AndrewsQuattros

Owned the 5ktq for a couple months now and(along with overboosting) this hesitation problem started to develop and get worse, you'd think vacuum leak so I started by changing the lower IC hose and the CIS intake boot with ones that looked much better (the original cis boot was pretty cracked up) .. Well now if anything it runs worse, not better as I would have thought- it hesitates very bad especially when you get on it, and even seems worse on a humid day(?). I checked and re-checked that everything is connected properly, I even played with the mixure setting a bit in hopes that maybe it was adjusted to suit the leaks... Checked a bunch of vacuum hoses that they're connected and such, fixed a couple minor things.. still nothing It still overboosts because as soon as I thought of changing the WG diaphram (as i'm pretty sure that'll solve the overboost problem) the hesitation started to happen, and proceeded to get worse. But I dont think the high boost and hesitation are related. It doesn't seem like a small vacuum leak, seems like something pretty big.. Any further ideas?

Thanks for reading

duder5kcstq

I have an 86 5ktq, she's had a stumble for a while. In the last week it got a lot worse, started surging at idle, and now backfires when I'm off throttle, or just barely on throttle. The wierd thing is, I too have a ripped wastegate diaphram, which I figured could be a pottential vacuum leak(air from pressure side through to other side of intake and vise versa). So I plugged up the hoses to the wastegate(for now). Another thing is she runs good on throttle(under pressure). I need to check/replace the TPS. The o2 sensor is within 20,000 and my A/F guage shows it reacting quickly. On that note it seems at idle the guage reads real lean(usualy bounces around). I suspect at least one vacuum leak, but can't find it. I just bought a good Mighty Vac, so that'll help. Today out of curiosity I tried unplugging the ISV, didn't change any thing. Is there an easy way to pressure test my intercooler? I also just replaced the fuel filter($7.50 ea. for bosch at autohausaz.com), so that's good. Does any one know symptoms for a failing fuel pressure reg. or accumulator? Could any ignition components cause this? I have a fresh cap, rotor, and plugs on hand, but the stuff in there isn't that old. The two temp sensors for ISV and ECU(little cheap ones) are new. What else, the heater/ac is on the fritz. It's either cold or hot as hell, and never the way you want it. I need to check the ac controller for vacuum leaks. Any suggestions, anyone? My other car is a motorcycle and it's getting cold! The seat is also being reaphulstered, so not an option any way. Could a big overboost surge cause a sensor/diaphram to blow out that I should check? Thanks in advance for any help. JB

RussB

<center><img src="http://pictureposter.audiworld.com/49589/audi_im_ground.jpg"></center><p>
Group: 25

Number: 91-13

Date: 10/31/91

Subject: Long Cranking Time, Intermittent Stumble and Misfiring

Model(s):
200, 5000T - With 2.22L, Engine Code MC All M.Y.

This Technical Bulletin supersedes Technical Bulletin, Group 25, # 91-01 dated March 31, 1991

Condition:

Intermittent long cranking time either hot or cold.

Possible Cause:

High resistance on ground stud caused by sealing compound (Loctite).

Service:

Remove the ground stud on the intake manifold. Inspect the stud and the threaded bore for signs of Loctite. Clean the internal as well as the external threads. Reinstall the stud and ground wire.

Complete a quality check with a cold engine and again with the engine at operating temperature before returning vehicle to customer

quattro_rocks

My car is doing a similar thing, but very intermittent-
Past experience from my previous 5ktq has shown that the fuel pump relay could be the problem (One of the problems).
One thing i have noticed if it's the fuel pump relay and you are getting intermittnent power or hesitation or bucking, you can switch the fuel consumption on w/ the trip computer and it will read close to 20L as apposed to the normal 12ish.

AndrewsQuattros

thanks for the input... but I some how think it's still something vacuum related. What a pain it is

duder5kcstq

My gut feeling(historicly very accurate) says I have a major vacuum leak somewhere. Could a totaly shot ISV stay open causing the leak? My idle surges from 1250RPM to 1600RPM. It also smells rich, and backfires out of the exhaust when off throttle. Would it work if I try to plug up the ISV circuit to test my theory? The ground was good. Thanks for any help. JB