hesitation backfiring

[Red88 RICK]

ok the otherday i installed a 255 fuelpump. it was all fine except my bro put the O-Ring on top of the tank on wrong and had a small fuel leak.i drove it with the leak for a week about it wasnt that bad, he fixed that for me and that whole night it drove fine still had power all the way. i just filled the tank drove about 3 miles home. Next morning woke up went to drive it and it backfires pops and barley moves untill higher RPM but even then it barly moves just dosnt backfire at high RPM. he said to look at the fuel lines they mite of got crimped i went under in my driveway and a line was stuck between the tank and the body, let it down an inch got it unstuck the car acted a little better but still not right. he took it back to his work ( a Chevy dealership ha) andtook the tank down and put it up right this time he claimd it was all good now but nope still doing it its got a bit better again tho now down to half tank it does it prety much only backfires in 3rd and up. my set-up is in my SIG. any additional info needed id be happy to add. i did look up codes the 1st time this all happened KOEO got code 11 and then 33. KOER got just 2 AIR codes cause i dont have that hookd up. and i dont think its a fuel problem cause it was good that whole first night. Thanks in advance.

 

[Red88 RICK]

Sorry i forgot to add that this only happens at WOT.

 

[jrichker]

Backfiring out the intake is either a valve stuck open or a lean mixture or spark plug wire(s) connected to the wrong cylinder(s). Check compression on all cylinders and then look for vacuum hoses loose, cracked, or misconnected. Check the line for the vapor recirculation system – it is easy to knock loose and not see it when you connect the air pump plumbing. If the vacuum line for the EGR valve and the air pump are cross connected, some very strange things can happen. Check the mass air flow electrical connection and see that it is tight, the same goes for the fuel injection wiring harness connectors up on top of the manifold near the firewall.

Sticking valves: If a intake valve is bent, has a bad spring or is misadjusted, the engine will sometimes backfire through the intake. Use a vacuum gauge connected to any convenient spot on the intake manifold. Run the engine at 1000 RPM & look for 18-21 inches of vacuum with a steady needle. A problem intake valve will make the vacuum gauge needle sweep 5-10 inches.

Lean fuel mixture breaks out into several sub categories:
A.). Vacuum leaks
B.) Air entering the intake without passing through the MAF on Mass Air cars (89-95 models).
C.) Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D.) Leaking exhaust gases from EGR valve at WOT or EGR opening when it should not be open.
E.) Poor fuel delivery due to bad fuel pump, clogged filter or bad fuel pump wiring. Look for low pressure or fluctuating pressure. Standard injector pressure is 39 PSI at idle, with the vacuum line disconnected from the regulator and capped.
F.) Clogged fuel injectors.- see the cylinder balance test below
H.) Fuel injector wiring problems causing injector not to deliver rated flow.
I.) Computer problems: (computer problems are not common like sensor problems)
J.). ROM has bad data in fuel or timing table. This should also set a code in the computer.
K.) Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one. Use a noid test light to test the injector wiring & injector drivers,
L.) MAF calibration off or mismatched to injectors.
M.) ACT or ECT bad. Sometimes the sensors will be off calibration, but not bad enough to set a code. If they falsely read too high a temp, the engine will back off fuel delivery.

Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure

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.

See Troublcodes.net Trouble Codes OBD & OBD2 Trouble Codes and Technical info & Tool Store. By BAT Auto Technical

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 Actron® 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 EQUUS DIGITAL FORD CODE READER (3145) – It has a 3 digit LCD display so that you don’t have to count flashes or beeps.. Cost is $30.

 

[allballsmustang]

you could have knocked something loose while doing the pump and possibly clogged the fuel filter?

 

[Red88 RICK]

ya i could have knockd something loose but it was just like that night it drove 100% fine the next day it drove horrable. my bro said i had 35 fuel presure that dosnt seem right to me and that it droped when he hit the throttle. im going to get a guage for the car now so i can see the pressure all the time. he use a snap-on guage. he also says it backfiring thro the exhaust. the car does run strong at like half throttle and almost anything above that it pops and like wants to go then just falls. if below 3500 rpm you hit the throttle down hard it will pop. ill get the vac guage also
Thanks alot

 

[Red88 RICK]

Ok today i went to ford to get a fuel filler neck gromet and the O-ring for the top of the tank (we must have put the old one on insted of the new one with the pump) because soemthing was leaking but i checked pressure and it wouldnt hold at all even when holding the return line it wouldnt reach higher than 22 PSI so i droped the tank in im bros driveway and cleand it up, took the pump out and noticed that the hose coming from the pump was loose on both ends we must have forgot to tighten them. hooked everyhint gback up and it ran like new. i was very excited after going thro 2 full tanks with a car that barly ran.
Moral of the story check everything the 1st time and i mean everything.
thanks for the help