Problems at low RPM's

[Steves LX]

I just dropped a new 306 in the car this past week and still trying to work all the bugs out of it. The car seems to backfire when you first try to put it under a load and then it clears up as you accelerate. If you sit and idle you can rev it to the moon but every once in a while when you go to take off and you start to accelerate, it starts cracking up initially and then it really takes off. It also bucks around every once in a while if you hold the RPM's steady at certain points. I pulled the plugs which are new and checked them. They look alright unless I accidently overlooked a possible crack. The wires are brand new. New TPS also its at .98 volts. My timing is at 16 initial and Fuel pressure at 40PSI. I tried the fuel at 37 and 38 and that changed nothing. I dont think its my coil you can hear that thing just a firing away. My cap and rotor look alright also. I am clueless I need some help here.

[graysonracin]

Mass air ok on the other motor, might try cleaning it, see what happens!

[Steves LX]

It was fine on the other motor the last day I drove it which was last weekend but I will try that.

[kennebellcobra]

I noticed at the cruise when you started it up it was real rich...I would try another meter....can you watch your FP while driving? Does it have any codes?

[12seclx]

I've been searching this over on another site...
I would try checking for exhaust/header leaks...
Sometimes if the leak is bad enough, your exhaust scavenge effect will actually pull air in and if this isn't being detected by the o2 sensors, it
might cause problems with the ecu...

Other than that, other people say to check the IAT sensor, plugs, fuel pump, or TFI module.... :confused:

Wish I could be more help!

[Steves LX]

Its not throwing any codes. I picked up a new Pro M meter yestarday and it didn't change a thing with it.

[12seclx]

Is there any way you can borrow a distributor from somebody? Could be one of the sensor/electronics in it causing issues... :confused:

When was the last time you changed the fuel filter? I doubt it's that but I change mine about every 6 months...

[kennebellcobra]

Splice into your o2 sensor harness with some temporary wire run to the inside of the car...hook it to a volt meter and drive it...read the volts .9 volts is rich .1 is lean see what it reads when it studders. This should give you an idea of what the AF is doing.

[graysonracin]

May have a vacum leak, spray brake clean, carb cleaner around the plenum and t/b area see if it revs alittle of dies when you spray a specific area. Check the vacum hoses on the underside of the plenum also.

[graysonracin]

Also, put a gt40 intake and other mods on a friends stang, it would backfire and break up, then rev. The metal vacum tee on the drivers side of the plenum was hitting the valve cover causing a vac leak, kind of sounds like what youv got goin on, just ideas hope they may help.:bigthumb

[dedpedal]

Also, put a gt40 intake and other mods on a friends stang, it would backfire and break up, then rev. The metal vacum tee on the drivers side of the plenum was hitting the valve cover causing a vac leak, kind of sounds like what youv got goin on, just ideas hope they may help.:bigthumb
I had that same problem. It looked like it cleared but when I tightend the intake, it hit.

[Steves LX]

Well I looked at my intake last night and it is clearing my valvle covers. I hosed everything down last night and the idle didn't budge. It stayed the same. I put new plugs in again last night and that didn't change anything. I rechecked my timing and fuel. I give up on this POS. I should have saved the 1900.00 it cost me for everything and kept my old motor in there that had very little oil presure and drove it until it blew up. At least it ran like it was suppose to. My damn weedeater runs better on diesel than this brand spanking new motor does right now.:mad:

[graysonracin]

Are you running an msd box, if so that could be your problem, ive had them go bad or act up for no apparent reason, also if anybody close has a stang try their coil or see if you can get another ign box.

[Steves LX]

The problem is fixed. It was O2 sensors. Appreciate the help guys.

[kennebellcobra]

The problem is fixed. It was O2 sensors. Appreciate the help guys.

Glad to see you got it:bigthumb Now to see what that new motor does at the track:evilgrin:

[12seclx]

Glad to see you got it:bigthumb Now to see what that new motor does at the track:evilgrin:

I doubt the car pulls the wheels with the new motor.... LOL!

:nono:

[graysonracin]

Good to see you got it straightend out, now go have some fun!:bigthumb

[Steves LX]

I doubt the car pulls the wheels with the new motor.... LOL!

:nono:

Pulled em all 6 passes.:lol:
It didn't pull em as high as the old motor but it still pulled them.