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12/28/2013 12:49 AM  #1


Hesitation under acceleration on 1988 mustang 5.0 LX

Hello Hello

We are having issues with our 1988 Ford mustang 5.0 LX. 

Under acceleration it has some hesitation and it feels like a bit lack on the power too.
The idle is also a bit funny it rises in rpm and  falls in rpm.

Have any of you experinced a similar problem with your cars?.

I have changed the spark plugs and the fuel filter on the car.

The car have not been used for several years.

So if you have any good leads on this subject and some hint where to look. Some help would be much appriciated.

Best regards Olling

 

12/28/2013 7:17 AM  #2


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

This sounds like a fuel problem to me
If the car sat for awhile, I'd suspect bad gas and possibly clogged injectors (If EFI) or clogged carb?  You might try something simple like injector cleaner.  If not you may have to clean old gas out of tank put fresh fuel in and possible clean carb or replace injectors depending on what the car has!

 

12/28/2013 8:03 AM  #3


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

I agree with Terry, but suggest to first dropping the tank washing it out then putting in a new pump and screen (rock auto have good prices on these) and a new inline filter, beleive me it will save a lot of headaches latter on, just confirm you get the right pump they do have different output pressures.

Last edited by bulletbirdman (12/28/2013 8:04 AM)


I made enough money to buy Miami, but pissed it away so fast
 

12/28/2013 8:35 AM  #4


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Is the car stock or has it been modded?  
I'd like to know if it is still a stock EFI system.




 

 

12/28/2013 9:57 AM  #5


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

EGR, PCV, and vac. line leaks are some things to consider/suspect on a 25 year old FI system and all have an impact on idle and driveability as well.

 

12/28/2013 10:26 AM  #6


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Hey

The car has the stock fuel injection system it was born with.

Olling

     Thread Starter
 

12/28/2013 10:35 AM  #7


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Go down to advance, auto zone etc and get a fuel pressure test gauge that will fit on your fuel rail its probably surging due to trash clogging Pump/pickup screen, check it against the manual for the car if you don't have a manual now is the time to buy one.


I made enough money to buy Miami, but pissed it away so fast
 

12/28/2013 10:41 AM  #8


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

bulletbirdman wrote:

Go down to advance, auto zone etc and get a fuel pressure test gauge that will fit on your fuel rail its probably surging due to trash clogging Pump/pickup screen, check it against the manual for the car if you don't have a manual now is the time to buy one.

Oh by the way check your exhaust after a test run of a couple miles if you are leaning out it will cause excessive heating of the cat. converters I mean glowing cherry red.


I made enough money to buy Miami, but pissed it away so fast
 

12/28/2013 10:53 AM  #9


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Simple and cheap stuff first...  Reach under the upper intake where the vacuum lines connect to the bottom of it.  Be sure they are all attached and any rubber caps are not split from age.

But I agree with the others it does sound fuel related.  Fresh tank of gas is main thing... then fuel pressure.


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

12/28/2013 1:57 PM  #10


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Olling wrote:

Under acceleration it has some hesitation and it feels like a bit lack on the power too.
The idle is also a bit funny it rises in rpm and  falls in rpm.

Do you have an EECIV code reader available?   I'd start by looking for some sort of EFI issue, and retrieving codes is a good place to start.  Check this listing:

http://www.ebay.com/itm/CP9015-SUNPRO-FORD-CODE-SCANNER-FOR-EEC-IV-MCU-SYSTEMS-MADE-IN-USA-u-/201006054168?pt=Motors_Automotive_Tools&hash=item2ecce4fb18&vxp=mtr

This guy has 12 of them brand new.  Can't beat that price either.  I have the exact same reader.

EDIT: He wants $16 to ship though.  I'd check other listings for better price/shipping total.

EDIT 2: Here is one shipped free:

http://www.ebay.com/itm/Equus-3007-Ford-Lincoln-Mercury-Computer-Code-Reader-191-1995-Innova-EEC-IV-MCU-/380803516727?pt=Motors_Automotive_Tools&hash=item58a9a88937&vxp=mtr

John

Last edited by John (12/28/2013 2:02 PM)

 

12/28/2013 2:01 PM  #11


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

most of the parts store will pull the codes especially if they think they can sell you the parts to fix!  and rightfully you should buy from them if they pull the codes.
 

 

12/28/2013 2:05 PM  #12


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Yeah they'll pull them but thet won't reset them. 


I made enough money to buy Miami, but pissed it away so fast
 

12/28/2013 8:11 PM  #13


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

My first guess would be the idle speed control.  When they go out you get a wavy idle and it can even cause a poor throttle response at part throttle.  Replacing mine did wonders.

 

12/28/2013 9:26 PM  #14


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Oiling,

As MS stated, start with simple and cheap first.

-pull the top off your air cleaner box and make sure, Ben and Willard haven't established a same sex, co-habitation rodent condo in there.
Those two dudes have a sweet tooth and fancy black licorice but, they tend to confuse it with rubber vaccum lines....check them really well.  The line MS pointed out is notorious to dry rot.....and rodent teeth sharpening.

-next, purchase a can of CRC MAF sensor cleaner from the parts store ($6.99) then, access your MAF and spray it/clean it really well.  It'll dry quickly so you should have it back together to test in no time. Do not use any other kind of clearner for this procedure and don't touch the MAF wire.  There should also be a screen in the MAF, make sure there' s no foreign matter on the screen (ie: WIllard turds) if there is, spray it clean.

On my 90 GT, I had an idle surge issue plus a throttle response hesitation. When I finally cleaned the MAF the issue disappeared.  This "could" be your issues as well.  If not, we'll go to the next step

If you decide to follow this suggestion, post your results.

I would also dump a bottle of Techtron Fuel Injection cleaner or a can of Sea Foam in the tank with that fresh corn blended gasoline.

Hope this helps..........

Last edited by josh-kebob (12/28/2013 9:27 PM)

 

12/28/2013 10:47 PM  #15


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

No MAF on an 88.  They were speed density...


Money you enjoy wasting is NOT wasted money... unless your wife finds out.
 

12/28/2013 10:59 PM  #16


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Olling wrote:

Hello Hello

We are having issues with our 1988 Ford mustang 5.0 LX. 

Under acceleration it has some hesitation and it feels like a bit lack on the power too.
The idle is also a bit funny it rises in rpm and  falls in rpm.

Have any of you experinced a similar problem with your cars?.

I have changed the spark plugs and the fuel filter on the car.

The car have not been used for several years.

So if you have any good leads on this subject and some hint where to look. Some help would be much appriciated.

Best regards Olling

I would start with the vacuum lines.  There's alot of them.  Only takes one to be cracked to cause a lopey idle and poor acceleration.  As they age they get hard and brittle, and lose thier flexibility and eventually break.  There's a 5 port vacuum tee bolted to the firewall.  One is the source vacuum coming from the intake, and the rest supply vacuum to the AC, the emissions solenoids, the egr, the brake booster, and one is extra and blocked off.  Under the intake, there is another vacuum tree, one branch of the tree is fuel pressure regulator, one branch to the vacuum tee on firewall, and another separate vacuum line to the pcv valve. 


 


GET HER DONE BULLETBOB!!! ..
 

12/29/2013 11:56 AM  #17


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

MS, good catch.....my bad on the MAF.................getting old stinks.......

 

12/30/2013 6:54 PM  #18


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

josh-kebob wrote:

MS, good catch.....my bad on the MAF.................getting old stinks.......

anyone catch your AC DC tag line already?  TNT


GET HER DONE BULLETBOB!!! ..
 

12/30/2013 7:37 PM  #19


Re: Hesitation under acceleration on 1988 mustang 5.0 LX

Just you Mark......when you drive about 500 miles from OKC back to Houston, you have plenty of opportunity to listen to tunes......some get stuck in your head too!!!!!!!

 

Board footera


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