My '92 F250HD 460 pings when under a heavy load even with higher octane gas. This is not just a moderate ping but very heavy. It does not do it all the time and appears to more prone to pinging in the higher altitudes. Any Ideas?

 

I have adjust my timing everytime I reach 4200+ ft above sea level.

Then re-adjust it the closer I get to sea level.

I live at 3400 ft above sea.


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If you're running Texaco gas, that's part of your problem. For some reason it has a tendancy to knock in 460's. Also try cleaning or replacing your intake air charge sensor if it's gummed up. I did that recently on Deen's recommendation, and noticed a huge difference right away. I used to get occasional knocking even empty with 92, but now I run 89 with out a problem. I even climbed a long hill this evening with 3200 lbs in the bed and not a problem arose. I'd make a quick check of your EFI sensors to ensure that they're all connected, and if it's not to much trouble check them with a voltometer and clean them. And like MIL1ION said, check to be sure your timing is at 10 degrees BTDC if you're below about 2500 feet. You may need to retard above 4000.

The Law
1989 F-250 HD 4x4
460, C6, BW 13-56, Sterling 10.25" (4.10:1), Dana 44 HD (4.09:1), twin K&N's, no muffler, stock lo-flo cat, Bosch Platinum Plugs (0.060") MSD 6A and TFI Blaster Coil

 

I vote with The Law...check your sensors. In a normal situation as you increase altitude you can normally increase timing, the reason being the air is thinner at higher altitude which leads to lowered compression and/or richer fuel mixtures...both help to control detonation. One thing I noticed as we traveled across six states this year is in states like Colorado, where the average elevation is 4000-6000 ft above sea level, there premium fuels had closer to 89 octane content. In lower elevation states like Oregon and Washington the premium fuels average 91-92 octane. Some areas (high altitude) had regular gas at 85 octane...something we never see at the pump in the Pacific NW. That tends to reinforce my thinking that higher altitudes have LESS tendency towards detonation, hence the use of lower octane fuels. Just my 3 1/2 cents worth...Deen

 

One thing for all you injected guys to try is this...
When driving up to a higher altitude that affects performance or driveability you must pull over, shut off your engine and restart it. By doing this your map sensor will be used by the pcm as a barometric pressure sensor. Thus it will sense the increase in altitude, and compensate for this. Every time you start your vehicle it will do this. Try it out, it will help.

Nick from the frozen north
1974 F-250 4X4
soon to be 429
dana 60 front and rear

 

Thanks for the responses. I'm still confused about one issue: If higher altitudes cause the mixture run rich, why would the engine ping at high altitude? I thought pinging was the result of too lean of a mixture.

 

>Thanks for the responses. I'm still confused about one
>issue: If higher altitudes cause the mixture run rich, why
>would the engine ping at high altitude? I thought pinging
>was the result of too lean of a mixture.

The higher the altitude, the LESS prone an engine will be to ping- for any reason. Operating an engine at high altitudes is the exact opposite of using a super- or turbocharger and you adjust your engine the opposite way for best performance (or your EFI does most of it automatically). That means you add a LOT more initial ignition advance, you lean the mixture and you can use lower octane gas. The regular gas sold in Colorado, for example, is 85 octane, the rest of the country usually gets 87 octane. Premium and mid-grade are two or three points lower, too.

I live at 6,000 feet, when I drive locally no problems. But when I take a road trip and drop down below 3,000 feet, my engine pings like crazy until I spin the distributor and retard the timing back to sea level factory specs.

As far as your pinging goes, one overlooked reason is a problem with your EGR. If your engine *doesn't* get adequate EGR flow due to a clog, plugged EGR valve or other reason, it's going to ping, mostly at part throttle, normal driving, especially when you accellerate a bit (not full throttle).

Is that the case?

-Bill in Colorado
Two Easters Ranch

1996 S/Cab F-250 4x2 Long bed 460
E4OD auto, 10.25" 4.10 posi, Air-Lift suspension,
homebrew cold-air intake w/K&N filter, modified ignition advance curve, Edelbrock 2x61 mm throttle body, Bosch Platinum plugs, Champion truck plug wires, L&L 4 into 1 headers, .060 milled heads, 3" exhaust system, cat & Flowmaster 70, modified MAF meter, Michelin LTX 265/75/16E, Mobil 1 10W-30, Red Line D4 ATF, Red Line 80W-90 in axle. Reese hitch.
10 to 12.8 MPG, 5,700 lbs.
{E\...F}

 

Hi Bill,

I replaced the crankcase ventilator but not the EGR. I'll give that a try. The pinging is most noticable under load in the mountains around 4000 ft. The truck lives at sea level. I will lessen if I go to 89 or 92 octane but it's still there.

 

MSD makes an electronic timing control unit that allows you to change the base timing up to 16 degrees using a control **** on the dash. It's easy to install and works great.

 

The Law mentioned Texaco gas above and that got me wondering. I live in a rural area and the choice of gas normally is Texaco and No Name.Anyway a couple weeks ago I had to pull a loaded horse trailer over a mountain pass 2 days in a row. This is about 1 1/2 miles of 6% grade going from 3000' to 3800'. One of the places where I ping with a load. So the first day I had Texaco Premium with the usual ping, the second day I had Union 76 Premium with no ping. Weather , temperature, time of day, etc. were all the same. And here I thought I was doing good by running a name brand gas. By the way, I do have C9 heads for 9.4 compression and headers. What I have done since then is put a valve on the timing vacuum advance line and mounted it by the trailer brake control. When I come to a long grade I turn the vacuum advance off, which takes away 10-15 degrees of overall advance and there is no pinging. this is cheap, easy , and on demand so you dont have to run in a perpetual de-tuned mode. Also this should work when I drop down to sea level once a year from 3000' where I live.