Y87bird00

iTrader: (6)

We have discovered that the MAF sensor on my car was bad, causing fuel to be off. The bad thing is, the car was tuned with this bad MAF, so even with the sensor tuned out my fueling was off. Part throttle was able to be fixed so I could drive it, and it started, drove, idled, everything perfect for about a week. Now it's starting to get increasingly worse, just like before...

Another thing it is doing is kicking the efilive offline. We cannot read the car and end up having to restart everything until it shows up, only to be thrown off a little later

Does anybody have any ideas?

Y87bird00

iTrader: (6)

The car starts fine, but when I put it in gear it hesitates and drops idle real quickly but regains it fast. Once I start rolling away the idle drops lower and lower until I give it gas. Coming up to a stop after driving (distance doesn't matter) it will choke down lower and lower until I reach a dead stop then buck (sometimes dieing, most of the time leveling out to a semi-low rough idle). It will do this over and over.

All battery connections are good, both the battery and alternator checked out good. No vacuum leaks or unseated intake.

The problem builds up, one day it's good, the next okay, then bad, and like today completely undrivable.

ACCLR8N

You mentioned in an earlier post about swapping out the PCM. I assumed you haven't tried that because of the expense.

If it were me, I'd be logging fuel trim cells, long and short term fuel trims, MAF g/s, MAP kPa, airpersecond, ECM voltage, RPM, VSS, TPS and monitoring fuel pressure (if you don't have a way to log it). Any chance you can post a log one good, one bad?

Y87bird00

iTrader: (6)

The cost is the reason I haven't swapped pcm's.

We are logging fuel trims now but I have no way of posting anything to the forum, I wish I could. That would probably help out.

LSX Power Tuning

iTrader: (4)

I tuned the car, it's not tune related. He has had a long laundry list of problems since doing the swap (v6 car originally). It's also his first swap so you can expect a couple of hiccups along the way but he has had a lot. The car looks to have been wrecked before, it was a v6, swap was done with a lot of used parts and now has a lot of weird electrical gremlins. So you have ton of long list of parts that have changed including a good bit of wiring. The maf (used) was originally working when it was on the Dyno, then started acting up, the o2's would work then stop reading all together, fuel trims haven't been consistent. It won't flash sometimes at all, it will kick off my laptop when data logging then may take minutes to be able to re-connect. I have already told the owner over and and over that these problems are not normal and he has an electrical issue.
I turned off the maf a week ago (+25 trims) or two ago and his fuel trims then went to -25. I adjusted the ve table off his stft's to get them -+3% and turned on his ltft's and told him to drive it a couple tanks of gas. I haven't plugged back into the car again since then to see what the ltft's are. I'm sure they will will be all over the place when I check. It's getting to the point of I don't want to plug into the car knowing it has electrical problems that can't be good on my efi live v2 or my laptop.

Y87bird00

iTrader: (6)

The car ran fine with the v6, and everything I changed with the v8 has been checked, double checked and checked again. I have no other ideas besides swapping pcm's, and that takes more money than I have to gamble with right now.

LSX Power Tuning

iTrader: (4)

How are you "checking" everything? Are you checking all your wiring with wiring diagrams and a digital meter? Without doing proper diagnostics your just going to end up parts swapping and guessing which could be expensive and you may never find the problem that way.

Y87bird00

iTrader: (6)

I've checked things like the engine bay fuse box, all fuses have constant voltage. Cooling fans drop them a little.

Other than that I don't know how to use a multi meter to get any results I need

LSX Power Tuning

iTrader: (4)

There's the first problem, you have not diagnosed anything yet. You're going to need wiring diagrams, a good digital meter and a understanding of wiring diagrams to start actually checking wires, connections, grounds, etc. Just looking at something is not going to find the problem. At a minimum pull the engine harness take all the loom off and ohm every circuit and connection. With a used harness there's no telling what kind of hidden surprises could be under the wire loom. Check the voltage drop for the pcm, check and re-do all power and ground connections.

Y87bird00

iTrader: (6)

I pulled the wiring harness off and took all the loom off. There were no obvious problems. (Cuts, melted wire, previous owner connections)

I have no knowledge of circuit testing, I have talked to a few local shops trying to get them to look at it for me with no luck. I have a few more I can talk to.

I have a huge ground strap (motor to chassis) as well as the stock braided straps.
The three grounds in the harness are in new locations after pulling the harness off
The battery is grounded to the chassis and engine, with power going to the alt, and fuse box.

LSX Power Tuning

iTrader: (4)

When you had the harness apart that would have been a perfect opportunity to check the harness with a multimeter. You'll need to check each individual pin on each connector and the corresponding pin at the plug for the pcm. Thats the only way to rule out the harness. Being the problem is intermittent and not always constant its going to be hard to find, it could be a chafed wire, broke pin in a connector, piece of trash in a connector, somthing grounding out, etc. Without wiring diagrams and testing each circuit you're fighting an uphill battle. I can probably find a local shop that will look at it but it will run $100/hr or pretty close to it for however many hours it takes to find it.

Y87bird00

iTrader: (6)

That's why I've hit a dead end, I am not good with a meter and cannot afford the hourly cost of diagnostics. I also have a good feeling the harness is good as I saw the car it came off of. It was a stock camaro that was wrecked at the track.

gagliano7

Do it right now or it will cost you way more in the long run. You need to get the harness tested I am sure that is your problem but you just don't want to listen. I continuity test is very simple to do. Do a search on the internet. Basically touch one end of the multi meter to a pin and the other end to the connector that pin goes to and you will get a steady beep. If you don't you have a problem. To check your multi meter put the dial for continuity and touch both ends of the leads together and you will hear the tone it makes.

Y87bird00

iTrader: (6)

It's been almost a month since I replaced the pcm and got the car re-tuned. At first we thought nothing changed because we still had the problem with the software not being able to read the car after starting. That was a unrelated issue because the car has not given me a single problem after driving it very day, over 1,000 miles. Not a single bad start, never dies at the stoplight. So happy it runs the way it should! It's finally enjoyable to drive!