14CUX Help

[Buddy]

Long Post Warning.

So I've got my trail truck mostly ready to start wheeling again. Everything appears to be running well, it starts on the first crank, idles smooth, pulls like a mule during acceleration and cruises nice and smooth down the road. Well as smooth as a linked truck on 37" Krawlers can cruise.

However, the exhaust smells like crap and gives me a headache. It definitely smells like it's running rich I initially thought it was just because it's a dedicated trail truck and rarely sees the road or rpms above 2k. But over the last week I've driven it on the road multiple times including about an hour long round trip and it still smelled. Now with the roof and sides gone it's impossible to keep the fumes out and I end up smelling like I've been sitting in front of the exhaust pipe all day.

So I thought I'd see if any of you 14CUX gurus have any thoughts on how to maybe lean it out.

Specs on it currently

GEMS 4.0 block converted to 14CUX. I think it's got a cam but I can't be sure since the ownership history is a bit murky. But it looked different than the stock cam in my 3.9 and why would someone install a stock cam if they are converting.
New plugs, distributor, coil and wires.
Re-manufactured Bosh Volvo injectors (the ones that had multiple threads on here).
Fuel pressure reads 30-32psi with the vacuum connected and 40psi w/o.
Catalytic Converters have been removed
MAF has been cleaned and I adjusted the CO Trim to around 1.25V.
O2 sensors looked clean and seem to switch back and forth on the RoverGauge
IAC valve is clean and seems to be working well based on smooth idle and readings in RoverGauge.
Timing is set to around 6' BTDC at idle with the vac unhooked. The vacuum advance works.

As I said it seems to run pretty good. The only odd symptoms are the exhaust smell and an occasional hesitation during initial acceleration but as soon as it's above 1,000 rpms it takes off w/o any further hesitation.

One thing that I'm not sure if it could cause this is that I have a 180' thermostat and an aftermarket radiator. So it typically stays around 179-180' at all times. I plan to install an electric fan which will hopefully allow the temp to get closer to 190's. I could always go back to a 195' thermostat but with it being a 99% trail use truck I was trying to keep temps a little lower.

Is there anyway to manually tune one of the sensors to make it run more lean? Or should I adjust the timing differently? I've had suggestions from none rover people to install an adjustable fuel regulator and manually turn it down. Not sure that would really work though. Assuming the O2 sensors are working Would the ECU not compensate for it and just turn the fuel up?

Is it possible to run one of the tune resistors on a NAS 14CUX system so it would not look at the O2 sensors?

Any suggestions?

 

[fishEH]

Might it be that you have no cats?

 

[robertf]

Fuel pressure should be 35-cylinder gauge pressure. Your 5 psi increase works out to about a 5% bigger equivalent injector. The o2 will correct for this in all cases except power enrich so it's like having a carburetor wth an accelerator pump 5% too big

That 6 degrees of timing might be what the sticker says, but they run better at 10.

I'd also go back to the 190 thermostat. They run richer when cold and I think 180 still blends in a small portion of the cold enrichment over fueling

 

[robertf]

Oh and that hesitation below 1000 could be ignition misfire.

 

[Buddy]

Might it be that you have no cats?

Could be but these trucks run all over the rest of the world w/o them and since there are no post cat O2 sensors the system would not really know. So it's possible it just needs to be tuned correctly.

 

[Buddy]

Thanks Robert,

Fuel pressure should be 35-cylinder gauge pressure. Your 5 psi increase works out to about a 5% bigger equivalent injector. The o2 will correct for this in all cases except power enrich so it's like having a carburetor wth an accelerator pump 5% too big

If spec is 35 psi it's actually running 1-4 psi below spec. It's only 40 if I disconnect the vacuum from the regulator. With everything hooked up it idles around 32 psi. When I hit the gas it drops to around 30 for a second and then comes back up to 32-33 range.

That 6 degrees of timing might be what the sticker says, but they run better at 10.

I'll have to give this a try and see how it works.

I'd also go back to the 190 thermostat. They run richer when cold and I think 180 still blends in a small portion of the cold enrichment over fueling

I've been leaning towards this. I'll have to see how things work when I get the electric fan hooked up. It's got a 195/185 switch so as long as I'm not running down the road (Which rarely happens) it will hopefully keep it around 195. When I installed the 180 I never thought the radiator would work as well as it does. But if the fan does not cure it I probably switch to a higher thermostat.

 

[Buddy]

Oh and that hesitation below 1000 could be ignition misfire.

True, could be the Pertronix ignition. I know some people have had issue with it.

 

[kk88rrc]

I agree with robert about both the t-stat & timing.

You could add in a tune resistor to get the proper non-cat map. From RPI.... "A Green tune resistor (green referring to the color of the wires) will always give a non-cat tune, and White is always a cat tune. By the way, the default (Limp Home) tune is a cat map, so this usually makes a non-cat car run very rich."
http://www.v8engines.com/carbs-2.htm#Tune-resistor

You could also try one of 92rrrandall's chips but you probably have to change / add a tune resistor also.
http://www.ebay.com/itm/Discovery-D...ash=item2ec8faa2f2:g:VaUAAOSw-zxWn-TG&vxp=mtr

 

[Buddy]

I agree with robert about both the t-stat & timing.

You could add in a tune resistor to get the proper non-cat map. From RPI.... "A Green tune resistor (green referring to the color of the wires) will always give a non-cat tune, and White is always a cat tune. By the way, the default (Limp Home) tune is a cat map, so this usually makes a non-cat car run very rich."
http://www.v8engines.com/carbs-2.htm#Tune-resistor

You could also try one of 92rrrandall's chips but you probably have to change / add a tune resistor also.
http://www.ebay.com/itm/Discovery-D...ash=item2ec8faa2f2:g:VaUAAOSw-zxWn-TG&vxp=mtr

So does this mean the tune resistor will still work in later NAS trucks? I've read in a few places that all non-cat tunes are disabled on NAS trucks.

 

[robertf]

Let me try to rephrase that injector pressure info

The vacuum ref hose measures pressure on one side of the injector and adjust so it's always 2.5 ATM higher on the other side. If you don't have a vacuum gauge hooked up while reading the fuel pressure on a running engine then the observed number is meaningless. If you turn then engine off you can assume manifold pressure is at atmospheric. So that's 0 psi. 0+2.5bar is 36 psi. That's the highest it should ever read


But now I'm thinking all the fueling problems are minor and you've got a bad ignition problem.

I've ran every type of ignition I could find except pertronix. Lots of junk out there. The oreillys rebuild hei for a 76 Buick century has been the best. Not much of a contest, but some hacking to make it fit.

 

[robertf]

And you can add a tune resistor to the harness. It won't do anything with the factory EPROM, that will have to be modified or replaced with one that allows tune resistors.

Right now I think tune resistor would be a bandaid masking some other problem

 

[rover4x4]

Yes you can add the tune resistor to a NAS harness. These trucks are whack. I could run a lawn mower off the fumes from my Classic, the 95 with no cats is as clean running as my 90. I've given up on my RRC, hopefully hipsters will take a liking to these trucks in the next few years.

 

[kk88rrc]

So does this mean the tune resistor will still work in later NAS trucks? I've read in a few places that all non-cat tunes are disabled on NAS trucks.

I thought they only removed the tune resistor but kept all the maps on the chip.

Might be worth putting a meter on both the coolant & fuel temp sensors to make sure they are in spec.

 

[robertf]

On the 3.9 chips all the maps are there. The 4.2 chip looks like it's missing a few
It doesn't matter though, because the bit that allows using other fuel maps is turned off so it won't do anything with or without a tune resistor when using an unmodified NAS chip.

Download tuner pro and the 14cux definition and you can see what settings are out there

 

[kk88rrc]

Was the change in the ECU or are the fuel maps locked out in the chip?

I've looked at a lot of the 14cux talk over on Pistonheads and it makes my brain hurt!

 

[robertf]

It's all in the chip.

 

[kk88rrc]

That's odd that they would include the maps but not make them accessible.

If you haven't seen the thread that makes my brain hurt here it is... https://www.pistonheads.com/gassing/topic.asp?t=1325176 All 61 pages!

 

[Buddy]

I've looked at a lot of the 14cux talk over on Pistonheads and it makes my brain hurt!

That's how I feel about it. I'm not a mechanic or an Engineer and I'd say engine work is probably my least favorite. I'd much rather work on suspension or drive line issues.

I'm really considering just ditching the whole 14CUX system and just going with a FITech setup. Of course if my issue is ignition related that probably won't fix it either.

I guess my next step will be trying to hook up an HEI distributor and see if that makes a difference. It's still a worthwhile upgrade regardless of the type of injection system I use.

 

[Buddy]

Let me try to rephrase that injector pressure info

The vacuum ref hose measures pressure on one side of the injector and adjust so it's always 2.5 ATM higher on the other side. If you don't have a vacuum gauge hooked up while reading the fuel pressure on a running engine then the observed number is meaningless. If you turn then engine off you can assume manifold pressure is at atmospheric. So that's 0 psi. 0+2.5bar is 36 psi. That's the highest it should ever read

Thanks that actually explains it well. I get what you're saying now. I always assumed from reading other posts that it was just a fixed value.

 

[kk88rrc]

I guess my next step will be trying to hook up an HEI distributor and see if that makes a difference. It's still a worthwhile upgrade regardless of the type of injection system I use.

Start cheap..... 190? t-stat & bump the timing up. Maybe even drop the MAF trim to 1.0 (RPI recommends 1.0-1.5). Do one thing at a time so you know what did what.