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Author Topic: Car stumbles around 2800-3200 RPMs  (Read 2232 times)

blackhandbeagles

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Car stumbles around 2800-3200 RPMs
« on: November 26, 2016, 11:22:05 AM »

Ok, I am at my wits end. My car acts like it loses fuel between 2800-3200 RPMs. I have replaced the plugs, wires, cap, fuel pump, fuel filter, and TPS. I pulled the codes and the only code was TPS. Any ideas? The MAF hose doesn't appear to have any cracks.

Could it be the MAF?
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #1 on: November 26, 2016, 12:00:09 PM »

This could be what is causing the problem. Rock Auto does not have a dashpot listed as an available part.

A dashpot is mounted on the RH side of
the throttle body to control throttle valve closing speed
during deceleration.
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NomakeWan

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Re: Car stumbles around 2800-3200 RPMs
« Reply #2 on: November 26, 2016, 09:47:31 PM »

Ignition coil, calling it. Or Ignition Control Module, I forget what the Capri guys call it. Anyway, they go bad, and when they do you get insufficient spark under load, causing a stumble at a certain RPM range.

First ran into that problem on a '71 Datsun, apparently is a common issue here too.
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #3 on: November 26, 2016, 09:51:07 PM »

Rock Auto has both. The ignition coil is $10. The ICM is $110.

Anybody else want to weigh in to narrow it down?
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Rocketman

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Re: Car stumbles around 2800-3200 RPMs
« Reply #4 on: November 27, 2016, 11:58:12 AM »

Have you tested/adjusted the new & old tps with a multimeter as per FSM?
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #5 on: November 28, 2016, 12:19:46 AM »

I haven't. I will try to find that in the service manual.
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socal1200r

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Re: Car stumbles around 2800-3200 RPMs
« Reply #6 on: November 28, 2016, 06:03:59 PM »

I had to replace the circuit board in the TPS housing for my '73 Porsche 914.  If replacing/adjusting the TPS in these Capris is anything like the 914's, and you didn't do it correctly or at all, that could very well be what's causing your stumbling issue.  I had to use the multimeter, set to ohms, gently slide the TPS until it read zero, then one more mark down and tighten the screws.  There's YouTube videos of how to do this... 
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JJ

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Re: Car stumbles around 2800-3200 RPMs
« Reply #7 on: November 30, 2016, 11:27:52 AM »

again. test the car with either the O2 sensor or TPS unplugged. does it respond the same? ....
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #8 on: December 04, 2016, 05:23:22 PM »

Sorry, been crazy busy. I will try to test it tomorrow with the TPS unplugged.
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #9 on: December 04, 2016, 06:46:59 PM »

JJ, if you posted earlier and I missed it I am sorry.

You nailed it, though I don't know what IT is. When I disconnect the TPS the symptoms go away. Of course the car won't start with the TPS disconnected, so that is inconvenient.

What does this mean? Do I have a bad O2 sensor?
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #10 on: December 05, 2016, 09:46:09 AM »

I have already installed a new thermostat and replaced the timing belt. No change in symptoms.

I went back through your old posts.
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NomakeWan

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Re: Car stumbles around 2800-3200 RPMs
« Reply #11 on: December 06, 2016, 07:27:46 AM »

If the symptoms go away when you unplug the TPS, it means your TPS is out of spec. This would also explain why your code for TPS did not go away, because the PCM knows that it's out of spec. Since the symptoms go away when you unplug the TPS and not the O2 sensor, it means the O2 sensor is not the culprit and likely has nothing to do with this issue (it was mentioned earlier as one of the possibilities, but you've now proven it's the TPS).

TPS diagnostic and adjustment requires a multimeter. Details can be found on pages 80-82 here: http://www.techcapri.com/ServiceManuals/1988/Section%204B%20-%20Fuel%20and%20Emission%20Control%20System%20EGI%20Turbo.pdf

(It says to use an SST, but all the SST is doing in that procedure is checking for continuity. They give you the table showing when there should and should not be continuity, and this is something you can check with a multimeter. There's no need for their special tester tool thingamabob.)
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #12 on: December 06, 2016, 08:11:24 PM »

Awesome. Thanks for the info. I will try that this weekend, barring any of my kids having their weekly, inopportune emergencies...
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #13 on: December 14, 2016, 12:34:59 PM »

Never got to it. Maybe this weekend.
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blackhandbeagles

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Re: Car stumbles around 2800-3200 RPMs
« Reply #14 on: January 15, 2017, 07:13:01 PM »

Ok, finally found time to adjust the TPS and check the voltage levels. The TPS was out of adjustment. Adjusted it, with no improvement to the issue. Tested all voltage levels on the TPS to make sure they were within spec, and they were.

Problem seems to be most prevalent when in fifth gear, about one third throttle. Let off or give it more gas and it corrects itself. Any possibility it could be a throttle plate sticking?
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