Backfires

[High Tech]

Hello,

Im kinda new here, and really need some new ideas. I have a 90 bronco, Its been sitting since 02. So i went to wroking on it, the fuel pump was frozen so i put a power lead from the battery and it started working. I pressure washed out the fuel tank, and got all the rust out of it. I have changed the spark plugs. and checked them 3 times. a new distributer cap and ignition coil. It had a fresh oil change and a fuel filter. And the timing is correct. The problem i am having is that when the truck gets warmed up it starts backfiring, and sputtering. does not bog down so the moter dies but it is close. I have checked the catalytic converter and it does not glow cherry red. I had a short in the wire to the distributer but i changed the wireing pig tail. I have about ran out of ideas, I had it checked on a computer, and the top oxygen sensor is reading bad, code 10 i think, and i have not changed it as of yet. does anyone have any idea what else might be wrong with my truck?

p.s - me and my friends are really stumped, and could use some help.

btw, thier is no check engine light on.

 

[BLADE262US]

I know you said you checked the timing but very easy to overlook is the firing order between a 351W and a 302 . A 351W is counter clockwise 1-3-7-2-6-5-4-8 and a 302 is --------------------------------------------------------------------------------------------------------------------------1-5-4-2-6-3-7-8 . It will start but will run kinda stupid like your suggesting . Also the cams are interchangable so if you have a 302 someone might have put an aftermarket cam in it with a 351W firingorder or vice versa . Without pulling the valve covers and rolling the motor over to see the timing events I dont know any other way of checking other than if it doesnt run with one try the other /emoticons/[email protected] 2x" width="20" height="20" />

 

[High Tech]

I know you said you checked the timing but very easy to overlook is the firing order between a 351W and a 302 . A 351W is counter clockwise 1-3-7-2-6-5-4-8 and a 302 is --------------------------------------------------------------------------------------------------------------------------1-5-4-2-6-3-7-8 . It will start but will run kinda stupid like your suggesting . Also the cams are interchangable so if you have a 302 someone might have put an aftermarket cam in it with a 351W firingorder or vice versa . Without pulling the valve covers and rolling the motor over to see the timing events I dont know any other way of checking other than if it doesnt run with one try the other /emoticons/[email protected] 2x" width="20" height="20" />

I have check the plug order. Twice. The truck idles like a new truck, does not miss fire at all. I can just about drive it 4 miles before it all goes to ****. after that, i have to put the gass to the floor to get it to move 10 feet. i did try this, and it seemed to work, but i have not tested it alot. i can slowly push down the gas pedle and it will rev up fine, but if i floor it, it back fires and sputters.

 

[BLADE262US]

LOL doesnt have a holley on it does it /emoticons/[email protected] 2x" width="20" height="20" />

 

[Shadow_D]

Have you replaced the ECM in the dist.? You said the wires were shotred out, that may have taken out that chip.

You will also need the special tool to remove it, no more than $8.00 at Advanced Auto. The chip is

HERE!

$35.48

 

[High Tech]

The ecm on the side of the dist has been replaced. lol, dident have the special tool, but a 5.5 socket, and a bench grinder, made the tool for the job. This bronco is fuel enjected. no carbs.

 

[Yardape]

Try using the 351w firing order, If not maybe your distributer cap is toast, causing the spark to jump from terminal to terminal like a mini electrical storm

 

[pastorbud]

Hello, Im kinda new here, and really need some new ideas. I have a 90 bronco, Its been sitting since 02. So i went to wroking on it, the fuel pump was frozen so i put a power lead from the battery and it started working. I pressure washed out the fuel tank, and got all the rust out of it. I have changed the spark plugs. and checked them 3 times. a new distributer cap and ignition coil. It had a fresh oil change and a fuel filter. And the timing is correct. The problem i am having is that when the truck gets warmed up it starts backfiring, and sputtering. does not bog down so the moter dies but it is close. I have checked the catalytic converter and it does not glow cherry red. I had a short in the wire to the distributer but i changed the wireing pig tail. I have about ran out of ideas, I had it checked on a computer, and the top oxygen sensor is reading bad, code 10 i think, and i have not changed it as of yet. does anyone have any idea what else might be wrong with my truck?

p.s - me and my friends are really stumped, and could use some help.

btw, thier is no check engine light on.

Check the Exhaust check valve (it is at the back of the engine, behind the back of the intake manifold and the firewall), and all the pipes and connections coming from it to the EGR valve.

 

[raceear]

Maybe bad distributor bushings i had problem with one and it only would give me trouble after it came up to temp. Drove me crazy for a while till I pulled the distributor and found the play in it.

 

[mbtech2003]

maybe the map sensor(on the firewall pass side of engine) when u slowly press down on the gas u don't loose as much vacum then if u stomp on it. also check the mass air flow sensor (after air filter) if equiped with one. u can clean it out and let it dry for 5 min. before reinstalling it. use electrical cleaner found at a local parts store or brake-cleaner will work in a pinch as long as it is the flamable stuff. map sensor u will just haveto replace to test. but i would put in a new OEM o2 sensor they will do strange things to an engine if it has the speed density fuel system.

 

[Justbust1n]

have you checked the exaust ??? alot of times an exaust bolt will break off causing it to have bad back pressure, causeing a back fire when it gets warm just an idea if everything else has been looked over ,, if the exaust has changed tones the past couple of days before it all went to $hit that might be a chance that be what is is sometimes people look over simple things .. it worth a shot

goodluck

J

 

[High Tech]

I went out today, and got a brand new dist. cap, and roter button. i will also pick up a o2 sensor. I will let you all know how it goes when i get back today. lol, i think im loosing my hair over this problem, or just pulling it all out.

 

[pastorbud]

I went out today, and got a brand new dist. cap, and roter button. i will also pick up a o2 sensor. I will let you all know how it goes when i get back today. lol, i think im loosing my hair over this problem, or just pulling it all out.

The guy at my parts store says there is a valve in the emissions system they actually nicknamed the "backfire valve" because it caused this when it went out. Just wish I remembered the real name for the valve.

 

[High Tech]

The guy at my parts store says there is a valve in the emissions system they actually nicknamed the "backfire valve" because it caused this when it went out. Just wish I remembered the real name for the valve.

Well i put in the new dist, roter, and cap. Still does the same thaing. And i replaced a bad sensor. emc, or something. I give up, im going to put it into a repair shop and let them deal with it. Im tired of guessing and spending money.. lol, but ill be sure to let any of you know, for future refernce. Its thursday, and im going hunting. see you all sunday.

 

[High Tech]

Found out what was wrong with my bronco. The fuel pump was not putting out the right amount of fuel. lol the 1 year war... expired 3 months ago. go figure. Btw i never new the fuel pump could cause a truck to backfire. but now i know. thanks for all the advice.