Dies in the bum uo hills!

[ytt105]

Hi all, I've got a 1996 4.6 P38, done about 180k kms.

Well maintained, new plugs and leads. Has a good LPG system, (not injection), never had any backfires.
It goes well enough on both fuels, but dies in the bum up hills.

I tow a Jayco camper trailer, (just over 1 tonne), and boy can it chew some fuel when its towing that, 25 - 30 l/100.
Verrrryyy slow up hills when towing.

My thoughts are worn camshaft, blocked exhaust, or just crap for towing.

How restictive is the exhaust?

[PaulP38a]

Hi all, I've got a 1996 4.6 P38, done about 180k kms.

Well maintained, new plugs and leads. Has a good LPG system, (not injection), never had any backfires.
It goes well enough on both fuels, but dies in the bum up hills.

I tow a Jayco camper trailer, (just over 1 tonne), and boy can it chew some fuel when its towing that, 25 - 30 l/100.
Verrrryyy slow up hills when towing.

My thoughts are worn camshaft, blocked exhaust, or just crap for towing.

How restictive is the exhaust?

Have never heard of a P38A being crap for towing. Here's a simple test (without the trailer)... challenge a young hoon in a late model 6cyl Commodore or Falcon at the lights... you should give him/her a good run up to about 80kph , maybe 100kph if you engage sports mode.

Suggest taking it over to Ray CMW in Mitchell to get some tests done. Not this Friday though... mine's going there and I'm borrowing their dodgy grey import Camry Diesel

For the exhaust, go see Peter at Complete Exhaust Service in Hume. He did a dual system for me for less than a grand... not very restrictive now

does it sound anything like this?
Replacing tappets, Cam and Rockers
Cheers, Paul.

[ytt105]

Thanks Paul

It goes fine at the traffic light grand prix, except for the vibration that I think is either the engine mount or the flex disc, but once you put a load behind it, its crap.

I must pop over and have a look at yours some time.


Regards
Trevor

[PaulP38a]

How's the transmission? Does the vibration get worse under load?

May not be related, but the vibration might just be the UJ's.

cheers, Paul.

[Hoges]

Have you checked for inlet manifold leaks... colour of exhaust tail pipe ? Have you checked a spark plug tip for colour... ? Easy stuff first before panicking... plenty of time for panic later!

BTW: where are the hills where it dies? You're not talking Alpine Way etc are you I have found that Rangie's are quite sensitive to altitude.. coming back from Sydney a while ago up the New England Hwy I thought the truck was "sluggish" ...till I realised that Guyra was damned near the same altitude as Cabramurra! Ahhh for a low pressure turbo in such situations...

[ytt105]

Hoges

How about the road from Wilcannia to Broken Hill? Not too much altitude out there!!

Plugs look good, just replaced 2000kms ago, exhaust always looks a bit black, but it doesn't blow any smoke.

Havn't check for exhasut manifold leaks yet. Any hints on the procedure for that?

[Hoges]

Ah Ha! the wide brown land indeed ... more aTTitude than aLTitude out there

Has it always been like this since you owned it?

If the exhaust pipe is black then think rich mixture...perhaps some sort of inlet restriction rather than a manifold leak...

some suggestions: check the air filter and look for (partial) blockages on inlet side?

Have the inlet manifold gaskets been replaced/disturbed... have they been put back correctly?

Is the GEMS engine open/closed loop? (i.e. does it have Oxygen sensors?)
Sensors may not be functioning properly if it's closed loop.
A simple scan gauge can tell you if the sensors are failing..
May be worthwhile getting the exhaust analysed for air/fuel settings...

keep exploring !

[PhilipA]

If the exhaust pipe is black then think rich mixture...perhaps some sort of inlet restriction rather than a manifold leak...

All unleaded cars have black exhausts.
Grey is lead.

I would first look at the accelerator linkage. When the foot um is flat is the throttle um fully open? (apologies to the Mereenie Loop sign)

So it has a vacuum type gas system? the one that puts a gas "ring" in the inlet pipe that cuts the area by about 50%? If so that is most probably your problem.

In any case the GEMS 4.6 makes its torque up high due to the inlet manifold length, so the Gas ring will affect it more. Thor has much better torque at lower revs. Remember also with over 1tonne on the back you are trying to accelerate/climb 3 tonnes.

My 3.9 RRC with Thor and o2 sensors on 14CUX gets about 16-17lper100Kms towing at 100Kmh on the flat my 700Kg camper. The GEMS is much more sophisticated than 14CUX so should get better economy.

The transmission in your 38A has electronic lockup of the converter. Maybe have someone check for fault codes on the trans as maybe it is not locked. Can you feel it lock in top?

Regards Philip A

[ytt105]

The tranny works fine. I can feel it lock and unlock properly.
The gas system is the sprint gas type, I think. There isn't a gas ring like my classic had. There is a large box type thing (gas carby?) in front of the throttle body.

I'm going to check a few more things on the weekend, my mate has a OBD2 scanner. However, I hooked up a vacuum guage today and it had a steady reading of 16" on petrol and 15" on gas. Went as high as 20 when throttled up and down to 0 when backed off.

Some info I've read says these reading MAYYY mean ignition timing or exhaust restriction.

What should a good 4.6 read?

[bee utey]

Sounds like you could do with colder running plugs. Normal heat range plugs are good for a quick squirt, then get too hot. Try Bosch WR7DC plugs, seem to do well for my customers.
Also your gas mixer/carby (probably IMPCO model 200 or copy thereof) should have a little adjuster on it where the gas goes in, I have found sometimes when it's set too lean performance degrades badly under load. Try moving it 1 notch towards "R". Your mixture controlling system should cope fine if this is all that is wrong.

The tranny works fine. I can feel it lock and unlock properly.
The gas system is the sprint gas type, I think. There isn't a gas ring like my classic had. There is a large box type thing (gas carby?) in front of the throttle body.

I'm going to check a few more things on the weekend, my mate has a OBD2 scanner. However, I hooked up a vacuum guage today and it had a steady reading of 16" on petrol and 15" on gas. Went as high as 20 when throttled up and down to 0 when backed off.

Some info I've read says these reading MAYYY mean ignition timing or exhaust restriction.

What should a good 4.6 read?