It's been a while since I've had time to go on these forums but now that I've done most of the stuff over break I needed to and still have a few days I've been trying to tackle this problem I have which has led me back to this awesome forum! I've been dealing with this pinging from my bronco for about a month now and its starting to worry me.

Basically, when I accelerate hard, in 3rd gear or higher, or when I give it lots of throttle on the highway (especially in 4th gear), my truck pings. Sometimes quietly, other times loudly. I do have a lot of miles (211k), but the engine seems to run quite strong despite the pinging.

Here are the things I've done recently:

- New spark plugs (had Motorcraft ones with about 30k miles and switched to autolite)
- New Spark plug wires (I had one wire arcing onto the headers, I now have all the wires separated from each other and anything they could arc from)
- Sea foamed the engine
- Cleaned MAF sensor with CRC MAF cleaner

As of about 4 or 5 months ago, I replaced my distributor, along with the cap and rotor. My PIP sensor was bad so I just got a remanufactured distributor to put in.

I have no engine codes or stored codes so it's kinda confusing where to look.

I went ahead and checked the timing and it was bouncing around... The timing is set MOSTLY at 10, but it bounces up about 4 degrees and back down sporadically at idle. I don't know if this is normal when its cold and the engine is still warming up, but I don't think so. EDIT: After checking timing again, it seemed to be closer to 13 but it still bounces around. I'm going to bring it down a little and see if that does anything for pinging..


If the bouncing timing has anything to do with potential pining (which I assume it may), then I need to correct that. However, the only things I can think of that would cause timing to bounce around should be good.

I installed a new timing chain about a year ago, so that is not worn, meaning that can't be the cause of my bouncing idle. Also, the distributor is "new" (remanufactured) so I don't think that would be causing an erratic timing because it was replaced fairly recently. Could a bad ignition coil cause this? I haven't checked (nor do I know exactly how) to see if the ignition coil is culprit to my issues. It is an MSD blaster coild and its about 3 or 4 years old. I have heard mixed reviews on them but haven't had any issues with it.

Is there anything else that could cause the erratic timing? Also, would you agree that this is the most likely culprit of the pining? The engine seems to run well and have as much power as it ever has, but the pining is sometimes fairly loud, and that can't be any good.

Any help would be appreciated!! I have kept my girlfriend waiting for too long though so I have to head out to her place. Hopefully someone knows where to point me to next!

 

it's been a while since I played with timing but don't you have to remove the SPOUT connector to set the timing?

 

Yes I believe so. I just went to adjust the timing, but with the SPOUT connector removed, the timing was pretty much exactly 10. It still did bounce around slightly but bounced less. I didn't adjust the timing at all then because it was at 10. When I plugged the SPOUT connector back in, the timing seemed up jump up to 15 or 14 average (with the random bouncing still).

Maybe the timing is advancing itself because its cold out? I really don't know how the SPOUT thing works and the computer's controlling of the timing, but with the SPOUT out, its at 10 at idle, and with it in, it was at 14-15.

 

Just an update,

I still have been having trouble with this pinging/hesitation. It has turned more into a hesitation, lack of power now though and only at higher rpm (It's not pinging quite as much). It's usually but not always giving me trouble when I'm pressing the pedal hard, but sometimes if I keep it up at higher rpm, especially in 1st gear, it will hesitate even if I'm not gassing it too hard. Sometimes the rpms drop from 3500 down to 3000 with almost no power, but when I shift into second, and the rpms drop, there is no problem. The issue seems to happen exclusively at the 3300-3500 rpm range. I believe the redline for the 302 is 4400 so I think I should be getting some good power within the range its stumbling.

I may add, this problem seems to happen more when the truck has warmed up. Also, I don't believe I mentioned it is starting to backfire pretty frequently on deceleration or in between shifting. On some trips, the backfiring happens a lot, on other trips it doesn't backfire too often.

I went ahead and bought a vacuum gauge and whipped out my fuel pressure gauge and just tested it. The vacuum gauge gave me a pretty constant 19.5" hg at the vacuum port on the throttle body. For the little I know with gauges, it seemed to functioned normally in throttle ranges (went to 0 when I pulled the throttle cable a good amount probably WOT but its hard to tell exactly under the hood). I don't know too much what to look for with the vacuum, but I would assume if some sort of vacuum was causing this issue, the gauge would be too low or start to decline.

With the fuel pressure gauge, the reading was at 35psi when key on, engine off, and about 31 when the engine was running. This seems to be in the specs of what the pressure is supposed to be. When I pulled the throttle, the fuel pressure would raise slightly, and then on deceleration drop slightly (under 30 sometimes but not too far.)

I did notice once, I believe the stumbling occurred (all of this is in idle in the driveway), and the fuel pressure dropped about 5 psi suddenly, but it was still above 30psi. I may have just revved the engine too hard and hit a rev limiter (if there is one). I couldn't tell exactly what RPMs it was at since I wasn't in the bronco.

edit: spelling

 

The 302 still has a KS (knock sensor). With the truck idling and at full operating temperature, smack the block with a hammer (near the aft end if possible). RPMs should drop enough for you to notice even at idle. If it doesn't, replace the KS. The PCM for the 5.0L (302) "expects" to see some kind of information from the knock sensor during engine operation. If it doesn't it does the next best thing... it "guesses". This would easily account for the slightly erratic timing readings. (or a timing chain that is beginning to die)

 

Thanks for the info I will definitely try that out in the monring. I was looking for the knock sensor last week but I couldn't find it. I thought it was supposed to be on the back passenger side up next to the intake manifold. I looked from under my truck above the transmission and I couldn't see it. I have read some things online that the Broncos didn't have a knock sensor so after I couldn't find it, I figured mine might not have had one. I'll look again and try hitting the end with a hammer or something i can reach back there and see if the idle changes. That makes sense what you said for the erratic timing reasons. I know the timing chain isn't worn because it's been replaced about 2 years ago so I better look harder for the knock sensor!

Edit: Just saw your post from 2003 https://www.ford-trucks.com/forums/1...ck-sensor.html about the knock sensor location on a 302. I would assume they kept it until 96 so I must have just plain missed it. I thought I was looking in the right spot. It seemed like I would have more clearance coming underneath the truck near the bell-housing to find it, but I'll also try looking from inside the engine compartment. That is if the tapping of the block at operating temps doesn't do anything. I know O'reilly Auto (they are the closest to my house) doesn't list a knock sensor for my truck on their website so I have to try and find a place to get them. Maybe Napa has them, they seem to have a bigger selection on uncommon parts.

 

Okay one last post before I go to bed..

If it does end up being that my knock sensor is bad when I test it tomorrow morning, it looks as if I am going to have a nightmare finding a new one. No retail stores seem to have it and apparently it is discontinued by Ford from what I read. Also Craigslist and eBay didn't seem to have any either..

I did some searching and found something came across an ignition misfire sensor. Autozone has them in stock for my Bronco. Is an ignition misfire sensor the same thing as the knock sensor? It sounds equivalent but what do I know. Here is the link to what autozone has Ignition Misfire Sensor | AutoZone.com It's part number for my truck is SU2037. If not then I hope I can get lucky at a salvage yard.

Edit: After some thinking, a misfire sensor probably isn't the same as a knock sensor.... I'm getting too tired it's 12:38 here I better get some sleep.

 

My 1996 Ford EVTM does not show there is a knock sensor on a 5.0L equipped Bronco. Ford started using the OBD-II system in 1996, I suspect they did away with the knock sensor.

The Misfire sensor is not the same as the knock sensor nor does it have the same functionality. If the timing is bouncing around with the SPOUT out then you have a problem with the timing chain or the distributor itself. You stated you already replaced the timing chain (and I assume gears?) as well as installed a "rebuilt" distributor. I suspect that distributor is most likely the cause of the problem assuming you installed a new timing chain AND gears.

 

Alright that explains why I can't find my knock sensor then. Yes I did install a new timing chain I don't remember if I replaced both gears... I know the camshaft gear was replaced but I can't remember if the timing chain set came with the crank gear. I believe it did, but I could be wrong. I should have kept the old gear and chain, I usually do so I can check. Otherwise I will see if O'Reillys lists what I purchased and can show me what it came with. I might do some more checking up, possibly the MAF sensor is getting old and a simple cleaning isn't quite cutting it for WOT.

It's confusing to me, the problem occurs only at 3500 rpm and on trips it does happen, my truck will be backfiring quite often. Like I said before though, sometimes it doesn't backfire (more than normal for when I first installed my exhaust about 2 years ago), and the cutting out at 3500 rpm doesn't seem to happen.

I've been thinking of installing new heads or potentially a camshaft, whatever would make a bigger difference for my engine, because I was told maybe the intake manifold may have a small leak that could cause this issue. I would think with my vacuum holding steady at the throttle body, I don't have vacuum leaks but I'm running out of ideas. I figured if I have to take the intake off, I might as well put some goodies in my engine while I'm there. I guess I'll do more searching around though before I make a decision. It's hard to decide what heads or cam is worth it for my small budget.