3b20t intermitant miss at WOT.. ??

[stocious]

just bought myself a 1991 s2 coupe.. best money i ever spent IMO, there is a intermitant miss that seems to happen when under full boost. im a mechanic myself. and i may be wrong but it seems to me that theres a little too much boost "sometimes"?? and with window down if it does miss it sounds like the WG is working hard.. 90% of time boot down pulls like a train with no problem at all. my god are these cars fast

[stocious]

anyone??

[UrS4boy]

Intermittant misses at WOT on a 20Vt engine are typically ignition related. On an AAN or ABY, the problem is usually a bad plug or a bad (weak) coil (one of the five coil-on-plug OE coils). In your case, because the 3B only has a single coil, I would suggest that you start with checking/changing your plugs and testing the coil. It's going to be plugs, coil-to-plug wires, coil OR...perhaps a bad rotor in the 3B distributor.

Start with checking/replacing the plugs (22 lb-ft, 30 Nm).

[mcandmar]

Welcome. As above make sure it has the right bosch plugs, and the distributor rotor and cap are in good shape. With these cars and there age Boost/vacume air leaks are your enemy, the ECU is very sensitive to the smallest of leaks. You really need to pressure test the intake and get it airtight. In my experience its usually best to replace all the small vacume hoses as they go porus with age.

As i see your in Ireland, what fuel are using? I find my car very fussy as i cant get proper 98 locally. As a substitute i use Maxol E5, or Applegreen E5. Just avoid Texaco fuel, mine runs horribly on it.

[stocious]

thanks for the replies guys.. dizzy ccap and rotor are on the cards allready.. she has brand new leads as they had broken down and i would not buy till replaced. also how can i guy tell if she been chipped or not? without use of the bum dyno? she is very very fast imo.. have about 15/20 grand of receipts in glove box but no remap receit, im all about tuning but if its not done right i want it out.. another thing is the upper chamber of the wastegate has a open pipe nipple, should there be a pipe there, and to where should it go? also the AFM has a brass screw on the side of it, should this have a anti tamper plug on it. ?? all suggestions on this car are welcome.. EVERYTING!!! if any off the top of there heads can suggest a way to take slop out of drivetrain and tighten up gearchange feel free to tell me.. im no going under this car its too heavy.. need to make/buy some new axle stands

[stocious]

valve stem seals are needed also.. any info/method do's and donts on these would be great.. this car is in my blood now. by by money!!

[UrS4boy]

The nipple on the wastegate cap is supposed to be open to atmosphere (see diagrams below).

While some of the items in the link below are AAN/ABY/ADU related, most also apply to the 3B (just click on the labels, they are live links):

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html

[newsh]

3B owner

You need to do a pressure test of the inlet tract to check for leaks. Do a search for a how-to.

The MAF connector is sensitive to corrosion, use some good quality contact cleaner on it and plug in and out multiple times. Very unlikely the MAF has been tampered with..

The brass nipple on the top of theWG is supposed to be open, no pipe (everyone asks that question! )

If it's smoking check that the crancase PCV system breather pipes are clear.

You must be sure to get the special narrow tipped rotor for the dizzy. A wide tipped one can cause spark hop and bent rods.

[stocious]

ok thats great thank you.. im getting a bit worried about my wastegate.. seems to have been adjusted, nut is down alot deeper that one shown in pic. ?? i need to get a boost gauge and get a number

[stocious]

suffering a monumental hangover at moment.. but i will check all things ye suggested guys and i will report back.. whit a boost figure too i hope

[newsh]

If it's boosting more than 1 Bar and not cutting out then it's been chipped.

[stocious]

ok thats cool... ill check what reading i get soon!! but if my brain serves me correct.. should the wastegate not be adjusted at all whatsoever ?? being electronicaly operated, a mechanical is a bit odd to me.. but that being said.. its gut wrenching fast in 4th gear and has cats removed so i think someone warmed over her at some stage.. im affraid to let it be put on a rolling road..

[UrS4boy]

The wastegate spring controls the initial rate of boost rise as well as the maximum boost with the N75 Waste Gate Frequency Valve (WGFV) disconnected. Stock WG spring in stock location = about 6 psig (0.4 Bar) boost withe WGFV disconnected. A "1.9 Bar" WG spring will give you about 13 psig (0.89 Bar) boost with no WGFV.

http://forums.quattroworld.com/s4s6/msgs/20987.phtml

[stocious]

i love this forum... ty

[stocious]

ok, i have taken the spanners to the car today and found quite alot of oil in the positive side of the intake, intercooler, throttle body ect.. , removed airbox ( missing inner clip and also drilled like one would do with the old k-jet 16v's ) removed rubber pipe at turbo inlet and found a very slight tight spot when i rotated it, thing is tho, i started the car to watch operation and to oil it good, tight spot gone ? but will pop its head up every so often if contiuasly rotated!! think its time for new one? or new core ? ££££????. any one have any experiace with tightspots in their turbos. tight enough that an oily finger just cant spin the nut anymore but can just fine after the tight spot!! today i started my mission of making my 3b give up the ciggy's lol. will start new thread in proper place soon.. any help welcome. valve guides also being thought about seriously