exhaust popping

[89 vert]

Cant seem to figure this one out. Half way to Carlisle the car started backfiring out of the exhaust while on the throttle. At wide open it goes away. It also has a miss to it while it is backfiring. The more gas I give it, the less it does it. It idles very steady and smooth. It runs great on full throttle. So far I cleaned the mass air twice, checked the wires for damage, checked all the clamps on the intake, cleaned the cap and rotor, adjusted timing, visually checked for vac leaks. I have a check engine light but it has been on for 4 years. It will do it no matter if its cold or warrmed up, consistantly. I also checked the barometeric sensor plug. Thanks for advice!!

[shockstang]

Shot in the dark here. I once had a similar issue and it ended up being that the bolts on the intake were working themselves loose and allowing it to suck air. Took it off, put on a new gasket, retorqued occasionally, all better.

[89 vert]

Good thought, ill check right now

[89 vert]

Checked all the intake bolts that I could and they were all ok, so was the throttle body. Still runs like crap

[Martin0660]

As a rough rule ... backfire out the exhaust is rich, intake is lean.

Have you pulled codes? Are you sure on the timing (spout out, etc)?

Both the idle and WOT stuff is mostly different areas in the tables than part throttle, closed loop stuff so it sounds like it's related to closed loop areas (TPS, O2 sensors, MAF).

One wild ass guess with no diagnostic information, have you checked you FPR? Pull the hose and look for / smell for gas. If there is, it's not supposed to be there ;) A bad FPR will do that becasue it does not pull down FP with cruise vacuum (but it's a wild guess).

[89 vert]

As a rough rule ... backfire out the exhaust is rich, intake is lean.

Have you pulled codes? Are you sure on the timing (spout out, etc)?

Both the idle and WOT stuff is mostly different areas in the tables than part throttle, closed loop stuff so it sounds like it's related to closed loop areas (TPS, O2 sensors, MAF).

One wild ass guess with no diagnostic information, have you checked you FPR? Pull the hose and look for / smell for gas. If there is, it's not supposed to be there ;) A bad FPR will do that becasue it does not pull down FP with cruise vacuum (but it's a wild guess).

Good info, I checked the FP line and no odor. I am going to check the tps voltage next. I will try to pull the codes tomoro after work, thanks

[wick]

As a rough rule ... backfire out the exhaust is rich, intake is lean.

Have you pulled codes? Are you sure on the timing (spout out, etc)?

Both the idle and WOT stuff is mostly different areas in the tables than part throttle, closed loop stuff so it sounds like it's related to closed loop areas (TPS, O2 sensors, MAF).

One wild ass guess with no diagnostic information, have you checked you FPR? Pull the hose and look for / smell for gas. If there is, it's not supposed to be there ;) A bad FPR will do that becasue it does not pull down FP with cruise vacuum (but it's a wild guess).

Not sure on this one big Bob. My wideband on decel goes straight to 16.0. It gets the poping out of the exhaust. So its considered the infamous "lean pop". Since the tune it does it. I was thinking he is going lean on his mixture here. But he also does not have a CEL light visible. Has to pull codes to see. I started thinking about mine last year with the PIP signal. But my tach was jumping around a good bit. Mine was all related to a bad ground.

[Martin0660]

Not sure on this one big Bob. My wideband on decel goes straight to 16.0. It gets the poping out of the exhaust.

All Ford EEC's shut off the fuel on decel until the RPM go below a threshold. TPS closed, and the fuel is cut until it hits a RPM target, something like 1800 rpm (not sure of the value in V8 EEC's) ... then it goes back to fueling for idle strategy.

He is talking about an exhaust back fire under some load, different set of conditions.

[wick]

Ah ha. Gotcha. Makes better sence now.

[PaxtonShelby]

Take a quick look at the vacuum hoses coming off of the MAP tree on the driver's side of the firewall. Once I had similar symptoms and found that one hose, while still connected, had split, resulting in a vacuum leak. 21 year-old hoses tend to get a bit brittle. The good news is that they're easy and cheap to replace. Good luck Jason!

[somethingclever]

Sounds like a vacuum leak to me....as Ron has already pointed out.

[89 vert]

Update: Found left side 02 sensor with 1 wire broken off. I re connected the wire and it made no difference. I sprayed everywhere there is vac. and intake with spray, and no idle change at all. It is getting a little worse. It will do it it now here and there at idle. Sometime it is a loud backfire when I start it. This weekend I will be trying to get the codes out of it. Should the 6al box be making a ticking sound when you put your ear near it??

[89stang]

If you want I can swing by tomarow or this weekend and you could swap my msd box on to your car.

[cwh19]

Update: Found left side 02 sensor with 1 wire broken off. I re connected the wire and it made no difference. I sprayed everywhere there is vac. and intake with spray, and no idle change at all. It is getting a little worse. It will do it it now here and there at idle. Sometime it is a loud backfire when I start it. This weekend I will be trying to get the codes out of it. Should the 6al box be making a ticking sound when you put your ear near it??

Maybe the broken wire killed the O2. Try a new one.

Did you pull the plugs?

[89 vert]

Maybe the broken wire killed the O2. Try a new one.

Did you pull the plugs?

I will be installing new o2 sensors tommoro, the plugs are a little rough to get out because of longtubes, but I will try that tommorow also, thanks

[wick]

If there are no codes then its going to be something simple. Have you tried a coil yet? Checked all grounds? My ground issue I had last year did something similar to what you are having now. When my fan came on it triggered the injectors and everything. Does this happen with the car hot or cold or both? How long after you start the car does it take to happen?

[venom]

I had something close to what you are describing. I sprayed and spray looking for a vaccum leak, and couldnt find anything. Finally I took up upper intake off, and one of those vac lines connected to the lower was off. I just couldnt get the spray to shoot under the intake.

[wick]

Sounds like the pip in the distributer.

[89 vert]

Sounds like the pip in the distributer.

Ok ill put the stock one back in and see what happens

[89 vert]

Put a new dist. in it, and no difference. This is frustrating as all hell !! Im done at this point