1st gear laggy

[mike diesel]

Having a weird issue with 1st gear and half way into second gear being very laggy and something is keeping it from fueling properly.

I know it is not a tuning issue because I got my new dual fueler tunes tuesday morning and the truck ran great. Parked the truck tuesday night and didn't drive it till Friday when I was heading to the track to race and that is when I noticed the lag. We flashed my old tunes in last night and it still does it. Didn't have time to mess with anything so I raced and dynoed the truck anyways...it fuels normal and everything if your already in second gear or higher. Also if you can get the boost up enough while doing a 4 wheel launch it seems to fuel fine as well.

When you mash the pedal from a dead stop it would take right off, shift to 2nd and blow the tires right off. Now with the lag if you mash it from a dead stop it takes right off and at about 8 psi of boost the power just falls off, makes it to 12 psi, shifts to 2nd gear and half way through second gear the power just kicks in full boar and the tires blow off and truck takes right off.

Few things I've done so far....cleaned maf, pulled intake and check turbo..it spins freely, balance rates are ok...#5 cylinder was a +10 Friday for some reason..its been a +5 since the day i bought it 2.5 years ago and has not change except for friday. Check again last night and it was right back to its "normal" +5.

What should I be logging to look for?

 

[mike diesel]

Checked all intercooler boots and none are split. It hits peak boost just fine as well, egts are "normal". I'm thinking maybe the maf sensor is on its last leg and not fueling properly till it sees alot of air moving over it (mid 2nd gear)..like I said, truck ran awesome all day tuesday. Parked it for a few days and all the sudden the issue showed itself. I don't get why if your cruising and mash the pedal it fuels fine and takes right off. Only does it from a dead stop.

 

[DIESELMAFIAPER.LB7]

Compression test my friend

 

[IOWA LLY]

Sounds like a MAF problem to me. Log it and see what your readings are. When its laggy, and when its not.

 

[mike diesel]

Compression test my friend

Compression is fine!

Sounds like a MAF problem to me. Log it and see what your readings are. When its laggy, and when its not.

Forgot to add there are no codes or anything scanning it with efi live. I will log the maf and see what I find. Should I be able to ohm across the maf sensor? I unplugged it and ohmed across every pin and got no readings.

 

[DIESELMAFIAPER.LB7]

I just thought I'd tease... just log and adjust the maf till it fuels correct the temp is getting warmer so could be hitting a different map

 

[Hot COCOAL]

Fixed or variable charger?

 

[DIESELMAFIAPER.LB7]

He has the 472

 

[mike diesel]

Well I've never had this issue before even last summer. And even last night it wasn't warm...probably about 50 degrees and it still does it.

I was doing a little logging just in my driveway a minute ago and the intake air temp sensor is reading correct, maf voltage was .5-.6 volts at idle and in drive with brake on hitting throttle it would climb to 1.2 volts or so before I let off. It reads about 7lbs/min at idle and looking at some logs from Friday it was peaking at like 48lb/min. Not sure how accurate that number is because my intake is 5" and the maf is scaled very aggresive, smokes alot spooling up like it always has.

 

[SickLL7Crenshaw]

What's your balance rates on with the stock tune loaded? My rates are -+1.0 have you changed that injector recently? +5. Seems scary to me.

 

[mike diesel]

What's your balance rates on with the stock tune loaded? My rates are -+1.0 have you changed that injector recently? +5. Seems scary to me.

Balance rates don't seem to change much on my stockish tune. I haven't touched that injector except for adding the 30% nozzles last August. It's been a pretty consistent +5 for 2.5 years. According to gm that's still "in spec".

 

[Chevy1925]

What's rail pressure doing? Since this started after the duals, I'd look for reasons around that.

 

[LWATSON]

Check your intake between the maf sensor and your charger. I had this issue once and I was drawing air through the intake after the maf . My symptoms were similar to yours, get on the pedal and it was very laggy. Once it started building boost it would go right on.

 

[mike diesel]

So i took a log and as far as I can tell everything is doing exactly what it's supposed to do. I sent the log to my tuner so we will see if there is anything he can see that may be causing it. I think im going to try the tune I ran all last summer (72mm vvt with egr still intact). I put my s472/full egr delete in back in december. So I will try what I had last summer and see if anything changes. I know that egr and maf codes can correlate so that's why I want to try the pre s472 tunes.

 

[mike diesel]

Anyone know if ABS codes could be related to this? I do have an active ABS c0055 rear wheel speed sensor (both wheels) circuit code. As far as I can tell everything on the truck works fine as far as brakes go. The abs and brake light are not on on the dash. If I clear the code it just comes right back.

I was researching the c0055 code and someone on one of those "justanswer.com" pages said that the speed sensors "help" the maf tell the ecm tell how much fuel to give based on airflow (maf) and speed (speed sensor)....obviously the maf tell how much air enter and the ecm fuels accordingly...i dont think i really believe the speed sensor part tho...the abs code has been active for atleast a month prior to the fueling issue I am experiencing.

With efi live open and was blowing on the maf sensor, the voltage and lbs/min all change according to how hard I blow air over it...intake temp sensor also changes accordingly.

Wtf

 

[NC-smokinlmm]

Log fuel temp...

 

[mike diesel]

I finally had enough time to really tear into it. On the ecm c1 connector pin #10 is ignition 1 voltage which goes directly to the middle pin on the maf plug...pin #9 on the c1 connector is a ground...and I have continuity between #9 and #10....i think im onto something here.

Not to mention I found half a dozen wires on the c1 connector that are almost worn in half and what's left is corroded to hell.

 

[mike diesel]

I've got continuity between these wires here...pink goes to maf, black is ground.



Made a few discoveries while tracing the wires....looks like some bastard rodent made home under my fuse box.



Wires galore chewed up. I'm not even sure how my truck didn't have major issues. Some wires wires have only 1 stand left. I found 1 or 2 completed chewed through.







These wires rubbed through on the conduit..



Going to be a fun few hours cutting and soldering new pieces in!

 

[Harbin_22]

Wow! Well at least you found it before it left you stranded somewhere.

 

[coker6303]

Holy crap you are lucky!!! That's crazy!!!