# 1993 Audi 90 S Hesitation, Dropping Idle When Cold



## Stik2885 (Aug 4, 2003)

Hello I have a 1993 Audi 90 S, I have encountered a problem when i start it after a few hours like the morning. The engine will start then after about 12 seconds the idle will drop to around 300 rpm and there is not really a response from the throttle. This problem also is encountered while driving there is a slight hesitation on a start from a light or a stop. I have replaced spark plugs, fuel filter, and fuel pump. And none of these have solved my problem, so if anyone could send me any ideas of to what i could do next it will be greatly appreciated. Thank You - Jason


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## Peter Badore (Jun 17, 2002)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Stik2885)*

Have you checked the fault codes? How long has it been since the throttle body has been cleaned? The 93 2.8l V6 has EGR which sends burnt gases into the intake system for NOx control. After a period of use substantial "crud" builds up in the throttle bore area and can upset the air flow and air flow sensing. There are other failure that can cause hesitation as well. A bad knock sensor or two can retard the timing a lot (12 degrees or more) to make the engine feel "doggy". Do you use premium gas or regular? The timing gets pulled back if the engine is run on regular gas and enough spark knock is detected. Are there any vacuum leaks? Have you checked engine compression? A slightly leaking exhaust valve will cause minor problems that will go away at higher speeds. Are you losing a little engine coolant? Head gasket leaking into the combustion chamber is not uncommon on early Audi 2.8l V6 engines. Good luck. Let us know what you find out?


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## Stik2885 (Aug 4, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Peter Badore)*

To the best of my knowledge there is a slight exhaust leak, i cleaned the throtle body out a couple of months ago when the problem first happened there is no coolent leak although i opened my air box for better flow of air which i will eventually be cutting a hole this week so the top wont flop around if it does. i am also running the 89 octane fuel in it i have used an injector cleaner 2 times so far and hasnt cured the problem. i have had 2 replys in the general audi discussion for an Idle Stablizer Valve to clean or replace it and another was to check the fuel regulator.


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## Peter Badore (Jun 17, 2002)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Stik2885)*

Have you checked for ECU fault codes?


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## Stik2885 (Aug 4, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Peter Badore)*

No not yet because the mechanic (my stepfather) doesnt have the correct adapter so therefore another of his workers is going to try and tap it manually. Also the check engine light will come on at an idle speed and then go off when i rev the engineso it could also be an O2 sensor


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## Stik2885 (Aug 4, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Stik2885)*

I have an appointment to go to the dealership and have it scanned on friday beacause my mechanic doesn't have the tool to run a diagnostic test. I will post my results when i come home on friday afternoon.


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## dataiv (Feb 2, 2002)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Stik2885)*

I have a 1993 Audi 100 CS Quattro with the 2.8L V6 and was (and sort of still am) having the exact same problem. I had the check engine light flickering on every once in a while after sitting at idle for 30 seconds or more. A check using the VAG software revealed a bad O2 sensor. I replaced both of those, and the engine ran much better. Not as rough at idle, and it started getting better mileage again.
Now, however, it sometimes hesitates at idle. I can sometimes make it stall if I give it a bit of gas right after starting it, then letting it fall back to idle. It falls below normal idle and sometimes recovers, but sometimes just stalls.
If I start the engine and don't give it any gas, then it seems to be fine most of the time. But I can always make it shudder quite a bit if I give it a shot of gas right after starting it.
I put premium gas only in the car. If I fill the coolant tank up to the normal level, then it always leaks out a bit and holds about 1-2cm below the minimum marking on the tank but doesn't go any lower than that.
I'm saying all this because a) It may be relevant to your problem, and, b) I want to see if there are any ideas for my problem based on what I've said.
Thanks everyone!


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## Stik2885 (Aug 4, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (dataiv)*

Well I sent mine to the dealership to be scanned it also revealed a bad O2 sensor, and the Idle Stablizer Valve, which I will have cleaned this week hopefully. Although it may be an easy fix I have found my own solution to the problem im going to clean the stablizer and sell it. I am hoping to go down to a Jetta GL 2.0 because of easier maintnence.


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## Peter Badore (Jun 17, 2002)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (dataiv)*

How many miles were on the car when the O2 sensors were replaced? Were there fault codes for both O2 sensors? What fault code, if any, was present for the idle stabilizer valve?


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## Stik2885 (Aug 4, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Peter Badore)*

The O2 sensors havent been replaced i didnt get a print out of codes but the print out said faulty idle stablizer valve and possible O2 sensors but like i said the problem will be fixed once i sell it, but im goign to clean it and see how it wworks out


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## Audi tech (Jan 7, 2003)

*Re: 1993 Audi 90 S Hesitation, Dropping Idle When Cold (Stik2885)*

It could very well be an O2 sensor. However, the most likely culprit will be a vacuum leak; this will also set a code for an O2 sensor. Check the hose cluster that comes off the front the intake manifold; just under your power steering pump, and follow that hose. It will gang into a cluster of different sorts of hoses. 
Chances are, it won't be your EGR valve. They typically won't open at idle. Now, having said that, that doesn't mean that the valve itself isn't closing fulling. A quick test would be to put a vacuum guage on the valve; find the small brown vacuum line at the top. If you can hear the valve making a full sweep, then you're probably ok. You really don't want to pull the EGR valve out. The bottom fitting can be quite troublesome.
It can also be your IAC valve; idle valve. It's just a mechanical valve that rotates when you come to idle. It can, over time, gum up and not fully articulate over. Just remove the 10mm bolts holding it in place and physically look at it; just be careful not to munge up the gasket.


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