TeamCapri
Tech, Repairs, Upgrades => Capri XR-2 89-94 => Topic started by: blackhandbeagles on November 26, 2016, 11:22:05 AM
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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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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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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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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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Have you tested/adjusted the new & old tps with a multimeter as per FSM?
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I haven't. I will try to find that in the service manual.
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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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again. test the car with either the O2 sensor or TPS unplugged. does it respond the same? ....
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Sorry, been crazy busy. I will try to test it tomorrow with the TPS unplugged.
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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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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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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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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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Never got to it. Maybe this weekend.
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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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Another guy described this perfectly, except I also get it when I slightly let off of the gas.
Here is the quote from him.
"To better explain the problem, if I'm cruising and hit the throttle slowly it sometimes feels like a bogging, or like somethings holding the car back, then a little more gas and it boosts up and seems fine, it doesn't do it all the time, and if you are on it hard all the time you don't even notice it. But it makes crusing in 5th a pain in the ass.
Anymore ideas? got a good fuel pressure reading, but I'm about to put a new fuel pump in it anyway just to see if it helps."
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Drove yesterday for 55 miles with the TPS disconnected. Car stopped searching for idle and the stumbling issue went away. I replaced the TPS with a "known good" unit I bought from Ebay.
I need to do some reading. I suspect that when I disconnect the TPS that stops the car from running a program(don't know how else to describe it) that involves other components. Maybe I can figure out what the TPS works with to control fuel/air/idle.
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But that did correct the issue?
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Sorry, I wasn't clear. I had already replaced the TPS with a used one. No, the problem still exists. If I figure it out I will try to give you guys the resolution.
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I found this in the 91 service manual.
"Injector time is controlled by the ECU, based on information supplied by the Vane Air Flow meter, coolant temp sensor, and Throttle Position Sensor."
I don't have a VAF sitting around. I can order the coolant temp sensor. I am going to try to remove clean the VAF and see if that helps.
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Ok, stupid question. Has anyone tried replacing the coolant temperature sensor to fix this problem?
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Be sure and use the proper cleaner.
Jack Byrd
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I guess I don't understand. What do you mean "proper cleaner"?
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I guess I don't understand. What do you mean "proper cleaner"?
The VAF is an electrical component and can react negatively is the wrong cleaner is used on it. There are specific cleaners made for a VAF, do not use throttle body cleaner or brake cleaner, for instance.\
Jack Byrd
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Okay, got it. I went to my mechanic friend and he thinks VAF. I will try to find a good spare first before I try dinking with it.
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I guess I don't understand. What do you mean "proper cleaner"?
The VAF is an electrical component and can react negatively is the wrong cleaner is used on it. There are specific cleaners made for a VAF, do not use throttle body cleaner or brake cleaner, for instance.\
Jack Byrd
This is good advice in general, but does luckily not apply to the Capri VAF. Many other cars use a MAF which use various schemes to calculate airflow (like the Hot Wire MAF) with exposed elements/sensors and are very sensitive to dirt and cleaner residues
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Thanks
Jack Byrd
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My Capri had 'stumble' problems for such a long time. The 'Stumble' was more like the car was struggling for gas or electricity (usually when accelerating). I read here, I think Russ said it was a ground wire problem. After reading the suggestion, I added another ground wire to the engine. It helped but, still the 'stumble'.
A couple of months, ago, my brakes were locking (up). I did my internet mechanical homework, most sites said my brake problem was the master cylinder. Lucky 'Rock' auto parts had the part, after receiving the new cylinder, I took the car to the car repair shop. A few days later, 'Tye', the mechanic calls me and tells me he cant bleed the brakes because the 'Brake pressure switch' is leaking.
Guess what? No one makes or sells these plastic switches. 'Tye' searches the local junk yards for 2 months, he cant find any suitable switches. I ask the mechanic if we can just plug it, but he tells me he cant because a different thread.
Lucky me, in 'Ebay', someone is selling a used complete MC for about $60. (sorry, Colin). My mechanic puts the ebay MC switch on the Rock auto MC body.
Guess what? the car runs great, no hesitations (or stumbles) when accelerating. me and my neighbors guess, is somehow the bad switch caused the electronics to falter? Also, the radio is not working, maybe a coincidence? Im happy to have a good running car, now, I'm not gong to even check the radio fuse.
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Just a two wire brake switch, innit?
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I'm going to go out on a limb and say there may have been a poor connection somewhere, and in the process of conducting the necessary surgery to replace the BMC the magic combination of pokes, prods, and re-fastening of harness connectors may have fixed the issue.
The main engine harness plug in the engine bay is quite close to the BMC/booster.
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My problem was indeed the VAF.
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Awesome. I have a similar symptom, so will try a VAF. Can anyone confirm if the VAF is the same on the turbo and N/A models?
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OK, the problem started to come back. More cutting out under mild throttle. Ran half a bottle of seafoam through the gas tank. Running good so far.
Read another thread that said the baffles under the valve cover could be causing the issue.
http://teamcapri.com/forum/index.php/topic,3936.0.html
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Awesome. I have a similar symptom, so will try a VAF. Can anyone confirm if the VAF is the same on the turbo and N/A models?
Rod, they are different. Check RockAuto's part numbers. Makes sense since turbo volumes flow more.
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Cheers. My problem turned out to be ignition components. Replaced everything and we're all good.
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Enjoy! My XR2 is under the knife at the moment, pulled the head and found that the oil passage in the front by the timing belt was the leaker I was fighting for most of the last year. Cometic head gasket, ARP headstuds and a head check including valve seals is underway. Hope to get mine going in a few days as well.
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blackhandbeagles: car still doing ok or is that stumble back? sorry after posting that I hadn't been on the forums in months...
i have a much longer post here describing that same issue. Mine happened to go away after a radiator replacement.. The mechanic also timed the car correctly. so not sure if it was timing, or perhaps ground related as there's a ground wire on/near the thermostat
i drove it for many months without the tps wire connected. that puts the ecu in a 'steady state' mode where it ignores most inputs and does the minimum to make car run. chased my tail on that one for a few years.
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Hey Rod , what distributor parts did you get into to get rid of stumble ?? Having same issue with my '91 na . Thanks