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Can someone help me diagnose my new Stroker build, please?

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Can someone help me diagnose my new Stroker build, please?

Old 04-24-2019, 04:17 AM
  #1  
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Location: Toms River NJ
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Year: 1999
Model: Cherokee
Engine: 4.0 6 Cyl.
Default Can someone help me diagnose my new Stroker build, please?

I feel like a horses *** to be honest. My 4.0 needed a head gasket, I had been reading alot about Stroker motors so there was no time like the present. I took my time and built a beautiful beast transforming my Headgasket starved 4.0 into a beautiful 4.7 liter thorobred Stallone ready for the dirt track.

I had alittle trouble with the distributor its been at least 25 years since ive rebuilt anything so it wasnt to bad. I only had to Indexed the distributor 2 or 3 times before I hit the mark dead on. She starts, shesounds good, she idles, she responds to the throttle nicely too! However, after 2 to 3 minutes it sounds like she is warming enough to kick off the choke and thats when the trouble begins.

After she gets warm she wont idle so I give her some throttle to keep her running but shes flucuating all over the place between 1000 & 2500 rpms. I have to keep adjusting the throttle because she's all over the place trying to change RPMs. If I start to rev her up and bring you RPMs up high she gets worse she starts backfiring missing and almost seems like she's loading up with fuel that she can't burn. If I stop and let it come down back to 1000 to 2,000 rpms and keep it there for 30 seconds to a minute it seems like that fuel Burns off and she runs a little better still won't idle and still isn't responsive to the throttle but not backfiring.

I said I feel like a horse's rear end because I did this rebuild without thinking at all about all the electronics and computer involvement there is which I know nothing about. The last thing I rebuilt was a 1979 4 wheel drive van which had not even 10% of the electronics that this has. I don't have the equipment or the knowledge to adjust the Electronics or test them, it didn't even cross my mind.

I know I could take it somewhere and tell them I don't know what I'm doing and see if they could finish it for me but you know what that'll get me LOL not at a reputable shop. But at the same token I kind of feel like a failure if I have to let somebody else finish my work. I started reading about the electronics and I'm learning how to test them with an ohmmeter the map sensor the cam positioning sensor things of that nature but I don't know anything about adjusting the computer or know what equipment to get if someone to please help tell me what I should be looking at or what tools and testing equipment/ software I should get or any kind of pointers whatsoever I really really appreciate it. Even if I did have to take it somewhere perhaps somebody here knows what type of mechanic shop I should be looking for so I don't just find somebody that doesn't know any more than me. As it stands right now I have a $5,000 anchor so if anybody can help please again I'd really appreciate it.

The only other thing I could think of is when I indexed the distributor it was also mentioning about indexing the cam positioning sensor. On my cam positioning sensor there are 4 holes in the flat plate and the article just said to line the whole up with the hole in the distributor I lined mine up with the last hole in the plate but I'm not sure if that's where it was supposed to be??? If anybody knows that whether I put it in the right place or not that would be a big help too! Okay i hope to hear something from somebody, I love this site, I intend to spend a lot of time here I learned a lot thank you very much in advance.

By the way my build is a 1999 XJ crank from an old YJ 4.2 engine. It was the desired lighter crankshaft, i forget the numbers right now. I had it mic'd, balanced and polished. I used my 4.0 longer rods with Keith Black pistons and Molly rings bored 40 over. I only went one step up on a cam for torque what is a Comp Cam the other modifications or I used 24 lb Ford fuel injectors I bought a bored throttle body 66 mm I have an Accel coil pack I have a high output oil pump and water pump naturally a new timing set gears and chain I have a cold air intake from K&N and stainless steel header. I followed a recipe that is supposed to make it a 4.7 however I'm not sure I haven't had it dynoed obviously. Other than the stroker I have a 3 inch suspension lift 31-inch tires front winch spotlights Aussie lockers front and back wish I may be changing to e lockers or air lockers I'm not sure. I also have a dual battery setup and I'm building a rear bumper with a swing down spare tire holder. An onboard compressor and some other creature features. I may go higher with bigger tires and beef up my drivetrain if I can get this stroker working right. Thanks again Tom
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Old 04-24-2019, 05:13 AM
  #2  
awg
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Originally Posted by Bayside64 View Post
n. She starts, shesounds good, she idles, she responds to the throttle nicely too! However, after 2 to 3 minutes it sounds like she is warming enough to kick off the choke and thats when the trouble begins.

After she gets warm she wont idle so I give her some throttle to keep her running but shes flucuating all over the place between 1000 & 2500 rpms. I have to keep adjusting the throttle because she's all over the place trying to change RPMs. If I start to rev her up and bring you RPMs up high she gets worse she starts backfiring missing and almost seems like she's loading up with fuel that she can't burn. If I stop and let it come down back to 1000 to 2,000 rpms and keep it there for 30 seconds to a minute it seems like that fuel Burns off and she runs a little better still won't idle and still isn't responsive to the throttle but not backfiring.
What choke ?

have you made sure there is no vacuum leaks?..connected a vacuum gauge?

TPS could be an issue, or IAC, loose or improper intake manifold fitment or quite a few other things, logical fault finding needed

there also exists a forum dedicated soley to Jeep Strokers

Last edited by awg; 04-24-2019 at 05:15 AM.
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Old 04-24-2019, 08:46 AM
  #3  
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So this stroker is controlled by a 99 PCM? If so you can purchase a obd2 scanner with live data. This will show you all of your sensor parameters from what the PCM can see. Voltmeter readings are also good but they show what is directly from the sensor and not the PCM interpretation of the voltage. I always recommend a wideband sensor with any type of engine modification. They pay for themselves in troubleshooting.
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Old 04-24-2019, 08:07 PM
  #4  
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Default Can someone help me diagnose my new stroker build please?

org, thank you very much for getting back to me and thanks again for the tips you gave me that gives me a real great place to start if nothing else. Not knowing anything about this stuff makes it hard to even figure out what to look at even though I know to look for a vacuum leak I never thought of a gauge. Now all's I have to do is find out what some of these other things are well TPS I know it's throttle positioning sensor IAC I'm not sure what that is? The manifold I could check however, that should be on good though, then again stranger things have happened lol. Thank you so much for the pointed direction so I can start.

Cummins93, Thank You also for the way and what to look for in a scanner w/ live data, whatever that means lol? Well I suppose its time to find out about this stuff unless im going to build mini bikes and lawnmowers lol. Thanx again guys great pointers.

Thanx, Tom
p.s. Ill let ya'll know how I make out!!!
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Old 04-24-2019, 08:37 PM
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You need to check for vacuum leaks first I believe as well .
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Old 04-25-2019, 07:38 PM
  #6  
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Default Can someone help me diagnose my new Stroker build please?

Yes, im so amazed how much info you can find on you tube lol. I , I was looking up information last night on what a vacuum pump looks like how to use it what it does and I came across a guy that gives information on the electronics the computerized stuff. The guy's name is like Matt Strode thing or something how to diagnose a map sensor sensor and he gets into fuel Trims and all kinds of things very interesting I don't know how asking what a vacuum Gage looks like got me to a class or seminar on fuel trims and computerized systems LOL but it sure came at the right time. Thanks for the pointer I really appreciate it everybody here thank you. Tom
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Old 04-25-2019, 07:51 PM
  #7  
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Engine: 4.0 6 Cyl.
Default Can someone help me diagnose my new stroker build please?

Just a quick update from yesterday I don't know how asking Google or YouTube what a vacuum gauge looks like; how I got to seminars on testing map sensors and iac sensors, and fuel trims LOL. But I'm glad I did because it's very interesting and I have a lot to learn but I know what a vacuum gauge looks like what the sensor. What the vacuum does and why is it so important and many other things. So today I tested the map sensor and the throttle positioning sensor both of those are good well within the parameters. SO! here I trudge on hoping I'll either find the magical problem was somebody here could lead me to it I've got backfiring sputtering missing and that's even @ 1ST. start up today!!!

OH, I DO HAVE AN IMPORTANT QUESTION FOR YOU GUYS!!! While I was working on removing the engine I marked and taped all or most wires, hoses, cables, ETC. While painting the engine and engine bay alot of things were oversprayed, including the taped markings numbering the injector wires. Putting the engine back i couldnt see 1 of them so I put the back according to the way the wires were bent, trying to use commonsense, alittle late, to get wires back on injectors!!! How can I make sure the wires are on the right injectors???
We'll see what happens !!! Thank you very much any help is appreciated. Tom

Last edited by Bayside64; 04-25-2019 at 08:05 PM. Reason: I wanted to add a question, i forgot to ask.
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Old 04-26-2019, 08:29 AM
  #8  
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With the battery disconnected and the PCM discharged you can un plug the PCM connectors and find the corresponding injector circuit. Test for continuity.

http://www.jtec.info/index.php?title=PCM_Pinout
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Old 04-26-2019, 09:57 AM
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Sounds like the distributor could still be a tooth off. When I rebuilt mine it revved up fine, then I tried to go with it and it sputter and backfired and ran like crap. Moved it a tooth and it ran better, then I was driving it around and it would randomly backfire at 2000ish rpms. Turns out I was still a little off. Finally got the distributor in there perfect and it runs great now.
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Old 04-27-2019, 02:40 AM
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Originally Posted by SatiricalHen View Post
Sounds like the distributor could still be a tooth off. When I rebuilt mine it revved up fine, then I tried to go with it and it sputter and backfired and ran like crap. Moved it a tooth and it ran better, then I was driving it around and it would randomly backfire at 2000ish rpms. Turns out I was still a little off. Finally got the distributor in there perfect and it runs great now.
I havent done any Jeep dizzys yet, but have read this is a problem with them, very easy for the teeth to slip forward when it goes into mesh, so I would mark it and try one forward or back.
Had this happen to me on another engine...its a happy moment when a motor runs good after a simple fix like that
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