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Discussion Starter · #1 ·
motor won\'t rev past 3000rpm!!!

i'm just about ready to send the thing over a cliff. just dropped a 302 HO from an 89 mustang into my cj7. everything works well but i seem to be missing a little at idle and i cannot rev beyond about 3000-3100 rpm before the motor just sputters. compression is good, fuel pressure is good, and threw a different coil in for giggles and got the same thing. am running a jacobs ultra coil now. increased the fuel line diameter and have no restrictions anywhere. if anyone has any ideas, they would be much appreciated. like i said, the jeep starts and runs fine, as long as i don't ever want to go fast. thanks in advance, mudncj in cleveland ohio
 

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Re: motor won\'t rev past 3000rpm!!!

You might try changing you fuel filter. This is a cheap fix if it works. In my truck about every three or four months my fuel filter gets clogged with debris and I have to change it. When this first started happening to me I was having the same symptoms as you are. I asked my uncle and he suggested a cheap fix by changing the fuel filter before I did anything drastic, so I did this and it cured what ailed me. Hope this works for you.

/wwwthreads_images/icons/cool.gif'46 CJ 2-A Rusty, but still fun to drive and easy to work on./wwwthreads_images/icons/cool.gif
 
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Discussion Starter · #5 ·
Re: motor won\'t rev past 3000rpm!!!

Alright I'll bite on this one.
You say a rough idle, and won't rev up.
The first thing I would check is to make sure that a couple of plug wires aren't crossed.
CTjeepnut

Funny thing is, the more I practice, the luckier I get
 

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Re: motor won\'t rev past 3000rpm!!!

CHECK YOUR FIRING ORDER... Sounds like you may have a problem with the ignition...

If it simply won't climb above 3,000 RPM, it sounds like you need a new ignition module.
If you have the first generation Dura Spark module on the fender, you can borrow one from anyone that owns a ford you hang around with to test, or you can by a new one for under $20 at Advanced Auto.
Look for the 'Blue Grommet' module for a jeep...

For an 89 HO 302, you have to change the distributor to use the first generation Dura Spark module.
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If you have the second generation DuraSpark ignition module...
(that's the module on the side of the distributor)
You will have to get a new module to test...
Static tests at the parts stores are never accurate.
There are a bunch of problems with the late 80's- early 90's second generation Dura Spark modules...
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You might also try testing the ignition trigger in the distributor...

Good luck, Aaron.

"I Have The Body Of A God... Buddha"
 
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Discussion Starter · #7 ·
Re: motor won\'t rev past 3000rpm!!!

aaron, thanks for the info on the ignition modules. this motor has the second-generation module that you mentioned. i have checked the wires several times and am 100% sure of the order. i have not replaced all of the wires though, but have tried a new cap and rotor. i hope to get a few minutes off of work today to try a different module and see if it works. luckily, a buddy has a new one sitting around that he did not know about, what luck. anyhow, thanks again for the info, if this works, i'll send you a couple of beers. thanks, steve
 
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Discussion Starter · #10 ·
Re: motor won\'t rev past 3000rpm!!!

allright, here is the story. took a lot of good advice and checked all that i could. replaced the ignition module with no change. bought new wires, and made sure they weren't crossed, no change, retimed, no change, disconnected exhaust flanges, no change. most of you were right about the timing thing. we scoped it and it seemed to revert back to ZERO DEGREES by the time it got to the magic 3000 rpm. it has the hall effect distributor in it, which i am unfamiliar with. will changing out distributors be a good next logical step? how unlikely that the computer may be shot? as you can tell, i am just reaching for anything here. any help would be much appreciated. thanks again guys, steve
 
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Discussion Starter · #11 ·
Re: motor won\'t rev past 3000rpm!!!

If you are running the stock efi and computer from the Ford, you must adjust the timing after removing the "spout" connector. The base timing is usually 10* BTC. The connector is a small grey 2 pin plastic plug in a plastic connector near the distributor. Turn off the ignition, unplug the spout connector, restart the engine and set the timing. Turn it off and reconnect the spout connector. If the timing is varying at idle, with the spout connected, it most likely is OK.
Some EFI systems require a vehicle speed sensor reading. If you don't have a speed sensor hooked up, and it is required for your system, you may get fuel shutoff/odd running, as MAP/MAF sensor readings under load don't jive with a 0 MPH indication. Conversely, if you have a speed sensor, be sure the number of pulses per mile/revolution coincide with what the EFI computer needed originally.
Maybe a Ford wiz can enlighten us on the requirements of the Ford EFI system, as I usually work on Jeeps/Chryslers.
Hope this is helpful, good luck!
P.S. Check your air intake hose carefully for holes or other leaks, if your Ford EFI has a MAF sensor.
 

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Re: motor won\'t rev past 3000rpm!!!

CJ-7/5.2Mag is right on with the timing. After you do the initial 10 degree base timing, you can also do a "computed timing" check. With the engine warm, and the spout connector re-installed, you can put it in self-test mode by jumping the eec-iv self test connectors. In the first 30 seconds of the "key on engine running" in self test, is the pre-programmed 20 degree curve that Ford builds into the computer. Your timing should be at 30 degrees btdc. This is the initial 10 degree base plus the programmed in 20 degree curve. If it is more than 3 degrees off (not between 27 and 33 degrees) you will need to change the "octane rod". The octane rod is the small strap that locates the hall gate in the distributator to the case. There will be a number stamped into the rod. Usually it is a 0, and is sold in the number of degrees the computed timing is off.

After you get the ignition correct, and you have verified that there is no mechanical problems like a vacuum leak or bad valve, you can run the "key on engine off" tests and verify your sensors are in parameters. It is kinda of hard to explain how to use the eec-iv connectors to retrieve codes without a scanner, because I don't think the '89 had a "check engine" light. Ford built in the capability of retriving codes without a scanner by using a volt meter or test light. Looking at the 6 sided eec-iv connector from the end without the wires, the upper right most terminal should be jumped to the single wire. And the lower left most wire is the ground for the test light. If the jumper wire is disconnected during code retriving with the key on and engine off, it will automatically clear any stored codes, and this is the only way you can clear the codes, as disconnecting the battery won't do it.

Another note on the eec-iv system is Fords use of the t.p.s. Most earlier manufactures used the t.p.s. to tell the computer how far the throttle is open. Ford also uses it to tell the computer the rate of change. So any "noise" in the t.p.s. will play havoic with mixtures, and the engine will want to "hunt" after the throttle is touched.

Hope this helps, any you may want to look at Chilton's electronic engine control book in the Ford section for the eec-iv test connectors.
 
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Discussion Starter · #13 ·
Re: motor won\'t rev past 3000rpm!!!

any ford people out there????? still can't seem to find the problem. replaced the module and the pip/pick-up, all with no change. the vehicle is still throwing no codes and has not changed at all with all these replacement parts. could running the high energy Jacobs ultra coil be the culprit? or would it be wise to just blame the computer, but at what cost. anyone who could help here i would greatly appreciate it. summer time is jeep time. or at least , it used to be. thanks in advance guys. steve
 
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