MS3 Basic 6000 rpm backfire and check engine light
 

Gents,

I made some changes to my 1999 that warranted a new tune. Everything was going fantastic. I have not had any problems like this in the past. We were nearly done with the WOT tuning when it backfired at 6000 rpm and threw a Code 64 indicating a loss of sync. The Check Engine light came on. It happens at 6000 rpm regardless of throttle position. Otherwise, the car runs great. Starts and runs just fine below 6000, and even runs fine after the backfire. The Check Engine light does not come on if the engine is turned off then restarted, unless I crack 6000 rpm again.

I replaced the crank position sensor, but no change. Any ideas?

Thanks much,

poormxdad

How far out is the crank sensor placed?

This sounds exactly like the issue that we had on Eds car when I forgot to adjust the VR conditioning pots correctly. But from what I remember @Reverant uses a different circuit for the crank input.

He will be able to answer better.

It's your basic hotel room key card, ~0.031".

This has to be a setting. It runs just fine. Pulls really hard, then bang. I haven't tried to keep going over 6000, but I don't think it will. It's like it has hit a rev limiter.

Thanks much.

Same thing with my issue. VR conditioner pots were set incorrectly. It lost sync at 6k rpm. Then wouldn't restart until it went all the way to zero and re-synced.

My Friend, I have no idea what "VR conditioner pots" are.

I changed the pre-Rotrex intake piping by deleting the gutted MAF and adding a sealed cold air shroud. The restriction had been bad enough to require a retune. I gained nearly two pounds of boost, so there were extensive changes to the tune but everything seemed fine. When the backfire and loss of sync happened the second time, the tuner reloaded the previous tune. No change, so maybe it's NOT a setting.

This blows. I'm over my head and supposed to be on track Monday.

poormxdad

If you have to be on the track on monday then set the rev limiter to 5000rpm and go to the track.

Post your tune and I'll take a look.

A loss of sync is not from a tune.

Post a log

I thought about that, but if something gets worse I'm 300 miles from home. I haven't registered yet, so I'm not out any coin, just the joy.

Here's one of each, tune and log.

Thanks,

poormxdad

I see 4 lost syncs. 2 reason 32 and 2 reason 31.

Those are both cam signal issues. Have you tried replacing the cam sensor?

Still waiting on a reply from Reverant.

Taking a composite log of the issue would also help.

No. It's on the agenda for tomorrow if I don't get some kind of other definitive answer.

Thanks,

poormxdad

Take a composite log.

I can't post a log right now but I did swap in a new cam position sensor. No change.

Try this, see if it's fixed.

Can you say what you changed? I am just curious and to lazy to go through both tunes and figure it out myself.

Opps, sorry. Changed noise filtering.

A few things.

First, I can't find an option for Composite log. I thought it would be in Tools.

Second. When I was at VIR a couple of weeks ago, I ran over the gator coming out of the Oak Tree turn. It shook the crap outta the car and I got a check engine light. No drivability issues though. I came into the grid, turned the car off and back on and all was well. No apparent issues till on the dyno a couple of days ago. I'm checking connections now.

I've got Shadow Dash installed on my cell phone. I hooked it up on the way home from work a little while ago and although it went through all the right notifications--it told me it was connected, loading the file and was going online, it never actually went online. Symptom?

Thanks for everyone's help so far. Beers on me if the opportunity arises.

poormxdad

Composite logger is under the Diagnostics and High Speed Loggers tab

Pat,

Your tune made the dropoff and Check Engine light come on at about 4000.

Since I can't seem to figure out how to make a composite log, I made a log with the SD card I have hooked up to the MS. Not sure if it will help. This should be from Pat's tune.

Thanks,