90 gt, running rough past 2500 rpms......

[webslinger67]

Ok, so my 90 GT (30 over with just a cold air intake and aftermarket coil) has been sitting for a while, as i do the body work on it, i would start it ever month and it would run fine....,,,

now, i have it on the road, its hard starting, and , between 2500 and 4000 rpm it stumbles, cuts out, and sometimes taking off from a dead start it backfires...

i have replaced the plugs with autolite platinums, i didnt replace the cap and rotor, they are worn , but i cleaned them up just for the road test, i cleaned the MAS with electronic cleaner and made sure the idle control valve was not stuck.......


i took it back out for another run.... still stumbles, feels hesitant and will not even hit 5000 rpm, let alone redline....

see post http://forums.stangnet.com/showthread.php?t=690314 for someone else having same problem, I am hoping they are related..

so, to see if it was lean or fat running... i took the K&N filter off for a test run, and it got even worse.... so that tells me its starved of fuel, maybe through the secondary circuit?

or, could this be the cap and rotor and i must replace that?

could it be the fuel filter?

has anyone run into this problem before?

could it be the setting of the throttle position sensor?

or even timing?

could it be the EGR?

my IAC doesnt look stuck and I cleaned it , but how do i really know if it is working?

sigh.......... so many questions........ my mustang has never run like this and i am boggled.... i think i am going to be a girl and just cry .........

this has never happend, my 5.0 has always been a perfect running beast and now it barely pulls its own weight.......

hellllllllp!!!!

 

[HISSIN50]

A couple random thoughts:

First things first, I'd pull codes. This is a prime example of a time when there can be a soft code stored (that won't illuminate the CEL).

If you can swap those plat plugs out for cheap copper plugs. The plats have been known to cause a strange idle and cut-out around 4K RPM (platinum does not conduct as well as copper, but it lasts forever, which is it's sales appeal to the masses). I dont think this is your issue but it might keep you from knowing you found the issue when you really do.

Have the MAS wire been cleaned anytime recently? With an oilable air filter element and some work on the stang being done, it's always 2 mins well spent to clean the two MAS wires.

If you can put a FP gauge on the car and watch pressure while the issue occurs. If you had any lean codes, that *could* also indicate a lack of fuel issue. That wouldn't mean it's the pump or even a fuel delivery issue however. But it is a clue.

Timing is set properly?

If you have a spare ignition coil, you might want to install it and see if the issue changes.

Random thoughts on where I'd start.

Good luck.

 

[webslinger67]

I have not pulled codes , well, because i got no check engine light... didnt think i had to pull codes till then...

I know its not the plugs , I had regular plugs in it before and it was doing the same thing, hence, i thought it was the plugs so i changed them.... the idle got better but past 2500 stayed the same...

I cleaned the MAS and the IAC

I dont know of a FP gauge i can hook up anywhere on the rail... will have to look into it...

Timing is set properly....

and i changed out the coild to a new MSD and to the stock one also... same thing.....

the reason i think its the cats is cause i would warm it up every month while i was working on it, by just letting it idle in the drive way till the fan cam on....

going to change out the fuel filter and the distributor cap today, if that dont make it better , i am heading for the x-pipe anyways....going to try the vacuum test also see if it starts to drop while running at 3000 rpms....

 

[webslinger67]

update...

ok, found out one problem... for some reason , my timing was off over 6 degs ..........i had it set at 14 deg btdc, when i checked it i thought it was at 10, but i have one of those stupid dial a light timeing lights, and it was actually at about 6-8 deg btdc.... the dial timing lights suck, and i dont think its correct, so i bumped the timing up and it ran right up to red line pretty good..... not the as i remember it, but , its alot better...

What would make my timing go that far off?


still a little hard starting though, so, going to go buy a standard timing light and check timing again and change the oil, its a little old , even though there is hardly any mileage on it....

anyone have any other ideas on why it could be hard starting?

 

[86foureye]

go and get a new timing light. timing is 10 btdc and that is stock any mods done to the car?

 

[webslinger67]

yes ... mods are...

30 Degs over, Dense Charger CAI, Flowmasters, MSD Coil.

and going to go get a new timing light today.... i hate those dial ones... then i will know the exact timing.

 

[jrichker]

Once you have your timing isuues laid to rest, be sure to dump the codes.

Dump the codes and see what the computer says is wrong…Codes may be present in the computer even if the Check Engine light isn’t on.

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

IF your car is an 86-88 stang, you'll have to use the test lamp or voltmeter method. There is no functional check engine light on the 86-88's except possibly the Cali Mass Air cars.

Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes.

For those who are intimidated by all the wires & connections, see http://www.actron.com/product_detail.php?pid=16153 for what a typical hand scanner looks like. Normal retail price is less than $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/p-7208-equus-digital-ford-code-reader-3145.aspx– It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[webslinger67]

your second link for the scanner at miday auto supply doesnt work... .can you give me the model and make of it... i will do a search for it?

i will dump the codes after tonite when i make sure the timing is right

thank you again, that will help alot..

where is the connection that i jumper to dump the codes, located on the car?

 

[webslinger67]

I just ordered one of those code readers from Amazon.com for 24.99 along with a cheap book, its free shipping...

http://www.amazon.com/gp/product/B000EW0KHW/ref=cm_sp_item/102-2928999-8680165

 

[jrichker]

your second link for the scanner at miday auto supply doesnt work... .can you give me the model and make of it... i will do a search for it?

i will dump the codes after tonite when i make sure the timing is right

thank you again, that will help alot..

where is the connection that i jumper to dump the codes, located on the car?

Try http://www.midwayautosupply.com/pc-7208-90-equus-digital-ford-code-reader-3145.aspx for the code reader


Code reader test socket: Look over behing the driver's side wheel well near the hood hinge.

Closer view:

 

[webslinger67]

ok...i am tired of throwing money at this piece of crap...

if this dont fix it, anyone wanna buy a 90 Mustang Gt , 306, about 30k miles on it, 5speed, Ford Racing HD clutch, aluminum drive shaft, 3.23 gears, adjustable clutch Quadrant and new clutch cable, Short Shifter ( its a 5.0 something or other brand) , flowmasters, and after it gets here, it will have a Pypes Cat X-Pipe.

before it sat, i took on a 2000 SS Camaro and put a good beating to him.... basically i had grip both times we raced... he didnt, but, i didnt tell him that...lmao

Then, i am going to go buy a Camaro.... lmao... oh wait, i have an 85 Iroc 5-speed.

Here is the new problem...... it seems as though the IAC has gone out. I wanna make sure, when you unplug it while its running, its almost suppose to die right, then plut it back it it will bring the rpms back up?

because when i unplug it, it only drops about 50-100 rpms in difference..

if an IAC goes out, and is leaking buy, will that give a lean mixture to the motor?

oh and THANK YOU Jrichker, you and your posts have been a great help along with everyone else, this is a great forum, glad i am here....

now i just hope i can fix this thing... i love this car , we have been through hell together..

 

[HISSIN50]

Here is the new problem...... it seems as though the IAC has gone out. I wanna make sure, when you unplug it while its running, its almost suppose to die right, then plut it back it it will bring the rpms back up?

because when i unplug it, it only drops about 50-100 rpms in difference..

if an IAC goes out, and is leaking buy, will that give a lean mixture to the motor?

oh and THANK YOU Jrichker, you and your posts have been a great help along with everyone else, this is a great forum, glad i am here....

The IAC's contribution depends upon how the idle is set, along with operating temps, the current EEC strategy, accessory load, etc etc. The computer has a commanded idle that it wants to stay at. Some folks manually set the idle higher than stock, which shortens the IAC's DC during hot motor, no load situations.
Of course, Jrichker's Idle Surge Sticky has info about theory, symptoms, solutions and how to clean and maintain items like the IAC.

Good luck.

 

[webslinger67]

update...

I got my scanner today and did a no run, key on scan and i got a 111 system check good, and a C code 172 and 176, that i cannot clear... even with the paper clip trick above.... any other way to clear these codes.... for the paper clip trick, must the key be on?

i tried with key on and key off.... still shows up, and i didnt run the truck yet...

that shows a lean condition on both sensors.....


help again!!!!

 

[HISSIN50]

I thought we were workin on a '90. You're getting 94+ 3 digit codes.

Disconnect the battery and turn on the headlights to clear the other codes.

Good luck.

 

[webslinger67]

ackkkkkkkkkk

lol.... i am very sorry.... i wont tell you what i was testing... but.... it was a 94... lmao

 

[webslinger67]

ok away from my Ranger, back to my Stang

ok, so i pulled the codes today and i got the usual 10, 11 and one i almost expected... a 95, which is Fuel Pump Secondary Circuit Failure....

ok tell me i dont have to replace my fuel pump?

has anyone else ran into this... and could this be a a code that the computer goes into failure mode as long as the code is stored there?

and should i clear it and try another run with it?

 

[HISSIN50]

Code 95 means the FP burped at some point when the car was on. This is sometimes a ghost code (it can be generated from something as simple as stalling). But if you're having issues, it's something to check into. The code indicates that there was a power-to-the-pump burp, not necessarily the pump itself.

Good luck.

 

[webslinger67]

i think the fuel pump is bad

there is only 20lbs of pressure on the rack.... could that be a bad relay though?

there is only one schrader valve on the rack right?

what else could cause the pressure to be low?

that is even with the vacum line pulled on the regulator......sigh

 

[HISSIN50]

In OEM form there is but one Schrader valve on a stock fuel rail. You should see 30 PSIG or more at all times with the vac line connected, and nearly 40 PSIG with the vac line disconnected from the FPR.

Other causes of low pressure: things like a bad FPR (not real likely, but you can use fuel line crimpers to *carefully* crimp the return line during the prime-out. If pressure all of a sudden goes up, you're onto something.
Leaky injectors can cause low pressure but that's unlikely here.

A bad FP circuit could certainly keep you from seeing proper fuel pressure but again, it tends to be an all-or-nothing type of thing with fuel pump wiring in a given time.

MHO.
Good luck.

 

[webslinger67]

all or nothing you mean there is pressure an then there is not right?

but never a low pressure from any other cause other then a bad FPR or pump?