New 5.0L built, low compression and horrible MPG

[1998Exp]

"ECT out of range" does not mean too cold, but producing a voltage that's out of its range of measurement. That usually happens when the sensor is bad, or much more likely, when there is a connection problem: an broken wire, a short to ground, or some such.
The data that you showed in the other post indicates that the ECT is working properly, so it could be just a fluke, or perhaps an intermittent. It's worth pursuing, because the PCM is quite clueless without a valid coolant temperature reading.

Here's some other tests I ran. Might have found an indication as to where my abs issue may be coming from. The ECT out of range I'm assuming is because I ran all these tests before the truck was warm, but maybe not? My ultra gauge reads engine temp no problem but maybe that's reading off a different sensor? It also looks like the ECT sensor is working well based on the real time data in the above post so I think I can ignore that.

 

[1997XLTRollover]

"ECT out of range" does not mean too cold, but producing a voltage that's out of its range of measurement. That usually happens when the sensor is bad, or much more likely, when there is a connection problem: an broken wire, a short to ground, or some such.
The data that you showed in the other post indicates that the ECT is working properly, so it could be just a fluke, or perhaps an intermittent. It's worth pursuing, because the PCM is quite clueless without a valid coolant temperature reading.

My ultra gauge reads engine temp just fine too. It sits right around 192 degrees so it's a little weird. Maybe I'll try it again tonight when the truck is fully warmed up. But I'll take a look at the ECT sensor and figure out how to test it.

 

[1997XLTRollover]

Ok so I checked my ECT tonight and it read fine. I changed it anyway. No change. So I've changed the ECT and both upstream o2's with good used parts from an 01 Navigator I parted out and the truck is still messed up. I think the o2's are the same, short of wire length, and the ECT had the same part number on it.

Here is another screen shot tonight after warm up and a few more fields. I found the proper RPM field so that works now. I also noticed that ever since I did the intake gaskets the truck seems to like to idle high. Maybe my throttle body is not set right?

Does anyone with a good running V8 truck have forscan that can do a screen shot like I have to see if we can figure out what might be out of wack? I have no idea where to go from here.

 

[1997XLTRollover]

Did some more reading and I guess EGR and or EVAP can cause a problem. I'm going to test that next. I do have an EVAP code popping up so maybe there's a massive EVAP leak (big surprise). I'm just going to pull the line off the manifold for EVAP and plug the manifold to see if that changes anything.

There is only one line going to the manifold that can cause a leak for EVAP correct? So plugging that line should take the EVAP out of the equation? I'll run a smoke test on the EVAP if I have time but for now I have to get this engine running right before I put a hole through a piston.

 

[rb142]

In the earlier posts, your fuel trims are way out of line -- indicates an air leak most likely, and may only be when cold or hot. It's affecting both banks, so it's probably in the manifold or intake tubing.

 

[1997XLTRollover]

In the earlier posts, your fuel trims are way out of line -- indicates an air leak most likely, and may only be when cold or hot. It's affecting both banks, so it's probably in the manifold or intake tubing.

You sir I believe are spot on.

Here's what I did tonight before my piece of **** starter stuck on. Now I can't drive the truck anyway, but that's yet another story with this piece of crap truck (missing my 99 so bad again). Another thread on that going up shortly since now I'm getting rides to work again looks like.

So I started with a good smoke test again and really looked things over better than last time. Noticed the EGR hose was pretty loose, and it was in fact leaking pretty good. I haden't noticed it last time because I thought it was all coming out of the EGR itself. I then saw the IAC leaking as it was last time but it was leaking around the crimp as well, so I sealed the crimp up with RTV but left the cap alone since I'm assuming that's designed to leak a little and probably programmed into the computer.

After that I took the EGR hose off and applied vacuume to close the valve. The smoke from the EGR virtually stopped and boy oh boy did my intake manifold start smoking. As soon as the EGR closed and the manifold pressurized my intake exblow seals starting blowing smoke all over the place.

So I think this entire time it may have been multiple bad intake leaks, I just couldn't see them because of the EGR losing so much smoke pressure. They're all new gaskets but I'll take them off and use RTV this time and replace that EGR hose that's leaking too. Hopefully this will end this engine saga, but first I have to deal with the starter because I can't run the truck now without the starter staying engaged.

Bare with me while I get the starter issue fixed but I will post back with my results after I fix these air leaks. Still weird I never got a lean code with how lean my truck is but whatever.

 

[rb142]

You probably won't get a lean code until it runs out of range on the fuel trim. The trim is pushing a lot of extra fuel in to compensate for the leaking air. If that's enough to satisfy the oxygen sensor, then no code. But you are pushing a lot of extra fuel through the system and your fuel economy goes with it. It also explains the idle issues. Should be fine with the leaks fixed.

 

[1997XLTRollover]

Ok guys I don't believe this but I sealed everything and just bought and replaced the 2 upstream o2's with brand new motorcraft ones. There are no more leaks in my intake. I even plugged my EVAP port on the manifold to see if there was some massive leak being pulled in there. I'm still getting 10mpg and here's a new screen shot after fixing my intake leaks. Can anyone decipher what might be wrong now?

 

[SoHK_alumni]

Your readings of .88 volts on both upstream O2 sensors are showing very very rich.

What really is odd is the fuel trims are showing deliberate enrichement from the PCM while the O2 sensors are showing maxed out rich already. Really really odd.

Have you tried a different PCM?

And, have you checked for excessive back pressure in front of the cats?

 

[Dono]

One quick thing I see is that you are showing you are in 'open loop' on this screen shot.

Are you going in to closed loop any more?

edit: above post brought something to mind...
Didn't you say your pcm came off a different motor?

 

[rb142]

Yeah, the open loop thing jumps out. Was that screenshot taken right after starting? If it is staying open loop all the time, that would explain a lot of the fuel problem. You need to look at those O2 sensor signals on a scope.

 

[1997XLTRollover]

Pcm is factory and truck is a true 5.0 truck not swapped. I actually noticed the open loop thing too. No it was not right after start up. Truck was driven probably 5 miles before this screen shot was taken and was fully warmed up as seen on the ect.

 

[1997XLTRollover]

Your readings of .88 volts on both upstream O2 sensors are showing very very rich.

What really is odd is the fuel trims are showing deliberate enrichement from the PCM while the O2 sensors are showing maxed out rich already. Really really odd.

Have you tried a different PCM?

And, have you checked for excessive back pressure in front of the cats?

No I have not tried a different pcm and as far as backpressue I did look down the exhaust at the cats when it was off the truck and they looked fine.

So if those values indicate a rich condition, and the pcm is trying to richen it further why the heck do my plugs look lean as all hell. Could my mechanical timing be off causing the initial fuel charge to be pulled out the exhaust?

 

[SoHK_alumni]

Yea, it might be time to double check all your timings.

I've seen out of spec harmonic ballancers, heck, took a week once diagnosing a no-start Chrylser 440 that had a incorrectly marked cam gear.

To "eye-ball" the external timing:

Roll the engine to TDC and remove the harmonic ballancer bolt.

The key way on the crank should be absolutely vertical, the gap in the teeth in the pick up ring should centered on the vertical and of course the timing mark should be at the 0 degree mark.

On the CPS, the "blade" should be about 1/8" into the window from the left side.

After that, might be worth the effort to pull the water pump and timing cover and verify the cam's key way is also absolutely vertical.

Oh yea, one thing that could hold the engine in open loop is an incorrect temp reading from the non-gauge temp sensor above the t'stat. The sensor over by the p/w pump is only for the gauge, the other is only for the PCM.

Anyway, if you're interested. I've a spare '96 PCM. If you want, I'll send it out if you'll promise to return it.

 

[1997XLTRollover]

Yea, it might be time to double check all your timings.

I've seen out of spec harmonic ballancers, heck, took a week once diagnosing a no-start Chrylser 440 that had a incorrectly marked cam gear.

To "eye-ball" the external timing:

Roll the engine to TDC and remove the harmonic ballancer bolt.

The key way on the crank should be absolutely vertical, the gap in the teeth in the pick up ring should centered on the vertical and of course the timing mark should be at the 0 degree mark.

On the CPS, the "blade" should be about 1/8" into the window from the left side.

After that, might be worth the effort to pull the water pump and timing cover and verify the cam's key way is also absolutely vertical.

Oh yea, one thing that could hold the engine in open loop is an incorrect temp reading from the non-gauge temp sensor above the t'stat. The sensor over by the p/w pump is only for the gauge, the other is only for the PCM.

Anyway, if you're interested. I've a spare '96 PCM. If you want, I'll send it out if you'll promise to return it.

Well for starters here's a couple pics of when I was putting this thing together. It's hard to tell from the pics but I'm 99% sure I had both timing marks straight up and down. The only thing I can think of is the timing set was machined wrong giving me a false straight up and down when lining up the marks, but then again I don't think the cam pin would line up unless the entire gear was machined a few degrees off or designed for a different engine. Is a carbed 60's 302 different than the fuel injected timing? Maybe this timing set is for a 302 with a carb?.

Now I don't really know how the old engine ran, but I did also check my balancer and it doesn't seem like it has slipped, especially because all the timing marks lined up when I set the shortblock to TDC.

Far as the ECT sensor I don't think it's bad. It reads 190-194 when running and the thermostat is brand new too. That being said I just replaced the ECT a few weeks ago with no change to fuel mileage.

As far as the PCM do you think that could actually be my issue? I'd hate to have you send it out before I've exhausted all options. Unless we find something pointing at the PCM being the issue.


Click for the large pic:

 

[1997XLTRollover]

Does anyone know what the manifold vacuum should be at idle? I'm thinking I can check that and see if it's out of wack. That should give me an indication of a mechanical issue no?

If it reads right maybe my PCM is screwed? My old engine was burnt up pretty bad at only 143k miles. The rear 2 cylinders on the drivers side looked like they got very hot and second from the rear was worn out pretty bad almost like the cylinder got washed out over time and wore very very bad. The engine still ran ok but made a hell of a racket most likely due to that piston slapping around.

The more I think about this the more I'm thinking I have some other issue going on and it's not mechanical. If the o2's are reading rich and the PCM is telling the injectors to dump more fuel, something doesn't make sense. What's really odd is the plugs look lean. But plugs aside, if the o2's are reading rich the PCM should be leaning out the mixture not adding fuel regardless of what's actually happening in the cylinder no?

 

[Dono]

Manifold vacuum should be 16-18 at idle.

I'm not sure whats going on either. Unburnt fuel thru the exhaust tends to make the o2's read leaner and tells the pcm to add more fuel.

Your right, there seems like a contradiction in what you are actually seeing.

 

[1997XLTRollover]

Manifold vacuum should be 16-18 at idle.

I'm not sure whats going on either. Unburnt fuel thru the exhaust tends to make the o2's read leaner and tells the pcm to add more fuel.

Your right, there seems like a contradiction in what you are actually seeing.

I'm going to check manifold idle vacuum and then make sure the EGR is closing the way it should. I would think I would have a code but maybe my EGR vacuum is not strong enough and my EGR is stuck part way open? I know I can close the EGR when I apply vacuum myself but maybe for some reason the engine is not able to.

I'll also get some more snap shots of the sensor readings.

Couple more questions though.

1) Is the EGR supposed to be opened or closed at idle? Basically when should I expect the EGR to actually close?

2) What is a good port to test the idle vacuum at?

 

[Dono]

egr closed at idle.

Any vacuum port off the intake manifold. There is one at the front of the motor more towards the drivers side for evap on a funny clip connector that is probably pretty easy to get at.

 

[1997XLTRollover]

egr closed at idle.

Any vacuum port off the intake manifold. There is one at the front of the motor more towards the drivers side for evap on a funny clip connector that is probably pretty easy to get at.

Closed EGR is when there is no vacuum correct? At rest the EGR is closed and requires vacuum to open? Or is it the other way around?

EDIT:

Nevermind it has to be, the thing would idle horrible if it had EGR flow at idle. I'm guessing as vacuum increases and the computer grounds the EGR circuit the EGR should open. Hopefully I can just rev and see it move. If not I'll have to close the hood on my gauge and try to watch it while I'm driving or just throw the truck up on 4 jack stands.