4.7 stroker built and installed in 99 WJ

[superstingray77]

built my 4.7 stroker for 99 WJ, installed properly broken in comp cam, ported head, big valves, new #24 injectors, headers, forged pistons, ARP fully balanced etc. Starts and runs good only been around the block thus far, one concern I have is it stalls on initial tip in of the throttle then jumps and pulls. Granted motor isn't close to broken in only about an hour run time and 25mins of that was cam break-in w joe gibbs oil and additives etc. Was thinking of using a split second piggyback, any thoughts? I set cam sensor in with locked in correct position @ # 1 tdc and allen key lining it up. Have not put it on something to read the cam sync yet. No codes on scanner. Wonder if comp cam will require altered cam timing sync? 9.2 compression. Haven't run it up to station for some 93 octane yet.

[superstingray77]

More data,
ST fuel trims at idle are 3.1-3.9
Idle MAP is 14.2 hg
Closed Loop @ 192 Coolant with IAT of 154

Can someone smarter than me explain the difference between the following...

ST FTRM11 and STFTRM1 ? i know they are short term fuel trim but why are there 2 different readings for each bank? AKA
ST FTRM1
ST FTRM11
ST FTRM2
ST FTRM21

The FTRM 11 and 21 are reading -50 to -90 % where the FTRM1/FTRM2 are anyplace between -3+3 %
O2 voltages are fluctuating from .140 at idle to 1.020 at throttle up, seemlingly cycling around the .470 range but perhaps a bit weak due to age. ( have 138k on them and need to replace them)

[SilverXJ]

I would look at the TPS for the problem. I am unsure on the fuel trims. Usually you will have "short term fuel trim bank 1, sensor 1", "short term fuel trim bank 1, sensor 2", "short term fuel trim bank 2, sensor 1", "short term fuel trim bank 2, sensor 2". The 11 and 21 could be the down stream sensors, sensors #2.

I would recommend the AEM FIC over the Split Second.

[superstingray77]

Thanks for the info much appreciated, I noticed my throttle % is 19.2 at idle. Isnt that kinda high? TPS is relatively new. Is there a specific voltage it should read at idle?
Oh one more thing, the stumble dissapears completely if i "create a vacuum leak" by pulling a hose off the intake manifold below the throttle body. (like the Fuel Vapor Line). granted the leak causes a slight rise in idle speed and the idle fluctuates as the PCM tries to hold it steady, but the stumble is gone and throttle response is much much more snappy overall.

[superstingray77]

tps tested solid. 1.0v at idle and smooth transition to WOT. I built a map adjuster which didn't change the off idle stumble regardlessof voltage from 3.5 to 6.0v. Based on my plug read its running wayyyy lean.

[racing89]

ANY vacuum leak will cause map to richen fuel mixture , which evidently eliminates your stumble. Are you getting proper vacuum to map?

[SilverXJ]

I am sure you checked this already but make sure that the 90* elbow from the MAP sensor to the throttle body is in good condition.

The TPS should be about .7v with the throttle closed. Fully open should be close to 4v. I would check its operation with an analog meter and watch for jumps or anything erratic.

Your plugs may look lean because the PCM wants 14.7:1 AFR in closed loop.

Did you ever figure out what your long term and short term fuel trims are? When you have the problem, what is the reading from the O2 sensor showing? Cycling, or a flat voltage?

[superstingray77]

MAP is clean, elbow is good and getting solid vac signal. I can watch it change from 8.4hg to 11-12hg when i remove the vac line.
I built a homebrew MAP adjuster last night and cranked the MAP voltage up from the stock 5.2 to 6.0 which sets the hg to the same as when the vac line is disconnected. (11.4-12.3) range and the engine still stumbles stalls out.
TPS Showed clear without any erratic (bumps) in transition.
Fuel pressure dead on 51 psi / load or not

I think the IAC might be sticking? ill check it again tonight.

I did learn that my expectations of the downstream 02 sensors was incorrect, i thought they were only there to measure catalyst efficiency of the mini-cats on the Ypipe. When i installed the headers one of the convertors was plugged up from the old engine and all the crap in it was loose and "fell out" so we cleaned out both of them leaving only the main convertor in place. I have the spark plug non fouler trick applied to the downstream sensors. My thoughts are now that they are calling for a lean out.
STFT on the upper 02 sensors fluctuates between -3 to +3 sometimes jumping to 8%
LTFT stays near zero occasionally while driving it pulled -.8 on the rear bank.
STFT on the downstream 02 sensors is jumping to a whopping -50 to -90 though... which might explain the PCM pulling out fuel.

Plan for tonight is to remove the non-foulers

voltage for the primary (upper 02's) is .120mv
voltage for the secondary 02 (lower post precat) is .780-.820mv

My plan was to have my local exhaust shop weld a new dual 2.5" Y pipe up with 2 new high flow cats (providing there is enough room for them) with a 3" pipe from the Y to the primary cat, then use a high flow cat there with a Dynomax muffler and 3" out the back.
Keep in mind the plan is to break this combo in and then add the turbocharger setup.

All the legal BS aside I live in Texas and dont need the CA emissions, all the other Jeeps here dont have the front cats just the one big main one under the truck. Id prefer to leave them out as they create a MONSTER amount of heat right under the intake manifold and in the engine bay. My 2000 WJ 4.0 got 19-22mpg this one never got over 15.3 same truck just with CA emissions and owned it since new. I always attributed the sluggish feeling and the poor mileage to the choked up exhaust and PCM calibration, the 2k model would just pull away from this one with ease, same rear gears tires and all. (owned both at same time) .

[SilverXJ]

Just because there is a fuel trim value for the down stream O2 sensors doesn't mean they contribute to the fueling calculations. Some makes they do, some don't. However, it is minimal. Unplug your down stream O2 sensors and see what happens. You may need to reset the PCM so their fuel trim is back to 0.

I try to stay legal, but sometimes you have to bend the laws a bit. When I got rid of my 0331 head there was no reinforced 0331 head and no aftermarket header for it. The aftermarket 00+ cali package header is said to cover the 0630 head exhaust ports. I was sure as hell not going to put in another 0331 head. I went with the 0630 and a Throrley header with two bungs welded in for the two upstream sensors. The down stream sensors have been simmed out. I still have the main cat though.

I have Casper sims and they are no longer available. Its a shame because they were plug and play and work well. http://www.epa.gov/compliance/resources ... -fcsht.pdf. There are a few companies that make other sims. Google should turn up a bunch of results. There is also this: http://www.bigdaddiesgarage.com/mini-cat-cel-fix.html. The other option it to have the PCM reprogrammed to ignore the down stream O2 sensors.

[superstingray77]

Appreciate the responses.
I think I will build a couple 02 sims ( not hard to build using the 555 chip) The issue here is the California emissions on this truck does actually use the downstream 02's in fact they are considered the "masters". An engineer on another forum sent me the pages out of the factory service manual explaining how the CA emissions for LEV work. Vastly different than I expected. Traditionally the downstreams are just there to monitor catalyst efficiency but do not play an active role in fuel tables. In the LEV/CA setup with 4 02 sensors the upstreams sensor 11 and 21 are the first to process the mix, then the 2nd set of sensors provide feedback to the PCM and the PCM will adjust the STFT on the 11/21 upstreams until the STFT on the 12/22 downstreams are satisfied. Long term fuel trim is modified after this process takes place and meets a threshold that requires LTFT to be adjusted. I ran the spark plug non fouler trick and the truck pulled -50/-90% STFT on the downstream sensors which triggered a -10-20% STFT on the primary and resulted in a MEGA LEAN condition. I removed those non foulers and put the downstreams back in normal mode and mixtures normalized and stumble cleared up instantly. Drove it to work today for its first drive out of the neighborhood. Super awesome TQ hardly have to give it gas to merge at 70-80 on freeway. I ran about 22 mile drive to the office and averaged 26.2mpg on the hwy doing speeds between 50-80 and that includes merging, exiting, stop lights etc but mostly hwy. It no longer has to downshift on grades to keep speed at 60-70 and merging is now effortless and does not require long range planning.

[SilverXJ]

Can you provide the parts of the FSM you saw? I have never seen anything regarding that in any Jeep FSM (XJ nor WJ).

[superstingray77]

one of the guys posted for me jeepforum...

http://i642.photobucket.com/albums/uu14 ... ensors.jpg.

[SilverXJ]

I see nothing in that FSM page to indicate that the downstream O2 sensors play a major part in air fuel ratio contribution. It is nearly identical to what is printed in the 2000 XJ FSM. Teh condition you have experienced could have been the PCM attempting to check the catalyst efficiency by changing fuel trims and seeing the response from the down stream O2 sensors.

Reading the downstream O2 sensors to majorly control the AFR would be a big mistake. Reaction time on the rear O2 sensor will be slowed due to the cat convertor. Also, the down stream O2 sensor would read much different from the upstream at most conditions. For example, hold the engine at 2000 RPM and the PCM will keep a 14.7:1 AFR. The upstream O2 sensor voltage will be fluctuating, which indicated 14.7:1. At the same time the rear O2 sensor will be holding a steady voltage (can't remember if ~.04 v or ~.4), indicating lean. You can see this on an oscilloscope hooked to the front and rear sensors. Going off the basis that the PCM will use the rears as a primary source then the PCM should be trying to get back to the 14.7:1 on the rears. Especially since the stock narrow band sensors are only good at showing 3 things: stoich (14.7:1), lean or rich. No points in between.

I wish I had that article from an industry tech magazine that stated how much of a roll the rear O2 sensor played in determining fuel trim. I do know that the most was 10% and it might have been GM.

[superstingray77]

See thats exactly what I always believed as well hence why i built the eliminators. I am going to build some SIMS using a 555 timing chip and call it done with the rear ones. I figured the dual cat header would flow better than the single outlet header on the non CA emission models, hence the use of the dual exit header with (special mini cats) With this design the 2 headers that are essentially separate headers on one flange like the BMW uses. The plan is to cut carefully at the Y pipe right where they join and have a 3" system welded in from there, also fabbing a turn to go to the turbocharger on the passenger side. I dont have the turbo installed as of yet, but likely in a few months ill get around to it, figured wouldnt hurt to let engine break in, finish the lift, get the AEM wired in and fully understand the tuning params before i go force inducted and blow up something