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Old 03-11-2011, 05:54 PM   #1
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Rebuilt 2.5L Running Bad

Hi guys, I'm new here. I got a lot of help from searching this forum so I figured I should just join it. Over the winter I rebuilt my 2.5L engine and I reinstalled it in the Jeep this week. Today I started it up for the first time. Did'nt get the results I hoped for. The tachometer goes up and down a few hundred rpm's during idle but it does stay running on its own. When I give it some gas it sputters and bogs, and backfires when I give it full throttle. I cant even get the rpm's above 2300.

I tried a few things.
-moved my ground wires to a few different spots
-tried using my old distr.cap, rotor and wires
-tried using my old plugs
-sprayed carb cleaner in the intake

None of these seemed to change anything, my guess is either something to do with timing, or fuel. Is it possible that I installed the timing chain one tooth off? Really confused and dissapointed. Does anyone have any ideas?

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Old 03-11-2011, 07:16 PM   #2
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After a little research on the forum i found the thread on resetting the ECU. Do you guys think a reset will help my issue.

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Old 03-12-2011, 07:10 AM   #3
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bump
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Old 03-12-2011, 08:03 AM   #4
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Any time I've made a major change or tune up that's over do I've done so and seems to help if not I believe driving around for awhile jeep computer seems to relearn itself.

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Old 03-12-2011, 11:11 AM   #5
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i installed a rebuilt 2.5 into my 97 this month, i was kind of having the same problem your describing, accompanied by backfires and stalling. What i found MY problem was, while not necessarily yours, was that i had a couple loose connections in the cam and crank position sensors. I didn't go the route you did, but it may be somewhere to start. I also had thought that it was my grounds at first, but alas, just a few loose wires.
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Old 03-12-2011, 04:55 PM   #6
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Thanks for the advice 415, Ill check on that tomorrow. I messed around with it a little today. It seemed to run better after pulling the distributor and putting it back in a tooth ahead of where I had but it still runs terrible. It idles better but randomly stalls and drops rpm's every minute or so. It backfires really bad above 2500 rpm. Ill post a couple of vids on youtube in a few minutes. I have one with the engine running before turning the distributor and one after.
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Old 03-12-2011, 05:13 PM   #7
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Ok here are the vids of it running.

Before turning distr.:
After:
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Old 03-12-2011, 05:15 PM   #8
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wow, i hope i don't have any issues with my new engine. a week ago i broke a piston rod and spun the bearing and the piston did some major damage. i went with a jasper engine and my mechanic is going to install it this week.
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Old 03-12-2011, 05:38 PM   #9
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Good luck with your build Jma, mine had a shattered piston skirt so thats why I had to rebuild. After disassembly I found out that my water pump fins were corroded off so no coolant was circulating, I guess overheating caused the skirt to shatter. I decided to just get the block bored and do a complete rebuild in my basement. This was my first time so I guess I'd have to say I had pretty good luck with it up until now. I just hope I get it figured soon, Im afraid that it wont break-in right from running like this.
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Old 03-12-2011, 06:37 PM   #10
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I have a check engine light and cant get my tach to read an error code. I can get it to show 2.4 which i guess is the firmware version? and I can get it to do the self diagnostic thing where the guages go all crazy and the tach reads from 0000000 to 9999999. Any ideas, its a 98 2.5L . I have a black key, not a grey key, not sure if that matters. Any ideas on that? maybe if i can read the code I can find out why its running so bad. I would take it to autozone but its not tagged and its not running good enough to drive there anyway.
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Old 03-12-2011, 06:51 PM   #11
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Quote:
Originally Posted by TripleEight View Post
Good luck with your build Jma, mine had a shattered piston skirt so thats why I had to rebuild. After disassembly I found out that my water pump fins were corroded off so no coolant was circulating, I guess overheating caused the skirt to shatter. I decided to just get the block bored and do a complete rebuild in my basement. This was my first time so I guess I'd have to say I had pretty good luck with it up until now. I just hope I get it figured soon, Im afraid that it wont break-in right from running like this.
yeah my block is done. the piston turned the cylinder egg shaped and had about a 1/4" of space between the piston and the cylinder. the new engine i got from jasper has been bored out and ran $2000 after i send in my blown motor. comes with a 10 year 100000 mile warranty.
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Old 03-12-2011, 07:07 PM   #12
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Sounds like a good deal for a motor thats already built and comes with a 100000 mile warranty. I ended up paying $375 at the machine shop and $450 on the rebuild kit.
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Old 03-12-2011, 07:17 PM   #13
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yeah its a fully rebuilt motor. i do plan on rebuilding the motor for my 73 cj5, blown piston rings in 2 cylinders.
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Old 03-13-2011, 12:26 PM   #14
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OK so today I checked Crankshaft Sensor and Camshaft Sensor and they were both kinda dirty. I cleaned them and reinstalled, no luck. Then I figured I would just mess with the timing a little more. Instead of putting the crank on zero I put it a few notches back. Then I put the distributor in lined up with the rotor at number 1. Fired her up and she ran great. I ran it for a about 15 or 20 minutes and revved it around 1500 - 2000 for a while to seat the rings. Then I took it around the block, the clutch feels good and the motor runs smooth.

Here's a video of it running now
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Old 03-22-2011, 12:22 PM   #15
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I now have 150 miles on the engine. It seems to run normal but I am still worried about the timing. According to the manual, the notch on the crank pulley should point at 0 when it is at TDC on the compression stroke. The only way I could get it to run good was with timing advanced. Am I hurting the engine by driving it this way? I dont feel like pulling the timing cover to check my chain but I dont want to ruin the engine by driving this way.

Part of me says "dont fix it if it aint broke" and the other part says "it's gonna be really messed up if i keep driving it."
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Old 03-22-2011, 12:45 PM   #16
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Have you put a timing light on it... Chances are that you are off a tooth or so either on the the distributor or the timing gears... and the advancement of the distributor is making up for it. Personally, I would recheck with a light and find the culprit.

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