Need help badly!!

95GTS · 02-02-2001, 12:28 PM

Ahhh!!!! This is driving me and my buddies nuts! The car is an 89 GT, same car I've posted about on here such as for the adjustable fpr, and we can not get it to run right. The problem is we can't get the fuel pressure to adjust and it will not idle correctly.

The problem started out to be that the car would not idle correctly. It's wants to surge and then die. It starts out at about 1200 rpm then drops and surges a few seconds before it dies. Also, at about 1800-2000 rpms, it would buck like it wasn't getting fuel (consistently in every gear) as well as some through out the rest of the rpms. You could tell it wasn't running right when driving down the highway. All plugs, wires, distributor cap, rotor, and fuel filter have been replaced. TPS has been checked and set correctly. Timing is set at about 13-14 deg.

So we hook up a fuel pressure gauge. Hmmm...25 psi. Ok, we replace the fuel pump with a new 190 lph. Now the fuel pressure jumps to 55 psi and won't come down (car already has an adj. fpr). So we figure, bad regulator. BTW, car still idles the same as mentioned before. We put on a new Paxton adj. fpr last night. Still idles the same and the fuel pressure pegs (gauge goes to about 65 psi) and then drops to about 55 psi whenever rpms go down and pegs when rpms come up. Same as it has been doing. BTW, with the car shut off the gauge reads about 25-26 psi. Before the new fuel pump it read 0 psi with the car off. With the vaccum off or on it won't adjust the fuel pressure. So we've replaced the regulator when it wasn't even bad. The only positive thing about that was the Paxton matches his car and the other blue anodized looking parts, hehe.

Now what to do??? The TPS was set at the correct voltage. I believe it was around 0.98 but can't remember exactly cause another buddy did it. Could the IAC be part of the problem?? We have no clue where to go now except off a cliff with the car. How exactly do we check the MAF to make positively sure that it is calibrated for the 24 lb. injectors? We are pretty sure that it is but not 100% sure. He's only had this car a few months and the guy that he bought it from didn't say anything about it and we can't get ahold of him.

To refreshen, for those that don't know, the mods for this sucker here ya go:
GT40P heads, Cobra upper/lower, E303 cam, 1.7 rr's, 24 lb. injectors and MAF, 70mm TB, K&N w/cervini's ram air, Paxton adj. fpr, 190 lph fuel pump., 4.10s, 5-speed, BBK lca's.

Oh I just thought about this. This car used to be an automatic. Could that be the problem? Like with the computer? We've run a computer scan but nothing comes up. Just a thought.

We're really confused about the fuel pressure. We need help bad. What do you think is wrong?

------------------
1996 Mustang GTS

302 LX Eric · 02-02-2001, 12:42 PM

You probably already know this, but I will say it anyways. The fuel pressure is the first thing you need to get taken care of. The adjustable FPR should be able to easily dial down the fuel pressure. I would recommend putting the FP at about 40 with the vacuum disconnected. If you can't get the FP down to this level, then (I hate to say it but...) maybe the FPR is defective?

As for the MAF, you didn't say what type it is (or, if you did, I missed it). But, regardless it really needs to be properly calibrated or else the computer will be getting mixed signals and will most likey end up running rich (thinking you have 19 #ers in there). If you, or another Mustang buddy has a properly calibrated MAF, then try switching it out to see if that corrects the problem.

You may also want to check the injector wiring harness to ensure that the proper connector is on the right injector #. I accidently switched the #1 and #2 injector connector and it idled like you are describing.

Last idea would be to hook up a code scanner and see what codes you get. Maybe a bad O2 sensor?

That's all I have for now. I hope this helps some or that you find out what the problem is.

Good luck and keep us posted.
E

------------------
1991 5.0 LX Coupe -37,800 miles

13.17 @ 106.14 mph w/ 2.138 60'

Pro-Charger D-1SC on the way!!!

LX XLR8R · 02-02-2001, 12:56 PM

if you got sticking high fuel pressure it could be sticking injectors(closed) or a kink in the fuel return line...test the injectors by putting a + and a - lead on the top to posts and listen for it to click open when the power is to it then it sould click closed when you take it off

auto computer can be used in 5spd with no problems..
as for the mass air being calerbrated you have to put a volt meter on the signal wire comming from the mass air to the computer and it should read about a .79166 if i rember corectly...if you get a product from pro-m you can adjust this # to fine tune your air/fuel mixture and you can use it to buy new injectors without replaceing your mass airmeter or getting it recalibrated..

i would suugest also fixing the fp problem first then working from there..also if you been running at that high fp then your plugs might be fouled so check them again also

------------------
1987 black notch(ex 4 banger)
DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..

95GTS · 02-02-2001, 12:58 PM

Before we installed the new fuel pump the fpr that the previous owner had on the car would adjust the pressure just fine but then after you drove the car a little bit the pressure would drop back down to 25 psi as I had in the above post. Then after the new fuel pump was installed the fuel pressure skyrocketed and couldn't be brought back down. Also makes it hard to adjust the pressure with it idling irradically. Whenever the rpms would come back down the pressure registered 55 and would not go any lower. So we replaced the adjustable fpr with another one and still the same results. Vaccum disconnected.

Like I said in the previous post we are not sure of the size of the MAF and if it is for sure calibrated for the 24 lbs injs. The car does have 24 lb injectos. We are assuming that it is but can't get ahold of the previous owner to find out. Thanks for the idea of the putting in of a buddies MAF to check. (Johnny, we need to do that

) We'll have to try that.

We'll check the harness, too. O2s are good. One is brand new. Nothing shows on a scan.

------------------
1996 Mustang GTS

302 LX Eric · 02-02-2001, 02:18 PM

LX LXR8R has a good point, an injector maybe be sticking closed, thus resulting in high than normal pressure.

And you might as well double check the plug for proper gap (.054") and to see if they are relatively clean.

Good luck,
E

Chevyguy · 02-02-2001, 04:26 PM

Hmm I 'll give it a stab

Since you are sure those are 24# injectors

If the fuel pressure is not set right, this will cause them to flow way too much fuel per duty cycle. The computer has a minimum cycle time for idle, and can't turn down the fuel flow enough to stabilize the idle. I also wonder if those injectors are just too large for that motor combo, kinda like running a 850 DP, larger aint always better. Maybe it would run better with the 19# injectors???

------------------
Frank W
90 5.0 LX coupe Stone stock soon to be daily driver
74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it
www.chevellepages.com/folingo

70stang · 02-02-2001, 04:57 PM

I don't know anything about newer stangs, but you might try running the car with the gas cap off and a funnel inserted. Some old cars that had vented tanks would run strange if the vents were plugged. I don't know if this will help, but its worth a try.

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02-02-2001, 12:28 PM	#1
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	Need help badly!! Ahhh!!!! This is driving me and my buddies nuts! The car is an 89 GT, same car I've posted about on here such as for the adjustable fpr, and we can not get it to run right. The problem is we can't get the fuel pressure to adjust and it will not idle correctly. The problem started out to be that the car would not idle correctly. It's wants to surge and then die. It starts out at about 1200 rpm then drops and surges a few seconds before it dies. Also, at about 1800-2000 rpms, it would buck like it wasn't getting fuel (consistently in every gear) as well as some through out the rest of the rpms. You could tell it wasn't running right when driving down the highway. All plugs, wires, distributor cap, rotor, and fuel filter have been replaced. TPS has been checked and set correctly. Timing is set at about 13-14 deg. So we hook up a fuel pressure gauge. Hmmm...25 psi. Ok, we replace the fuel pump with a new 190 lph. Now the fuel pressure jumps to 55 psi and won't come down (car already has an adj. fpr). So we figure, bad regulator. BTW, car still idles the same as mentioned before. We put on a new Paxton adj. fpr last night. Still idles the same and the fuel pressure pegs (gauge goes to about 65 psi) and then drops to about 55 psi whenever rpms go down and pegs when rpms come up. Same as it has been doing. BTW, with the car shut off the gauge reads about 25-26 psi. Before the new fuel pump it read 0 psi with the car off. With the vaccum off or on it won't adjust the fuel pressure. So we've replaced the regulator when it wasn't even bad. The only positive thing about that was the Paxton matches his car and the other blue anodized looking parts, hehe. Now what to do??? The TPS was set at the correct voltage. I believe it was around 0.98 but can't remember exactly cause another buddy did it. Could the IAC be part of the problem?? We have no clue where to go now except off a cliff with the car. How exactly do we check the MAF to make positively sure that it is calibrated for the 24 lb. injectors? We are pretty sure that it is but not 100% sure. He's only had this car a few months and the guy that he bought it from didn't say anything about it and we can't get ahold of him. To refreshen, for those that don't know, the mods for this sucker here ya go: GT40P heads, Cobra upper/lower, E303 cam, 1.7 rr's, 24 lb. injectors and MAF, 70mm TB, K&N w/cervini's ram air, Paxton adj. fpr, 190 lph fuel pump., 4.10s, 5-speed, BBK lca's. Oh I just thought about this. This car used to be an automatic. Could that be the problem? Like with the computer? We've run a computer scan but nothing comes up. Just a thought. We're really confused about the fuel pressure. We need help bad. What do you think is wrong? ------------------ 1996 Mustang GTS

02-02-2001, 12:42 PM	#2
302 LX Eric or '331 LX Eric' Join Date: Jan 1999 Location: Columbus, Ohio Posts: 2,142	You probably already know this, but I will say it anyways. The fuel pressure is the first thing you need to get taken care of. The adjustable FPR should be able to easily dial down the fuel pressure. I would recommend putting the FP at about 40 with the vacuum disconnected. If you can't get the FP down to this level, then (I hate to say it but...) maybe the FPR is defective? As for the MAF, you didn't say what type it is (or, if you did, I missed it). But, regardless it really needs to be properly calibrated or else the computer will be getting mixed signals and will most likey end up running rich (thinking you have 19 #ers in there). If you, or another Mustang buddy has a properly calibrated MAF, then try switching it out to see if that corrects the problem. You may also want to check the injector wiring harness to ensure that the proper connector is on the right injector #. I accidently switched the #1 and #2 injector connector and it idled like you are describing. Last idea would be to hook up a code scanner and see what codes you get. Maybe a bad O2 sensor? That's all I have for now. I hope this helps some or that you find out what the problem is. Good luck and keep us posted. E ------------------ 1991 5.0 LX Coupe -37,800 miles 13.17 @ 106.14 mph w/ 2.138 60' Pro-Charger D-1SC on the way!!!

02-02-2001, 12:56 PM	#3
LX XLR8R Dirk Diggler Join Date: Feb 1999 Location: SLOATSBURG, NY Posts: 1,931	if you got sticking high fuel pressure it could be sticking injectors(closed) or a kink in the fuel return line...test the injectors by putting a + and a - lead on the top to posts and listen for it to click open when the power is to it then it sould click closed when you take it off auto computer can be used in 5spd with no problems.. as for the mass air being calerbrated you have to put a volt meter on the signal wire comming from the mass air to the computer and it should read about a .79166 if i rember corectly...if you get a product from pro-m you can adjust this # to fine tune your air/fuel mixture and you can use it to buy new injectors without replaceing your mass airmeter or getting it recalibrated.. i would suugest also fixing the fp problem first then working from there..also if you been running at that high fp then your plugs might be fouled so check them again also ------------------ 1987 black notch(ex 4 banger) DSS 306 w/ main support...Elderbrock 6028 heads..gt-40 intake..24# injectors...70 mm tb..77 pro-m...accel 300+..mac full legnth..tremec w/ pro5oh...full MAC exhaust,off road h-pipe,long tubes, catback...ron davis radiator..subframes, control arms...CFDF II..o yea holley FPR sucks..dont buy one..

02-02-2001, 12:58 PM	#4
95GTS Git jiggy Join Date: Oct 1999 Location: MO USA Posts: 865	Before we installed the new fuel pump the fpr that the previous owner had on the car would adjust the pressure just fine but then after you drove the car a little bit the pressure would drop back down to 25 psi as I had in the above post. Then after the new fuel pump was installed the fuel pressure skyrocketed and couldn't be brought back down. Also makes it hard to adjust the pressure with it idling irradically. Whenever the rpms would come back down the pressure registered 55 and would not go any lower. So we replaced the adjustable fpr with another one and still the same results. Vaccum disconnected. Like I said in the previous post we are not sure of the size of the MAF and if it is for sure calibrated for the 24 lbs injs. The car does have 24 lb injectos. We are assuming that it is but can't get ahold of the previous owner to find out. Thanks for the idea of the putting in of a buddies MAF to check. (Johnny, we need to do that ) We'll have to try that. We'll check the harness, too. O2s are good. One is brand new. Nothing shows on a scan. ------------------ 1996 Mustang GTS

02-02-2001, 02:18 PM	#5
302 LX Eric or '331 LX Eric' Join Date: Jan 1999 Location: Columbus, Ohio Posts: 2,142	LX LXR8R has a good point, an injector maybe be sticking closed, thus resulting in high than normal pressure. And you might as well double check the plug for proper gap (.054") and to see if they are relatively clean. Good luck, E

02-02-2001, 04:26 PM	#6
Chevyguy Backyard Mechanic/Chemist Join Date: Feb 2001 Location: Acton MA USA Posts: 435	Hmm I 'll give it a stab Since you are sure those are 24# injectors If the fuel pressure is not set right, this will cause them to flow way too much fuel per duty cycle. The computer has a minimum cycle time for idle, and can't turn down the fuel flow enough to stabilize the idle. I also wonder if those injectors are just too large for that motor combo, kinda like running a 850 DP, larger aint always better. Maybe it would run better with the 19# injectors??? ------------------ Frank W 90 5.0 LX coupe Stone stock soon to be daily driver 74 Chevy Laguna Type S-3 305 apart in garage, getting a 454 to put next to it www.chevellepages.com/folingo

02-02-2001, 04:57 PM	#7
70stang Registered Member Join Date: Dec 2000 Location: Twelve Mile, IN USA 46988 Posts: 17	I don't know anything about newer stangs, but you might try running the car with the gas cap off and a funnel inserted. Some old cars that had vented tanks would run strange if the vents were plugged. I don't know if this will help, but its worth a try.