need advise; power range at about 5000 RPM

reyesjo · Feb 7, 2006

"UPDATE"power range at about 5000 RPM

I have a 66 stang, with the following.
5.0 L out of a 1989 mustang with AL9P computer
mass air flow, and a 5 speed t-5 with an 8" with 3:55 gears

The engine is stock an has been rebuilt as well as the transmission, it has a T-Rex fuel pump and Windsor Fox wiring. the car starts great and runs great... HOWEVER.. in 1 and 2 gear about 5000 RPM the car runs out of power... It feels like the computer is not letting the injectors push out more fuel... I can't be exact on the RPM I'm lacking a Tech for now.. Don't know what it could be.. If you guys can think of something let me know please

http://www.cardomain.com/ride/2215774

HistoricMustang · Feb 7, 2006

reyesjo said:
I have a 66 stang, with the following.
5.0 L out of a 1989 mustang with AL9P computer
mass air flow, and a 5 speed t-5 with an 8" with 3:55 gears

The engine is stock an has been rebuilt as well as the transmission, it has a T-Rex fuel pump and Windsor Fox wiring. the car starts great and runs great... HOWEVER.. in 1 and 2 gear about 5000 RPM the car runs out of power... It feels like the computer is not letting the injectors push out more fuel... I can't be exact on the RPM I'm lacking a Tech for now.. Don't know what it could be.. If you guys can think of something let me know please

It may be more like 6000 and you are running out of air.

HistoricMustang
www.historicmustang.com

Welcome.................

mustangdave · Feb 7, 2006

No problem, the stock head/cam/ intake combo run out there. I found the best shift point in a stock 5.0 to be 5600 r.p.m. for the best E.T. Give or take a few hundred r.p.m. for gearing differences but never over 5800 r.p.m. Open up the intake tract from start to end.

red65 · Feb 7, 2006

Check to make sure that the #5 and #6 spark plug wire are separated by a few inches (the plug wires should be in some kind of clips or harnesses to keep them separated). On a 5.0, the firing order is 1-3-7-2-6-5-4-8 - Check a Chilton's manual if you're not sure which is which, but 5 and 6 are the two front cylinders on the driver's side. Without going into the physics, it's possible for the #6 wire to induce an early spark in the #5 wire if they're too close together, creating an effect something like pre-ignition in #5.

When I got my 5.0l conversion running for the first time, it missed a bit at the top end. Separating the plug wires made a remarkable difference. Easy and free to try...

65ShelbyClone · Feb 7, 2006

reyesjo said:
I have a 66 stang, with the following.
5.0 L out of a 1989 mustang with AL9P computer
mass air flow, and a 5 speed t-5 with an 8" with 3:55 gears

The engine is stock an has been rebuilt as well as the transmission, it has a T-Rex fuel pump and Windsor Fox wiring. the car starts great and runs great... HOWEVER.. in 1 and 2 gear about 5000 RPM the car runs out of power... It feels like the computer is not letting the injectors push out more fuel... I can't be exact on the RPM I'm lacking a Tech for now.. Don't know what it could be.. If you guys can think of something let me know please

Thr problem is not the computer, but that the intake tract on the engine wont let any more air in. Stock 5.0 roller engines run out of steam around 4800-5200. The stock rev limiter is ~6200. Do you have an A9L or A9P computer? A9L is out of a manual car, P = AOD trans.

LUCAFU1 · Feb 8, 2006

he said he had the a9p.
Are you positive its not hitting the rev limiter? you really need a tach or a shift light at a minimum.

65ShelbyClone · Feb 8, 2006

I couldnt quite tell from this:

reyesjo said:
5.0 L out of a 1989 mustang with AL9P computer

LUCAFU1 · Feb 8, 2006

65ShelbyClone said:
I couldnt quite tell from this:

LMAO nice catch. Me I just see the first and last letter. I will slap myself now

reyesjo · Feb 8, 2006

replys

Thanks for the fast replys,

I have a A9L for manual transmission, I will try to add a tech on her, but money has been tight... forgot to mention it has a K&N air filter just a cone at the end of the mass airflow metter..

Also the sensors going to the trasmission the Neutral sensing switch, backup lamp switch and the speed sensors.... are not hooked up... Only concern with the SPEED SENSORS, do they need to be hooked up..

thanks again

red65 · Feb 8, 2006

reyesjo said:
Only concern with the SPEED SENSORS, do they need to be hooked up..

Vehicle speed sensor doesn't have to be hooked up, although it can improve driveability a bit if it is (it'll ramp engine speed down more gradually if it senses that the car is moving than it would if the car were still). That's not your high-RPM problem.

5.0ina66 · Feb 8, 2006

reyesjo said:
I will try to add a tech on her, but money has been tight...

Sun SuperTachII...$45 at your local Advance Auto or AutoZone

65ShelbyClone · Feb 8, 2006

5.0ina66 said:
Sun SuperTachII...$45 at your local Advance Auto or AutoZone

Dang, the Blottozone here has them for $35(black one).

The VSS should be connected for the drivability reasons red mentioned. It is also there for the cruise control on the 5.0s.

5.0ina66 · Feb 8, 2006

65ShelbyClone said:
Dang, the Blottozone here has them for $35(black one).

Crap...stupid college town...every business in town tries to screw the population (eg the students) into the ground.

reyesjo · Feb 9, 2006

I think I made progress maybe, still no Tach

Ok gents, let see what you think.

I disconnected the MAP sensor electric connector.. the vacume line was not connected... It feels like it has more ump, more power.. what do you guys think..

The MAP sensor is for Speed density I think... SHOULD IT BE HOOKED UP?

I don't know hopefully I will get a sticking tach soon, I have a bid on ebay for one..

65ShelbyClone · Feb 9, 2006

Be aware that I'm getting into a shakey area of my EEC-IV knowledge, but I think the mass air engines still use a MAP sensor and that it should be funtional. Reconnect the plug and vacuum line.

ashford · Feb 9, 2006

reyesjo said:
Ok gents, let see what you think.

I disconnected the MAP sensor electric connector.. the vacume line was not connected... It feels like it has more ump, more power.. what do you guys think..

The MAP sensor is for Speed density I think... SHOULD IT BE HOOKED UP?

I don't know hopefully I will get a sticking tach soon, I have a bid on ebay for one..

well technically speaking on a mass air system its called a barometric pressure sensor. electronically its the same as a map sensor, only difference is that the map sensor has a vacuume hose hookup where the baro has a little filter. if the vacuum line was hooked up this would probably give you a problem. i think on the eec-IV the computer takes a reading when the key is first turned on and at wot, if ther was a little vacuum there the comp would see a drop in atospheric pressure and lean you out a little.

when i did my first efi conversion i had no air filter so i zip-stripped a couple rags to the throttle body to see how it ran. i couldnt get over 2500 rpm and it ran just fine there smooth as silk at wot. it took me awhile to figure out what the hell caused that i thought it was the rev limiter because i didnt have the neutral sensing circuit hooked up.

65ShelbyClone · Feb 9, 2006

Dont the mass air cars have MAP and BAP sensors? Heck, I thought the speed density cars have both also.

reyesjo · Feb 24, 2006

update, got a Tech on her

Well, I finially got a Tech on her, and to my surprise the engine runs like a bat out of hell up to 5K RPM and as soon as it get to 5K it feels like it looses power....Is that normal for a stock 5.0L.. I think that if I shift around 5.2K or alittle higher it runs great.... I just have to learn to shift faster.... I guess..... or start saving money to upgrade the engine. If only I could convience the wife to take money out of savings.

mtbdoc · Feb 24, 2006

Yep. Those cars will keep rev'ing, but don't make any power. Need more breathing!

65ShelbyClone · Feb 24, 2006

reyesjo said:
as it get to 5K it feels like it looses power....Is that normal for a stock 5.0L..

On all the stock parts, yes. Depending on how many miles are on the engine, you might run into valve float before the 6250 rev limiter. However, you know first hand that its unnecessary to rev that high because the induction runs out well before that.

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