1999 Mounty 5.0 aka My Great Bad Idea

[410Fortune]

Okay so I’ve had several sets of tmh that will not seal well at collector
I have solved it

Usually The collectors (downpipe) get over tightened and stretch and then sealing is difficult
I’m Guilty for sure, in my bii, I for sure stretched those pipes out years ago

There is hope

You can access thoseBolts! It is not that bad! Use 3/8 drive and wobbly extension, get truck high up in the air so you can a shot at it
The access angle is back by the cat converter

So first you need to make sure the ball flange is straight to the downpipe, even gap all the way around

The snug up the bolts evenly
If that does not solve the leak, there is still hope

Chevys use a crush ring inside some of their exhaust connections. They fit the header and Downpipes perfectly. I use some
Hot glue (just a dab) to hold it in place and then aligne the downpipe and torque the bolts

No more leaks from the collectors
I have had to do this on more then one truck since

I can get the part number but basically I went to the parts store asked to see their exhaust gaskets and chose two rings that are 2.25-2.5” in dia, they are for a sbc I believe
In dia

Oh you are taking about your repaired collector on the header itself! That stinks!!
I misread and thought it was the ball flange at downpipe…
Dang!!

 

[97Sandbox]

Oh you are taking about your repaired collector on the header itself! That stinks!!
I misread and thought it was the ball flange at downpipe…
Dang!!

Yeah, the one ball flange leak looks negligible compared to the driver's side collector leak. It's the actual part of the collector where the primaries come together at the merge star that's leaking bad, not the ball flange connection. As I'm sure you recall, that's where I spent hours blasting, welding, grinding, and repeating to get the holes filled as best I could before the plating and ceramic.

The irony is that if I'd just bought a new set TMHs, I would've saved money overall (not to mention time) and they'd probably be coming soon had I ordered them last summer when I started this mess...

 

[97Sandbox]

I swapped the mangled washer on my B2 upstream O2 sensor last night (fun fact, it's the same size as a Honda manual transaxle fill plug crush washer). That's really the only leak I could address with parts I had on-hand.

Tonight I went for another drive to see if anything changed. Interestingly, the intermittent tapping didn't show itself again. I also stuck a hose into the collector area of each header and listened for exhaust leak noise -- I heard none. While the pinholes in my collector welds certainly fail the "soapy water test," they don't appear to be bad enough to cause that exhaust leak "ticking" sound.

However, my B2/B1 lean codes are now showing up as stored (technically they're showing as stored and pending, not sure what that's about). My EVAP monitor is also still not showing as ready and I don't know if that's because of the lean codes or something else.

You can call it rationalizing, but between the header leaks seeming not that bad and the functionality of the EVAP system remaining in question, I'm wondering if there could be something besides the headers causing the lean codes. Before I go ruining another set of headers with some expensive magic goo, what else should I check?

I'm curious if a local shop would smoke test it for me. Would a mechanic normally smoke both the induction side and exhaust side or just the induction side? I'd want to check both, otherwise it'd be hard to know whether there's a true lean condition due to air sneaking in behind the MAF or a "perceived" lean condition from exhaust sneaking out before the O2 sensors.

 

[410Fortune]

How much have you driven it?

I’m guessing it still needs some
More drive cycles to complete all tests and present Evap codes

Any manufacture specific codes present?

 

[97Sandbox]

I've put around 20-30 miles on it since the battery was reconnected. That includes a mix of highway and in-town driving, 4-5 cold starts, sitting and idling (while I poke around for leaks), and hitting WOT a few times.

I was reading more and it sounds like EVAP systems "like" to operate with the tank between 1/4 and 3/4 full. I've been running under 1/4 since the battery was hooked back up, so maybe the EVAP cycle really hasn't completed yet. My new PCM for the manual swap is tuned for 91 octane, so I was trying to run most of the 87 out of the tank before filling up with the good stuff. I might just go ahead and get a 1/2 tank of 91 to see if the EVAP system is satisfied afterwards.

 

[Blown]

I looked this up:

Run the engine at 2,000 RPM and observe your oxygen sensor voltages. If your O2 sensor is in good condition, it should react to oxygen content and change voltages quickly. A properly functioning oxygen sensor will show a rapidly fluctuating output voltage between approximately 0.1 and 1.0 volts. When the air-fuel mixture is perfect, the O2 voltage value will be exactly 0.45V. As the mixture becomes rich, the voltage will increase (up to 0.9 volts).

A reading only up to .75V is throwing the lean codes.

I agree with you if your thinking the EEC, being tuned for 91 octane is probably not able to compensate enough for the 87 Octane. The timing is higher and is kicking the burn off sooner. 87 octane fuel burns faster than 91, so igniting early with 87 is allowing a more complete burn of the fuel and is using more oxygen. That could result in the lean condition. I'd reset the codes and top-off with 91.

If this is correct the O2's should bounce higher with the 91 octane.

 

[97Sandbox]

I like your thinking, but need to clarify.

I only mentioned the 91 tuned PCM because it's the reason I've been running the Mounty low on gas -- preparation for switching to the tuned PCM. The stock PCM and 4R70W are still in the Mounty as of now. My goal is to get the engine running happily on a stock PCM before I dive into the driveline swap an peripheral upgrades.

Now to what you're saying about O2 values. Yes, I was only seeing values in the range of say 0.18 to 0.79 V while cruising at 1500-2000 rpm. So that means the PCM is unable to push the mix to what the O2 sensor would see as its richest, 0.8-1.0 V. You've answered my earlier question about what are "good" O2 values, and mine are are consistent with a lean condition. Worth noting, my B2 O2 is reading richer now than when it was severely loose and originally triggered the B2 lean code (previously it was only going up to around 0.4-0.5 V). Now to figure out what's causing both banks to run (or appear to run) similarly lean...

Your last comment has me thinking what if I did put in a fresh tank of 91? The 87 that's in there has been sitting since July, and while I did add stabilizer around September, it's not likely giving the engine, the PCM, or the O2 sensors their best chance to figure things out. Code reset and a fresh tank can't hurt anything. Would a fill up with 91 on a stock tune make things look better than they should though? Or will the octane not matter to the stock tune?

 

[Blown]

Whoops

I suppose old gas that has lost octane could do a similar thing. It shouldn't currently benefit from premium unless you are needing to add some octane to the old gas. We know premium wont hurt. That gas doesn't seem that old and with stabilizer added, but I would rule it out as it is easily done.

There is a resistance spec for the HEGO heater wires and sensor wires that can be checked and as you know it could be the other stuff posted-up here.

Good Luck eliminating items and getting it right!

 

[Blown]

I did a quick look and see 3-6 month for gasoline to degrade and the 10% alcohol in it degrades at twice the rate. With stabilizer, 6-8 months. I'd add at least 3X's premium to what you have in the tank now which is might be almost full anyway.

 

[97Sandbox]

To I'm sure no one's surprise, lean codes came back with the fresh gas. I was watching the O2 values on the way to and from the gas station and I never saw them go above 0.8V.

When I got home from the gas station, I also spent more time looking for a vacuum leak. This time I used the carb cleaner technique and sprayed my way along the breather tube, TB, intake, PCV and related hoses, HVAC/EGR/EVAP lines and fittings. I got no sign of a change in idle anywhere. I'm thinking a vacuum leak is not my #1 suspect. I was very thorough with the carb cleaner (not to mentioned I'd be surprised if my new gaskets were leaking. Before I ruin my headers with sealant, I at least want to rule out other possibilities, which I think are fuel and the O2 sensors themselves.

To evaluate fuel delivery, I just need a pressure gauge and to check for 55+ psi at the fuel rail while idling, right? If I have pressure there, it seems unlikely there'd be any other fuel issue because I have a fresh fuel filter and I sprayed out all my injectors with carb cleaner (while held open with a 9V) before reassembly.

Can anyone confirm a resistance spec for the Bosch 4 wire narrow band O2 sensor? I keep reading 5-20 ohm is typical for narrow bands, but sources vary. The heater circuit is a loop between the grey and black leads I'm guessing? I really doubt this is an O2 sensor issue given that both are still reading a range and a similar one, but I'd like to rule it out. I'll also check that the grey lead is getting 12V and the black lead is truly grounded if that's how they're supposed to be. O2 sensors ground through the PCM at the firewall, right?

Only other thing I'm seeing that could cause a lean condition besides the above and n exhaust leak is an ignition issue. Is there anything I should try to rule out on that front?

 

[410Fortune]

I e never seen ignition cause a lean condition on both banks

Check fuel
Pressure spec is 64psi +/- 8 psi

No leaks in the intake tube after the mas either, not just the plenum and elbow gaskets

Keep it up you are doing great, these are the front lines in the battle. Look how
Much you have learned

 

[97Sandbox]

I e never seen ignition cause a lean condition on both banks

Good to hear, I'll focus elsewhere.

Check fuel Pressure spec is 64psi +/- 8 psi

I'll pick up a gauge. It might be a day of two before I can run to Harbor Freight, have to check if Tractor Supply has something decent.

No leaks in the intake tube after the mas either, not just the plenum and elbow gaskets

Yes, I sprayed down where the breather tube meets the MAF, the vent barb from the oil fill neck, and where the breather meets the TB -- no idle flare for any of them.

Keep it up you are doing great, these are the front lines in the battle. Look how Much you have learned

Thanks. I know it probably looks like I'm making excuses not to pull the headers back off, but it's not about the labor of pulling them (I think I could do that in an evening now) as much as it's the fact I haven't identified any good way to seal them. And I really don't want to go back to stock manifolds because I already received my PCM with airflow tables updated for the headers and drivetrain swap.

 

[97Sandbox]

Got an interesting update tonight.

I rented a fuel pressure tester from O'Reilly, but it didn't work. I couldn't get fuel to pass from the Schrader adapter to the gauge. Boy did that gas spray when I pushed the pin on the Schrader adapter to though! At least I confirmed valve on the rail and the one in the adapter worked. I may rent a tester from Autozone tomorrow, just so I can rule out the fuel system once and for all.

Now to the interesting part. I've been racking my brain for an easy way to rule out the header leaks as the cause of the lean codes and today I had an idea. I packed the area between the four primaries on the left header with fiberglass and then shoved aluminum foil on top and cinched it down with baling wire (this is an experiment, not a permanent solution). My thinking was that if the exhaust leak is the main thing making my sensor read lean, reducing the leak should at least have some positive effect on the sensor reading. And by only packing one side, I should see a difference in B1/B2 readings (assuming each leaky header is what's causing it's related sensor to read lean).

Driving around, I noticed peak B1S1 values were up to 0.810V and B2S1 values were up to 0.835V. While that is richer on the side packed with fiberglass, I didn't think it was really that much and both sides were reading richer than past days, so I didn't think much of the difference. But the codes see it differently: I started the drive with P0171 and P0174 both pending, but when I ended the drive, the pending P0174 had disappeared but P0171 was stored. Maybe my theory is right and slightly reducing the leak is enough to make the PCM think all is well. Tomorrow I'll pack the other collector and tie some header wrap around the EGR fitting to slow the leaks on the driver's side. If that's enough to keep P0171 away, at least I will have confirmed the exhaust leaks are the issue.

I still don't have any solutions, but it feels like I might finally be close to confirming a root cause.

 

[410Fortune]

Those stupid fuel pressure testers they rent. I had the exact same issue a few weeks back, dude rented one and we could not get it to read pressure. My $35 harbor freight one works with our fuel rails and works every time.

Not sure why the oreilly unit would not work, the adapter looked correct but threaded on and nada… no fuel. Very odd. He returned it, we used mine… works great. I find it odd we both had the same Results? He did not tell oreilly about the issue because did not want to be charged the $150’or whatever it costs to “rent” it. $150!! Similar tool at hf is $40

Keep Going! No air leaks allowed!

 

[97Sandbox]

It looked to me like the inside of the fitting on the gauge side was chewed up so it wasn't actually pushing the pin on the Schrader adapter. I should probably just go buy the $35 HFT one, but I'll try Autozone's first.

If I can verify the lean code is just due to pinhole leaks in the headers, I have some ideas for how I can use pieces of muffler insulation (that's the source of the fiberglass I was using, not the stuff for your house or for bodywork) to cover the leak paths and pieces flexible aluminum and header wrap to hold everything in place. While this seems like an almost literal "band aid" repair, I have a feeling it'll hold up better than some gimmicky sealant. And more importantly it can be easily undone if there's an issue in the future.

The main downside I see is that as long as there are some leaks in the headers (even if the leaks are reduced by forcing them to push/pull through insulation) the engine will always be running richer than the O2 sensors think it is. That won't be ideal for fuel economy or making power, but I think it's something I'll probably have to live with as long as I have these headers. I can't imagine any exhaust on a 25+ year old vehicle is perfectly leak free anyhow.

 

[410Fortune]

Only has to be leak free to the upstream 02s lol lol

Rich is better than lean!

 

[97Sandbox]

Only has to be leak free to the upstream 02s lol lol

Right. When I pull the downpipes during the trans swap I think I'll go back with donut gaskets. I'll put a new crush washer on B1S1 too.

That just leaves blocking pinhole leaks in the headers themselves (the main hard part) and finding a way to get the EGR fitting to seal better. Has anyone ever used an M22 crush washer on the EGR fitting where it meets the header? I know it's supposed to seal on that conical surface, but mine is not perfect and leaked slightly when I tested it.

Rich is better than lean!

Agreed, it just rubs me the wrong way knowing that the PCM is getting biased input data.

 

[97Sandbox]

I may be on the verge of a breakthrough, and it's another plot twist.

I rented a fuel pressure tester from AutoZone and it worked about as well as the one from O'Reilly. Although it appeared unused, the Schrader adapter leaked a bunch so it couldn't build pressure to the gauge.

In the back of my mind, I was thinking the fuel test wasn't even worth doing, because I suspected my leaky headers were leading to falsely low O2 sensor readings. So I slapped more fiberglass and baling wire around the right collector and hit the road.

In past tests, I've just been looking at the raw O2 sensor and fuel trim live data values, but today something told me "how about you actually plot each sensor value?" I was thinking this would be good so I wouldn't have to constantly glance at my scan tool while driving. Only downside is I can only plot one value at a time. So I started with bank 1. It all looked like normal up-and-down O2 sensor data until I had to climb a hill. When I really put my foot into it, the O2 sensor value flatlined at 0.045V. It stayed there until I let off. Interesting. Switched to bank 2. Same story. When I got home I had both P0171 and P0174 pending again.

To me, the total flatlining at basically zero is a sign that when I approach WOT, I'm not getting anywhere near enough fuel. But at low and mid throttle, everything feels pretty good and O2 data looks normal. When I've had fuel pumps fail in the past, it was like someone hit the off switch, not an intermittent failure or slowly losing ability to pump at a higher rate situation. But does what I'm describing sound like a bad fuel pump? Given that I cleaned all eight injectors and replaced the fuel filter, I'm not suspecting those are limiting flow. What about the fuel pressure regulator, could it be choking down the flow abnormally at WOT?

It now seems like what's happening is the throttle opens and draws more air -- as it should -- but then fuel doesn't ramp up to match (maybe even cuts off) and O2s go drop to nothing. It's affecting both banks and it's repeatable (hit WOT and both O2 values fully flatline for the whole time as long as you stay at WOT).

I think I need to go buy that HFT tester!

 

[410Fortune]

Good idea

In the past a fuel pump worked or it did not work

With these systems that is less true. These pumps can make enough pressure to run but not enough pressure to keep up with demand. The fuel spraying from the injector will be more of a drip and not a spray. You need 64 psi +|- even when the pump is hot and has been running all day. Lean both banks is the first clue to check fuel pressure.
Air leaks of course are not allowed but I can tell iou these trucks run around all the time with small leaks at the headers and egr without
Throwing 171 and 174 codes… heck most of the 5.0 explorers still on the road the 96-97 have a broken welded manifold or the 98-01 trucks are usually missing a manifold
Bolt or two…they just fall out. And still no lean codes. I’m not saying it’s your fuel pressure for sure… the tester will do that for us! These are not the same old it either works or it doesn’t, the way the pumps are made they are super tough and they last 200k miles..
Instead of just dropping dead they keep spinning but they lose the ability to maintain demand

I have found similar results with the rent a tool pressure testers…
Very difficult to get one that fits our schrader valve and works properly, I think people just use the wrong fitting or over tighten or?? User error for sure

Good
Luck! You have come a long way! This is the school of hard knocks I’m always talking about

 

[97Sandbox]

Yesterday I didn't do much for the Mounty except degrease the M5R2. The transmission seems to be in decent shape, aside from the play in the input shaft and it shows evidence of having leaked around the shifter. I'll get a new rubber piece to seal it up, but otherwise I think I'm going to run the trans as-is. If it the input shaft chatters/growls, I'll be sure to pick up a rebuild kit for the 2wd M5 I have for my Sport (still theoretically the ultimate destination for the Mounty's 5.0).

Today, I finally picked up the $35 fuel pressure tester from HFT and it worked like a charm. I saw about 38 psi at idle and by 2k RPM it dropped to 35 psi...well there's my problem! Does anyone have a recommended fuel pump? There's quite a few options on RockAuto as far as brands and prices. Should I get just a fuel pump or the whole fuel pump and housing assembly?