Question about 1987 Volkswagen Cabriolet

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Engine idles up and down

Hi , my husband just rebuilt a 1.8 cis for my cabriolet and when he starts it up it has a couple of issues 1st it won't start by the key so we put a new starter on it same thing we put a new key switch same thing and when it idles it idles fast then slow . He pulled off a vaccum hose off of one of the sensors and it would idle fine but we're not sure what the sensors are or what they are called to see about replacing them. I hope you can help

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Most likely it was the egr valve or the Iac valve that your talking about. however you might want to check to make sure the throttle adjustment if it is carburated or the tps sensor if it's fuel injected.please rate this solution. thanks

Posted on Aug 29, 2008


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the intake valves could be coked up with carbon (this requires walnut blasting and it is done with the head on at the dealer)
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May 12, 2011 | 1985 Volkswagen Cabriolet

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I have a 1978 Chevy longbed with a 350 engine, dual tank. I have a new fuel sending unit, spark plugs, rebuilt carter quadrajet, new fuel pump, new spark plug wires, new distributor rotor. During...

The problem is in your carburator. Was it rebuilt in a shop or by yourself or a friend?Did they know what it was going on? It could be that the float level is too low. It could be that you have the plunger rod for the power valve in the wrong hole. It could be that you just need to adjust the mixture screws on the front. I would start with the mixture screws. Turn them in until they seat but don't force them,be gentle. Turn them out 1 and 1/4 turns each and start from there. You will have to turn each one separately from here.Set your curb idle about 500 RPM and turn 1 screw out until you hear the idle start to go up and then back it off until it starts to falter or miss, them come ahead just enough to bring the engine out of that. Then do the same with the other screw. Reset your idle and rev the engine by hand, a couple of cracks and then crack the 4 barrels open and let go. If it stalls then open the idle screws about 1/8 turn and try again. When the engine will return to idle off the 4 barrels without stalling your mixture screws are set right. Make sure you keep resetting the curb idle, usually 500RPM for a standard and 750 RPM for an automatic.
If you rebuilt the carb yourself then look on the rebuild sheet that came with the kit for your engine application and make sure you have the power rod in the right hole and that you have the correct float level. Different applications have different float levels even with the same size engine. Set them for the engine you have it on, if the carb came off something else. Hope this helps.

Mar 21, 2011 | Chevrolet Silverado Cars & Trucks

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My 87 Cabriolet doesn't want to start (but it will pop-start). It also stalls a lot; it seems to have something to do with whatever it is under the back seat (fuel relay?), which starts to hum as the...

If you car wont crank start I dont think the fuel system is the culprit.

You probably have a sensor issue that starting the vehicle in motion overcomes.

You should see about having the engines diagnostic codes read and see if any sensors are out of range or stuck.

It sounds like an idle air control valve or throttle position sensor has gone bad *(perhaps both?)

Be safe and good luck!

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Ignition system sounds probable on vhicle when everything gets warmed up. High pitched hum could be bad tire or worse bearing.

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check this out and see if it helps. It sounds like you are priming the psi up when cranking then it can go. but when you let it sit the pressure drops and has to build up again. I a not a VW person myself but love tinkering, so let me know how it goes.


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Idling Problems

Note that all cars don't have the same symptoms as stated in the following procedure to cure your problem.
Here are the most common causes of surges, stalls at stops, low erratic idle speed, rough idle and engine hesitation, it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

Mar 31, 2009 | 1989 Volkswagen Cabriolet

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