I have a '98 GT and I have a "herky jerky" type acceleration. It's not "smooth" like it used to be. I had a tune up in Jan '05, and recently (Monday) I had the intake manifold replaced (old one was cracked). The old cracked intake allowed coolant to leak across the the spark plug boots. This caused me to get a "check engine" light. The errors pointed to Cylinders 1 + 8 saying those cylinders were misfiring. Last night I replaced ALL of my spark plugs. Cylinders 5 + 6 wer FULL of coolant, as the other ones were damp at best. The wiring of the plugs is correct (1-8). When replacing my plugs, I noticed sand like dirt inside of the chambers of the plugs. I tried getting as much out as possible with a rag and screwdriver. I replaced all plugs with Motorcraft plugs, and wratcheted them until snug/tight. Now I am looking for what could be wrong with my engine's acceleration.

I have no codes or check engine light

During the last tune up, I didn't change the plug wires (but the car has run great all year until the intake crack and coolant leak was discovered)

I have a K+N filter

I had my exhaust checked for leaks this morning (it's good)

I had new O2 sensors put on the car earlier this year (if they go bad you get a check engine light, so I don't suspect them)

 

Try chsnging the plug wires, also run some fuel injector cleaner to help clean out the cylinders. A mechanic can also "powerfoam" the motor to clean up the combustion chambers. Check seal on the manifold as well. Timing may need adjusted, it could be a lot of things.

 

Took my car to Ford to diagnose:

Problems found: MAF sensor is reading low, should read around 158, it reads around 142

"Dead Miss" on Cylinder #8

Fuel injectors have a slightly high resistance

They recommend a new MAF sensor, new plug wires, and Fuel Injector service. Over $600 parts and labor. I will attempt to replace my plug wires myself tonight, and go from there.

 

Maybe you can just clean the MAF with some electric cleaner or brake cleaner.. You may have some oil residue from the K&N. I'd do the wires first to see if it feels normal.

 

If you just cleaned your K&N you might have run some oil from the filter to the MAF. It really doesnt need to be replaced. Go to your local auto parts store and get some carb/MAF cleaner. DONT USE WD-40!! The cleaner has to evaporate in order to fully work and clean the MAF.

Try those plug wires...only after replacing those wires would I go and replace the fuel injectors.

 

Well, I replaced my plug wires and......................EUREKA my pony hauls *** again! I wanted to buy the Motorcraft wires but it was too late to catch an open Ford dealership, so I went against my wishes and bought some knock off wires from Auto Zone for $60. The have a lifetime warranty, so we'll see. The only complaint I have is that the length on a couple wires is too long (plugs 7 + 8). I dressed them the best I could for looks, but the "look" wasn't my 1st concern, my DRIVE was. No need for the MAF or fuel injectors (at least not yet). I will get a better test drive to work in the morning (35 miles most of it free way), and I will report back. Thanks for the tips. I feel great that for the $60 wires, and $30 on plugs (I installed yesterday), and 4 hours of my own labor, my car seems to be fixed. Especially since Ford quoted me over $600.

 

Clean that MAF anyway...it shouldnt be dirty in the first place

 

Well my drive to work was great No problems at all. My car is screaming in every gear as normal, and begging for more pedal! No hesitating, put putting, or sluggish accelerating. My car is cured. I will take a look at my MAF sensor and clean it if necessary. I have NOT just cleaned my K&N though, so there should be no oil from the K&N affecting the MAF. Thanks again to all that gave their advice.