4.7 Stroker Issues

[uscav_Scout]

I have searched high and low for advice in regards to my situation, and really haven't found any real concrete answers. I am going to fully document my build once I get this thing running perfectly, I think I got a good recipe and think the stroker community would really benefit from getting to read some original stuff all in one place (One of my biggest sources of aggravation when planning this build was how much information was either based upon unfounded theories, or regurgitated information)

I started planning this build before I even bought a jeep. I was in Afghanistan for the better part of a year and needed something to occupy myself with, that being a stroker. I read almost every post I could find on stroker builds, starting from those recipes that have been passed around the net a million times. Combined that with several PMs from several guys that have done some pretty amazing stuff with the I6, and read two solid books on four stroke tuning, and high performance engine design (The books never mentioned the I6 directly, but it was a great way for me to learn the theory behind engine performance, etc).

I am including the above as a quasi disclaimer, so you guys know that I didn't haphazardly whip this motor together.

Some basic info on my build.

Vehicle: 98 Wrangler, 4.0 manual, 112K miles good shape

Everything was fluxed and double checked by the machine shop, real good guys, more on them in my build thread.
Block was out of a 88 Cherokee, had about 200K miles when it was pulled running, for a V8 swap ($50 off ebay) Not alot of block issues in terms of it being so old, bolted right up for the most part
Alabama Cylinder Head, with hescco performance valves and springs, whopping 62.5cc chambers with spark plug (Part of the reason the block got decked), a performance valve job was done, and the valve seats were cut to bring spring pressures down
Comp Cams 68-235-4 Xtreme 4x4™, X4254H, nice overlap lowered my DCR, Comp Cam lifters, stock push rods and rockers
4.2 Crank, Stock 4.0 rods (out of the 88), kb944s
Block decked to zero, quench was .043 with head gasket
I don't have exact numbers for DCR and SCR (Will do a calc again once I do a proper write up) DCR was prolly around 8.8/8.9, SCR mid 9 to high 9s
26lb Accel Fuel injectors, 01 Manifold w/ 4.7 dodge t-body, I cut a six by six square out of it, had a aluminum plate welded in place(which I painstakingly cut the tbody hole out by hand, made a gasket, mounted map sensor directly behind t-body on plate
Gale banks Header, gibson cat back, hesco high flow water pump, stock thermostat

So I finally get the thing started, really high idle, somewhere around 2K, sounds like it was misfiring a little bit, but its happened maybe once every 20 seconds, very light miss, so I continue with initial cam break in. Idle settles around 1400, shut her down changed oil.

Start it up the next day, take it out for a spin, more sluggish than original 4.0, dies on me a few times, bring her home a little disappointed. Started conferring with the fellow gear heads in the family, my gramps is old school and tells me it is the timing and that we need to loosen the distributor and adjust it a few degrees. Show him the FSM and and he backs down. We pull the plugs and re index the dizzy just to be safe. Some of the plugs were way out of spec, one was around .060... (younger brother gapped those for me..... yeah) brought them all back to stock, put them back in. Crossed my fingers and she starts up, no longer missing, still idling high around 2k, no MIL.

Take her out for a gentle spin that night a good hour or two, mixed between highway and side streets. MIL is on now, figure the PCM is just a little freaked by the 4.7. Get some food, start it back up, no MIL still high idle, but is running like a champ, never went over 50% of WOT, but shit, she pulls and purrs like she should. Still got weird looks at the light because the idle is so high but who cares she is running decent.

Long drive to school about 150 miles, varied speed, was pretty gentle (compared to my 90mph dashes back and forth from school I normally do), at one point got stuck in a tight spot between a semi and a large moving van, give it some gas and she is pulling fine, hits 3K and I wouldn't call it a stumble, its like the PCM had a governor on it and cut the motor out for maybe one or two revolutions of the motor (I experienced the same thing in a Dodge Dakota when I tried to take it up 100mph, the governor cuts in around 98 . MIL is on again, but she is trying to idle around 700-1000, died the first few time she tried but she is getting the hang of it. If I feather the throttle off idle she dies 50% of the time if I dont get back on the gas pedal. Really weirded out by the "stumble" happens randomly when the motor is under load and throttle is more than 20%. Its not a ping or pre-det, like a hesitation almost. Take it real easy the rest of the way back. You guys should here the idle now, fucking sexy.

Took it to Autozone to get the codes read, three are pulled: P0113, P0121, P1391.... Bust out my DC Powertrain Diagnostic Procedures for the wrangler

P0113 - Intake air temp sensor voltage too high
Cause: When the IAT sensor goes above 4.9v
Thoughts: I had to extend the wires from wiring harness to get it to reach. I think this is the IAT off of the junkyard intake manifold I bought

P0121 - TP sensor voltage does not agree with MAP sensor
Cause: The PCM performs two tests. When the manifold vacuum is low, the TPS signal should be high. When the manifold vacuum is high, the TPS should be low.
Thoughts: The TPS is an original off of the 4.7 junkyard t-body, maybe at fault? The manual also speaks of the MAP sensor having issues in this section we will see, This code seems to explain poor idle

P1391 - Intermittent loss of Cam pos sensor, or crank pos sensor
Cause: when failure counter reaches 20 for 2 consecutive trips
Thoughts: I feel that this explains the cut out at higher revs. To be honest when we were putting the motor in we had a hell of a time fighting with this thing, I noticed that the Crank sensor was getting smashed into the firewall.... Never thought twice about it because she was running strong that night I took her out, despite the high idle.

Things I am considering at this point.
Tomorrow I am going to test the sensors as best as I can individually as per the FSM, and then going to try and follow the Powertrain manual as best I can sans the DRBIII, I think I can pull off most of the tests with a multimeter and a little ingenuity. If i find failing sensors (FSM tests are pretty straight forward, replace them)
If no luck here swap out TPS with known working one.
Test for vac leaks too.
If that fails going to take her to the dealer, and have those boys square her away.
If that doesn't work, going to try building an adjustable MAP, and pray

Any thoughts or comments would be greatly appreciated. The motor is good, it just some sensor issue. I am posting all of this to help my fellow jeepers out there, so we can debug this together I am not just doing this for me, but for the next guy that is in this situation. Thats why I am being ridiculously thorough.

Thanks in advance.
Mike

[4.whoa]

You said a few times that you used several of the jy sensors. If the donor was a 88-renix and the jeep is 98- obdii that's probibally it. They don't all mix. I put a renix flywheel on a obdi ( in a hurry) and had all kinds of codes.I don't know about the 4.7 dodge stuff. I'd start with that n go for a ride Good luck

[uscav_Scout]

I can't believe I am still up, my sleep schedule is all screwed up from school. Thanks for the reply, but I am going to clarify a few things.

The YJ sensors do no plug into the TJ harness at all. I left the coolant temp sensor in the thermostat housing (off the YJ), and the plug was similar but there was no way it was going to plug n'play. I used the flywheel off of my TJ, pretty much used as much of the TJ material as possible (engine mounts, accessory brackets, I even had to steal the oil filter fitting from the TJ, because the YJ had some weird elbow device on the oil filter, I assumed I wouldn't be able to get gaskets for and the last thing I need is a bad oil leak with a HV oil pump)

When I say I used old sensors or sensors from junkyard parts, that means they either came off of the dakota throttle body, or the 99+intake manifold. I only point this out because when I was trying to get the manifold squared away I was going to use the fuel rail I got off of the 99+ manifold, but to my dismay once I got the injectors off, I lightly tapped the fuel rail on the work bench and a slew of rust fell out. Thus I used the fuel rail off of my TJ. I must have been lucky, but everything bolted up, the PS pump, the fuel rail, if it weren't for the big throttle body, it would almost look like it belonged there.

I have two sets of sensors from two dakota tbodys (Lets just say the first one didn't make it through engineering), and I also have a set of sensors from the 99+ manifold and its throttle body, plus all of the sensors off of my TJ motor. I know those work, so I am probably going to swap those in tomorrow. If I remember correctly I put the TJ map sensor on the stroker though.

Thanks for the input.

[lafrad]

The cam you chose is a pretty serious cam... The increased duration and overlap will decrease idle quality, and shift the torque and HP peaks up in the rpm range (significantly less torque and HP right off idle and below 2000 rpm or so). Also, due to that fact, it will also require LESS fuel in most daily driving positions, and MORE at high rpm WOT...

I would suspect that some of the "fun" you are having is due to being really REALLY rich at idle and around town, with an overall low vacuum situation.


The "TB" vs "MAP" value may also be part of it, but I would suspect that it may be a little more simple: is the map sensor hooked up backwards for the jeep application? I would check that the Voltage on the new TB has similar voltage levels at Idle, mid, and WOT as the old jeep TB does.

[gradon]

I had a 1391 when my distributor wasn't indexed correctly(which becomes a miss at higher rpms when fuel timing is more crucial). Read the article.pdf in bratcop's project build if you haven't already. I was fooling around last week with rc12s and the bluetops(I had been running rc9s and LT1s). I had to go back to the rc9s due to the rc12s causing pinging, so I'd recommend a colder range plug. If you have a high overlap cam and a big combustion chamber, your DCR should be below 8(8.5 is the max recommended for pump gas). The reason why plugs make all the difference in mine is because I'm running 10:1 scr and 8.57:1 DCR.

[uscav_Scout]

So its about 4am and I am working on my homework I just had a remarkable realization about my jeep . I tested the IAT today and it came up clean, I didn't test the MAP or TPS because I didn't want to needle the wires to get a signal, and didn't have any little alligator jumpers for the signal wires.

Then I remembered something very critical, when I brought my jeep back from the first test drive, when it was missing, I was frustrated, kind of cocky (blame this on the army) and wanted to see if one of the sensors was puking up bad data. So I disconnected the IAT.... being disconnected there was no sensor, no sensor means no resistance, no resistance means that the input voltage = the output voltage = 5V!!!! 5V>4.9V therefore this would explain the P0113 code.

After removing the IAT and not seeing any improvement in my missing idle, I got even bolder and and unplugged the MAP sensor, she continued running fine for about 4 seconds, then died. Is it a weird coincidence that the P0121 code is set after 4 seconds, nope. If there was an issue with the map or TPS sensor values they would have thrown their own codes. Thus I think that I can assume that the map and tps are good.

Now you maybe wondering, if the MIL went off after this and then came back on, then why the hell is it still throwing these codes......

"* 40 Warm up cycles are required to erase DTCs after the MIL has been extinguished" as per the PDP manual.

Thus the IAT and MAP DTCs would still be in memory, because there was never anything close 40 code free warm up cycles.

So now my next course of action is head to autozone, get all the codes reset, drive her around wait for the MIL to come back on, take her back there, and verify that it is the cam and crank sensors, still throwing codes. Then I am going to do something crazy and probably just replace the crank sensor, get it cleared again, and see if it runs better. (I spoke to the dealer's shop foreman, 92 dollars an hour labor, fuck that).

Thanks for the replies, wish me lucky guys, hopefully I can fix this thing, and work on my build thread.

[Cheromaniac]

I think you need to:

1. Replace the junkyard IAT sensor with a new one.
2. Replace the Dodge TPS with an original one for an OBD II Jeep 4.0L TB.
3. Check the CPS and MAP sensors. I suspect the former may be lightly damaged and the latter is probably good.
4. Check the indexing of the distributor.

[uscav_Scout]

So I solved my problem and feel quite foolish about what caused it. The distributor was indexed correctly, despite me not having a timing mark on my harmonic balancer. The CPS and Cam sensors were in sync (I borrowed one of my departments O-scopes) The IAT was good, verified that with the multimeter. So that left the TPS and the MAP sensor. Map checked out, and the TPS seemed to be working (the resistance varied from idle to WOT like it should. But it really wasn't. This is where I got stumped.

Then reading over the manual once more I realized my mistake. The TPS values were backwards, high when they should be low and low when they should be high. I was using the TPS from the dodge throttle body. Same connector, different pinout, different function. So basically when my motor was at idle, it thought the throttle was at WOT, and when at WOT, it thought the the throttle was closed. This was throwing off the whole system. It was adjusting the fuel timing to the point that my idle vacuum pressure was around 7hg, now it is at 18hg.

So i took it to the dealer, had them clear the codes and the adaptive memory for a case of bud light that I have to deliver on Friday Idle is where it should be 800-900 rpm, it no longer dies if I feather the throttle at idle, it is no longer cutting out, has more power and uses less gas. The top end power from that high overlap cam is just stupid, if I stomp on it over 3K rpm while in first or second the wheels brake loose. I buried it in four gear, and it was still pulling strong after I buried the speedo and my gps said I was going 130

Thanks for all of the input. I appreciate it.

LESSON LEARNED:
Dodge tps does not equal jeep tps even if the connectors are the same.

Time to go work on my build thread.

[Cheromaniac]

I think you need to:

1. Replace the junkyard IAT sensor with a new one.
2. Replace the Dodge TPS with an original one for an OBD II Jeep 4.0L TB.
3. Check the CPS and MAP sensors. I suspect the former may be lightly damaged and the latter is probably good.
4. Check the indexing of the distributor.

Glad to see at least one of my suggestions (no.2) worked out 4U.

[uscav_Scout]

Me too, its too bad I am ridiculously stubborn and wanted to know why. I am just glad the shop foreman over at the dealer took my bet over the sensor issue, its just to bad I lost, but at least I got the memory cleared and got to save my radio presets

[Don H Jr]

CAV Scout:
Does this stroker live?

Don Jr.
SFC USArmy Ret. 2002

[Don H Jr]

Good for you finding the issue. I was about to write to you and suggest same thing. It might not have anything to do with anything, but I know the Renix TPS reads exactly backwards when testing from my OBD1 in my 94' Cherokee. You have so many different parts I lost track of which was from which. Now you have a 4.7 TB on a 4.7 stroker, sounds workable.

Don H. Jr. :cheers: