Weak at high RPM

[davtbaum]

Hey guys,

Long time lurker here - I've been observing some strange behavior on my s50 e30 and I'm looking for some technical expertise.

Relevant Info:
S50B30US 77k miles
540i MAF
24 lb Injectors
TRM Tune

I finished the swap last month with no major issues. Just yesterday, driving back home for Easter, the motor threw trhe CEL for code 1221 after about 30 miles of driving. I immediately noticed a power decrease in the upper register - at about 5k RPM the car felt weak, and after doing a 2k WOT pull, I found that the motor basically stopped accelerating after 6500 RPM. Unlike hitting the rev limiter and feeling the motor bounce off, it was struggling to get any higher. (At this point I didn't want to lay on WOT for more than a few seconds so I backed off).

Overnight I reset the DME, got back in the car this morning and BAM, no CEL for 1221. Low and behold, the motor no longer feels limped. I took it on another WOT pull and hit the limiter easily in 2nd gear (not to mention it felt much stronger).

So here's my position, I have no idea how persistent this code will be. As simply resetting the DME didn't fix anything, it likely just cleared the memory stored from the o2 sensor. I'm going to assume it will come back.

I want to get your guys input on my diagnoses. My question is: has anyone else with the TRM tune noticed a 'limp' mode while receiving a 1221 code?. I couldn't find any definitive information on this and a solid answer will hopefully confirm this isn't indicative of a bigger issue like failing VANOS.

Thanks,
David

[ArtClassShank]

I have a TRM Chip and get that code often. Only when sitting at idle for 3-5 minutes though.


Been diagnosed as the chip, so I'll try and swap them out at some point.

[matthugie]

Granted I've only had my TRM tune for a few weeks, but I have had no such issues, either on street or at the couple autox's I've done since it's been in. It's actually been running much better than it was before on a Dinan tune, but there may have been some other factors in play there.

[wakdog]

Sounds like how mine ran when the vehicle speed sensor wiring from the cluster to the dme was bad.

I plugged mine into a code reader and got o2 sensor and VSS codes. Rewired speed sensor signal direct to the DME and both codes no longer throw.

I am also running the same setup except Euro S50 MAF instead.

[davtbaum]

Thanks guys.

Sounds like how mine ran when the vehicle speed sensor wiring from the cluster to the dme was bad.

I plugged mine into a code reader and got o2 sensor and VSS codes. Rewired speed sensor signal direct to the DME and both codes no longer throw.

I am also running the same setup except Euro S50 MAF instead.

This is great advice - ultimately leading to me discovering that I do not have VSS connected to the DME. Definitely will install that before doing anything else.

So how did this happen? Well I swapped into an early model and used a late model pinout description (this one http://i29.photobucket.com/albums/c2...swapwiring.jpg) then cross referenced with the 'Love your c101' post (http://www.r3vlimited.com/board/showthread.php?t=163088) to find all pins that were early model specific. Well, the post has pin 14 as empty, which I believe is only true for early models. I ended up following the late model pinout and splicing c101-14 into x20-14 which is just a floating terminal in my car :p.

Whoops.

[E30_pilot]

yea for the early models there is a 3 pin plug in the glove compartment.

[davtbaum]

yea for the early models there is a 3 pin plug in the glove compartment.

The 3 pin plug on my 87is was the c104 tach (engine speed) and econometer going to the cluster. The pin I missed was vss from cluster to DME (via x20 pin 14).

[wakdog]

Mine was bad somewhere in the dash wiring. My car is RHD so it travels through the inside of the dash to the C101 and I was getting no connection between pin 14 on the body side and the plug on the back of the cluster...

When I fixed, I could tell just by reversing the car out of my garage that it was fixed - car didnt vibrate and react so much to clutch disengagement (I have a lightened m20 fly and clutchmasters clutch.