Jeep Strokers

2004 Jeep Wrangler Unlimited. Purchased with the Golens 4.6L Stroker already installed. Chokes out briefly on acceleration (if stomp on it) from a dead stand still. No issue if I ease into it or I am moving and stomp on it. Previous owner replaced plugs, coil, o2 sensors and fuel pump assembly. It does not run rough and no check engine lights are on.

Thanks in advance for any help!

Nick

How many miles on the new engine? It takes several thermal cycles for the PCM to adapt to changes. When you stab the throttle, you dip into open loop. If the LTFT% hasn't settled in yet, you are getting a lean condition.

The Fuel Delivery strategy Chrysler used was all math -- no Look-Up Tables. Your fuel trims (LTFT% and STFT%) are used in the calculations for Injector Pulse Width (IPW). In Closed Loop, the STFT% and O2 readings keep the AFR where they should be. In Open Loop, it ignores O2 and STFT%. If you have a Scan Tool capable of viewing Data Stream information, drive it and monitor your LTFT% and STFT% values. They ARE stored in an X-Y Look-Up Table, so will change as load & RPM change. If you are still getting > +/-10% on your STFT%, it could still be adapting.

Thanks Mike. It has about 12,000 miles on it. I do not have a scan tool. Do you have any recommendations on a decent scan tool that will perform this function. Also, it only cuts out for maybe a quarter of a second. I had JSCAN for my Jeep JK but they do not offer anything prior to 2007. Thanks for the info!

Check Amazon. There are inexpensive systems where they supply a dongle and an app for your phone. A friend of mine has one and really likes it. Personally I have an expensive professional unit.

Img 3823 was driving around the neighborhood.

ntucker782 wrote: ↑May 14th, 2026, 5:22 am Thanks Mike. It has about 12,000 miles on it. I do not have a scan tool. Do you have any recommendations on a decent scan tool that will perform this function. Also, it only cuts out for maybe a quarter of a second. I had JSCAN for my Jeep JK but they do not offer anything prior to 2007. Thanks for the info!

Golen includes 24lb/hr injectors sized for their package with 4.0s. However the 05/06 TJs run a higher fuel pressure which would result in more fuel. Chrysler does not use LTFT to modify the open loop behaivior. They are unusual in that.

I would strongly recommend an HPTuners MPVI3 if you can find one. They updated to the MPVI4 last year and so far say it can't support TJs. Not only will it allow you to scan, but you can modify the programming to correct the tables (or pay someone for a tune). However, you'll get no useful data about fuel ratio unless it is indeed lean. The stock narrowband O2 sensors will usually peg at max voltage immediately, but could go the other way if lean. You need a wideband O2 sensor to tune fuel.

I have tuned my dad's 06 LJR with the same NGC3 PCM you have. But he has a stock 4.0.

BTW, the LTFT below -10% suggests you are running considerably rich which is being adjusted out in closed loop.

This corresponds to my suggestion that perhaps the injectors Golen supplied did not plan for the higher fuel pressure of on 05/06.

I haven't spent enough time data logging my dad's to know exactly what the open loop strategy is on those. On my 04 with a JTEC+ PCM, it was almost 12 seconds of wide open throttle before it would go into open loop and power enrichment. I can check the file for my dad's to she what I did.

But it may need some timing adjustment as well.

Thanks for the response Gorilla. Is there a specific injector that I should consider in this situation? I reached out to the fuy who had the engine installed and he said they put in new injectors but was unsure of the size. I know Golen says 24lb but wasn’t sure if I should change them to be sure. They also said the stock fuel pump would suffice. I will check out the hptuners. I went to them first but couldn’t find anything so thanks for letting me know which model to get.

This is probably as close as you can get to an optimal injector, but some tuning would . There might be a stock injector for the standard 43.5psi fuel pressure that might work. Something in the 20.5 pph - 21pph (or lbs per hour) range in 60mm length USCAR spec.

This is a screenshot of HPTuners VCM Editor from my 04 TJ which is a bolt-on modified 4.0L at this point, so exactly relevant for you.


There is something relatively similar in the NGC3 setup. Basically, you would need to reduce these injector pulsewidths by enough in the basemap so that the LTFT built closer to 0%. You could multiple by 0.90, drive for an hour in mixed conditions and check the results.



HP Tuner VCM editor logs are much more thorough.
Note: I have installed a PLX wideband O2 sensor and feed it into the logs via the HPTuners Prolink

Note, the structure for the 05/06 PCMs is significantly different. Fueling is largely made off volumetric efficiency calculations. I just don't have screenshots online for them.

Thanks for all of the insight, Gorrilla! I have never tuned anything like this so it seems a little over my head. I did find an HPTuners MPVI3 on marketplace but it is out of state. There is a shop here that is known as the place to take your Jeep and he said he could get it running correctly. My biggest concern is that once a tune is installed, will I be able to add a flash paq or something similar to change tire size and gear ratios when that time comes.

How far are you from Mississippi? lol I could just pay you to tune it for me!

Somehow I confused myself that you had an 05/06. The fuel pressure on 04 Wranglers is supposed to be 49.5psi. But Chrysler does weird mid-year stuff, so perhaps the LJs got the higher fuel pressure regulator used in all the 05-06 Wranglers. Annoyingly, they don't provision the Schrader valve for checking it, but Racetronix does make an adapter to put a fuel pressure gauge inline with the fuel line, or you can use a Fuel rail by NRT motorsports and a 90 degree adapter. I've setup an NRT rail to attach use a Honeywell 0-100 psig sensor which I'll be wiring into my HPTuners prolink to monitor fuel pressure.

Speed sensor
For the 97-04 Wranglers, you cannot use programming to change the speed signal. I'm pretty sure it doesn't work with the 05/06 Wranglers either. The easiest way is the Speedohealer and it's the only way with Rubicons with the 241 transfer case. With your Unlimited, you should be able to use a speedometer drive gear to modify the speed signal.

Tuning;
Basically you download the whole stock tune from your vehicle and then make 3 copies. Lock one of them so it cannot be edited. Use one for comparison. And use the third to make your first tune.

The fuel tuning in this case on an 04 really wouldn't be too difficult. I'd probably start with selecting all the cells in the Fuel Base - EGR Off table and multiply the table by 0.90. When you write that file, it will reset the STFT and LTFT tables in the vehicle. Then go drive for 20 minutes to reset thhe LTFT tables.

Once you've got the LTFT reset, run the VCM Scanner software and go for a drive in mixed conditions, without using wide open throttle if possible for 15 or 20 minutes. Some neighborhood, some highway, etc... You'll get some new LTFT numbers in the table. You want them in the 0-3% range. Still too rich, multiply the table by .97 to shave a bit more off. Too lean - multiply the table by 1.03. Got some low or high spots? You can dial those a bit closer by selecting just the cells.

When you have the fuel setup better, then you can dial in the spark. Adding a few degrees in most areas works well on the stock 4.0L, but I'm not sure if the stroker will like that. I'm waiting on parts for my own, so haven't gotten there yet. I'm also going to run the Edelbrock Performer head, so that'll also have some of it's own preference.

Important note:
Because detonation is a major risk and the TJ has no knock sensors, you do not want to go into high load, low RPM lean conditions. Going wide open throttle is the only thing that triggers open loop in the 04 JTEC+ PCM that I've seen. If you've trimmed too far, open loop WILL go lean.

Make sure you try/do NOT go full throttle while checking these LTFTs on the road. The computer will compensate and automatically add fuel if you've trimmed too low in closed loop. You can read the LTFTs and adjust accordingly if they switch from negative (rich) to positive (lean). Goal is to be within +/- 2% in all cells, but it takes time before you get enough sample size in your data. With 20-40 minutes of mixed driving you'll have built enough sample data to get good directional indication.