85 8v gti studdering under load

[JC91]

So recently my car began studdering while accelerating past the halfway mark. It just randomly started doing this one day and only will occur after the car has gotten up to temp. I've searched around but haven't found anything specifically with the symptoms like mine, only similar cases. Can anyone point me in the right direction to start looking? Thanks a lot in advance.

[ps2375]

When was the last tune-up done?

[JC91]

Honestly, probably close to a year ago

[WaterWheels]

I'm guessing, always bad to do, that this is not a CIS-e system and more like basic or Lambda CIS (Is it a GTi or do you just call it one like some others do?). If so you really need to have the fuel pressures checked. A bad control pressure regulator can act like that but aside from just swapping another one in you have to test the fuel pressure. I was thinking maybe fuel filter but you say it only happens when warmed up, are you sure?

[JC91]

It is a true GTI, and yes it only happens when it is warm. I also just found out that if i ease VERY slowly onto the throttle before the point when it starts studdering, it runs fine all the way to WOT..

[Glegor]

It is a true GTI, and yes it only happens when it is warm. I also just found out that if i ease VERY slowly onto the throttle before the point when it starts studdering, it runs fine all the way to WOT..

have you cleaned your CIS fuel distributor assembly yet?

my car was starting to act up, in a different manner from yours, and cleaning the sensor plate, fuel distributor assembly, as well as lubing every moving piece, helped me out..

[EuroTrash_miT]

I'm barely starting to have spuddering under load and i suspect my fuel dist is having issues also. I checked the plate when i had to air boot off and made sure it was spotless but i want to check the lever with the frequency valve on it and make sure everything is clean and working properly.

Is there a FAQ or How-to for properly cleaning and checking my fuel dist?

EDIT: never mind, answered my own question

http://www.vintagewatercooleds.com/t...MAF/cismaf.htm

[Bun-Bun]

This sounds a lot like the problem that I'm having. Try pulling the battery connection and resetting the computer. Then drive around all easy like for 5-10 miles. Then see if it continues to sputter. If its anything like mine, it will run slightly rough for those first few miles, then it will go away (for a while) it will likely come back. I'm checking sensors for the culprit

[Bun-Bun]

So I found a solution to our similar problem. The problem was the thermo time switch. It's super easy to test if you have a multimeter. Simply wait till a car is cold, and then pop the connector off the switch. The thermo time switch is near the engine, in line with the upper radiator hose. With the multimeter set to ohms, place each prong on the seperate terminals in the switch to close the loop. If the switch is good, it should read somewhere between 0-5 ohms to still be good. Then, start your car and allowit to come up to full temp, and test again. It should read between 75-80 ohms. If one or more of these is off, or the resistance doesn't chang the switch be, replace the switch. The thermo time switch basically tells the ecu to run a cold start up map, and ignore the o2 sensoer for the first few secinds after start up. If the switch isn't working, the ecu wont be getting a solid signal from the o2 sensor, and will throw off the amiunt of fuel being burned. If yours is like mine and stuck somewhere in the middle, it will throw of the fuel levels warm or cold. Hope this helps you!

PS: remember to reset your ecu after replacing the switch!

[JC91]

I checked the fuel dist. and everything seems to be moving smoothly. I will try testing that sensor right now and get back with the results. It also is now studdering at all rpms but once it finally makes it up to high rpms it revs fine across the board for about 3 minutes and then it goes back to studdering again....

[Jon85]

well how about that, my 85 golf with the 8v gx engine is doing the same thing, well sort of. When the car studders does it sound like a subaru WRX? but with no power? ive found that advancing the timing a whole 30 degrees makes it run smothly and it gets back the power it once had. when i first started having my issue it was intermiten then it just would do it all the time. ive replaced the fuel filter and the plugs, wires, coil, O2 sensor. ive reset the timing mechanicaly several times and talked with multiple shops, they all say different thngs are the cause. ive even had one shop check my fuel pressure and its right where it should be. another shop saysits an air leak on the intake side so ive replaced the injector seats and found that that has helped but very little so im getting close. i wil check that sensor like one of you suggested and see what that is doing. do any of you know about the fuel pressure regulator that mounts to the front of the engine?

[ps2375]

PS: remember to reset your ecu after replacing the switch!

You don't have an ECU, your fuel injection system is mechanical. With the ever so slight exception of the Lambda control portion which is essentially slightly smarter than a rock.

[ps2375]

Seems you guys really need to check the spray pattern and flow of you fuel injectors. A dirty or clogged nozzle that doesn't control the fuel spray correctly can cause these symptoms too.

[WaterWheels]

. . . ive found that advancing the timing a whole 30 degrees makes it run smothly and it gets back the power it once had. when i first started having my issue it was intermiten then it just would do it all the time. do any of you know about the fuel pressure regulator that mounts to the front of the engine?

That is a control pressure regulator, named so because that is what it does. If bad or going bad it can give you problems, but it is one of the tests you are supposed to do when doing fuel pressure tests on CIS engines. So either your mechanic failed at this station or it is not your problem.

Your 85, like other older systems, has a mechanical/vacuum ignition advance in the distributor. I never read where people service or check these systems. The vacuum canisters can and do leak over the years. How old is yours? It is simple to test with a vacuum pump and they are rather cheap if found bad. They can also fall off the advance plate inside the distributor and the Hall sender will move around then. There are weights and springs inside to do the mechanical portion of the advance. I have found one spring missing or popped off a few times on these distributors, and weights installed wrong. They also need lubrication once in a while, not just after 25 years, but nobody ever seems to do this. There is a small felt pad under the rotor which should be oiled once a year. Some of that oil finds its way down the large shaft to keep it lubed. The entire thing comes with some grease on it from the factory, but that dries and becomes dirty after many years. So although this may not be your problem, you might want to look into it as you should never have to set the initial advance that far just to get a smooth idle.

[Jon85]

ive gone and replaced the entire ditributor, no help. I've had the injectors cleaned and they are in good shape. and there is a on board computor, the jet-tronic which is up under the ashtray in the lower center counsole

[Jon85]

[QUOTE=WaterWheels;78649503]That is a control pressure regulator, named so because that is what it does. If bad or going bad it can give you problems, but it is one of the tests you are supposed to do when doing fuel pressure tests on CIS engines. So either your mechanic failed at this station or it is not your problem.

I had the fuel pressure checked at Double J's MotorWerks in portland Or. the results were fine, system pressure was normal cold and at operating temp.
I have also unpluged all the sensors for any change and no effect so i dont think its sensor related......I will be doing the carb cleaner test arond the intake-to-cylinder head area for any change

[ps2375]

ive gone and replaced the entire ditributor, no help. I've had the injectors cleaned and they are in good shape. and there is a on board computor, the jet-tronic which is up under the ashtray in the lower center counsole

That thing you call a computer is so limited in what it does and it has no memory of what it was doing the last time the key was on, it has no cmos memory. It is reset every time you turn the IGN off. And you could disconnect it and set the mixture with a tailpipe sniffer or a WB and the CIS will stay at that setting.