My car runs like shit...running out of ideas

[1990m3]

I'll try my best to describe...'95 m3 motor, conforti EWS delete chip

Idles normally and seems to run perfectly normally until ~4000RPM

Once it goes above 4000RPM it starts to rev slowly, the exhaust gets loud and closer to 5500-6000RPM it starts to hesitate pretty severely. Still idles normally though and throws no codes. When I unplug the vanos solenoid and take the car for a ride it behaves the same as if the solenoid were plugged in.

I've done a number of testing and part swappings. All swapped in parts have been either new or from a friends running and working motor. Here is the list:

Tried different coil packs
Swapped in a known working vanos solenoid
Swapped in a known working ECU, but put my chip in it
Swapped in a known working spare vanos unit
Installed brand new cam position sensor
I've confirmed spark plugs in good shape, no oil in the spark plug holes either

The problem occurred mid-turn at Gingerman, mid-range RPM in 4th gear. I've considered the exhaust is messed up but after a once over from under the car it seems fine. Everything is in tact and there are no apparent holes. It gets really loud though when the car starts missing at 4000+. Car has modified OBDI cats and e36 m3 muffler.

Please throw some ideas at me, I'm stumped.

Thanks

Dave

[static]

couple of things:

1. how are your cats? may be clogged up restricting the exhaust at upper end and causing misses

2. get a WBO2 somewhere, hook up the narrow band output to the proper wire at the ECU and datalog the widwband signal. This will tell you if there are problems with AFR (which could mean bunch of things related to the mixture: pump, regulator, filter, etc..)

[aeryk7]

Scan the DME for codes anyway.

It sounds to me that you might be running pretty rich over 4k , when you run rich your exhaust will be louder than normal.

[1990m3]

1. Cats might be clogged, that is a theory of mine, I will be removing them this weekend and taking an open header ride to see if it acts the same or not.

2. How do I scan the DME for codes if the Peake code reader at the diagnostic port isn't giving me anything?

[aeryk7]

I thought you meant you werent throwing a code at the cluster. I didnt know you had a peake. With everything else you have checked and no codes i guess the cats would be the next thing to check.

I am curious though are you having any popping and is the exhaust getting louder exponentially to rpms over 4k.

Do you get a code at the cluster when you experience the problem?

Sometimes having a bad knock sensor has similar characteristics of what you are describing and will sometimes throw a code at the cluster intermittently only when the engine experiences the problem ,some times not logging it into the ECU....Just trying to save you an exhaust tear down if i can.

[matt]

1. Cats might be clogged, that is a theory of mine, I will be removing them this weekend and taking an open header ride to see if it acts the same or not.

2. How do I scan the DME for codes if the Peake code reader at the diagnostic port isn't giving me anything?

Do you get codes when there is a code? Unplug a coil and see if you get a code.

[1990m3]

I get codes when there is a code, and the peake tool completes all its other functions properly tooo (inspection reset, si light reset...)

aeryk7 - The exhaust does get louder over the period of the powerband. I'm taking the cats off on saturday, I'll know more after a thorough inspection. This did happen for the first time on the 5th track session of the day (late in the session). Cats were hot, could have broken apart at the bumpy track I was on...I don't know. I guess I didn't think that clogged cats was capable of being such a drastic problem, I always assumed it happened gradually and didn't realize it could affect the power as much as it has for me.

Cross your fingers, could be an easy fix!

[aeryk7]

I drove a e38 740 with bad cats one time and it plainly didnt move under any angle of throttle it felt like it was running on 2 cylinders . I didnt, however have any popping.

Hope things come to a conclusion for ya.

[1990m3]

BTW- I unplugged a coil pack today and it threw the code, so I know that works.

[matt]

Is it 100% consistent? And it started on track recently... motor was running well before with no changes?

[1990m3]

100% consistent, happens every time i drive it since i was at Gingerman in August. haven't really driven it too much though, I bought an iX to hold me over :)

Motor was running like a champ right up until it bucked and hesitated on me mid turn. I was having a great track day and about two weeks earlier had a flaw free day at a different local track as well. those were the only two days it saw on track, otherwise I daily drove it for one year without a problem. 12k miles since the swap

[matt]

Do the gauges do anything when the motor starts going nuts?

It does it under load (say third gear 60-90) and sitting still?

[1990m3]

gauges react normally and reflect the engines poor performance. I've never seen the tach move so slowly and you can feel it when you drive. My iX feels like a racecar in comparison.

yes it does it under load and standing still, but is less noticeable. Idles like a million bucks - part throttle up to 4K is smooth and feels pretty normal. once you get deep into the pedal and above 4K it chokes

[1990m3]

Thanks for all the help everyone -- solved it today!

Cats are completely clogged up. I removed the exhaust today and an open header ride made the car feel like it is supposed too, lots of tire spinning hp again! I can't believe it happened that drastically and quickly, literally right on the track.

Guess it's time to build a new exhaust, good thing winter is just about here.

Dave

[static]

guess i was spot on

glad you found it!