Friends car has no power over 4000rpms

[94YellowStang]

Friends car has no power over 4000rpms.

Heres whats been done so far:replaced plugs&wires, cleaned mass air, cleaned k&n filter, replaced fuel filter, and timing is set at 12 and runing premium fuel because of pinging.

Please post any ideas as to what the problem might be.I'm not going to replace any expensive parts yet.I was gonna check with you guys first before I go get a engine checked on a computer.It just started through a code last week and has came on 3 times so far but seems like autozone or advanced auto have to OBD1 computer checker thing,its all 96-up.

Thanks guys

 

[94YellowStang]

I need to check the fuel pressure but autozone and everywhere else says the gauges are $40, what is stock fuel pressure set at?

 

[sociopath5.0]

Stock FP is usually 39-43 psi without vacuum lines attached, I believe. Feel free to correct me anyone.

 

[grrrrrrr]

Honestly why don't you take it to a dyno? Most charge about 60 - 70 bucks for 3 pulls. If they're anything like the place I go they're real helpful as well. So for the price of a fuel pressure gauge and a half a tank of gas you can figure out what your problem is and tune the car for max power. Every car is a little different, who knows, maybe you can tweak the timing a bit while you're there?

 

[fords2fast4u]

ok, so it's wither timing or fuel...

has he ever ran the car out of gas? does he have alot of miles? If either is true, the fuel pump may be weak and need replacing. Also check the cap/rotor.

i had simular problems when my inline fuel pump had a bad power contact... it would run fine until 2 or sometimes 3 and then cut out. the intank pump was having to push through the inline and that seriously reduced the amount of fuel getting to the motor. I replaced the fuel filter, but the pump never accoured to me until after i had replaced damn near the entire ignition (dist, coil, wires, cap/rotor, plugs...)

good luck

 

[Car Nut]

I'd get those injectors cleaned, because you've got to rule that one out. Replace the PCV valve and clean the metal grommet real good with Carb cleaner (keep spraying on it at all sides until nothing but clear liquid comes out the bottom).

Cleaning injectors is inexpensive. In fact, I think Seafoam will help clean those up as well as the intake area and fuel lines. Suck up 1/2 a can using the Brake Booster line and dump the other 1/2 can int the tank. Do a search on this for the procedure thats worked for lots of people.

What does the car sound like as it crosses the 4,000 rpm mark? Does it "sound" different or just lose power?

I'd do the cheap cleaning stuff I mentioned and then see what happens. Gotta clean all the appropriate places first to rule things out.

 

[mackey]

I bet the computer is not advancing the timing. When you rev the car up does the timing change or does it stay at 12?

 

[fords2fast4u]

yeah, the spout could be out? lol

 

[94YellowStang]

we set timing at 12 yesterday with spout out and turned the car off, then plugged the spout connector back up.I did the same on my car yesterday and my timing was a 8degrees but i changed it to 12.

His car has is a coupe 5 speed with 103k mods so far u/d pulleys,h-pipe,flowmaster muffs, and 3:73's.We went to the track the last 2 sundays and its ran in the 16's-low 17's with around 80-86mph trap speed 1/4 mile.

 

[94YellowStang]

timing was set at 12 and with spout in it looks to be 2 notches from 30 running, mine is the exact sameway on my vert

 

[mackey]

Have you done cap/plugs/wires recently?

 

[fords2fast4u]

i'm telling you, it's fuel related man....

 

[94-302-vert]

replace that fuel pump... I have heard more than once that when you start losing your top end suspect the fuel pump....

That is how I am going to know when to replace mine...

Chris

 

[94YellowStang]

Yeah I think that we are going to buy a fuel pressure gauge and check the fuel pressure. We checked the codes and it didnt throw any. The problem does sound fuel related but he doesnt want to buy a pump just yet.

 

[ALMOSTFINISHED]

What happens if you snap throttle the car? Does it fall on its face once it hits 4k? I would try a fuel filter 1st off, Its cheap enough also so if its not the problem you didn't lose much $$. When you listed his mods, it says "h-pipe". Meaning without cats or with? If it has cats, do an exhaust system pressure test to see if the cats are clogged up causing it to lose power. Good luck with everything. Read the codes too!

Nick

 

[fords2fast4u]

i thought that he said he already replaced the filter...

the fuel pressure gauge may not help... if the car idles fine and runs "ok" until 4K and then shuts out, but only under acceleration, you won't be able to tell that unless you can view the gauge, under load throughout the RPM range.

The pump can probably keep regular fuel pressure in the rails at idle (less than 1000 rpms) but as the injectors open more and more frequently (past 4K) in order to keep that much pressure, it has to pump much more fuel through the line... I know that it may sound crazy, but if you really want to check this to be sure before replacing the pump, you're going to have to watch it over the rpm range. If i remember correctely, you said that it would go to the top, just without power - which may mean that you'll have to watch it under load... which i have done, believe it or not, with a gauge on the rail (dont ask me how i did that lol), but now i have an electric autometer on it.

 

[94YellowStang]

no cap and rotor have not been replaced but looked ok,the cap doesnt have any cracks in it and the rotor looks fine, fuel filter was replaced yesterday.


I guess he needs to buy a fuel pressure gauge next $40 and see what its set at then buy a fuel pump if the pressure is fine.Could the o2 sensors cause any of these problems?

 

[fords2fast4u]

ive never heard of 02 sensors causing such a problem.. and that is an expensive part to have it not be the problem. A new pump is expensive too, but a higher volume one (155 - 190) is always a good upgrade.

if he does decide to change it, make sure the grease the filler seal or it may break on you.

 

[final5-0]

On the older Stangs a bad coil would do that kind of thing.

It would be an easy test to put your coil on his car to see what happens.

Later
Grady

 

[94YellowStang]

On the older Stangs a bad coil would do that kind of thing.

It would be an easy test to put your coil on his car to see what happens.

Later
Grady

Thanks, I will try that