cars still loosing power starting around 3500rpm

crazy5.0 · 03-08-2002, 11:39 PM

The car runs strong up to around 3500 rpm then it starts going flat. My fuel pressure is good. The fuel filter was changed less than a year ago. I have test for vaccum leaks and exhaust restrictions witha vaccum gauge and everthing is fine. I have replaced the coil,plugs a few times,plug wires,distributor cap and rotor. The car runs great at low rpm's. The timing is set at 12'. Could a have a bad cat even though when I tested for restrictions, the vaccum gauge went up when revving up to 2000rpm and held there? I have checked for codes and got a code 91 which was caused by faulty left 02 sensor harness,which was replaced along with that 02. I reset the computer already.

fordgasm · 03-09-2002, 10:13 AM

This is a tough one but I would consider the following:

1) Fuel problem, fuel filters should be changed yearly. Maybe fuel pump problem or injector problem or regulator problem.

2) If it's not a fuel problem then possible electrical, sounds like you have replaced these items like coil, cap, wires, plugs, etc.

3) You mentioned a plugged cat which is also possible, they usually will get real hot if they are plugged, maybe check that. Might be a good time to get that off road H pipe you always wanted

That would be my approach to solving this one from what you have described.

Good Luck!

crazy5.0 · 03-09-2002, 11:25 AM

This problem has been going on for over a year and a half now. I had the fuel pressure checked 3 times and it was within specs. If the fuel pressure was fine would that mean the injectors,regulator are good? The filter has maybe 5000-6000 miles on it. How can I test the fuel regulator? As far as the cats possible being bad I will check that tonight when it's dark and see if there glowing. My other car that my dad drives now had the same problem. Which turned out to be a bad seal where the didtributor meets the timing gears. It used to run out at it's peak torque just like mine. The car looses power through it's power band. I live in Cal,so forgot getting a aftermarket exhaust. I have to have the nazi sniffers run my car in August.

crazy5.0 · 03-10-2002, 12:54 AM

After driving tonight I looked under the car to see if the cats were glowing red and there not. How can I check the fuel pressure regulator?

fordgasm · 03-10-2002, 10:28 AM

You need to have a fuel pressure gauge so that you can see what pressure you are holding. Preferably one that you can read while you are driving to see if the pressure drops as the rpm increases.

The regulators can fail also, they have a rubber diaphram in them that can develope a leak. With a fuel pressure guage you can see if the fuel system is holding pressure or not.

Do you have an aftermarket adjustable regulator or the stock one? Do you have a fuel pressure gauge?

What about your fuel pump? Is it original equipment? There is not all that much with the fuel system. You have the fuel pump, the fuel filter, the fuel regulator and the injectors. I would try to eliminate each item one at a time, starting at the least expensive.

Your type of problem is usually going to be either electrical or fuel related and it sounds like you have already addressed all the electrical items. I would now focus on the fuel system. It is very difficult to diagnose your problems over the internet, but from what you have described this is the approach I would take.

What year is your car and how many miles are on it? What is the general condition of the car?

Just because a cat is not glowing does not mean it is fine, they can have a restriction and not glow, but may be hotter than normal. Too bad your not closer, I have a brand new factory H pipe with the 4 cats on it that I took off in 1990 after a Ford recall. My local Ford dealer put the new H pipe on then I took it home and put a set of long tubes and off road H pipe on. They have been sitting in the rafters of my garage for years. If you were a local guy I would let you install them, but if you were a local guy you would probably go with an offroad H pipe

Hope that helps, just address each item one at a time and only make one change at a time so that you know where you are at.

crazy5.0 · 03-10-2002, 09:42 PM

About a hour ago I drove my car around my neighborhood to dry the tires for tires dressing and when the car was cold it pulled well at higher rpm's. Once it warmed up it stopped pulling hard. This goes back to thinking I am still having problems with the left 02 sensor, but when the car is warmed up it goes flat at higher rpm's at wot, partial throttle. The 02 sensors only signal the computer at partial throttle and have no function at wot. I have replaced the ect sensor already alond with all other sensors.

PKRWUD · 03-11-2002, 05:29 AM

What condition are your valve springs in?

How did you test your exhaust for restrictions? Your first post mentioned the vacuum rising at 2000 rpms. Try these tests instead: With a vacuum gauge, there are two easy tests you can run to determine if your exhaust is restricted (cats clogged).

First test:
1) Attach vacuum gauge to manifold vacuum source.
2) Observe vacuum at idle.
3) Snap throttle to WOT and release, while watching the gauge.

The vacuum gauge should drop to almost zero when you hit WOT. When the throttle snaps closed immediately after, the vacuum should read 4" to 6" higher than what it did at idle. It should then settle back at the same reading it was at idle before the WOT snap. This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. If it takes longer for the gauge to return to the same idle reading, your exhaust is restricted. The longer it takes, the worse the restriction.

Second test:
1) Attach vacuum gauge to manifold vacuum source.
2) Warm up engine.
3) Observe vacuum at idle.
4) Leave engine idling for 10 minutes. Do not touch anything on the car during this time. In fact, go inside and fix some coffee.
5) After 10 minutes, observe the vacuum.

If the vacuum is the same or higher, you don't have any resctrictions. If the vacuum gauge has dropped, you do have a restriction. The more it drops, the greater the restriction. If it drops 1" or more, you have a serious restriction. 2" or more and you might as well have the exhaust welded shut. Keep in mind that a rich exhaust will clog up cats in a hurry.

Take care,
-Chris

theforce · 03-11-2002, 06:10 PM

I would check valve springs or test fuel injectors. Hard to tell without hearing the miss.

crazy5.0 · 03-11-2002, 09:19 PM

I just now did the two tests that PKRWUD said to do and the guage stayed at a steady 18psi for the 10 mins and at wot the vaccum went to zero. The car doesn't miss at all. What happens is once the car warms up it starts loosing power at 3000rpm on up. I always warn my car up for 1-2 mins before driving ,but yesterday I didn't since I drove earlier in the day. Once the temp gauge started moving up it stopped pulling hard past 3000rpm. It does this at wot throttle and partial throttle so I can ruleout 02 sensors since they go to closed loop at wot.

HAITHAM · 03-13-2002, 12:13 AM

Quote:

Originally posted by fordgasm
You need to have a fuel pressure gauge so that you can see what pressure you are holding. Preferably one that you can read while you are driving to see if the pressure drops as the rpm increases.

Which one we can consider it as a good symptoms when the rpm increases, decreasing or increasing the fuel psi ??

66StangGuy · 03-13-2002, 03:01 AM

sounds like its a computer problem. sounds like the air fuel ratio is off. maybe when your engine is cold and the computer runs the engine rich ( where the ratio should be) it runs fine but once it warms up and the computer lowers the fuel air ratio is ends up running lean. This is the only thing that makes sense to me. if it were exhause restriction then it would also be affected when it is cold. Check the computer. something seems wierd there. Is there any way you can trick your computer into thinking that your engine is always cold? if so then it should run fine. then you know what your problem is.

LX XLR8R · 03-13-2002, 04:29 PM

this sma ehting has happened to me 2x..first it was the fuel pump going bad..was fine when cold but once warmed up it would cut out up top cuz of lack of fuel..thisg sonded like it was screaming fast but wastnt pumping for anytning..and that was a 155 aftermarket
2nd example..could not figure this one out for a while..was running lean up top and cutting out..plugs were allways white so i checked everyhting in fuel system..it ended up being the distributer module..go figure..i guess that affects injector pulse

crazy5.0 · 03-13-2002, 09:28 PM

I took the car t omy local mechanic and he says the car is probable running lean at higher rpm's. He recommened that I get a adjustable fuel pressure regulator and a in the car fuel gauge. I'm not gonna do anything at this time. My car had been running weak for over a year and a half. I'm just gonna buy another stang,perferable a notch and swap mytrans,driveshaft,rearend,lower control arms. My car looks like crap and still needs front lower control arm bushings and softer struts and shocks, the ride is extremely harsh and has no weight transfer. The bumpers are yellow gray and the blue paint looks very faded in the shade. Sorry to rumble on about my car, but I hate my car most of the time. I had to pay $285 in diagnostic work over the past 3 months and nothing was fixed. I'm tired of spending money on my car.
Thanks for the help anyhow.

crazy5.0 · 03-13-2002, 11:17 PM

I was in a bad mood earlier because I had to pay my mechanic $285 for the 3 times I took my car to him to figure out this problem, which is still a mystery. He said the car is possible going lean at highe rpm's. I don't know how this can be only when the car is warmed up. He tested the fuel pressure and did a battery to computer aid tests. My plugs are slightly black meaning it's running rich more than lean. Can a car run rich at low rpm's and run lean at high rpm's? I have a new mass air meter that I had on the car for a week back about 4 months ago and it made the car run very rich,popping exhaust,surging at idle. It says on it was calibrated correctly for my injectors. The car ran great for a week after that when I put my stock mass air back on. Could the mass air still be the culprit?

crazy5.0 · 03-19-2002, 07:02 PM

Well my car was only running better when cold, but now it's the opposite sometimes. The other day it ran totally gutless when cold and when it heated up it started to run much better at times. The car is running rich all the time. I had someone stand behind the car and I gave it about 1/3 throttle and a little smoke came out. Past 3000rpm it feels like the car is over revving. Last night it ran like usual, gutless. I can think of 4 things that could be causing this .
1. Bad computer
2. Bad injector,injectors
3. Bad fuel pressure regulator
4. Worn out engine, time for shortblock

tough90pony · 03-20-2002, 04:25 AM

Had the same thing happen to my car last May. I tried everything electrical, O2 sensors,ACT,TFI,cap wires and plugs, different FPR, different fuel injecton harness,fuel pressuretests, etc. Then I finally got a crazy idea and thought it was the engine itself. Wrong. It still did it, so I just carburated it and got rid of all the computer controlled crap. It runs fine now.

03-08-2002, 11:39 PM	#1
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	cars still loosing power starting around 3500rpm The car runs strong up to around 3500 rpm then it starts going flat. My fuel pressure is good. The fuel filter was changed less than a year ago. I have test for vaccum leaks and exhaust restrictions witha vaccum gauge and everthing is fine. I have replaced the coil,plugs a few times,plug wires,distributor cap and rotor. The car runs great at low rpm's. The timing is set at 12'. Could a have a bad cat even though when I tested for restrictions, the vaccum gauge went up when revving up to 2000rpm and held there? I have checked for codes and got a code 91 which was caused by faulty left 02 sensor harness,which was replaced along with that 02. I reset the computer already. __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-09-2002, 10:13 AM	#2
fordgasm Registered Member Join Date: Jan 1999 Location: Clayton, North Carolina, USA Posts: 803	Tough One This is a tough one but I would consider the following: 1) Fuel problem, fuel filters should be changed yearly. Maybe fuel pump problem or injector problem or regulator problem. 2) If it's not a fuel problem then possible electrical, sounds like you have replaced these items like coil, cap, wires, plugs, etc. 3) You mentioned a plugged cat which is also possible, they usually will get real hot if they are plugged, maybe check that. Might be a good time to get that off road H pipe you always wanted That would be my approach to solving this one from what you have described. Good Luck! __________________ fordgasm CLICK HERE to see my 87 GT

03-09-2002, 11:25 AM	#3
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	This problem has been going on for over a year and a half now. I had the fuel pressure checked 3 times and it was within specs. If the fuel pressure was fine would that mean the injectors,regulator are good? The filter has maybe 5000-6000 miles on it. How can I test the fuel regulator? As far as the cats possible being bad I will check that tonight when it's dark and see if there glowing. My other car that my dad drives now had the same problem. Which turned out to be a bad seal where the didtributor meets the timing gears. It used to run out at it's peak torque just like mine. The car looses power through it's power band. I live in Cal,so forgot getting a aftermarket exhaust. I have to have the nazi sniffers run my car in August. __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-10-2002, 12:54 AM	#4
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	After driving tonight I looked under the car to see if the cats were glowing red and there not. How can I check the fuel pressure regulator? __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-10-2002, 10:28 AM	#5
fordgasm Registered Member Join Date: Jan 1999 Location: Clayton, North Carolina, USA Posts: 803	You need to have a fuel pressure gauge so that you can see what pressure you are holding. Preferably one that you can read while you are driving to see if the pressure drops as the rpm increases. The regulators can fail also, they have a rubber diaphram in them that can develope a leak. With a fuel pressure guage you can see if the fuel system is holding pressure or not. Do you have an aftermarket adjustable regulator or the stock one? Do you have a fuel pressure gauge? What about your fuel pump? Is it original equipment? There is not all that much with the fuel system. You have the fuel pump, the fuel filter, the fuel regulator and the injectors. I would try to eliminate each item one at a time, starting at the least expensive. Your type of problem is usually going to be either electrical or fuel related and it sounds like you have already addressed all the electrical items. I would now focus on the fuel system. It is very difficult to diagnose your problems over the internet, but from what you have described this is the approach I would take. What year is your car and how many miles are on it? What is the general condition of the car? Just because a cat is not glowing does not mean it is fine, they can have a restriction and not glow, but may be hotter than normal. Too bad your not closer, I have a brand new factory H pipe with the 4 cats on it that I took off in 1990 after a Ford recall. My local Ford dealer put the new H pipe on then I took it home and put a set of long tubes and off road H pipe on. They have been sitting in the rafters of my garage for years. If you were a local guy I would let you install them, but if you were a local guy you would probably go with an offroad H pipe Hope that helps, just address each item one at a time and only make one change at a time so that you know where you are at. __________________ fordgasm CLICK HERE to see my 87 GT

03-10-2002, 09:42 PM	#6
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	About a hour ago I drove my car around my neighborhood to dry the tires for tires dressing and when the car was cold it pulled well at higher rpm's. Once it warmed up it stopped pulling hard. This goes back to thinking I am still having problems with the left 02 sensor, but when the car is warmed up it goes flat at higher rpm's at wot, partial throttle. The 02 sensors only signal the computer at partial throttle and have no function at wot. I have replaced the ect sensor already alond with all other sensors. __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-11-2002, 05:29 AM	#7
PKRWUD Junior Member Join Date: Mar 1999 Location: Ventura, California Posts: 8,981	What condition are your valve springs in? How did you test your exhaust for restrictions? Your first post mentioned the vacuum rising at 2000 rpms. Try these tests instead: With a vacuum gauge, there are two easy tests you can run to determine if your exhaust is restricted (cats clogged). First test: 1) Attach vacuum gauge to manifold vacuum source. 2) Observe vacuum at idle. 3) Snap throttle to WOT and release, while watching the gauge. The vacuum gauge should drop to almost zero when you hit WOT. When the throttle snaps closed immediately after, the vacuum should read 4" to 6" higher than what it did at idle. It should then settle back at the same reading it was at idle before the WOT snap. This whole exchange should go from idle reading to idle reading in 2-3 seconds, tops. If it takes longer for the gauge to return to the same idle reading, your exhaust is restricted. The longer it takes, the worse the restriction. Second test: 1) Attach vacuum gauge to manifold vacuum source. 2) Warm up engine. 3) Observe vacuum at idle. 4) Leave engine idling for 10 minutes. Do not touch anything on the car during this time. In fact, go inside and fix some coffee. 5) After 10 minutes, observe the vacuum. If the vacuum is the same or higher, you don't have any resctrictions. If the vacuum gauge has dropped, you do have a restriction. The more it drops, the greater the restriction. If it drops 1" or more, you have a serious restriction. 2" or more and you might as well have the exhaust welded shut. Keep in mind that a rich exhaust will clog up cats in a hurry. Take care, -Chris __________________ Webmaster: Rice Haters Club Jim Porter Racing Peckerwoods Pit Stop Support Your Local RED & WHITE!

03-11-2002, 06:10 PM	#8
theforce Registered Member Join Date: Jun 2000 Location: Deer Park (Houston), Texas Posts: 39	Miss I would check valve springs or test fuel injectors. Hard to tell without hearing the miss. __________________ 86 Capri "Don't Laugh It's Turbocharged!!!"

03-11-2002, 09:19 PM	#9
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	I just now did the two tests that PKRWUD said to do and the guage stayed at a steady 18psi for the 10 mins and at wot the vaccum went to zero. The car doesn't miss at all. What happens is once the car warms up it starts loosing power at 3000rpm on up. I always warn my car up for 1-2 mins before driving ,but yesterday I didn't since I drove earlier in the day. Once the temp gauge started moving up it stopped pulling hard past 3000rpm. It does this at wot throttle and partial throttle so I can ruleout 02 sensors since they go to closed loop at wot. __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-13-2002, 03:01 AM	#11
66StangGuy Registered Member Join Date: Feb 2002 Location: Diamond Bar Posts: 258	sounds like its a computer problem. sounds like the air fuel ratio is off. maybe when your engine is cold and the computer runs the engine rich ( where the ratio should be) it runs fine but once it warms up and the computer lowers the fuel air ratio is ends up running lean. This is the only thing that makes sense to me. if it were exhause restriction then it would also be affected when it is cold. Check the computer. something seems wierd there. Is there any way you can trick your computer into thinking that your engine is always cold? if so then it should run fine. then you know what your problem is. __________________ 66 mustang-292-Holley 4160-World Castings Windsor Sr.-Hooker super comp headers-MSD box & Coil.3.55 gears. B&M Z-Gate-Black leather racing seats with 4pt harnes.

03-13-2002, 04:29 PM	#12
LX XLR8R Dirk Diggler Join Date: Feb 1999 Location: SLOATSBURG, NY Posts: 1,931	this sma ehting has happened to me 2x..first it was the fuel pump going bad..was fine when cold but once warmed up it would cut out up top cuz of lack of fuel..thisg sonded like it was screaming fast but wastnt pumping for anytning..and that was a 155 aftermarket 2nd example..could not figure this one out for a while..was running lean up top and cutting out..plugs were allways white so i checked everyhting in fuel system..it ended up being the distributer module..go figure..i guess that affects injector pulse __________________ 95 undecided cubes, AFR 185s,undecided cam, undecided intake, and a 150 hit 89 "turbonotch" 2.3T You might want to hold on..i saw this on a cartoon once

03-13-2002, 09:28 PM	#13
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	I took the car t omy local mechanic and he says the car is probable running lean at higher rpm's. He recommened that I get a adjustable fuel pressure regulator and a in the car fuel gauge. I'm not gonna do anything at this time. My car had been running weak for over a year and a half. I'm just gonna buy another stang,perferable a notch and swap mytrans,driveshaft,rearend,lower control arms. My car looks like crap and still needs front lower control arm bushings and softer struts and shocks, the ride is extremely harsh and has no weight transfer. The bumpers are yellow gray and the blue paint looks very faded in the shade. Sorry to rumble on about my car, but I hate my car most of the time. I had to pay $285 in diagnostic work over the past 3 months and nothing was fixed. I'm tired of spending money on my car. Thanks for the help anyhow. __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-13-2002, 11:17 PM	#14
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	I was in a bad mood earlier because I had to pay my mechanic $285 for the 3 times I took my car to him to figure out this problem, which is still a mystery. He said the car is possible going lean at highe rpm's. I don't know how this can be only when the car is warmed up. He tested the fuel pressure and did a battery to computer aid tests. My plugs are slightly black meaning it's running rich more than lean. Can a car run rich at low rpm's and run lean at high rpm's? I have a new mass air meter that I had on the car for a week back about 4 months ago and it made the car run very rich,popping exhaust,surging at idle. It says on it was calibrated correctly for my injectors. The car ran great for a week after that when I put my stock mass air back on. Could the mass air still be the culprit? __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-19-2002, 07:02 PM	#15
crazy5.0 Registered Member Join Date: Nov 2001 Location: Mission Viejo,Ca Posts: 37	Well my car was only running better when cold, but now it's the opposite sometimes. The other day it ran totally gutless when cold and when it heated up it started to run much better at times. The car is running rich all the time. I had someone stand behind the car and I gave it about 1/3 throttle and a little smoke came out. Past 3000rpm it feels like the car is over revving. Last night it ran like usual, gutless. I can think of 4 things that could be causing this . 1. Bad computer 2. Bad injector,injectors 3. Bad fuel pressure regulator 4. Worn out engine, time for shortblock __________________ 89gt,3.27's,Auburn,tremec 3550,Steeda tri-ax,aluminum driveshaft,Asp underdrives,Flowmast er 3 chamber,March ram air,130 amp alternator,Koni yellow struts,Kyb shocks,Pirelli p-6000's,MM's lower control arms and full length subs

03-20-2002, 04:25 AM	#16
tough90pony Registered Member Join Date: Jan 2002 Location: Indiana Posts: 5	Had the same thing happen to my car last May. I tried everything electrical, O2 sensors,ACT,TFI,cap wires and plugs, different FPR, different fuel injecton harness,fuel pressuretests, etc. Then I finally got a crazy idea and thought it was the engine itself. Wrong. It still did it, so I just carburated it and got rid of all the computer controlled crap. It runs fine now. __________________ 99 Cobra- 4:30 gears,FRPP springs,Steeda tri-ax, NX wet kit.

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