The Car: 1989 Formula 350

Motor: L98, Forged Rods, Hyperreutectic Pistons, Dyno Don Headers/Y Pipe, Hooker Cat Back, Fast Burn Heads, ZZ4/Fast Burn Cam, Edelbrock Vortec Base Plate, AS&M Runners, Accel 24 lb. Injectors, Ed Wright Chip, Fluidampr, Hypertech Cap and Rotor, MSD Street Fire Wires, Air Foil. Just over 1,000 miles on motor.

The Symtoms: started doing this right at about 1,000 miles. getting on the gas, it would show a very slight stumble. and off the line, even more noticeable and consistent. in park and at idle, feather the gas pedal and it would stumble - you could see the tach needle stumble before rising. the symptoms got progressively worse to the point that, at speed, if you got on the gas, the car would seemingly almost die. to me, this seemed indicative of a failing fuel pump.

Therefore, i replaced the fuel pump with a Walbro 255 unit. that did not fix it. Then, i replaced the Throttle Position Sensor. that seems to have fixed the stumble in park at idle, but at spead, or off the line the problem still remains - intermittently at speed, consistently off the line.

ive got a buddy with a scanner - gonna see if i can get him to come over and see if the scanner shows anything. anyone else have similar issues or have information on what this could be?

Thanks

Dave

 

Failing MAF sensor?

 

^yeah, i thought about that. i did check the wiring and gave it a thorough cleaning. hopefully that scanner will tell us something.

thank you.

 

Any luck with this? I have the same stupid problem with mine. I have replaced my MSD 6AL along with the ign module and o2 sensor with no luck. Mine only does it when it warms up though. I also thought the MAF with mine but havent bite the bullet to buy one.

 

not yet, the car has been (and still is) at the paint shop for a couple of days: getting the Hawks Fiberglass Aerowing painted. i'll post up any updates positive or negative.

 

HAve you checked your fuel pump relay. its on the firewall on the drivers side. To see if this is the problem you need to use a jump wire from your fues bax 12 volt accesory power to the G pin in your diognostic terminal. When you do this it will run power to the fuel pump and not use the fuel pump relay. IF your problem goes away with this then there is your answere. Now if you replace the relay and the problem still exsist then maybe a ground, most of these wires are over 20 years old remeber.
Good luck.

 

If your chip was mail order take it out and put your stock chip in.
Also check your dizzy parts, the pick up coil and ICM for proper operation. If yo have some miles maybe just replace them for peace of mind..
Running a K&N?? if so clean the maf wire with electrical parts cleaner.

 

Did you ever figure out what your problem was/is. Please let others know

 

okay, unfortunately, the car has been incarcerated at the paint shop for over a week now. took the car in to have the Hawks Fiberglass Spoiler painted/installed. they forgot to test fit it BEFORE painting it, which was pretty weak in my opinion. anyway, havnt had the car in over a week. i'll look into these suggestions when i get the car back.

do have a K&N and i did clean the MAF thoroughly with MAF Sensor Cleaner.

this symptom started very recently - more recently than the installation of the Ed Wright chip. the car is running the stock distributor with new Hypertech Cap/Rotor, & Coil.

i have half a mind to just take the car to a tuner in my area and pay the 10-12 hundred bucks or so, and hopefully get the peace of mind that im getting the best out of my combo. of course, i will see if i can diagnose this particular issue before doing anything like that.

 

Update: though not much of one. they did a nice job with the paint and color matching on the wing. they did not do such a great job with the fitment. professional paint shops are supposed to know that fiberglass parts need to be test fitted before being painted - i thought.

scanned the car. most readings were good, although the slight stumble off the line still persits. TPS was at .70 - backed it off to .50. scanner picked up a fault code: (engine light had come on intermitently for a few seconds, then went away) code 41: improper chip installed. called Ed Wright, he said the chip may have come loose or something.

i just ordered a Caspers 4-Wire Heated O2 Sensor. see if that helps. and of course, when i get a chance, make sure that chip did not come loose (i doubt if it did.)

here's a pic taken Easter Sunday.

the little one is POSITIVELY OBSESSED with my Formula. he thinks its his. its very difficult to get in it and drive it because everytime i step out of the house, he assumes it's time for me to take him for a drive in it and is on me like a pit bull. the older one perfers the 5.0 Mustang.

 

Nice pic. I have girls they are not into the car to much. My 8 year old doesnt like it ever since we pulled out of a parking lot and I told her to hold on and threw it sideways out of the lot. She hit her head on the sail panel and told me to never to that again but I think she did secretly like the ride.

Still watching for the update I havent taken mine out of the garage yet for the season.

 

Have you checked your fuel filter? I had a somewhat similar situation many years ago. Your symptoms remind me of that. Once I changed the filter, it ran great.

My four-year old told my wife that "Daddy's car is fast, your car is slow."

 

cant imagine it would be the fuel filter because it was replaced when the engine was rebuilt - and that was only just over 1000 miles ago. i guess it couldnt hurt, but damn it feels like it would be a waste of time. might try it though cause ya just never know.