CEL turns on only after 5k rpm then dissapears

[PedraM5]

I just put a cold air intake on the car, had some trouble getting the coolant bypass sensor to fit without hitting the throttle cables, but ziptied everything out of the way. When I drive the car, floor it in first, it feels great and sounds amazing until 6000-6200rpm, then the cel comes on. Shift to second, feels great till about 5k rpm and then again the CEL comes on. Immediately if I put it in neutral or just let the revs fall back down, the CEL goes away, but everytime i floor it and it goes above 5k in any gear, CEL comes on, car feels ass slow anywhere above 5k, and the smile comes off my face. Anyone experience this or know what it means? I tried doing a search but saw nothing similar. Car is a 95 M3 with TMS chip, supersprint exhaust and cosmo racing CAI. Kind of smell somthing burning, but nothing is hot to the touch in or around the intake area, nothing is touching where it shouldnt and car drives normal otherwise. Please help, I want to feel the power I'm missing up there:(

[Jrdeamicis]

Im going to say your MAF is creating the error. Try repositioning the MAF.

[PedraM5]

Im going to say your MAF is creating the error. Try repositioning the MAF.


tried to reposition it, but the car would just turn off if i played with it at all. Sux I'm depressed about this

[M3Alpine99]

It is supposed to be at a certain clock position.... I believe it is either 3 or 9 oclock... I can go check mine real quick.

[Balthazarr]

10 o'clock.
CEL might be due to knock sensors which would explain why they appear and disappear.
You must be running lean up top.

[PedraM5]

the cosmos intake I got replaced the HFM, I previously had on there a stock airbox with a 3.5" HFM. I didn't know what to do with the coolant bypass sensor if I got a regular intake because there's nowhere to plug it in. The cosmos intake had a second hole specifically for the valve. I was thinking that the problem is that I have a turner chip that was supposed to go with the 3.5" HFM, and now that it has a 3.5" intake pipe that is connected to their 3" HFM pipe, I was thinking this is the culprit as it ran perfect before. I was going to stop by home depot and see if I can buy a silicone coupler to put the HFM back on and maybe drill a hole for the coolant bypass sensor to hook up to.

[art@rmeuropean]

Might be your knock sensors, like mentioned above.

[PedraM5]

Might be your knock sensors, like mentioned above.

what can I do to properly diagnose/fix a problem with the knock sensor? is it somthing I can do myself?

[Balthazarr]

Find out why you are lean.
Knock sensors do go bad, but your problem is highly coincidental.

[Balthazarr]

the cosmos intake I got replaced the HFM, I previously had on there a stock airbox with a 3.5" HFM. I didn't know what to do with the coolant bypass sensor if I got a regular intake because there's nowhere to plug it in. The cosmos intake had a second hole specifically for the valve. I was thinking that the problem is that I have a turner chip that was supposed to go with the 3.5" HFM, and now that it has a 3.5" intake pipe that is connected to their 3" HFM pipe, I was thinking this is the culprit as it ran perfect before. I was going to stop by home depot and see if I can buy a silicone coupler to put the HFM back on and maybe drill a hole for the coolant bypass sensor to hook up to.

I have a first generation Cosmos Intake if it's the same one I think you are speaking of and my bypass is just tied to the HFM plug not the connector.
I ran with both a 3.0 and 3.5 HFM with no trouble so your problem is not the chip...or shouldn't be.

[freakStocker]

i can scan for free...and got a compression checker...in da OC...

[PedraM5]

i can scan for free...and got a compression checker...in da OC...

where in OC are you? I really appreciate it

[McoupeBobby]

the cosmos intake I got replaced the HFM, I previously had on there a stock airbox with a 3.5" HFM. I didn't know what to do with the coolant bypass sensor if I got a regular intake because there's nowhere to plug it in. The cosmos intake had a second hole specifically for the valve. I was thinking that the problem is that I have a turner chip that was supposed to go with the 3.5" HFM, and now that it has a 3.5" intake pipe that is connected to their 3" HFM pipe, I was thinking this is the culprit as it ran perfect before. I was going to stop by home depot and see if I can buy a silicone coupler to put the HFM back on and maybe drill a hole for the coolant bypass sensor to hook up to.
sounds like it should work :)

[GodFather]

sounds like a timing issue to me...check the vanos and cam positioning sensor...if timing is off, you could be running lean or rich, and also you can set off your knock sensor...

Stan

[PedraM5]

damn so many things could be the problem, I thought OBDI cars are supposed to be less of a hassle

[PedraM5]

I went to home depot and found some pipe to serve as an extension for the 3.5" HFM, put the two together, trashed the cosmos HFM and ran the car around town. Good news is problem solved, that was definetly the issue. Having a chip tuned for 3.5"HFM and having less airflow definetly causes some weird shet to happen. Car still feels slower than with the stock airbox though, which is weird, but atleast there's no sudden power loss and check engine light!

[widebody_bimmer]

I'm gonna say it is probably a lazy O2 sensor which would explain why the CEL comes on briefly and then turns off especially since its an OBD1 car... I'm led to believe that the o2 sensor switching time is too slow so the computer can't compinsate for the raising throttle rate. because it is still in rich swing the computer trys to lessen the fuel which would explain why you feel less power when the light comes on. best way to check that would be with a DSO (digital Storage Ocilloscope) to check the response time from the O2 sensor... there are other causes but that best describes the issue you are having...

[Casebrius]

the cosmos intake I got replaced the HFM, I previously had on there a stock airbox with a 3.5" HFM.

Are you saying you totally took off the HFM?

[Balthazarr]

What is an HFM pipe?
The 3.5 to 3.0 adapter that attaches the HFM to the TB boot?

[PedraM5]

What is an HFM pipe?
The 3.5 to 3.0 adapter that attaches the HFM to the TB boot?

I had no sort of BMW OEM HFM on the car with the cosmos intake, and that was the problem, I put the 3.5" HFM back on the car (came with the car) and then went to home depot to find an extension from the HFM to the cosmos intake pipe.

I had orginally taken off my 3.5" HFM because the cosmos intake came with its own HFM pipe, and there's is longer so I couldn't just keep the 3.5" HFM on there without some kind of extension to reach the actual intake pipe. Their HFM pipe is longer, has a place to put the coolant bypass sensor and the MAF, but it is only a 3" diameter inside.

The 3.5" HFM had the 3.0 adapter that attaches to the TB built in pretty much, I took them off together, and now put them back on together.

[Brent_Vino]

many 95s have the cel go on and off briefy.... most likely the O2 sensor.. dont worry about it until the CEL comes on and STAYS on.:)

[JohnDojah]

I would agree with knock sensors. And I hear they CAN go bad.