Engine stumbling under hard acceleraion

[funkalicious]

Thanks for any help with my situation. Here is an example scenario of the problem I am having (car is a 93 GT, bone stock except for removal of air silencer and addition of K&N air filter, approximately 90,000 miles, 5spd transmission):
Scenario: Cruising on the freeway at 70mph, 2000rpm, 5th gear. Drop into fourth and punch accelerator to floor and car will immediately begin to stumble and struggle to accelerate or will pull hard to approximately 4200rpm and then stumble really bad. If I slowly ease up on the accelerator when the engine begins to stumble in either case, it will eventually begin to pull strongly again up to the point that the built in fuel cut-off kicks in but only if I press down on the gas pedal slowly. Car will pull strong and steady to approximately 6,000rpm in every gear as long as I begin the acceleration by pressing down on the gas pedal very slowly. Flooring it at any point in the rpm range of any gear causes minor to major stumbling and bogging down. Any solutions or suggestions? Is this a normal problem? Am I expecting too much of a stock setup?

 

[Jack's95gt]

Possible tune it and timing needs to be set for ignition. Possible clogged injectors or fuel filter for fuel. Possible clogged cats for exhaust. There are many possibilities for what your describing.

 

[vristang]

Pull your codes from the ecu.
JRichker has details on how to do this...

From what you are saying, I would guess the TPS is FUBAR, but that is just a guess... it could be a lot of things.

Check for codes, and we'll go from there...

jason

 

[Drinknbuddy]

how long have you had the car?? when was the last time you did a tune up, if ever?? If not recent... id start there... plugs, wires, fuel filter etc. etc.

if that dosent work thats fine.. its something you needed to do anyways... and helped narrow down the possibiltys
good luck

 

[funkalicious]

Thanks for the responses! Leaving to go out of town this weekend, but will start by pulling the codes early next week and then post what I find. It has been at least two years since the last tuneup (bad divorce, broke as Hell, just getting back on my feet) and I have owned the car for about three years. I will purchase what I need and do the tuneup myself next weekend.

 

[BK_CAULEY]

check for vacum leaks also

 

[rpm182000]

it wouldnt hurt to give the ol mass air meter a good cleaning too

 

[jrichker]

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. You watch the flashing test lamp or Check Engine Light and count the flashes.

See http://www.troublecodes.net/Ford/

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.

89 through 95 cars have a working Check Engine light. Watch it instead of using a test lamp.

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 about $30 or so at AutoZone or Wal-Mart.

Or for a nicer scanner see http://www.midwayautosupply.com/pc-7208-90-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.

 

[funkalicious]

Pulled codes. Everything is o.k. according to the code #s (79 and 11). Diagnostic run in the Key On Engine Off mode. Anymore suggestions to fix my problem? Will do tuneup this weekend. Will also check for vacuum leaks and clean the throttle position sensor.

 

[cenok is family]

Pulled codes. Everything is o.k. according to the code #s (79 and 11). Diagnostic run in the Key On Engine Off mode. Anymore suggestions to fix my problem? Will do tuneup this weekend. Will also check for vacuum leaks and clean the throttle position sensor.

dude, if codes are okay, and it's been over 2 years since it's last tune up, that's probably what it is.

 

[Aliate X]

Your MAF is dirty. The K&N uses an oil that gets all over the MAF and insulates the wire thats supposed to read the amount of air coming into the motor. Pull out your MAF and clean it with rubbing alcohol and a q tip, it will feel like you picked up 40hp lol. I had the same problem.

Another solution that im willing to bet money on. Already got someone to paypal me $10 for figuring out their problem lmao.

 

[blackstallion89]

sounds like the MAF. Mine did the same thing

 

[funkalicious]

Just wanted to say, "Thanks!," to all those who replied. Cleaned my MAF (black deposits on it) and set my TPS (was reading .789 with key on and engine not running. Now reads 1.010 with engine idling). Car now pulls hard with absolutely no stumbling!