[mxnate116]

i have had a problem with a intermittent backfire since i rebuilt my motor and recently it has gotten to the point where if i try to accelerate and the rpms are below 2k it sputters, pops, backfires, hesitates, ect until it gets past that magic 2k rpm mark. after 2k it runs amazing. no problems at all. it pulls as hard as normal no popping or anything.

just now i took out the ACT and both ECT sensors and cleaned them(if you can "clean" a temp sensor) put them back in and it ran amazing. so smooth and perfect. for about a min of driving then slowly(over about 2 min) worsened back to where i was before.

i pulled codes and i got codes for the charcoal canister and air pump system which i removed, and a out of range ECT sensor.

i dont know where to go from here. should i just get new ECT sensors and see what changes?

its a mostly stock motor. timing at 12*, no mass air, it did the same thing with my catless h pipe and with the cats(i had to put them back on for emmisions testing, which i also failed at idle...)

i also have a problem with losing coolant, which i believe to be a leaky head gasket. it drops below the ECT sensor on the heater core rails when its not running. could that be a part of the problem?

[1slo5.0]

I'd try an ECT since it shows a code for it. They are cheap. I'd also do a pressure check on the cooling system to find that leak.

[mxnate116]

its weird though it holds pressure but i lose coolant.

after a get home i can come back to it a few hours later and release alot of pressure from the cap. it will hiss a pretty good amount.

but thanks im gonna go pick up a ect in a few.

[1slo5.0]

Originally Posted by mxnate116 its weird though it holds pressure but i lose coolant. after a get home i can come back to it a few hours later and release alot of pressure from the cap. it will hiss a pretty good amount. but thanks im gonna go pick up a ect in a few.

That is not a pressure test. A pressure test uses equipment to pressurize the cooling system along with dye and ultra violet light to find the leak.

[e3sean]

this might sound funny but double check the fireing order... i had an 85 gt and the owner sold it to me cause it was doing the exact same thing and he couldnt figure it out it would start and sound good till it warmed up then it would pop and ping could drive it it would studder and buck. he had it on the regular 302 fireing order not the 351/5.0 HO order we switched it and it worked like a charm ran like a rapped ape.

not saying thats it but its the cheapest place to start.

[mxnate116]

i checked the firing order and it seems to be right.

i changed out the ECT and the problem didnt change. so i checked for codes. now i got code 54 which was ACT circuit open.

so im going to go get a new act tomorrow. although the ACT ohm'd out within range and i checked the circuit to the 60 pin connector at the computer and it was a working circuit.

[mxnate116]

ok so i got a new ACT sensor today and the problem only got slightly better.

its still the same. i pulled codes again and got:

engine off-

85 which could mean canister purge solenoid failure, which i have removed or adaptive fuel limit reached-lean
10-cylinder one has a problem
and 11 which is system ok???

engine on

40-cylinder 4 has a problem(this popped up as soon as i started the car the tester was still on...)
94-air diverter circuit solenoid fault
44-thermactor air system fault

now i have also gotten cylinders 1,4,6 have a problem but i get these inconsistently...

im not sure where to go from here...i dont think the air pump system being removed should affect performance.

so should i chase after ignition or fuel system or what?
any advice? thanks guys

[e3sean]

what do your plugs look like? if u pull each injector plug 1 by one do u notice a difference in they way it runs... if no then thats a problem cylender. lack of fuel shouldne cause popping.. maybe your timing is horribly off? did you set the timing @ 12* with the plug out then put it back in?

[mxnate116]

well the tester did the balance test and it said cylinder 6 wasnt working right. but im sure if i ran it again it would be different

the plugs looked fine. a light brown tint. i had some bosch platnums in it and switched back to some standard NGK's with no difference.

timing was at 12 with the spout out then i let it sit for a min or so and put it back in

[e3sean]

i am out of ideas then what fireing order do you have on it?

1-3-7-2-6-5-4-8 or 1-5-4-2-6-3-7-8 ? it should be the first one

[e3sean]

when you rebuilt it did you put a new cam in it? if so which one? are your valves adjusted right?

[mxnate116]

the firing order is 1 3 7 2 6 5 4 8

stock cam advanced 4 degrees we had the heads rebuilt at cylinder head service, rockers are stock pedestal mount torqued to spec.

im taking it to the shop soon because i have to get it certified for emissions because i failed and im going to have them look over it.

really the only things i can think of now is a faulty TFI module (i tried to test it but dont have the right tool to get it off)

an air leak

or a bad head gasket.

[gotn20]

I Have the exact same problem. I recently rebuilt my motor as well and ever since I have had the exact same problem as you. As soon as I hit 2k it clears up but under load low rpm's it pops and hesitates. my firing order is correct my rr's are adjusted correctly, I have done a new tfi, tps, coil, plugs, wires, fuel pump, filter, adj fuel pressure regulator, replaced the vaccum lines to map and checked for leaks. My plugs are perfect color and consistent. All of this helped absoulutley none. I'm lost. Keep me posted if you figure it out man.

[78mach1]

this sounds like a truck my friend had not to long ago, its was a 95 ranger with a v6 in it, it would intermitantly mis fire and was consuming cooland, we did a coolant pressure test and it tested fine, but when we did a cylinder leakage test on number 4 it would fail miserable.

the coolant was getting into the cylinder and causing a mis fire, so i would start with the basic engine tests, compression test, cylinder leakage and then see what you get

[mxnate116]

^^ yeah im starting to think its a head gasket. i had to take it back apart and reused the head gaskets and i see it seems to be seeping a little coolant from under the head gasket at the corner outside the block.

the motor has to come out to replace a warped oil pan anyway so i think im going to tear it down again.

i just tested the TFI module and on all the values i tested its low but near the OHM's it should be. there is also white stuff all over the back of it. does anyone know what TFI's cost i may just buy another just because.

[mxnate116]

i finally got the motor out and torn down and the pass side head gasket was leaking coolant but it was straight out of the block not into the cylinders.

on the driver side however cyl #6 has some probs. the intake runners are soaked in oil and gunk. the piston is just gunky not carbon coated like the other pistons the spark plug is oiled up and the exhaust runner is covered in crap too. but when i looked in the header it looked white and like it was super lean. the others were a nice dark carbon color.

any idea what this is? is it oil from the PCV system??

[gotn20]

FUCK! I still have this same problem as you. I also have a slight build up of oil in my intake manifold but I've lost no coolant since the day i rebuilt the motor. I'm thinking about tearing mine back down again to, to see what i find since nothing else is working.

[mxnate116]

im thinking its the pcv just pumping oil into the intake.

im gonna make a oil/air separator for the pcv and put breathers on both valve covers.

if it is just oil buildup i bet you could run some sea-foam or something through the intake and do the same as i plan to.

[1slo5.0]

Originally Posted by gotn20 FUCK! I still have this same problem as you. I also have a slight build up of oil in my intake manifold but I've lost no coolant since the day i rebuilt the motor. I'm thinking about tearing mine back down again to, to see what i find since nothing else is working.

Oil in the intake is pretty common on 5 liter Mustangs. I've yet to find one that doesn't have some oil in the intake. The problem seems to be worse with aftermarket intakes for some reason. I'm sure its related to the PCV system.