uneven idle

[WV75Z]

I am starting to track down an idling problem in my 83 turbo 5spd. It will idle normal and steady holding 18.5 on the vacuum gauge at about 7-800 rpm on the not so easy to read digi tach. After 5-10 seconds it will start to bog and the rpms will go down by one bar on the tach so maybe 600 rpm? When it bogs it continues to idle weakly and the vacuum goes down to a less steady 15 -16. After 5-10 seconds it will return to normal and cycle repeats itself. I have searched but haven't found any posts that exactly relate to my problem as it also manifests itself as a subtle miss when cruising or accelerating at any rpm range. It is like a steady pulsing subtle miss. I pulled the oil filler cap and the engine sputtered and died which indicates no vacuum leaks? It does however have a major #6 manifold leak. The car also sputters and protests a bit when starting out easy in first gear especially when cold. If you punch it it straightens up and runs pretty good. I have never had a turbo before but knowing the stock 0-60 is 7.1 or so I'd say its running pretty strong and close to that mark.

 

1)I pulled each plug wire and restarted the engine. Not really any difference. A bit ruffer since the missing wire but same pattern of good then bogging down each time.

 

2)There is an MSA rising rate fuel pressure regulator hooked up by the po that I know nothing about. I don't think its necessary to run up to 10psi so I'm thinking about removing it. I wonder if that could cause a problem?

 

3) I have yet to check the TPS or AFM nor do I even know how.

 

4) I am just trying digest all this new info and figure out a good starting point to try and track this down. I am just familiarizing myself with the car and all of the sensors.

 

5) I'm pretty sured these are the original injectors with 165k on them. How do I test the injectors to see if they are working properly? I started to pull the injector plugs one at a time but the conectors are so old and brittle the first one cracked on the tab. They all look they could just disintegrate.

 

6) can the fuel pressure be tested with the car at idle? Wouldn't the fuel pressure change under load? How do I know what the initial setting should be vs the pressure when driving hard? How does the aftermarket rrfpr interact with the stock one?

 

Thanks

 

Jon

 

Thanks

[madkaw]

Jon,

have you found anything yet? It sounds like your car is running the same as mine, so if you come up with anything -please post. You can use the old screwdriver to the ear trick to listen to the injectors. I am going to try some seafoam this weekend to see if the injectors are clogged. Search and you will find a FSM somewhere on this site and get out your ohm meter and start testing everything. There are a days worth of ohms tests that will help eliminate stuff. Good Luck!

[greasymonkey]

Not sure about the rest of the issues you mentioned, but as for checking the fuel pressure, yes, you can check it at idle. You can check it with the key on engine off as well. Never worked on an older car with a turbo, but I do know that the newer ones have a consistant pressure at the rail regardless of whether it is running or not, remember to have key on, and regardless of the rpm range.

[roger.svoboda]

It might be related to the fast idle circuit for the air conditioner. there is a solenoid that opens closes. if there is a blown air hose in there that would give you a vacuum leak. Anyway I would definitely check for a vacuum leak causing the problem. another quick and dirty test is to take off the oil filler cap when the car is idling (expecially when at the low idle) and see if the car runs the same or worse. if runs the same then indicate vacuum leak. if runs worse then maybe ok.

[roger.svoboda]

Oh yeah by the way since you have a digital dash you probably have the auto climate control which is another headache. Could be one of the vacuum lines going thru the dash to that monster.