Possible flaw in AEM CAI manufacture

[Griffin]

Jaysong came over today and we took a loof at his car 'cause hes been getting P0171 Lean codes and his lift is not kicking in intermittently. We took off his valve cover and confirmed that the set bolt for his intake side rocker shaft was snapped allowing it to spin and give intermittent operation. I probably should have taken pictures except I dont have a digital camera. All well and good. We also did a good amount of testing of his intake system - I have Toyota Handheld Diagnostic Tester so we took some readings and did some research - heres what I did and what we found:

To begin with I checked the codes history (he had a stored P0171 system lean - set at idle) and Grams per second reading of his intake. He was reading like 1.4 - 2 G/S at idle and 5.4 - 6.4 G/S at 2500 RPM. This is way below norm with a factory intake. His MAF wasn't dirty but had a split O-Ring so the first thing we did was to drop the MAF off my wife's RAV4 in there (same part number). It read exactly the same as the old one. His fuel trim was also jacked up - I observed long term fuel trim of anywhere from 10% to 34% positive while we were driving around. Obviously this is the source of his lean codes. So I checked the O2 sensor waveform which was oscilating normally with a slight lean bias - it didn't seem to be unresponsive or fouled from the look of the waveform so I ruled that out for the time being. Next I looked for intake leaks - I tightened his intake hose connections a tad, no change. Well I figured there must be a small vacuum leak somewhere to account for the jacked MAF reading so I got a can of propane and started spraying around near all the joints for all the intake hoses, the MAF itself, and other places. No change in RPM, no dice. I even tried using a plastic bag to encapsulate the MAF affembly in case the leak was there... again no dice. So I'm getting annoyed now - this isn't making any sense at all. The engine if functioning properly pretty much HAS top draw a given amount of air at idle and 2500 PRM, its a simple mechanical fact. We're pretty much at sea level, its maybe 80 degrees out, his idle speed is normal, whats going on.... So then we looked at the actual disposition of the sensor itself with regards to the intake and I suddeny got very wary. The old mark one eyeball showed that the MAF centerline was offcenter to the pipe, and not even parallel with the direction of airflow. I double checked and it was in fact installed offcenter and at at a slight angle to the direction of airflow. I then checked the insertion depth into the pipe and that seemed off as well. To verify I removed the retaining bolts, and brought the axis of the MAF back in line with the pipe as much as I could. It seemed to cause an average rise of about 0.3 grams per second. I'm currently guessing that the insertion depth being off may account for the rest of the problem.

Jay is going to put his intake back to stock and get his lift fixed. Then we'll check his Grams per second readings and fuel trim with teh stock intake and see what there is to see. I imagine it will be back to normal and it will be time for Jay to talk to AEM. My guess is that the riser block for the MAF is hand welded and hence subject to some variance. The pipe interior around the block is also rough and not uniform which may disturb the airflow even more. As such this may be just a one off poorly made peice. I posted this here because I figure some of you might get a chance to check similar units and see what you think. I don't want to alarm the people in the performance forum unecessarily.

Griffin

[Raymund]

"We took off his valve cover and confirmed that the set bolt for his intake side rocker shaft was snapped allowing it to spin and give intermittent operation. I probably should have taken pictures except I dont have a digital camera"

could this be the bolt you are speaking of?

http://www.imagestation.com/picture/sraid25/pc8cc679151591f68c0b122d47f541fce/fd90420a.jpg

guess what.. the broken one came from the intake shaft!? I had to use a bolt extractor to take it out.

[Griffin]

Originally posted by Raymund
"We took off his valve cover and confirmed that the set bolt for his intake side rocker shaft was snapped allowing it to spin and give intermittent operation. I probably should have taken pictures except I dont have a digital camera"

could this be the bolt you are speaking of?

http://www.imagestation.com/picture/sraid25/pc8cc679151591f68c0b122d47f541fce/fd90420a.jpg

guess what.. the broken one came from the intake shaft!? I had to use a bolt extractor to take it out.

You thats the same one :) Interesting you had the same problem on the same Cam, I may have to call a few guys I know and see if they have looked into this at all yet. If not I'll have to light a fire or something :)

Griffin

[Raymund]

The old mark one eyeball showed that the MAF centerline was offcenter to the pipe, and not even parallel with the direction of airflow. I double checked and it was in fact installed offcenter and at at a slight angle to the direction of airflow

I have an Injen intake and I noticed the MAF is instaled in the middle of a 90 degree bend. Looking from the stock box and the AEM the MAF is mounted on a straight portion of the piping. Do you think that can also affect readings? Last I check, the MAF seem parallel with the pipings direction. I'm not sure about MAF depth though.

I

[GTS LAID]

wow ... really interesting info... so in actuality it was 2 separate problems... and the bolt thing really had little to do with the error codes but had more to do with the lift problem?

[Griffin]

Originally posted by GTS LAID
wow ... really interesting info... so in actuality it was 2 separate problems... and the bolt thing really had little to do with the error codes but had more to do with the lift problem?

The bolt has nothign to do with teh lean code. The VVTLi problem and lean code are definitely 2 different issues.

Griffin

[Griffin]

Originally posted by Raymund


I have an Injen intake and I noticed the MAF is instaled in the middle of a 90 degree bend. Looking from the stock box and the AEM the MAF is mounted on a straight portion of the piping. Do you think that can also affect readings? Last I check, the MAF seem parallel with the pipings direction. I'm not sure about MAF depth though.

I

It can definitely affect them. The MAF works by taking a sampling of a small portion of the air coming through. Its is affected by both air velocity and density. Hence localized disturbances and the maf being offcenter to the direction of airflow will affect readings. The thought is that the sensor being towards the edge where there may be more turbulence and slower moving air (because of depth and imperfections in the pipe itself) and tilted out of the direction of airflow (by being off axis) would result in a reduced amount of air actually flowing through the sensor at what may also be reduced velocities, which would cause a lesser reading than the correct one. This has teh same net effect on base fuel calculation as a dirty MAF or an intake leak... the air is not metered and the base fuel calculation is too lean. It is then up to the O2 sensor to make the correction which it does, but the fuel trim exceeds acceptable values and causes a lean code. This may also result in reduced sensitivity to increased load and acceleration which could cause some amount of bogging or slow throttle response.

Mind you untill we put the intake back to stock this is all still theory. I want to make sure his engine is in fact flowing normal amounts of air and the sensor is reading accurately before I condemn the CAI.

Griffin

[autxr]

Griffin-

This is an interesting analysis. I certainly will buy into the idea that the MAF needs to be turned the right way, but I'm less convinced that the location in the pipe matters (as much), so long as it has full exposure to the air.

But, this answers a question you have raised before...

What's the S-AFC for...

It will let you dial in the needed MAF corrections to have the right airflow signals reaching the ECU.

Scott

[Griffin]

Originally posted by autxr
Griffin-

This is an interesting analysis. I certainly will buy into the idea that the MAF needs to be turned the right way, but I'm less convinced that the location in the pipe matters (as much), so long as it has full exposure to the air.

But, this answers a question you have raised before...

What's the S-AFC for...

It will let you dial in the needed MAF corrections to have the right airflow signals reaching the ECU.

Scott

Not necessary if the CAI was built properly. And it still won't fix the bog on acceleration if the MAF positioning is causing delayed and muted exposure to airflow conditions - all the correction is being made on the O2 side and teh feedback circuit is not responsive enough to prevent bogging.

Anyhow I don't think proximity to the side would matter if it wasn't for all the irregularities and lips and stuff where the riser to bolt the MAF on is welded up. If it was seated deeper I would be less tempted to attribute part of the problem to depth on this particular CAI. However the inside of the pipe is, as I said, very rouch and I can definitely see the MAF being close to this having an effect on airflow. Not to mention that I was not able to prodice a full corretion of MAF numbers by rotating the sensor, merely a partial one. If his readings go back to normal with a stock intake then I will KNOW this was a problem.

Griffin

[Raymund]

"The thought is that the sensor being towards the edge where there may be more turbulence and slower moving air (because of depth and imperfections in the pipe itself) and tilted out of the direction of airflow (by being off axis) would result in a reduced amount of air actually flowing through the sensor at what may also be reduced velocities, which would cause a lesser reading than the correct one. This has teh same net effect on base fuel calculation as a dirty MAF or an intake leak... the air is not metered and the base fuel calculation is too lean."

I see. I suppose the same could be said about the sensor being placed too deep in the inner part of the bend where air flow would normally travel at a quicker rate and a rich mixture can result? Would it be possible to run a rich mixture enough to hinder noticable performance without ever triggering an engine light? Or, will the 02 censor be enough to compensate for the little difference and adjust the proper air/fuel ratio? Reason I ask, I recall the MAF being placed in the inner bend of my Injen CAI. So far it has not triggered an engine light but Im always up for any bit of hp gains specially since we cant tune much on our cars like ignition timing, fuel pressure, etc..

What would be nice is if someone can fabricate some gaskets with 1mm thickness and place it on the MAF mount and see if there are any noticable difference on the dyno at the same time have a Diagnostic handheld tester note out fuel mixture readings.

[RJpinoyGQ1]

Interesting...

I have an AEM intake, and like many others who own one, my check engine light is on. Went to toyota today and got it serviced because my car was due for one. While i was there i asked them about the CEL thats been on for a week and told them i had an after market intake system installed as well. They told me that the intake is probably the cause of the light coming on. So they told me i could get them too look at it for 95 bucks. They'll prolly come up with the same codes you guys said. So im wondering should i have them pull it up and see if they can diagnose the problem? or wait here and see what happens with AEM.

[Griffin]

Originally posted by RJpinoyGQ1
Interesting...

I have an AEM intake, and like many others who own one, my check engine light is on. Went to toyota today and got it serviced because my car was due for one. While i was there i asked them about the CEL thats been on for a week and told them i had an after market intake system installed as well. They told me that the intake is probably the cause of the light coming on. So they told me i could get them too look at it for 95 bucks. They'll prolly come up with the same codes you guys said. So im wondering should i have them pull it up and see if they can diagnose the problem? or wait here and see what happens with AEM.

Well, it depends what code you have. If its a P0171 then the first thing I would check is the cleanliness of the hot wire and thermistor elements in your MAF. If its dirty/oily try cleaning it. If you do a search there are some threads that address how to clean it. Also check all your hose connections and your MAF to be sure they are sealing properly and that you don't have a vacuum leak.

Griffin

[RJpinoyGQ1]

define sealing properly...all i did was tighten the hose clamps down.

and the mafs is clean. is the color suppose to be black or clear. mines black, but doesnt have any residue whatsoever on it. ran a q-tip across it, q-tip remained white.

[Griffin]

Originally posted by RJpinoyGQ1
define sealing properly...all i did was tighten the hose clamps down.

and the mafs is clean. is the color suppose to be black or clear. mines black, but doesnt have any residue whatsoever on it. ran a q-tip across it, q-tip remained white.

The MAFS should be silver... the element you need to clean is down in the black plastic tube - vcants see it without a flashlight. Its very delicate and must be cleaned with a non residue cleaner. If its black and ont clean off you may need to get it replaced.

Griffin

[RJpinoyGQ1]

i guess i was talking about the air temp sensor. is that suppose to be a dark color? The two wires in the plastic are silver. Im guessing thats what ur talking about.

Ive been reading a lot of stuff that hafta do with CEL's and CAI's. Mainly everyones talking about leaks and dirty MAFS

Griffin, can u sum up what to do if you installed an aftermarket intake and recieved a CEL 2-6 months after installation?

Some say they take theyre car to the dealership and they can get the code cleared for free under warranty. others say it cost a hell of a lot to fix the prob at the dealership. some fix it themselves but end up prolonging the CEL.

I took apart my AEM and put everything back on together my self. after reading a couple of these threads, i feel like i hafta seal that o ring real tight. still have a CEL. should i take it to toyota? i dont kno what to do. lost man needs help

[Griffin]

Originally posted by RJpinoyGQ1
i guess i was talking about the air temp sensor. is that suppose to be a dark color? The two wires in the plastic are silver. Im guessing thats what ur talking about.

Ive been reading a lot of stuff that hafta do with CEL's and CAI's. Mainly everyones talking about leaks and dirty MAFS

Griffin, can u sum up what to do if you installed an aftermarket intake and recieved a CEL 2-6 months after installation?

Some say they take theyre car to the dealership and they can get the code cleared for free under warranty. others say it cost a hell of a lot to fix the prob at the dealership. some fix it themselves but end up prolonging the CEL.

I took apart my AEM and put everything back on together my self. after reading a couple of these threads, i feel like i hafta seal that o ring real tight. still have a CEL. should i take it to toyota? i dont kno what to do. lost man needs help

Me - I'd first take your car to autozone and find out WHAT CEL code you have. If its P0171 lean code I'd check all your connections and make sure they are tight. Get a acan of carb clean sporay it near any potential intake/vacuum leaks and see if the rpm jumps (if it does theers a leak). Also clean the MAFS even if it is clean and maybe get some kind of thing rubber gasketing material to help seal teh MAF to teh CAI. Also get an injector flush and make sure your using good quality high test. Then clear the CEL and see if it comes back.

[RJpinoyGQ1]

Originally posted by Griffin


Get a acan of carb clean sporay it near any potential intake/vacuum leaks and see if the rpm jumps (if it does theers a leak).

if i walk into a store and ask for carb clean..they'll kno what im talking about? and when u say if the rpm jumps, are you saying spray the carb clean near any potential intake/vacuum leaks WHILE the engine is running? and an example of a leak or vaccum would be....the sleeves, throttle body, mafs mount??

[Griffin]

Originally posted by RJpinoyGQ1


if i walk into a store and ask for carb clean..they'll kno what im talking about? and when u say if the rpm jumps, are you saying spray the carb clean near any potential intake/vacuum leaks WHILE the engine is running? and an example of a leak or vaccum would be....the sleeves, throttle body, mafs mount??

Carb Cleaner = aerosol carburetor cleaner - its a combustible aerosol.

Yes - I mean to do it when the engine is running. It is combustible, hence if there is an intake leak and it is sucked in with the air it will cause a rise in engine RPM.

and yeah - check anything starting at the MAF all the way back to the engine that is a joint or junction and might leak.

Griffin

[MOHRSPD]

Hey,

Me CEL came on today and I have an AEM. It's been on for more than a year now. I am going to check the codes tomorrow and see what I get.

Any updates on returning the to the stock air box?

MOHRSPD

[Griffin]

The light hasn't been back on since he went back to stock, but Jaysong's car has been in teh dealer getting the VVTLi fixed for the last week. Hes coming over tomorrow morning with his stock box on and his AEM intake in the trunk and we're gonna finish our testing. He did talk to AEM and they indicated that the MAF riser is indeed positioned and welded by hand without a jig, and that they have heard of thisproblem before. We want to confirm it before Jay decides what hes gonna do. After were done tomorrow I'll let you all know whats goin on.

Griffin

[Griffin]

Okay - heres the final results. Jaysong came by today and we checked out his car with the stock intake, and all fuel trim and MAF values were totally normal. (MAF at about low 2s at idle and high 6 / low 7s at 2500 with fuel trim staying below 4% + or - at all times which matches my car) Then we threw his AEM CAI on and tested again after resetting the battery. Instant problems showed up in the form of long and short term fuel trim readings in excess of 18% at idle, and anywhere from 3 to 25% under load. And the MAF readings were high 1s low 2s at idle and high 5s low 6es at 2500 RPM. We tripple checked all connections and even went so far as to seal his MAF bolts with teflon tape and double check for leaks near the MAF, but nothing yielded any results. Hence, problem confirmed as a design / manufacturing issue. In this case I think its mostly manufacturing. AEM confirmed that they hand position and weld the MAF riser, and this one is obviously messed up. It will undoubtedly set another P0171 code before too long. Hopefully Jaysong will be able to get AEM to either give him a CAI that works properly or his money back. We shall see. I'm going to post a link to this thread in the performance forum.

Griffin

[MOHRSPD]

Thanks for the update.

My code was the random misfire code P0300, so I do not think the AEM intake is the problem. I have seen the TSB were they replace the injectors and the ECC, do you know if the new ECC will change the fuel cut or rev limiter?

MOHRSPD

[Griffin]

Originally posted by MOHRSPD
Thanks for the update.

My code was the random misfire code P0300, so I do not think the AEM intake is the problem. I have seen the TSB were they replace the injectors and the ECC, do you know if the new ECC will change the fuel cut or rev limiter?

MOHRSPD

No, the ECM from that TSB still has the old Rev Limiter (Its actually just a 2001 ECM) so you have no worries.

Griffin

[WAR]

The same bolt broke on the intake shaft on my car too, toyota replaced it under warrenty. This is now making me really nervouse that so many of the same bolts are breaking. Maybe we need a stronger bolt in there or something else is wrong if that much torque is going through that shaft to break that bolt. And I had the same problem, not lift and then I'd get a CEL.

[jaycee]

wow great investigation! im just wondering how come my cel has never come on:confused: Had the aem cai for over a year

[Griffin]

Originally posted by jaycee
wow great investigation! im just wondering how come my cel has never come on:confused: Had the aem cai for over a year

The problem results from a degree of variation inherent in their manufacturing process. Your unit probably had it welded on parallel to the direction of airflow and without the tilt to it that brought it so close to the side walls of the CAI.

Griffin

[Jesse IL]

Any time you you have something like that hand welded, I'd say you're at risk for this problem. Most manufacturers do not inspect 100% of their product. I would say this problem could effect any intake, regardless of manufacturer. I have had my AEM intake on since March 2001 and have had zero problems.

The locationof the sensor in relation to the wall would probably have little effect. Because of the density of air and the low velocity of the intake tract, the boundary layer near the tube walls will be very thin. I frankly do not understand why the Injen intake locates the MAF sensor in a bend of the piping. The bend could create localized turbulence and will definitely have a velocity gradient across the cross-section of the tube. In this case, location top to bottom would make a large difference. Most likely, the sensor being parallel to the airflow will make a much larger difference.

A second consideration would be location of the sensor along the length of the piping. Since a tubular intake lacks any sort of damper, it will resonate like any pipe at certain frequencies. When I had a 3rd Gen Injen intake, I had major driveablility problems at part-throttle at around 4500 rpm. My guess is that the MAF was located at a resonance point for that particular engine rpm/throttle position.

[Griffin]

Originally posted by Jesse IL
The locationof the sensor in relation to the wall would probably have little effect. Because of the density of air and the low velocity of the intake tract, the boundary layer near the tube walls will be very thin.

I would normally agree with you, except the weld penetration, irregular edges of the opening in the piping, and gaps in the MAF riser are very likely to create turbulence and the MAF entry is right in the middle of it all.

Your right about nothing to even out the intake pulses though, that does probably play a part in it. I think in this case its probably a compound effect thought, as others with the AEM don't have this problem. Then again whos to say that the cutout position is fixed....

Griffin

[RedNOSceli]

Griffin--thanks for the info, I havent had an issue, but ill check it out to see how my mount looks for the mafs..

btw, when you use "teh" it makes you sound kinda lame...its old and played out...

[Griffin]

Originally posted by RedNOSceli
Griffin--thanks for the info, I havent had an issue, but ill check it out to see how my mount looks for the mafs..

btw, when you use "teh" it makes you sound kinda lame...its old and played out...

Not intentional bro - that would be easy to fix. Its a typo that I can't seem to rid myself of as much as I would dearly like to. I don't know why I always screw up "the", but its probably because I don't touch type - I have a weird hunt and peck that has evolved over the last 24 years into a very FAST hunt and peck with a few strange irregularities such as my propensity to turn THE into TEH ala typo. Almost every time I type "the" at speed it comes out that way, but I go back through my posts and try to catch it most of the time. Its obviously somthing to do with a speed differential between my left and right hands but whatever...

Hey - Never said I was perfect OR that I could spell or type normally.

Griffin

[larrbear]

my cel comes on and off on its own....you think its the manufacture defect?

[Griffin]

No way I would even guess at that without knowing what code it is. Its certainly possible.

Griffin

[MOHRSPD]

Originally posted by Griffin


No, the ECM from that TSB still has the old Rev Limiter (Its actually just a 2001 ECM) so you have no worries.

Griffin


WC toyota replaced my injectors and ECM. The car seems smoother and more responsive now.

MOHRSPD