TeamCapri

Tech, Repairs, Upgrades => Capri N/A 89-94 => Topic started by: 94daves on November 10, 2018, 03:44:44 PM

Title: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: 94daves on November 10, 2018, 03:44:44 PM
I just replaced the distributor, cap and rotor (along with all the belts, water pump, alternator, spark plug wires) and the engine stumbles around 4500 rpm.  It stumbles at 4500 going into first, second, etc.  Could this be something due to the timing or new distributor?  Or something else?  It did not do this before I put in all the new parts.  Thanks.
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: Rocketman on November 19, 2018, 05:53:18 PM
I would double check everything, make sure none of the plug wires are loose. Have you verified engine timing? Does the car feel like it has normal power up to the point where it stumbles?
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: 94daves on November 23, 2018, 10:10:32 PM
The plug wires are tight.  The car feels like it has normal power up to 4500 rpm.  I just drove it again today and it was doing the same thing.  It's very repeatable.  I have not verified the engine timing.
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: Pappy T on December 17, 2018, 03:55:49 PM
Get it fixed ??
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: 94daves on December 22, 2018, 11:51:44 PM
No, and I’ve stored it for the winter so it’ll sit until March or April. 

Does anyone have any ideas?  Could it be fuel related?  It just seems such a coincidence that it started stumbling after I had some work done to it.  Could one of the mechanics knocked something off or loose by accident?
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: chukT on December 23, 2018, 12:46:12 PM
With what you had done, I would also suspect the base timing first. Verify that it is set properly as your next step.
Title: Re: Engine stumbles around 4500 rpm - new distributor, cap and rotor
Post by: 94daves on June 02, 2019, 09:52:29 AM
I'm back at it again to fix this problem.  Timing has been checked and verified by the shop that did the work in 2018 before I put it away for the winter.  There are no codes, no check engine light.  Does anyone have any ideas what could be causing this misfire/stumble at 4500 rpm?
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Rocketman on June 02, 2019, 07:32:46 PM
I wonder if your new distributor is faulty. Is it new/used/rebuilt? Do you still have the old one? What was the reason for replacing?

I saw a Capri distributor with bad internal bearings cause a miss in the past. The shaft was bouncing around and would not give a reliable signal to the pickup coil at higher RPM
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: 94daves on June 06, 2019, 04:12:46 PM
Actually I only replaced the cap and rotor, not the distributor itself. 
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: 94daves on May 20, 2020, 10:05:22 AM
I'm back at it again!  I still have the same stumble around 4,500-5,000 rpm.  Could it be bad wires or bad spark plugs?  If the wires were attached in the wrong order on the distributor, would I notice a stumble at lower RPM, too?
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Rocketman on May 20, 2020, 03:57:33 PM
It could be a faulty cap/rotor or plug wires.

If the plug wires were in the wrong order the vehicle would barely run if it all. But, double check. Cylinder #1 is on the passenger side.

Does the car stumble when revving in neutral?
Have you tried revving the engine at night in a dark area to look for arcing on the plug wires?

A common problem with the N/A is the plastic intake tube - it cracks and opens up creating a vacuum leak. Often on the underside where it is not visible. It may be that your engine is moving enough at 4500rpm to cause the issue. Just spitballing on that one. Will need to remove to do a visual inspection.
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: jdp on May 21, 2020, 11:09:28 AM
I am following this one too.  My wife's NA stumbles at 70 mph which is just over 4000 rpm. I replaced the common ignition system parts twice.  Can't seem to find it either.  She only drives it around town, so it doesn't cause her any issues unless she shifts gears over 4000 rpm.  Being the good husband I am, I told her to never go over 4000 rpm.....smile! 

John
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Pappy T on May 21, 2020, 03:36:35 PM
Hi all, glad we all made it thru the winter ! Just got mine out of mothballs yesterday , still sputters  :-\ .New cap, rotor , wires , plugs, fuel filter too last fall ... no go . It'll be going up for sale pretty soon, not for the issues but we do rv'ing now more and more . Free up garage space too . Oh yeah, grandbaby # 7 on the way too by August , she'll be needing some toys  ;) . 'll be putsin with it as I can and hopefully someone will find a solution other than dynamite ! Stay safe And healthy out there now .
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Rocketman on May 21, 2020, 03:40:09 PM
Just a reminder. Make sure you've got fresh fuel in your Capris. It can cause it to run poorly
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Pappy T on May 21, 2020, 05:44:57 PM
Yep , that too ! A little seafoam doesn't hurt either .
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: 94daves on June 19, 2020, 02:10:06 PM
It could be a faulty cap/rotor or plug wires.

If the plug wires were in the wrong order the vehicle would barely run if it all. But, double check. Cylinder #1 is on the passenger side.

Does the car stumble when revving in neutral?
Have you tried revving the engine at night in a dark area to look for arcing on the plug wires?

A common problem with the N/A is the plastic intake tube - it cracks and opens up creating a vacuum leak. Often on the underside where it is not visible. It may be that your engine is moving enough at 4500rpm to cause the issue. Just spitballing on that one. Will need to remove to do a visual inspection.

Thank you for this info.  The plugs are in the right order, thanks for telling me where Cylinder #1 is.  The car does stumble when it's in neutral.  It will stumble sitting in the driveway.

Car sounds great idling in neutral in the driveway with the parking brake on.  No issues at all, no surging.  Very steady.

I haven't checked it at night.  It's past my bedtime when it's dark now in the summer!

New development - it doesn't stumble at 4500 rpm when shifting from 2nd to 3rd, nor from 3rd to 4th.  It will stumble from 2nd to 3rd but I can't tell exactly when it does it.  I haven't driven it around much lately to notice a repeatable pattern but I think it's higher than 5000 rpm.
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Pappy T on November 16, 2020, 11:34:13 AM
Hi again all ! This issue ever get resolved ? Mine's still doing it , haven't messed it with it for a while either. Did put about 10-12 miles on it this year along with some fresh gas . Will be up for sale next spring too. Outside interests keeping us busy ! (RVing)
Have a good turkey day, stay safe and healthy too !



Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: 94daves on December 09, 2020, 06:45:43 PM
Nope, was never resolved this summer.  Now it's in storage for the winter.  I will try again in 2021!  Hopefully someone here will have a few ideas over the winter that I can try next year.
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: ZJCapri91 on December 27, 2020, 11:00:47 AM
A suggestion:
When I got my car, it has a bad Ignition Control Module. I replaced it with the cheap one off rock auto, where the car then only revved up to around 4k RPM. I ordered the expensive Ignition Control Module, and it worked brilliantly after that.
Perhaps you replaced this part, and your experiencing this issue?
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: Pappy T on December 29, 2020, 03:11:20 PM
Thanks for the suggestion . On it's 3rd distributor, no more cardone for me. Did replace  ICM with a good one and no problems with starting . Problem just came out of the blue one day and does it around 37-4000 rpm , levels out a little over 5000 . No codes except very faint check engine light that goes away about as quick as it comes on during sputtering . Quite a list of stuff I checked to no avail , stumped . Starts and idles great, only acts up at that rpm . Da heck  :-\  . 
Title: Re: Engine stumbles around 4500 rpm - new distributor cap, rotor, wires
Post by: ZJCapri91 on January 02, 2021, 09:30:07 PM
The only other suggestion I can offer is the main ignition ground. Its a ring terminal with a bolt straight into a bracket, right near the distributor. I had my ground come slightly undone, and the car misfired like crazy under certain conditions. If yours is on tight, maybe take it off and clean the contact surface. It only takes a little to create massive headaches.