Gq patrol driving me insane - Ping

Hey everyone, I have a 97 4.2EFI patrol. I still haven't had it tuned on gas (runs well, slow, uses a lot of fuel, but don't they all) because I'm yet to find a tuner that seems to have any idea and a dyno.

Now my problem is, other than standard crappy fuel economy, is when I run on petrol, it pings, its been hot lately so intake temps will be up and adding to the problem, but I can't for the life of me find any info as to why it's doing it. I'm a mechanic by trade, have been chasing the problem on and off for a long time now, as such, I really can't run on petrol.

I know I should just put it on a dyno and get them to have a play, but I get satisfaction from solving my own problems. Plus its a pain getting my car to places.

Now I know, everyone will say use 98, but no, I'm running standard 10 degrees static timing set with the aac unplugged as its meant to be so I don't see any reason why I should have to run 98. I am running a colder gas plug BPR6E, instead of the warmer BPR5E stock plug, so that should contribute in no way to detonation or pre-ignition.

Its done about 250,000, and 100,000k of that was with us. It was straight petrol, then converted to gas a while after we got it. Cracked a head, replaced with genuine nissan head, hardened valves for the gas. It had a leaking aftermarket head gasket 5,000k ago, so I replaced it with a genuine gasket, new head bolts, head checked again just to be sure.

It has a 3 core brass/copper radiator, extractors, 2.5 inch exhaust which admittedly needs replacing but again, is not the cause of the problem.

I put the plugs in when I replaced the head gasket, the leads aren't old, the rotor cap and button are good air filter is clean, valve clearance is right.

I had the amplifying head phones from work on it today, definite ping on petrol and when switched over to gas, ping gone.

Engine runs at 78-92 degrees depending on outside air temp (ecu talk gauges and my autometer gauge are very much the same reading).

I just can't put my finger on it.

I'm a diesel mechanic and don't claim to know everything about anything but have a great know how and believe a good mechanic can fix everything given enough time and right information.

Can worn out or leaky injectors cause a lean burn? Increasing combustion temps? Low fuel pressure? When I eventually get the exhaust replaced I will run a wide band air fuel sensor and gauge. ECU Talk shows up to 50 degrees of advance under low throttle free revving and 35-40 degrees of advance under loaded conditions. Which I can't alter anyway because its electronic. I have knocked static timing out of it to no avail.

Anyone got some ideas? Send the tb42 and patrol to the ocean floor? Haha.

Thank you in advance!

Dale. :tongue:

Is there any possibility that the replacement cylinder head had been machined resulting in a higher compression ratio?

Have you tried the higher octane fuel just to see if the ping goes away?

Although it may not make sense I might also be tempted to try the warmer plugs to see if they made any difference. These & the fuel would at least give you a bit more info I would have thought.

Is the advance mechanism working as it should. (Can you substitute it with a known working one). If the advance curve wasn't quite right would the result be more noticeable on petrol & gas?

You may be able to tell that my knowledge is limited (& largely based on experience with old British motorcycles)' but if my questions jog any further thoughts they may be useful. If not feel free to ignore.

The cylinder head was new the first time and very very lightly skimmed the second. The tbs have a very low compression ratio to begin and a lot of people do skim them to gain. So unfortunately we are stuck there :(

I have tried 98 and still shit. I dropped timing back to 5 degrees static which is half of spec.

The injected tbs have no vacuum or mechanical advance. Its all electronically controlled.

Im borrowing a mates fuel pressure gauge tomorrow and will post results.

Once i get my company car back (i crashed it haha) i will whip out injectors for a clean and see.

I like any information given and I appreciate your reply!

Also once its sorted, i will get a new exhaust, wide band afr, gas tuned (see how i go for economy) and if the gas turns out ok, i may shell out for a nistune circuit board and tune the petrol side as well.

I know its money on a puss engine, but i can't justify a new vehicle atm.

From my understanding, and i have been reading ALOT, lpg benefits most from a high static advance, with a lower overall advance. Where as petrol benefits from lower static advance and high overall advance.

Hey mate - leaning the fuel - whether from low fuel pressure, worn injectors or some other reason will definitely cause higher temp. The leaner the fuel delivery, the better the economy but the higher the burn. I fly 4 pot planes which you lean for economy but depending on atmospherics will definitely cause a ping if leaned too much - and a god awful stutter which trust me can leave the adrenaline running if you get it wrong when you're at 7,000 ft and descending! Plus will cause higher carbon buildup as well - are you blowing smoke?

Jas

I'm with jas, a possible fuel issue. But don't take factory specs as a must be thing. Every engine is different, every location is different, every setup is different.
Now you said you went back to 5 degrees static? Did it change anything? Power, efficiency? Peppy'ness?
Your car has done 1/4 mill. Things will be worn so factory specs may not be right.. I'd say just take it to a dyno tune, and get it done.
You've had a good crack..

Kallen Westbrook
Owner of
Westy's Accessories

My last Petrol/gas 4x4 No brand mentioned {T}all we did was start it up and twist the MSD dizzy till it just off pinging.
Gas likes it advanced, as Kallen said all motors are different so your 5 or 10 degrees static is only a Starting point.
, twist ,nip dizzy go for a quick spin repeat until no ping, easy as IMO

I do agree every engine is different. But its an engine that was running fine at 10 degrees originally.

No smoke that i can see, but once it pings i go back to gas or fill up.
250,000 is a few ks. But its not insane.

At 5 degrees it still pinged. I was down on power on gas and petrol. The turn it till it doesn't ping method is ok if you have headphones on it. A engine will ping before its audible.

Ill check fuel pressure. Clean injectors and if i still haven't achieved anything i'll take it to someone.

Yea do what the women do, turn the radio up... :D
Well they only thing I can really think of left is injectors/ jets.


Kallen Westbrook
Owner of
Westy's Accessories

Tried it again this morning. Started it on petrol. Drove to the shop, 10k down the freeway sitting on 110kmh overtaking in 5th. Started pinging can hear it through the firewall.

It doesn't start straight pinging straight away.

Engine is running almost 10 degrees cooler today as well. Outside air temps are 10 degrees cooler this morning than last night

Try a bottle of injector cleaner. One that I've recently been using that I've actually noticed a difference and is called fuel doctor. Bought it at supercheap. It's bright green.

I'd also go to a Subaru dealership and buy a can of their upper cylinder cleaner.
It works well, spray half the contents of the can into the intake when hot, start it, then spray the remaining contents in while still idling. This stuff foams up inside your intake and engine and works well for cleaning the horizontally opposed boxer engines that suffer from oily tops ends due to their design. Works just as well for our engines too...;)

Worth a shot.