Ford Mustang Forums banner

1 - 20 of 101 Posts

·
Registered
Joined
·
582 Posts
Discussion Starter #1
This is a long running problem and I think there are two other threads I've started and got no where with 2 and 3 years ago. But I really would appreciate any suggestion you think may help.

Not all the time, but lets say 3-5% of the time, if I'm accelerating as you would from a normal stoplight speed, and then let off the gas, or even if going roughly 40mph you just let off the gas, the rpms drop and bounce around 600/500/400/300 until dies. Not fun having 305's with no power steering and brakes while in traffic.

Normal operation happens the rest of the time, in that the RPM's slowly fall to 1000/11000 and then more slowly fall to 800/850 as the final idle speed.

So far I've checked all the vacuum lines, ran a smoke test looking for vacuum leas, checked grounds and all connections, and replaced the idle speed motor and the EGR valve. It used to do it more, but changing the EGR valve helped it not happen as often.

Anyone have any ideas?
 

·
Registered
Joined
·
1,065 Posts
needs more dashpot simply fix it in the tune
 

·
Registered
Joined
·
22,364 Posts
you never posted results of the data you logged 3 years ago.

that is why those threads never went anywhere

you keep saying you have looked for air leaks, and bad electrical connections, but never mention what is actually happening that the ecm is seeing.

with data streaming, you dont even have to lift the hood to get direction
 

·
Registered
Joined
·
582 Posts
Discussion Starter #4
Our tuner added more in the tune and it didn't change. He also went through the data stream and didn't find anything but I'll catch it again and post it.
 

·
Registered
Joined
·
582 Posts
Discussion Starter #5
I have two other thoughts, one I think you debunked a few years ago. The first one is this started right about the time I found a BBK 62mm twin throttle body and added it. Would the difference between a factory or BKK gasket or the TB itself cause this, assuming the TB is defective somehow? And the next thing is I relocated my battery to the trunk and only ran a positive to the trunk, and connected a negative to the interior metal of the trunk. Our tuner had some issues with something, I think flashing the ECU, and he claimed he's seen the same issues when a ground wasn't run all the way back. He claimed the thing metal of the body couldn't carry the same current a proper cable could.. I did measure resistence using a megger I borrowed and the body did exhibit more resistance.
 

·
Registered
Joined
·
22,364 Posts
your tuner must have tuned for a different TB

if you think you have a voltage drop, load the body with current and measure for it.

Your tuner added more of what in the tune?
 

·
Registered
Joined
·
582 Posts
Discussion Starter #7
I went to my storage and found my SCT x4. It has my original tune and my other tunes. I ran it through the updater on my PC and it said running the updater will erase 'your original tune." Does anyone know for sure what is erased if anything? And is the update feature on the SCT itself undfer the settings tag the same thing or different?
 

·
Registered
Joined
·
582 Posts
Discussion Starter #8
I am absolutely new to doing anything with my x4 other than changing tunes. I think I've saved the datalog properly though I can't make out much from it looking in the Link software. I attached the file.

I've long suspected the BKK 62mm TB so I changed back to the stock Ford TB (I know I'll need to get my tune updated to reflect this) and a new Ford TPS I had.. and the car ran better than ever. The idle reacted like it should. You take your foot off the gas and the RPM's drop to 1100-1200 and over the next 15-20s slowly drops to 800. With the other TB almost every stop the rpm's would drop to 600-500-600-400-300-800 or in other words they'd be all over the place. Now it's not. Though, when I first brought it out of the garage after the TB change the RPM's dropped down to o400-600 that one time, and then worked perfectly for about 20 minutes with maybe 100 cycles between 0-30/40mph-0 All perfect except for one instance where it dropped and died like it did before. The first time out of the garage I attributed to the computer re-learning.. possible? But the second time? I drove for another 5-7m after the last drop and everything was fine.

Any help would be greatly appreciated. I've been afraid to drive my car during hours of traffic for several years now, wasted hundreds at the Ford dealer, and not really enjoyed the car like i should. Thank you.

Apparently I can't directly attach this file.. so I put it on one of my servers. Just use this as the URL and you can then download and save it. http://bangkokimages.com/log.csv
 

·
Registered
Joined
·
582 Posts
Discussion Starter #10
No. I know better and just forgot to do it. I'll go flip the switch and let it simmer for a hour or so and then try again.
 

·
Registered
Joined
·
22,364 Posts
that is not why i am asking

you are jumping ahead of this systematic process, this leads to misdiagnosis.
 

·
Registered
Joined
·
582 Posts
Discussion Starter #12
Understood and I'll refrain from doing so again.

Changing back the TB while not part of this logical process, was part of a process I've been running in the back of my mind for a while and I was hoping to rule out the TB before starting this new process of collecting a datalog.

I bought the BKK used and from a guy who in retrospect I didn't feel good about. His reasoning for selling. At the time I made a mental note and didn't install it or piece together the correlation for nearly a year. Throughout my ownership of this car I've often taken assignments overseas for months to years at a time so keeping the pieces of information in order can be a chore at times. And by the time my suspicions grew my stock TB became lost. I found it while looking for the x4 and thought I'd swap it out and take it out of the equation and record a log on my test ride just in case..

And the car ran much better. Before the rpm's would waver but most of the time not die, but occasionally it would. With the stock TB, gasket, and a new TPS (bought to fix my 2002 5.4l FX4 Crewcab)I had waiting to go into another repair but put it in to rule it out. Anyway, the rpm wavering has stopped. It works like it should other than when pulling out of my drivie where it wavered and didn't die, and the one time it died in thie last few minutes of the log.

l've got the battery disconnected with the neg shorted to ground, and will connect and repeat the test tomorrow. Maybe I'll get lucky.
 

·
Registered
Joined
·
22,364 Posts
I think you will understand a little better if you know

Idle is learned over run time, and a number of starts

When you erase the Kam, you erase the learned corrections

When you changed TB, you most likely changed how much air if flows when closed

you would have seen this while logging idle short and long corrections

are you able to log corrections?
 

·
Registered
Joined
·
582 Posts
Discussion Starter #15
That was the one with the stalling. Once in the first maybe 20% and another int he last 10% of the file.

I don't understand what logging corrections means. Is there a link where I can learn more about how to use these files with my software?

I left the battery disconnected all night and this afternoon when I started it, the idle quickly stabilized and I drove for about an hour with zero issues. Actually the idle has stopped surging and the car is running great. I stopped and erased that log and started a new one to keep the size manageable and soon after when I stopped the idle fell down to 400-450 and then corrected. I noticed at the time, when I had my foot on the brake I was also rolling the window up to turn on the A/C. I drove around again and about 5m later turned the A/?C on while braking, and it again dropped down to 400-450 before correcting. Is this the ECU learning to handle increased electrical load? I attached the new log file, one more in a link: http://bangkokimages.com/log1.csv
 

·
Registered
Joined
·
22,364 Posts
so i graphed the last log

do you blip the throttle when rpms are dropping?

I can see it in the log just as rpms lose control to a stall
 

·
Registered
Joined
·
582 Posts
Discussion Starter #18
That's strange, no idea why it wasn't showing a running engine.

Second graph: I don't blip the throttle. I just let off the throttle and move my foot to the brake.
 
1 - 20 of 101 Posts
Top