Backfiring/Hesitation/Powerloss

Jeff7477 · Sep 7, 2005

Ok, I've got a couple different things going on. Its been doing this for awhile now but I would like to figure it out.

When my car is cold in the morning, It will backfire once or twice as i'm pulling out onto the main street. Thats problem one.

Number two is this: The car will be warm and I will be at a stop light or whatever. I usually pull away slowly through first and if I shift into second and get on it, it will accelerate slowly up till about 2500-3000 rpm then all of a sudden you get this kick in your butt as it takes off. Sometimes it will give a backfire as you roll into the throttle.

I'm pretty stumped. Timing is at like 12 or 13, at least it was last time i messed with it. Just replaced my coil/cap/rotor/wires/plugs and it still does it.

So i'm

srothfuss · Sep 7, 2005

Have you done the cylinder balance test to determine that each cylinder is operating properly?

Backfiring under load (to me) is indicitave of a miss (broken plug wire or crossed wires)

legalize420 · Sep 7, 2005

check firing order. i had similar symptoms from accidentaly reversing wires on plus #2 and #3.

Jeff7477 · Sep 7, 2005

Nope, firing order is right.

I just cleaned the MAF, reset the idle and TPS voltage and it still does it.

I also noticed when I got on a straightaway that if I just barely touch the throttle while cruising about 2k RPM that it will kind of stumble/hesitate.

I'm lost

srothfuss · Sep 7, 2005

It's missing a cylinder! Do the balance test to find out which one is causing the problem.

Jeff7477 · Sep 7, 2005

Yeah, but if I get into it it picks up fine....missing cylinder would run like crap all the time though wouldn't it? Either way i'm going outside to do the balance test now.

90mustangGT · Sep 7, 2005

When you check the TPS, press the throttle slowly and the voltage should climb slowly. Be sure all electrical harness connectors are clean and there is little to no resistance between them. Go from there. Check for codes while your in there.

slick88GT · Sep 7, 2005

I had a similar problem that turned out to be bad gas. Run the tank dry, replace the fuel filter and fill it up with premium from a different station. I finally did this and it was like driving a brand new car.

Jeff7477 · Sep 7, 2005

ok, Cylinder Balance Test passed. Went over the TPS again and somehow it went from .98 to 1+. I dunno. But I set it back to .98.

Full throttle it reads 4.66. That alright?

I don't think its bad gas because its been doing it through several tanks, and the way it drives doesn't feel like it is either. Its got top end power and stuff....its just being wierd.

Jeff7477 · Sep 8, 2005

Anyone have any other ideas? I think i'm going to pick up a timing light today and set it back to factory 10 degrees and see how it runs.

Polter83 · Sep 8, 2005

Did you pull your codes?

Did you pull all your plugs?... perhaps one is different than the others. Did you do the cycl balance test? If it isnt missing a cycl...
then Im going to go with its a fuel pressure problem. A fuel pressure gage straped the window or in the somewhere you can read it while underload will tell you alot about whats going on.

5.02GO · Sep 8, 2005

Polter83 said:
Did you pull your codes?

Did you pull all your plugs?... perhaps one is different than the others. Did you do the cycl balance test? If it isnt missing a cycl...
then Im going to go with its a fuel pressure problem. A fuel pressure gage straped the window or in the somewhere you can read it while underload will tell you alot about whats going on.

Ok, i'm dumb.

Whats a cycle test?

markc522 · Sep 8, 2005

Jeff7477 said:
Nope, firing order is right.

I just cleaned the MAF, reset the idle and TPS voltage and it still does it.

I also noticed when I got on a straightaway that if I just barely touch the throttle while cruising about 2k RPM that it will kind of stumble/hesitate.

I'm lost

i have had the same problem for the last month. just today it got worse. now when i hit a bump my car studders.

is it fuel pump? is it the computer? do i have a clogged fuel injector?
i dont know

a friend of mine had the same prob. turned out a plug wire fell onto the header and melted it half way trhough. the car ran fine unless you were cruising around 2 grand. i guess the spark was strong enough to bridge the gap while under hard acceleration, because there was no sign of a problem when WOT.

Jeff7477 · Sep 9, 2005

Well I bought a Fuel pressure guage. At idle with the vac line attached it reads 32. If i goose the throttle it will rise to like 33 then fall to 31 and then back to 32.

With the line off it reads a constant 42.

These numbers alright?

Checking my timing next but I need to go out and mark it so that will probably be tomorrow.

foxterror93 · Sep 9, 2005

Hey, Just a couple of suggestions, I was reading that you have checked the timing and that you said that it wqas ok, but have you checked how your harmonic balancer is , cause if it is warped or shot in anyway, your timing could be off still even though it was right before. and just in case you need to check the firing order it is 1-3-7-2-6-5-4-8 incase you don't have it. good luck

Jeff7477 · Sep 10, 2005

Balancer is alright.

Set timing back to 10 degrees. Seems like it might be a little better but I haven't driven it from a cold start so I won't know till tomorrow.

I have been running 89 octane Ethanol gas for awhile since its always the cheapest. I wonder if that has anything to do with it?

I filled up with 87 since my timing is at stock so I will see if it clears up.

Jeff7477 · Sep 12, 2005

Well, its not the gas and its not the base timing.

So far I have replaced Cap/rotor, Coil, plugs, wires, Coolant Temp sensor, Air temp sensor.

Just gonna keep replacing stuff till it goes away

Next will be TFI module, then injectors.

Any ideas?

92streetstang · Sep 12, 2005

Not to sound stupid bud, but how are you setting the timing. Pulling the jumper and then setting?

Just a shot

Darkwriter77 · Sep 12, 2005

Sounds a lot like what I was experiencing with my own car. Here's the seemingly neverending thread of parts I wound up testing/cleaning/replacing before finally concluding it was my TFI ignition module...

http://forums.stangnet.com/showthread.php?t=572496&highlight=Satan

Might give that a shot, even if your module tests good. Mine was passing the bench test, but it was ancient, so I threw on a new unit. Sure enough, it cured it. Best forty bucks I spent on it ... as opposed to the other $250 worth of whatnots I poured into it in trying to solve it (although those did help to resolve some other issues like my idle and gas mileage).

Hope this helps!

Jeff7477 · Sep 12, 2005

Awesome Dark, you are the first person that I have seen that had this problem and actually was able to solve it. TFI module tomorrow =)

Backfiring/Hesitation/Powerloss

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