No power till i hit about 2100 RPM

Haus · Apr 25, 2009

i dont know whats going on but i have like no Power like i used to on my 92 5.0. power doesnt kick in till i hit about 2100 RPM. and anything under that the car feels like its running out of gas. kind of like shakes at time.

i changed out the fuel filter about 3 weeks ago, TPS is fine, Maf has the right voltage, changed spark plugs checked the codes and all i get is 94 on the KOER test.

my FPR doesnt have the line going into it cause i got 41/91 codes. so taking off the line helped my 41/91 code disappear cause it raised the FP from what it was when the line was connected. i have the line plugged but do i need to have the part on the FPR capped off??

please help

95Vert383AOD · Apr 26, 2009

Don't remove the vacuum line.....the vacuum helps raise fuel pressure based on vacuum/ how much the throttle is open. Get a fuel pressure Gauge on there! I usually set mine to about 40-43 psi with the vacuum line off which is around 39 with the vacuum on.

Oh yeah...if you're stock then its not adjustable.....so make sure you put the vacuum line on when you test it with a gauge. It should read around 39...when you rev the motor it should go up to around 44.

Chris

Haus · Apr 26, 2009

its stock. the pressure with the line on was 30ish PSI and had the lean code 41/91

taking the line off increase it to 41 PSI and that took away my lean codes away

the pressure when turning off the car drops instantly even when i had the line connected.

obviously something is wrong if the FP drops instantly.

95Vert383AOD · Apr 26, 2009

The FP is supposed to drop when the line is connected. But its only supposed to drop to about 38 or 39.

You're getting a lean code based on what your O2 sensors are picking up. The FPR isn't an electronic system its mechanical vacuum regulated.

I would guess you had a stock regulator thats going. Or Possibly a very improper Spark plug gap.

When you say 30ish....do you mean like right around 30....Because with the line disconnected you should be at about 39psi. If your're getting 30 i would check your Fuel pressure regulator.

Like i said....properly running it should read about 39 with the vacuum line hooked up.....revving the motor should increase it to 46PSI ....But seeing how you have no vacuum connected...when you step on the gas your car isnt changing fuel pressure as intake manifold pressure changes. (Vacuum line) If you're at 30 You need a new regulator.....i recommend a Kirban or something like that thats adjustable.

I have a $150 Aeromotive regulator thats adjustable with a gauge on a fuel system built to support 1000hp.....I use the Vacuum line!!! You should too!!!

Haus · Apr 26, 2009

this was doing it long before i changed out the plugs. i gapped them right. just regular copper Autolite 25.

so yes the FPR is not connected to vacuum so i guess its not working anyway at the moment. but thats the only thing i could do at the moment to take away the lean codes.

when i say 30ish it was around 31 psi with the vacuum CONNECTED. and around 40 with the line DISCONNECTED. doesnt matter if the line is connected or not. the FP drops to 0 with in 3-5 seconds of turning off the car.

so ill go ahead and pick up a new adjustable Fuel regualtor.

and with the problem with the no power till i hit 2100 RPM. when im in say 4th gear and im at low RPMs the car feels like it stutters like its starving for fuel but only at lower RPMs

and the car is very sluggish until i hit about 2100 RPM and i guess its like turning on NOS. it just picks back up like a bat out of hell at that certain RPM

95Vert383AOD · Apr 26, 2009

Yeah sounds like a regulator....get an adjustable, set it to 39 with the vacuum connected and go from there. I believe Stock should be about 39.

31 is a bit low thats about 1/4th your pressure gone. and the 41 PSI is about 2 PSI higher than what your car needs at idle. So when you go to WOT at 41 psi its not keeping up.

Haus · Apr 28, 2009

got the FPR and no change at all. its happening at lower speeds. like it's stumbling. like at 2 and 4th gear. if i drive it in 3rd gear that car is for the most part fine. but stop and go traffic you can really tell. it bucks at times.

the way the car is in those gears it feels like my dads car did when he had a bad VSS.

i know i dont have a working Speedometer. it bounces around when i drive but i had that lack of speedometer problem for a while.

let me tell you when i first started noticing the car do this.

when my Starter went is when this problem happened. after i got the starter replaced and my shocks and struts put in my problems occured right after.

my luck its probably my tranny or something in that area.

FastDriver · Apr 28, 2009

fuel pressure should always be set, assuming you have an adjustable regulator, with the vacuum line to the FPR disconnected.

Chris

Haus · Apr 29, 2009

yep. Fuel pressure is fine now. Nothing changed when i put in the Adj. FPR and got the correct FP.

I dont know what else to check.

2 things really bothering is me is lack of Bottom end power and slight jerking feeling in the car at lower speeds and all this happened when i had the new starter put in and the Shocks and struts.

FastDriver · Apr 29, 2009

This doesn't have anything to do with those parts. The starter doesn't do anything when the engine is already running. Shocks and struts can't make the car sluggish.

This is some kind of an issue with the tune or with hardware that controls the tune. You might check your TPS and your MAF to ensure the correct voltage is being sent. It sounds like you're running too lean at low speeds.

The fuel pump and injectors must be alright if it's making power up top without issue. The situation is really strange because it sounds like a fuel issue, but usually these issues would occur at higher rpm instead of lower RPM. Your EEC has not been modified or tuned has it?

I'd look at the voltages mentioned and check timing, too.

Good luck,

Chris

matts90lxhatch · Apr 29, 2009

I would definitely check your maf. I have had several Pro-M mass air meters that went bad suddenly for no reason at all years ago. I have also had a tiny piece of trash on a stock maf sensor and the car would buck like crazy below 2,400rpms.

Take your maf off and look for any trash. Clean it by lightly blowing compressed air through it. I used to take some rubbing alcohol on a q-tip and lightly wipe off the actual sensor. It fixed the stocker that I had problems with. Also if you have a buddy that has a maf that's calibrated for what injector size your running just swap them out and take the car for a test drive.

I also had an intake gasket once that caused similar problems to what your experiencing. The car would drive fine at 2,000 rpms and up but anything lower than that and it was bucking and jerking and felt completely gutless.

FastDriver · Apr 29, 2009

You know, it evaded me earlier, but a vacuum leak might cause this problem. It would cause you to run way to lean down low because you're getting un-metered air into the system. However, under load where your motor won't pull hardly any vacuum, you won't notice much of a difference. Check all your hoses for a vacuum leak.

Chris

Haus · May 4, 2009

ill check all the lines again. would the line that goes under the driver side dash that makes the heat/AC come out of the vents cause a vacuum leak if it wasnt connected. i only get the air coming out of the defroster and floor. the yellow hose isnt connected. but its been like that since i owned the car back in 2004. just curious if it would cause a vacuum leak

i forgot right before i got the starter replaced i replaced the Coil. so right around that time my problems started. so ill try to put back on the stock coil and see if anything changes.

and i dont know if this has anything to do with fuel pressure or can take away from it but my filler neck grommet is messed up and leaks a bit and fuel vapor goes through it.

95Vert383AOD · May 4, 2009

Change the PCV valve lately?

1990lx5oh · May 4, 2009

check your base timing. my dizzy slipped and was way advanced and it did somewhat of the same thing, but i also had a BAD surging idle as well.....

Haus · May 7, 2009

I think the lack of power is fixed. i adjusted the TV cable and put back on my stock Coil and it solved the problem so far. so we shall see.

but the thing with slow speeds is still there. i could be in 4th gear going slow(sometimes the RPM is at 900 in 4th when it happens) and i get that feeling of starving for fuel. like its gonna run out of gas even tho i have 1/2 a tank in there.

i noticed the fuel pump doesnt prime as loud any more. so i dont know

Haus · May 7, 2009

1990lx5oh said:
check your base timing. my dizzy slipped and was way advanced and it did somewhat of the same thing, but i also had a BAD surging idle as well.....

i dont have a surging idle problem. in gear my idle is at like 600 rpm. maybe 650. and it stays steady

Haus · Jun 22, 2009

In case your all wondering it ended up being in the throttle. when i was stepping on the gas pedal i was pushing it at the very bottom and doing that made little throttle response. so when i put my foot on the whole pedal and mash down on it it doesnt do that. so it was driver error. haha

but still have that low rpm/slow speed in 4th gear issue. but keeping it in 3rd when i driving around alot of traffic solves it. so it makes me think its in the tranny. cause sometime it wont go in to 4th at all unless i put it to Drive then put it back to OD. or just take my foot off the gas when in 3rd makes it go into 4th.

95Vert383AOD · Jun 23, 2009

4th gear on an AOD Trans isn't an accelerating gear. O/D is to save gas. So when you ease off the gas pedal in 3rd it goes to 4th (O/D).

If you're going slow enough (like under 30-35) cruising and punch the gas pedal the car will down shift from 4th (O/D) to 3rd.

O/D is a weak gear and is only there to save gas. Older cars with C4/C6 trannies only had 3 gears (no OD) Some GM powerglides only had 2 gears.

Haus · Jun 23, 2009

it just wont go into 4th most of the time. from a stop i step on the gas, it goes to 2nd, then 3rd then it wont go into 4th gear sometimes unless i put the shifter into D and then put it to OD. or when my car is in OD and stuck on third i have to step on the gas and then take my foot abruptly off of the pedal and it goes to 4th.

No power till i hit about 2100 RPM

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