e041 enigma

[Guest G Froelich]

For the past couple weeks I've been getting an intermittent e041 code, along with the service engine light on/off. I replaced the cam sensor the other day and the code hasn't been set for about 80 miles of mixed driving.

Now for the enigma: for the first 30 miles it drove smooth and steady. But now it seems to miss big time and sometimes to be operating at about 40-50%. If I hold off on the gas a little it seems to "catch" the rhythm and stop missing and I can keep it from missing for quite a while at various speeds. If I accelerate too fast while in gear it starts missing (or rather acting like it's missing). It will also do this while idling in gear, but will sometimes smooth out all by itself.

Before I installed the new sensor it did idle rough and sometimes lose power, but not anywhere like it is now. Plus, before this I was getting the code (and only that one, besides the every pesky e027).

I intend to run through the diagnostics in the FSM as if the code's still being set, but was wondering if anyone can suggest some place obvious to look first (btw I have the Delco ignition). Thanks!

[DAVES89]

I would suspect it is your Mass Air Flow sensor. As a quick test when it starts to act up, tap the sensor with the handle of a screwdriver and see if it corrects itself. If it does that is your problem.

[harry yarnell]

Code 41 USUALLY means the magnet in the cam sproket has fallen out, not a bad sensor.

[Guest Mc_Reatta]

You have lost one or two of the four magnets in the holder in the camshaft end flange. Sometimes the sensor gets enough stimulation to emit a signal and sometimes it doesn't.

Need to replace the magnets not the sensor which rarely goes bad.

What I find hard to believe, with the thousands of 3.8 L GM engines in service that use this same magnet pack to create the camshaft position signal, that no one has seen fit to manufacture a replacement magnet that installs from the front rather that just selling the OEM style that has to be installed from the back side or modified and held in place by an adhesive.

It wouldn't be any harder or more expensive to make and would make this job so much easier for the thousands of 3.8 L uses that do this procedure yearly.

Just reverse the design to give the proper clearance in the front and the hold in clips in the rear, reverse the magnets and viola. Just remove the old one from the cam shaft flange, press the new one in and your done. No removing the ring so you can install reversed and having to glue in place and waiting for the glue to set etc.

Any takers? You could sell a ton of em. Just remember who gave you the idea.

[Guest Kingsley]

Now that is a volume that is really attractive, thanks McReatta!

[Guest G Froelich]

Thanks for the replies.

Just to be sure, you're thinking the magnet is responsible even though it's no longer throwing the code?

[Ronnie]

I don't think the cam sensor will cause the miss that you describe even if it is bad.

[DAVES89]

That's why I ignored the code and suggested the Mass Air Flow sensor which throws no code...

[padgett]

Four cam sensor magnets ? Thought that took four cars. Also, when they fall out, they do not heal.

Can use the disgnostic or snapshot capability to see what the MAF is doing.

[Guest Mc_Reatta]

Not that the MAF isn't worth checking too, the E041 code is not thrown until the signal disappears for 2 seconds. A signal that comes and goes can interfere with the ECM calculating the injector timing but not throw the code.

Is that the problem here??? If there isn't still an issue with the Cam Position Signal, then the whole engine miss with no codes set can of worms comes into play.

The forums batting average of figuring out the solution without shotgunning replacement of many parts isn't that great. There are just too many parts that can cause the miss without setting a code.

Check this still undetermined miss thread still active for how difficult diagnosing a miss can be and all the suggestions that have been made to date:

http://forums.aaca.org/f116/new-icm-coil-pack-egr-fuel-303640.html

[padgett]

Problem is that a remote diagnosis can rarely use the proper tools.

[Guest G Froelich]

For what it's worth, here's the ECM snapshot while it was misfiring:

01 0.40

04 59

06 5.7

07 0.4

08 24

10 14.2

11 895

12 0

16 0

17 359

18 18

19 126

20 131

21 8.2

22 54

23 24

98 11

99 8074

Thanks for taking a look. Tried the MAF rap, but there was no change (it didn't smooth out or get rougher). Disconnected the CAM sensor as per FSM but also no change.

[2seater]

What's the fuel pressure? This sounds sort of similar to the other thread just seems to have died without resolution. Padgetts suggestion of a snapshot, or recording sensor readings individually may be helpful here. Cam sensor shouldn't cause a real loss of power, just smoothness at idle and low speed. Was anything other than cam sensor replaced or modified recently?

[2seater]

Oops, I posted at the same time. The numbers look pretty normal but it doesn't appear to be fully warmed? Does it run better when cool before closed loop? It looks like it is right at the closed loop threshold temperature and idling in park.

[Guest G Froelich]

Thanks. I thought it was in closed loop ("HIGH" on temperature control panel), but could be wrong. Before this misfire it had a consistent but tolerable problem of running rough once it went into closed loop.

Fuel pressure seemed good. 40 psi at ignition on, then with engine on and the rough idle it dipped to 36 or so.

But newsflash: I disengaged the MAF then started the engine and it ran without the noticeable misfire (which I could easily hear before at the tailpipe, not to mention feel it throughout the car). So...bad MAF??? I hope it's that simple!

[DAVES89]

Mass Air Flow sensors are about $25.00 from a salvage yard and $120.00 or so from a parts store. If you don't have a back up unit, not a bad investment...

BTW I have two '89 Reattas and I have 4 back ups...

Edited May 20, 2011 by DAVES89 (see edit history)

[Guest G Froelich]

Checked the voltage into the MAF and looked good, so must be the sensor. The filament-like wires looked clean, but who can tell?!

$25 at a salvage yard! My local boneyard wants $75! Maybe I can talk them down. eBay used going for $40-50, and above! Reman Python for $155 on Amazon.

[DAVES89]

About 3 months ago I bought 3 for $10.00. Last time in 3 @$10.00 each. But the guy behind the counter said they normally charge $25.00 each, it's just that I am in all the time...

[padgett]

Well the PROM is for a 1990 California car. Coolant is at 138F and is not fully alive until 146F. TPS is showning idle (.38 to .42) but RPM is almost 900. Air temp showing 75F.

At 900 with a cool engine my MAF is reading 6.8-7.2 at 900ish rpm

[2seater]

I have a few spare tested MAF's too if you get in a pinch. By the way, the MAF generates a frequency output that is read by the ECM. I am sure there is some voltage reading but it is not what GM uses for the air flow conversion. If you have a VOM with frequency capability the range is 2kHz @ 3.19 gr/sec to 10.4kHz @ 170 gr/sec. Running better with it disconnected is a good indicator it has problems. Fuel pressure and your ECM fueling numbers look good too. You could just take a look at the MAF reading and see what it does at different engine speeds or while driving. The closed loop threshold on my '90 seems to be about 130*F. but, to confirm that everything is good and hot and active, fully warmed would be a good double check.

[Guest G Froelich]

To try to make sure:

1. Ran a vacuum test. No leaks.

2. Tested resistance at the MAF sensor leads. Might as well have been testing the resistance of plastic! No circuit at the leads in any combination. That's a pretty clear sign, right? The filament posts showed resistance, so the inner electronics must be fried.

Am I thinking right here that it's definitely the sensor? Thanks.

[Guest jwin]

No. MAF is a solid state device. No internal circuit connections between the sensor leads. (and you can actually damage the sensor by testing it for resistance)

[2seater]

I have never checked one with a VOM to see if a good one reads anything of value or not? I think the FSM doesn't indicate any test readings and actually states it has a "special" output.

I just tested a known good one and I get ~ 31.4 mOhm from B-A and C-A, the first letter connected to the red lead and .515 mOhm between B-C or C-B. I do not know if this actually means anything or not except to say that is does show something.

[Guest jwin]

I have never checked one with a VOM to see if a good one reads anything of value or not? I think the FSM doesn't indicate any test readings and actually states it has a "special" output.

I just tested a known good one and I get ~ 31.4 mOhm from B-A and C-A, the first letter connected to the red lead and .515 mOhm between B-C or C-B. I do not know if this actually means anything or not except to say that is does show something.

Sorry. I stand corrected. Wiring diagrams in manual show no connections. I have never tested one with an multimeter either. Only oscilliscope.

Edited May 20, 2011 by jwin (see edit history)

[rjfranken]

pics show the Motorolla older coils I would not go further until I did the coil-pack upgrade. EZ found in a serch.

[Guest G Froelich]

Good news. I decided to test the coils with a noid light and discovered that the top coil on my upgraded Delco system had little to no spark on either post. Replaced it and the car has stopped missing (keeping fingers crossed).

But I'd like to get to the bottom of the MAF question. And since having a spare is a good idea, I'm in the market. Unfortunately, I struck out at the local salvage yard (all the right looking sensors--I'm talking about only the electrical component--had the wrong sized plug into the adapter body).

[2seater]

Thanks for letting us know what corrected your issue. This is a learning experience for all of us and it is something to file away in the memory banks.

Odd about the sensor plug being different. I have never encountered that before? As a matter of fact, the plug is the same for the 3300 Buick engine (and the frequency response is close enough that it will work also), as well as the early model TPI style and the 3" MAF for the Chevy 3.4. The last two are not physically interchangeable for the vin C engine but the frequency range is the same as ours. Maybe I am misunderstanding and you meant the part that inserts into the MAF housing? Do they look like this? The one on the right is for a TPI style.

Edited May 21, 2011 by 2seater (see edit history)

[padgett]

Maybe the later "L" has a different connector. It has a wider range.

[Guest G Froelich]

Yes, the sensor with the wider fitting/o-ring for the grilled housing is all I was finding yesterday (I didn't find a 3800C in the lot). I suppose I could have taken the entire unit (electrical component with housing)...you're saying they're interchangeable? Thanks!

[2seater]

If you are only finding the type of MAF with the design on the right of photo, it is most likely the vin L variant. It probably has what Padgett colorfully, and accurately, calls the snakes manifold. The photo is of a sensor from an aluminum snakes style manifold, also called Tuned Port, and the later models are plastic. While the sensor has the same frequency range, the housing is different. The one I have is made by Hitachi, the same maker as the vin C MAF, but, it is a unified throttle body and MAF assembly, not two discreet parts bolted together. As a matter of fact, I have that exact unit installed on my intake and it works just fine, however, it required fabrication of an adapter plate due to the totally different mounting flange. I suspect the yard in your area doesn't have anything 20+ years old, but you may find something in things like a Buick Century with the 3300 engine, a little brother to the 3800. I know they were available up until at least 1993. I have tested air flow vs frequency on the flow bench and it is very close to the response of the sensor we are interested in and it works fine.