Stock Mustang Dyno'd - Lean?

Had a place here local that just got a dyno....so they were offering free pulls on it.

Anyways, never done such before, and took my son's stock mustang over to the place, to get a baseline before we start doing any mods to it.

It's stock '88 mustang, with exhaust bolted on. Frpp shorties, BBK X, and Magnaflow.

Last month pulling codes, I believe it was clean. New O2 sensors, new plugs, wires, cap, rotor, and coil. Timing set at 10* I believe.

Anyways, they dyno sheet showed it running lean, like 15/1 ratio. Shop guy said to maybe get a adjustable fuel pressure regulator, and run 93 octane with the timing turned up some towards 14.

So any suggestions???

mustangdyno.jpg
 
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It's stock '88 mustang, with exhaust bolted on. Frpp shorties, BBK X, and Magnaflow.

I don't want to sound pedantic but I see people doing this often, saying that their car is stock and then quoting all the bolt-on mods. The bottom line is the car isn't stock.
I wouldn't advance the timing without dealing with the lean issue first. If it's still got the original 22-year-old injectors, there's a good chance they're clogged up and not flowing enough fuel.
 
Ya I get what your saying about saying it's stock then listing the bolt ons. didn't really consider changing exhaust due to the original being rusted out, much of a "fuel system" or engine change from stock, but I gotcha.....

What's easiest way to check if one or more injectors are clogged? Take of the intakes and pull them, or possible to pull plugs and look at their condition?

If I do have to change them, would it matter or make a difference to go ahead and put 24# in for future upgrades, or would that start to cause it to go rich??? Guess it's time to go JY diving.....
 
unless you plan on doing a lot of mods, just keep 19s in there, maybe upgrade to the 3 hole 19# injectors, you can usually find them cheap on ebay or craigslist. definately put a new fuel pump and strainer in there too. Those are actually pretty decent numbers for an 88' mustang with only exhaust and the timing still at 10
 
If it was really running 15:1 then I would think you would most likely detonate. What everybody here hasn't considered is the fact that the metering device this dyno is using maybe old and worn out too. Either which way headers and complete exhaust can lean out the system a little bit. I don't think injectors or pump is tired being the A/F stays consistent across RPM, if it was a fuel delivery issue the A/F line would fluctuate or have a positive slope. But then again who knows if this guys equipment is any good.
 
If it was really running 15:1 then I would think you would most likely detonate. What everybody here hasn't considered is the fact that the metering device this dyno is using maybe old and worn out too. Either which way headers and complete exhaust can lean out the system a little bit. I don't think injectors or pump is tired being the A/F stays consistent across RPM, if it was a fuel delivery issue the A/F line would fluctuate or have a positive slope. But then again who knows if this guys equipment is any good.

Yea, the first red flag I see is that the A/F stays dead steady the entire run. If the fuel system was having some sort of a failure, the A/F would probably jump around, and probably get leaner as the revs climbed. This kind of looks like it is actually getting richer, but not by much.

Also, I could be on drugs, but isn't a stone-stock 5.0 tuned to run around 14:1 at WOT? That graph is hard to read, but it looks like you're right around 14:1, or maybe a little North. Remember, 14.7:1 is stoichiometric.
 
Was the O2 sensor a tailpipe sniffer or was it screwed into a bung in your H pipe? (Assuming you have a bung welded into your H pipe.)

If it was a tailpipe sniffer and you have an exhaust leak anywhere, you'll read lean.

As the exhaust pulses pass the leak, the low pressure portion of the pulse will pull in fresh air.

Good luck...
 
car has an aod in it. And it was a tail pipe sniffer. There doesn't appear to be any evidence of exhaust leak that we have found, though we did put on the exhaust ourselves, so anything is possible....

To TMOSS you say the a/f is right where it should be? Looks to be 14 all the way across until the upper rpm range, where it looks to get a little richer. Are you still doing port work?