared to be identical to the one removed. Reused lifters and push rods in their original locations.

Pistons were stock spec Speed Pro pistons and rings were stock spec Speed Pro/Federal Mogul rings. Pistons were identical top to the ones removed (oval dish in center).

I did all the work except for pressing the wrist pins into the pistons. Reused original rods.

Also, Mad Porter, I was just looking in more detail at that FPR you suggested from Summit in the other thread. Says the range is 35 psi to 70 psi, but standard pressure (without vacuum) should be 32 psi, right? will 35 be too high? Should I look for a different one?

No the adaptive learning will trim fuel if the idle and part throttle pressure is a bit high.

I take that as the regulator can be adjusted from 35 to 70 with no vac and then vac will lower pressure. Some literature lists the range from 30 to 70. It is not crystal clear however.



S

 

[DanE]

Were the injectors cleaned/replaced? Especially on the cylinder that ate the piston.

The cheaper fuels and known to plug injectors over time.

 

[SafariJeepXJ]

Were the injectors cleaned/replaced? Especially on the cylinder that ate the piston.

The cheaper fuels and known to plug injectors over time.

no, injectors were not cleaned (outside of wiping them off) or replaced. I can throw some injector cleaner in the tank and see what happens.

Porter - OK. If you recommend that brand I will give it a shot.

 

[SafariJeepXJ]

Just to cover my bases, this is the link you sent. It says it's for 4.6 and 5.0 but not 7.5. We're sure this will work?

https://www.summitracing.com/parts/aei-13102/overview/

Don't know enough about the engine differences to know myself.

 

[DanE]

I would get a little more serious about the injectors. You may have a piston being damaged as you drive the truck now. When an injector starts to plug, it acts like a cutting torch, and it's bye bye piston.

 

[SafariJeepXJ]

I would get a little more serious about the injectors. You may have a piston being damaged as you drive the truck now.

Meaning replace the whole set? Ugh, that's an expensive proposal. Are there alternatives to that, or ways to check/test them?

But yeah, I know about the piston, and I'm sure that's what killed it originally.

BTW, the truck thinks things are fine now. CEL has not come back since replacing the O2 sensors. Fuel trim is within acceptable limits from what I can tell (monitoring with Torque). The only time it pings is partial throttle going up hills, but that is completely unloaded - not towing, no payload.

 

[The Mad Porter]

Meaning replace the whole set? Ugh, that's an expensive proposal. Are there alternatives to that, or ways to check/test them?

But yeah, I know about the piston, and I'm sure that's what killed it originally.

BTW, the truck thinks things are fine now. CEL has not come back since replacing the O2 sensors. Fuel trim is within acceptable limits from what I can tell (monitoring with Torque). The only time it pings is partial throttle going up hills, but that is completely unloaded - not towing, no payload.

Dan makes an important point about injectors !!!

You are absolutely sure the EGR valve is functioning? I'm not referring to the position sensor but rather the solenoids that direct vacuum to the egr valve. Have you put a manual vac pump on it to see if the engine stalls or severely stumbles while at idle?

Fuel pressure reg style was by year it will work.



S

 

[SafariJeepXJ]

Dan makes an important point about injectors !!!

You are absolutely sure the EGR valve is functioning? I'm not referring to the position sensor but rather the solenoids that direct vacuum to the egr valve. Have you put a manual vac pump on it to see if the engine stalls or severely stumbles while at idle?

Fuel pressure reg style was by year it will work.



S

You mean put manual vac pump on the valve, right? I have not done that but the valve is brand new so I am pretty confident that is OK.

I am not sure about the solenoid - not sure how to test that, do you have a link to the diagnosis?

Also how do I test or clean injectors aside from fuel additive? Injectors were out during the rebuild and they got wiped off, but internally I don't know. One or two fell in the oil that was drained, and I asked about that in a different thread and folks seemed to think they'd be fine if they were cleaned off.

 

[The Mad Porter]

You mean put manual vac pump on the valve, right? I have not done that but the valve is brand new so I am pretty confident that is OK.

I am not sure about the solenoid - not sure how to test that, do you have a link to the diagnosis?

Also how do I test or clean injectors aside from fuel additive? Injectors were out during the rebuild and they got wiped off, but internally I don't know. One or two fell in the oil that was drained, and I asked about that in a different thread and folks seemed to think they'd be fine if they were cleaned off.

Just because a part is new assume nothing. Put vacuum to the valve to be certain...

I would have some concern about an injector falling into oil. Telephone around your area. Many outfits can clean your existing injectors for a nominal cost. If one or two fall short you can replace them individually.



S

 

[SafariJeepXJ]

Just because a part is new assume nothing. Put vacuum to the valve to be certain...

I would have some concern about an injector falling into oil. Telephone around your area. Many outfits can clean your existing injectors for a nominal cost. If one or two fall short you can replace them individually.

S

OK no problem. I'll report back, but pretty sure that is fine.

I will see what I can find out about cleaning injectors locally.

One question, since normally this thing isn't pinging - really just happens under partial throttle on hills - is it OK (but not ideal) to keep driving it, or in ya'lls opinion should I stop driving it ASAP until I can 100% stop the pinging?

 

[The Mad Porter]

OK no problem. I'll report back, but pretty sure that is fine.

I will see what I can find out about cleaning injectors locally.

One question, since normally this thing isn't pinging - really just happens under partial throttle on hills - is it OK (but not ideal) to keep driving it, or in ya'lls opinion should I stop driving it ASAP until I can 100% stop the pinging?

What octane fuel are you running?

Light ping on hills, the operative word being "light" is tolerable but not ideal. This always almost indicates too much part throttle timing or lack of proper EGR operation. It can also indicate a lean or hot cylinder as well as a vacuum leak.

Address the injectors, check EGR valve operation even if you have to tee into the vacuum line to check for vacuum while experiencing the ping unloaded on grades. I assume that you have replaced ALL vacuum lines, checked your vacuum diagram etc???



S

 

[SafariJeepXJ]

What octane fuel are you running?

Light ping on hills, the operative word being "light" is tolerable but not ideal. This always almost indicates too much part throttle timing or lack of proper EGR operation. It can also indicate a lean or hot cylinder as well as a vacuum leak.

Address the injectors, check EGR valve operation even if you have to tee into the vacuum line to check for vacuum while experiencing the ping unloaded on grades. I assume that you have replaced ALL vacuum lines, checked your vacuum diagram etc???



S

Agree it points to EGR operation but figured new valve took care of that so was eliminating that possiblity. But I will verify valve is working and see if i can find something on testing the solenoid. Will report back.

Did not replace all lines, but replaced/patched several and dealership smoke checked it and no leaks.

Ok. Wife really needs to drive the truck while I'm replacing the motor in her WJ... too many things going on at once, and I'm supposed to go to work in there somewhere.

Thanks all.

 

[The Mad Porter]

Agree it points to EGR operation but figured new valve took care of that so was eliminating that possiblity. But I will verify valve is working and see if i can find something on testing the solenoid. Will report back.

Did not replace all lines, but replaced/patched several and dealership smoke checked it and no leaks.

Ok. Wife really needs to drive the truck while I'm replacing the motor in her WJ... too many things going on at once, and I'm supposed to go to work in there somewhere.

Thanks all.

If you are running 87 octane fuel just use better fuel in the interim.

A 180 stat would help here if you are currently running a 195.



S

 

[SafariJeepXJ]

are there any solid tests for this pinging situation or is it just a matter of throwing parts and seeing what sticks? seemed like this started with "buy the FPR" and now I'm replacing a ton of stuff lol.

I replaced the MAF just to eliminate that as a possibility. Didn't really think that was it, and I don't think it made any difference, but I just tried to throttle hard a few places, didn't get to that hill yet. Feel like I felt it ping at one point, not bad but a little. Might be a little more peppy, but that could just be in my head.

I put a vacuum on the EGR and it did idle down quite a bit, but did not stall out. Eventually I think the IAC compensated and brought it back to something more normal. I have not tested the solenoid yet or measured vacuum while driving.

I went ahead and put 89 in for the wife to keep driving it for now and I'm going to focus on getting her WJ back together - I'm putting a replacement engine in it after the original seized with 130k... I either have terrible luck or I have no business working on a vehicle, lol. Jury's still out.

Since we're here, I have also been chasing a hard shift issue. Replaced VSS and TPS. I feel like a notice a difference in that maybe it doesn't wait as long to shift, but it's still shifting hard. Only sensor left that I'm aware of is the MLPS. Given the symptoms I really thought the VSS might do it, except for the speedo seemed fine. But now I'm guessing there is either a shift kit (pretty sure the owner before previous - previous being my dad - had trans work done) or there is a bad solenoid. I still need to look into that more though. Hoping to have the WJ back together by the weekend so I can take the truck out of commission and get the motor and trans running right. Then I can deal with the other stuff - wheel bearings, center bearings, blah blah blah.

Not sure why I do this to myself...did you know you can actually PAY people to do this stuff FOR you?!

 

[DanE]

Here we go around in circles. Tell me, What do you think killed the piston in the first place?