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Interesting… If the exhaust is leaking before the o2 sensor it won’t be able to calculate correctly the relationship of what is going in and what is coming out.
There is no chance of an exhaust leak as I’ve replaced both exhaust donuts with new ones and there is no traces of a “tick” from a typical exhaust noise.
Something I ran across the other day that just dawned on me is that one of the things that I was messing with when I was trying to fit the stock airbox on, was the oil filler tube. I needed to reposition it to the passenger side about 2 inches or so. I unbolted it, drilled a new hole on the frame that goes over the alternator and bolted it down. The reason I bring this up, is that while I was messing with the airhorn gasket, I somehow managed to unscrew the oil cap and dropped it on the ground. Apparently that was a big no no as my STFT’s both shot up to 25 on my Actron scanner….this was the second time while working on it that day that I had done that very thing.
Now, I don’t know if you believe in it or not, but I think that dumb cap coming off the second time may have been someone telling me something. For the fuel trims to go so haywire just from removing the oil filler cap, I’m thinking that if the gasket that the filler tube goes into the valve cover is leaking that my problem lies within that area.
It would make a lot of sense too. The van ran great before I worked on the E fan. While working on the E fan, I decided to get side tracked with the air cleaner assembly. In order for the air cleaner assembly to fit, the oil filler tube needed to be moved out of the way. That was seemingly an easy thing to do-drill a new hole and bolt it into the new position.
So, I’m going to find a way to test my theory…but this time I’m going to make a video of the process. I’ll either fail or I’ll succeed, but either way, I’ll post it here for everyone to see.
Oh, and to answer some questions raised….both 02 sensors are brand new as of spring 2011 ( Standard brand ) though one problem I had with the drivers side was that the bung hole when the custom exhaust was made wasn’t large enough for the end of the new O2 sensors. I ground it out with my dremel the best I could, tried to get a tap in there to open up what I couldn’t with the dremel ( very tight fit…couldn’t drop the exhaust enough for clearance…most of it was done blind ) and when I installed the drivers side O2, it was still pretty tight, I’m sure at the very least the end of the O2 sensor got a little dinged up. The plan was to find an actual 18mm tap and run it through the hole to clean it up completely since the one I had borrowed was just to clean up the threads, So I’ve always suspected that that sensor might not be at 100%. It got the van running and the readings never seemed out of range, so I’ve left it be.
Dude it has an intake gasket leaking vacuum.
Confirm test with propane while watching fuel trims, they should go negative when you find it but from the sound of it it is leaking into the lifter valley area.
The reason the thing runs good is because the computer is designed to correct for issues up to a certain level. (They do an awsome job at hiding problems which is why god made guys like me)
When that threshold has been met then the vehicle will run like crap.Also since that is a express van 5.7 the original intake gaskets are made of plastic and commonly break down and leak vacuum.
I suggest you buy the felpro problem solver metal gaskets instead of the oem gaskets.I won’t discount your advice, and I will do the propane test as I do have a propane torch I can use for that. However, the simple fact remains that there were no codes being set and no smell of rich exhaust before I started working on the E fan conversion and the fact that I screwed around with the air cleaner assembly and the oil filler tube need to be removed from the equation before I’m going to believe that suddenly out of no where I’ve got an intake gasket leak.
My tranny guy tried to get me to buy that I had an intake leak because of all the misfires he was seeing on his scanner. He also told me that my CMP retard was at 20 counts. Huh, I adjusted the CMP retard with the OTC Genysis to 0 and all those misfires disappeared from the scanner!
I wasn’t seeing any misfires when I had it on the scanner just recently either, and if I had intake gasket leaks, wouldn’t we assume that we’d be seeing misfires to some degree?
Either way, I’ll do the propane test…who knows, stranger coincidences have been known to happen ( like an in tank fuel pump dying on us while doing an routine oil change when I worked in a shop ).
Oh, and I’m going to replace both the valve cover grommet and the oil cap since it appears to be worn out if it’s popping off just by brushing up against it the wrong way.
Intake gasket leaks may not show up as misfires but according to the data you posted it looks like there is what the computer interperates as a lean condition and is richening the mix, since intake gaskets are known to be a problem on that engine it’s a good place to start looking.
Well, I did my best to do a propane check and didn’t get very far with that as far as finding any kind of leak, so I switch to carb cleaner. The only place that I got the O2 readings to change were around the ducting on top of the throttle body. I’m not completely convinced though. I made a gasket for the base, and then put a rubber band on it ( a thin one, about 1/8th inch wide ) and then put the duct back on. It was pretty tight, but I still get the codes. However, that may be causing more problems for all I know.
I’m going to see if I can source another intake duct and see if there is any change. Beyond that, I’d love to do a smoke test on the van. Had thought about buying a cheap cigar and try to draw as much of it into the intake as I can. I may try that on Sunday if the weather holds out for me.
As it sits though, I’m getting pretty much the same single digit numbers when I run the engine at 2500rpm with a slight spike when peak vacuum is attained. The freeze frame data seems to be taken at various RPMs, from idle to the current freeze frame @ 2250 rpm, engine no fully warmed up ( about 150F ) under about 1/3 throttle.
It might help if I understood the relationship of the MAF and MAP sensor data. Might be a good basic video for you to shoot Eric! There are plenty of cheap scanners out there in the hands of guys like me that give us data, but we don’t truely understand what it means. Live data and freeze frame data can tell so much, but it’s like a white guy trying to read the tea leaves…if you haven’t been taught, you can only guess and assume so much.
Well, I replaced the intake duct and have no change in the code. My Mileage stays at a steady 14.5ish mpg, down from 15.5ish mpg. I’ve seen as high as 16mpg since the code showed up, but I’ve seen that before the code showed up when I look back at my fuel logs. Sadly, it’s gotten damn cold around here and I’m more reluctant to just go outside and pop that doghouse off again and start looking for the problem to verify what needs to be remedied. My thought was to disconnect and plug any unnecessary sources of vacuum ( vac line to the heater controls, the hose off the duct from the passenger side valve cover ( non pcv side ) to see if I can reduce the number of sources for potential leaks.
One thing is certain, my heating system suffers at an idle vs off idle, which leads me to believe that I’ve got something going on. The Previous owner had not reconnected the vacuum ball which is what I thought was the culprit, but since I still have the problem after connecting it back up, I need to double check that I have that system connected properly. Wish I had a garage to work in, I may have just yanked the intake off already and replaced the gaskets just for good measure by now. I’m don’t like throwing parts at this without being able to verify the problem, but I’m running out of ways to do it…and this darn dual exhaust is too noisy to hear anything that isn’t obvious….I need to muffle the exhaust more.
Interesting note about the heat not working at idle, I’m wondering if you have enough flow through the cooling system, if not then it’s possible that the coolant temp readings are off thus causing the fuel mix to be off. What kind of shape do you think your water pump is in?
Keep us posted I’m interested to see how this pans out. Good luck and stay warm.
Quoted From EricTheCarGuy:
Interesting note about the heat not working at idle, I’m wondering if you have enough flow through the cooling system, if not then it’s possible that the coolant temp readings are off thus causing the fuel mix to be off. What kind of shape do you think your water pump is in?
Keep us posted I’m interested to see how this pans out. Good luck and stay warm.
I rerouted some of the vacuum connections to take proper advantage of the vacuum ball, and reconnected a fitting that was disconnected. Not sure if that happened while driving or when I was rerouting the vacuum ball connection. I’ll have to check to see if that corrected the problem. It seemed that it was relative to engine vacuum, not engine speed. The heat works great in the van, it was just that it would go away temporarily. I’ve watched the temp gauge on the scanner and it never hits over the 195F that the T stat is designed for.
An interesting side note though…I had replaced the temp gauge sender because I broke off the wire by accident, and when I replaced it with a STANDARD brand sender, it shows my temps at 210 running, but when the thermostat is closed, the temp will read almost up to the 260F mark…as soon as it hits it, you can see the gauge drop off down to 210 again…I didn’t have that kind of movement with the 180F stat that was in there before. I do think the higher temps may be because I think I may have put thread tape on the new sending unit, which would increase the resistance and cause a higher reading if my thinking is correct…
Alright, I’m beginning to wonder. I was out today working on my cars and decided to revisit my van ( I only drive it every other week ) and decided to clean the MAF with the appropriate cleaner. Then I decided I was going to start the van with no air cleaner housing connected. My STFT’s were in the negative single digits, around 3 on my scan tool. While the engine was running, I hooked the air cleaner back up and the readings flip flopped to positive 3’s. I get a feeling that this old air cleaner needs to be replaced. I’ve been still searching for a way to put a conventional air cleaner on this van, but without actually modifying the hood to accomodate the space needed to do it properly, I’m stuck with what I have until I can come up with something else. For now, I’m going to replace the air filter ( cone style ) wtih the exact same type and see where that gets me.
You need to make sure the MAF is in the airflow of the air going into the engine and that there are no leaks between the sensor and the throttle body, if not it won’t be able to get proper readings.
Yup and Yup. There’s only a short collar between the plastic intake duct and the MAF, so chances of it being any source of a vacuum leak are slim. However, I did replace that year plus old cone filter with an exact replacement. I’m now getting STFT readings pretty steady in the plus 10 range. I’d really like to get a smoke test done on this before I plunge into an intake gasket replacement, because I’ll tell you what, if it’s not the intake gasket and something else I’d really pop a cork.
Honestly, if I had a garage I think I’d have probably just bit the bullet and replaced the gasket whether it was the problem or not, just for piece of mind.
A leak in the tube between the MAF sensor and throttle body is not a vacuum leak, it’s actually something referred to as ‘pirate air’ meaning air that was not measured by the sensor and therefore it can offset the fuel mix and cause performance issues. A MAF sensor actually measurers the incoming air going to the engine and the fuel mixture is based off of this reading. YOu don’t need a smoke machine to find these leaks often you can often just ‘play’ with the hose as the engine is running listening for a change, if you hear one it’s worth a closer look.
Well, no new good news, but some more information gathering.
So, I did a little experimenting. With the new Air cleaner on, my STFT ( short term fuel trim ) readings were reaching into the double digits positive. So, since it’s winter and there isn’t much for environmental debris floating around, I decided to just run the MAF sensor open with no filtration. Huh, the STFT readings were right down close to 0 where it’s supposed to be ideally. However, when I started the van, it stumbled a little and the RPM had more fluctuation to it ( it would drop RPM slightly from time to time ). It is smoother with the air cleaner on, though you can see the needle dip slightly every few seconds.
This of course got me scratching my head. I’m certainly not a savant when it comes to deciphering engine data. I’m still working on figuring out the correlations between what the MAF and MAP sensor are telling the computer what’s coming into the engine, vs what the O2 sensor is telling it that is coming out of the engine. The cross talk and how the computer compensates for the values is still a bit of a mystery to me.
What my limited knowledge tells me though, is that there is certainly something wrong. If the Air cleaner assembly is causing a restriction, then any source of new intake air via a gasket leak or “Pirate air” as Eric referred to is going to be more evident due to a higher relative manifold vacuum. With the air cleaner off, the restriction is gone and the engine can breath freely. I put a plastic bag over the cone filter and restricted it down as far as I could without stalling the engine at idle. With a brand new filter, it seemed that the amount of filter area exposed was really small for a v8 engine. I had probably 90-95% of the filter covered with the bag and it still ran smoothly. I suppose at idle the engine really doesn’t require a ton of airflow though.
One other thing that struck me odd was that when I first started the van up ( with the air cleaner on ) was that I could hear the intake suction through the cone filter plain as day. It went away completely after a minute or so of idling.
I have to say one thing for sure, I probably would have been able to discover the problem on my own easier if I were dealing with a truck just due to the trouble I have to go through to access the majority of the motor.
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