98 XJ - Stroker won't run

[98XJEastTN]

Hello to those who have had success with converting a 4.0 to a 4.7. My son and I have been trying to get ours working for about 4 years now. We have had a few bumps in the road along the way, but overall, what we have done should be working and it simply is not. Maybe someone has been through this and can help or can advise us of who might be able to. Here's our sad story:

In 2011, I drove my 98 Jeep Cherokee to work on the coldest day of the winter and 20 minutes into the ride, the engine blew. My son and I decided hey, make it into a project we could work on for him to drive to school and go four-wheeling during High School. So, my son began to do research and compile a parts list from the stroker sites. (See all purchased below)

In 2012-13 We started ordering parts and found a local engine builder "Bob", with many wrinkles on his forehead, knowing he would do good work. "Bob" helped us work out all of the details, parts list, etc., and began to build our new stroker motor for us. He found that the head was cracked so he got another one for us for $125.

In late 2013, we got the motor back from Bob and were making plans to get it dropped into the Jeep. However, I was helping a friend put a roof on his daughter's new house and fell off the 30' roof, nearly dieing. I'm about recovered with only minor disabilities.

In 2014, we got the engine dropped into the Jeep. Everything got hooked back up and she fired up. She idled OK and we were able to complete the cam break-in, but she didn't drive well at all. Not wanting to cause damage to our costly investment, we began to turn our efforts toward finding a reputable mechanic who could help. By way of many people in our area, we were given a guys name who has been working as a mechanic in the area for 30 years, "Tom".

Late 2014, "Tom" began diagnosing it (mainly in his spare time to prevent having to charge us much) to figure out what can be done to get the Jeep running, however without success. Tom installed the Fuel/Air gauge. He replaced the TPS without any changes. He adjusted the new CPS and said there was only a slight improvement. The new, stock distributor was getting pushed up and eventually out so far that it sheered off. Tom ordered a new distributor and had a machine shop trim a bit off the shaft to prevent this from happening again. One of Tom's former workers "Larry" is now working for a local Jeep dealership and Tom knew Larry had built a TJ stroker previously and would be a good source for diagnosing our issue further. So Tom towed the Jeep to Larry. Larry made a custom clamp for the distributor to try and advance and retard it, which has not cleared up the issue.

Meanwhile, Tom called me and advised that we may have better success if we could tune the cam and crank shafts. He said he does this with Mack trucks all the time. He said I should contact Superchips and give them the details (as above) so they can recommend what product to purchase. Tom says we need to be able to adjust the Jeep from 500 to 5000 RPMs in different sequences. He says that while the Jeep may start up and run, when it gets to 2000RPMs there is an open hole and at 3200RPMs it will just fall on its nose.

I checked with "FlyinRyan" who seems to be the most respected tuner on the Jeep boards for the excellent work he does. He graciously took the time to read over my sad story and says a tune may be in order eventually, but at this stage, he feels like we have a fuel sync, cam timing or some other issue. He also says we need to use NGK BKR7E spark plugs only. (Comments?)

So, my son graduated High School last month. He has a job and starts college in the Fall. At 6'4" and 330# it would be great for him to get out of the 4 door Saturn he has endured getting in and out of for so long and finally get into the Jeep!!!

Needless to say, we have a ton of money in the Jeep motor, spare parts here and there, labor from Tom and Larry, plus towing costs, etc, etc, etc....I'm far beyond tapped out!!

Tom says back in the day he had a 2 barrel Ford carb that he could make work on many applications. He says we may need to begin to research the option of going to a carburetor, but looking into that so far has had many, many negative reviews.

Larry is currently looking into the option of replacing the flexplate in the hopes that this may allow the CPS to work correctly and clear up the issue we have been seeing.

I know there is a logical explanation out there, and I feel like between the two mechanics we have worked with to get help something will work out, but I also know there is strength in numbers and someone on here has had experience with the 98 Jeep Cherokee Sport Classic and modifying the 4.0 motor to a 4.7 we just might be able to figure this one out.

Thank you in advance for any and all advice you can spare.


Part Description
Upper Radiator Hose Ebay autoparts.titan1 - Gates 23283
Lower Raditator Hose Ebay wizardautoparts - Gates 21615
Thermostat Ebay 19dartswinger70 - Gates 33508
Motor Mounts Direct BrownDogIndustries - CU2572-DK2
Motor Mounts Hardware Direct BrownDogIndustries - OEM12-130-2 - Included w/above
Oversized Cooling Fan Ebay demotorperformance - 14" Qty 2
Cooling Fan Mounting Screws Lowes - 72942 - 50 count 1/4in 20 x 3/4
Cooling Fan Wiring Lowes - 87959 - 12-AWG Red Copper Wiring - 13ft Bulk sale
Cooling Fan Mounting Flat Bar Lowes - 72553 - 5ft x 1-3/8in Steel Slotted Flat Bar
Cooling Fan Relay and Thermostat kit Ebay demotorperformance - 180 to 200 F
Cooling Fan Toggle Switch Northern Tool - 96856
Cooling Fan Quick Splice Northern Tool - 96837
Driveshaft U Joint kit Ebay ventures_truck_parts - 4 x Spicer 1310 U Joints
Ujoint Replacement Strap kit Advance Auto Parts - 43710
Harmonic Balancer Ebay bigredautoparts - Powerbond - PB1439N
Idler Pulley Ebay mackman_173 - Gates - 38019
Serpentine Belt Ebay lulu_autoGates - K060950
Spark Plug wires Ebay autopartsexp - Bosch 09284
Water pump - stock Ebay autopartsexp - GMB - 110-1080
Engine to trans Star bolt replacements Napa - 301-630B Rockford Hex Head Bolts Qty 2
Spark Plugs RC12LYC (412) Champion - RC12LYC 412 - Gap .035 QTY 6
Cam bolt washer Engine Shop - Hesco - J3173284
Cam bolt,pin,&spring Engine Shop - Hesco - 83502890
Cam bearings Engine Shop - CLEVITE SH-549S
Camshaft Engine Shop - Melling - MC1376
Connecting rod bolts Engine Shop - ARP 146-6001 rod bolts
Crank - upgrade Engine Shop - Scat 258 9000 series 2" snout 3.895" stroke
Freeze plugs - stock Engine Shop - SLP-381-8084
Head - replacement Engine Shop - 98 Jeep Cherokee replacement
Lifters - stock Engine Shop - VL-39 Qty 12
Lower gasket set Engine Shop - Victor Reinz - CS5713X
Main Bearing set - stock Engine Shop - Clevite MS1947P
Oil Pump - stock Engine Shop - Melling - M81A
Pistons - upgrade Engine Shop - Keith Black Icon .030 over IC944KTM-030
Push Rods Engine Shop - Melling MPR-437
Timing Chain Set - upgrade Engine Shop - Cloyes double roller - CLO-9-3127
Upper gasket set Engine Shop - Victor Reinz - HS5713Z
Rod Bearings Engine Shop - CB460P Rod Bearings Qty 6
Rings Engine Shop - Piston Ring Set 2M667
Miscellaneous Bolt Replacements Lowes - 63322, 138277, 214413, 214477, 138144, 138085,
138182, 138115, 138109, 138077
Distributor Mechanic
Crank Position Sensor Ebay automartint914 - PC308 56027866AE
Power Steering Reservoir Tank Ebay tennesseeautosales - 603-902
Exhaust Header Ebay Rodpartsdealer
Exhaust Downpipe Ebay truckpartsnation - Walker 55277
Muffler Ebay rpd-inc - Flowmaster Super 44 2.25"
Exhaust Flex Tube Oreillys - 520008 2" Flex Tube
Exhaust Elbow Oreillys - 548705 Elbow
Exhaust Chrome Tip Oreillys - 583091 Chrome tip
Exhaust Joint Seal Oreillys - 10160 Joint Seal
Exhaust Clamps Oreillys - 517212 Clamp Qty 3
Exhaust Strap Kit Oreiilys - 10105 Strap kit Qty 2
Fuel Injectors XJWonders Cherokee Forum - Dodge Neon 703 24# spray
Fuel /Air gauge Ebay Lightningmotorsports - AEM 30-4110 DWB BOSCH 4.9LSU
Throttle Position Sensor Mechanic - Included with Distributor above
Engine break-in oil Jegs - Brad Penn - BPO-009-7120 QTY 6
Motor Oil x 12 quarts Napa - 205 - Valvoline VR1 10W30 - RACE10-30 Qty 6
NapaGold Oil Filter Napa - 1348 Napagold Oil Filter

[Cheromaniac]

From what I can tell from your parts list, it looks like you've built a 4.6L modified 'poor man's" stroker which is the simplest build. By all accounts, your parts combo should work including the stock Champion RC12LYC plugs (which I'm also using).
There's a possibility that the timing set has been installed incorrectly with the cam timing off by one tooth so you might want to have that checked out. Then when it's correct, you can index the distributor in the original stock location so that the injector firing pulses will be properly synched to the spark. The CPS should be installed in the stock location.

[98XJEastTN]

Hey Cheromaniac - thanks for the info. I have checked with Larry and he says he has removed the timing cover and confirmed that the timing set is installed correctly. Thanks for confirming the spark plugs are Ok to use as well.

[SilverXJ]

Have you checked the fuel pressure when the problem is happening?

What is the air fuel ratio when this is happening?

What is the compression like?

What is the preload on the lifters?

Exactly what was done with the CPS? It shouldn't need "adjusting." Also, a Mopar CPS may be the best way to go. I've heard of cases where the after market ones don't work well.

Any history on the flex plate? Like was it dented or dropped or anything?

Besides looking at the timing set the cam install should be checked via degreeing the camshaft. Especially in this case.

As Cheromaniac said, this should run fine on the stock computer. I would do with a different spark plug, but they aren't causing your problem.

No to the carb. It is not needed as the stock EFI should work fine.

[98XJEastTN]

Hey SilverXJ Thanks for the post.

I will check with Larry on where the fuel pressure, air/fuel ratio, and preload are.

Larry did say he has completed compression checks and everything is correct.

Tom didn't specify exactly what he did to "adjust" the CPS. I'll check on getting a Mopar replacement.

No word on the flex plate, it should be getting replaced this week as Larry suspects it may be causing this issue.

Pending the flex plate replacement results, I will update...

[christuned]

As others have mentioned, you must check the basics first.

1)Check cranking compression, if the engine is that much of a dog, cylinder pressure is a likely culprit, then see below.
Remove all spark plugs.
Unplug ecu so you won't get any fuel or spark.
Crack throttle.
Crank engine until you don't get any appreciable gain in compression readings, usually about 10-15 "pumps".
Post results.

2)You cannot assume that the cam timing is correct by just visually inspecting the cam-crank gears with the timing cover off. There have been issues with aftermarket timing chain sets. It's not too hard to check valve timing, I've heard of some Jeep guys using timing tape from Jegs or Summit to avoid having to buy a degree wheel. If you were handy enough to install the engine, you can degree the cam.

http://www.compcams.com/technical/instr ... es/145.pdf

https://www.youtube.com/watch?v=7cNoVRLb73c

[SilverXJ]

2)You cannot assume that the cam timing is correct by just visually inspecting the cam-crank gears with the timing cover off. There have been issues with aftermarket timing chain sets.

This. It is so easy to get the timing off and not even notice it. Especially with the smaller link double roller chains. I ran into this. Lined the timing set up dot to dot. Then I degreed the cam shaft. It was 13* out. Verified that it was dot to dot and fixed the alignment. It was one tooth off. After fixing it it still looked dot to dot.

Once you get the feel for what you are doing and the simple math degreeing the cam in is really easy. And not a step to skip.

[98XJEastTN]

Thank you christuned and again SilverXJ.

I will spend some time this evening checking out the links and check in with Larry today to see how the flexplate replacement is going.

If that doesn't take care of it, I will have them tow it home and begin to check the cam timing as described.

I really appreciate the help...hope to have a good update soon.

[98XJEastTN]

OK - At this point I'm $5,000 (probably more) into this Jeep stroker and got horrible news today:

The dealership has checked everything to check. Compression, flex plate, CAM degreeing. Everything checks out OK.

However, it idles very rough, doesn't run right and they said they cannot recommend it be driven period.

They say we could try a new ECM, but that may not be the fix...the only true answer seems to be convert to a carburator.

I'm in desparate need of some guidance to a mechanic known for being able to get these strokers running.

[rammit11]

hi, sorry to hear about your dilemma. After reading thru your posts I see that there is no mention of what you have checked on the fuel system ie: fuel pressure, fuel pump , injectors and if there are any kinks or blockages in your fuel lines. I have a '98 also and have had some issues with the filter/regulator assembly that is on top of the tank where the fuel line is attached to. You should have around 49psi at the engine connector when the key is turned on without starting the engine on the fuel pressure gauge and should hold that pressure for a short period after the key is turned off. I should think that your mechanic would have gone over this as well , but then again sometimes the small items get overlooked . Hope this post can give you a direction to go in and possibly lead to a solution for you.

[christuned]

OK - At this point I'm $5,000 (probably more) into this Jeep stroker and got horrible news today:

The dealership has checked everything to check. Compression, flex plate, CAM degreeing. Everything checks out OK.

However, it idles very rough, doesn't run right and they said they cannot recommend it be driven period.

They say we could try a new ECM, but that may not be the fix...the only true answer seems to be convert to a carburator.

I'm in desparate need of some guidance to a mechanic known for being able to get these strokers running.

What did the dealer determine was the cam timing ? How much vacuum does it pull at idle ?

I have to say, the answers you are sharing do not give me much confidence in the dealers diagnosis.

[christuned]

What city / state do you live in ?

[SilverXJ]

Did you provide a cam card (cam timing specs) to the dealer?

[98XJEastTN]

The dealership said the cam timing was correct. They cannot figure out what isn't working without running up a ton more in labor. So I paid them $420.00 and am no further than I was when it got there, except for sure now going to convert from EFI to Carb.

I'm in Greeneville, TN.

The dealership ordered a timing dial and have been working closely with Chrysler for all of their diagnostics.

My mechanic buddy is going to try and use our existing intake to mount a carb and fabricate an adapter. I have all the confidence in the world in his abilities as he has been working on cars for 30 years...and making hot rods.

If anyone has advice on the EFI to Carb conversion, please let me know so I can pass it on to him.

Thanks again everybody!!

[bigal389]

I personally wouldn't go with a carb set up for a daily driver! Unless I missed it somewhere the what was the fuel pressure?
How was the cps adjusted. It does sound as if you have an issue with the cps or injector timing issue.
Al