Unclebob

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Hey guys!

I'm new here - and more or less, a "new" owner of a 95 Mustang V6.
I already went through a lot of threads looking for a solution (or maybe even a hint) on the probs i got with my pony.

At this point, i'm sorry for the long text.
And also sorry for probably having a strange way of punctuation and spelling - i'm not a native speaker :(

The problem itself seem to be pretty easy:

while idling, rpms around 700, Short-term fuel-trim is around 7.5-8%, which seems ok.
Long-term fuel-trim skyrockets up to 25%. It idles a little rough, but nothing thats really bothering imo.
As far as i know, the closer both get to 0%, the better. but stft+ltft <10% is ok, which is not the case.

As soon as i rev the engine, ltft drops to round about 3%, stft,depending on how much i hit the pedal, oscillates between 10-17%, which seems fine to me tbh.
CEL pops up every now and then, throwing p0171 and p0174 codes (Bank1 and Bank2 running lean).


Most of the time those are symptoms for a vacuum leak, but sadly not in my case.

Things already done / checked:

- standard maintenance (sparkplugs, air-/ fuelfilter, oilchange including oil, transmission-oil + filter)
- intake-manifold gaskets (lower + plenum gasket)
- Vac-hoses replaced (every single one, except the one dissappearing in the fender)
- IAC (incl. gasket) replaced
- egr (incl. gasket) replaced
- o2 sensors (up + downstream) replaced
- maf-sensor replaced
- throttle-body cleaned, just in case it gets stuck open a little

I'm kinda running out of ideas tbh, maybe anyone has had that kind of problem and might help or lead me to the things i'm overlooking.

Greetings from good ol' Germany!
 

lwarrior1016

Mr. Secondary Timing Chain
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Welcome to the forum and sorry for your issues. I have to ask on the vacuum stuff, did you smoke test for a vacuum leak or are you thinking there is no leak because you’ve replaced the hoses?

The fuel trims show adding fuel at idle and going back to normal when vacuum in going away, really does point toward a vacuum leak.

Just for laughs, have you checked fuel pressure?
 
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Unclebob

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Welcome to the forum and sorry for your issues. I have to ask on the vacuum stuff, did you smoke test for a vacuum leak or are you thinking there is no leak because you’ve replaced the hoses?

The fuel trims show adding fuel at idle and going back to normal when vacuum in going away, really does point toward a vacuum leak.

Just for laughs, have you checked fuel pressure?
Thanks for the repl!

The vacuum was actually my first guess, I did replace them because some were brittle on the connectors.

But I did smoke-test it after replacing the hoses, with no leaks at all.
So either a deadend here, or they tore again. But I think that’s unlikely to happen within 3 months?

Forgot to mention I checked that too - I remember someone complaining about a bad fuel pump in inevitable the threads.
I also replaced the injector o-rings while I was at the intake manifold, because the pre-owner hasn’t got any proof on maintenance or whatsoever.
Car is on 86k miles now
 
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Here is how to set base idle.
1 Disconnect neg terminal
2Disconnect AIV idle motor
3Reconnect neg terminal
4Start engine , set idle via
stop screw
5Turn engine off
6Reconnect idle motor
7Start engine , all accessories off
8Run for 2 minutes
9Shut off for 2 minutes
10 Run for 2 minutes all accessories on
11EECIV should have learned new idle
12 Remove both battery cables and touch together. This drains capacitators
13 Reattach the terminals
14Idle for 10 minutes , all accessories off
This should reset the computer to the idle you chose
 

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