So i read through the threads and the FAQ's to try and find an answer to my question. i have a 1987 s4 t2 and i have the dreaded 3800 rpm hesitation. i noticed this issue after a night of driving. first thought was blown engine. car runs great up to 3800, but once turbo should start to spool the car bogs and seems to have no power. the stock boost gauge shows that the turbo is making pressure. strange enough, sometimes it will spool and other times it wont. also after 3800 the car is seeming to pop alot. FAQ's say check all grounds, which i did. I replaced one ground wire and even added a grounding kit. i have also cleaned my fuel injectors which i have read can be another problem. if anyone has any ideas, or has had a similar problem i would love to hear what you did to fix it, thanks a million.

 

I've read about this problem. Seems the ECU can act up. If you can find a used ECU at the junkyard cheap try replacing it. Otherwise Hailers has some writeup on how to fix this(ECU grounds). Maybe he'll chime in

 

forgot to mention i didnt have an 02 sensor.
picked one up today and am also swapping to an r tek tuned ecu
ill keep everyone posted

 

is it possible a clogged cat could cause this

 

IF the RTEK does not solve the problem, then a LOT of people with series four have had success with adding additional ground wires to the ORIGINAL ground wires at the ECU plugs.

You might try to just add an additional gnd wire to pin 2C of the middle plug. It's a brown/black wire in case I forgot the pin number.

And or also add additional gnd wires to the EXISTING ground wires at the ECU. Pins 2R, 3A, 3G. You can do that by following those black wires up the harness a half foot and finding where they all come together in a splice. Add one additional wire to that splice with solder, then put a ring terminal on the OTHER end of that wire and bolt it to one of the nuts that hold the ECU BRACKET to the chassis.

You look at the jpg attached out of the FSM and you can see how all are related to each other and terminate on top of the rear rotor housing in a ring terminal as the official ECU ground point on a series four car.

All those sensors come together in mechanical splices inside the harness. That is most likely where part of the problem exists. It's worked for people in Tx, Fla and NZ.

Then again your problem could be a honked up Alternator with a blown diode feeding a/c voltage into the dc lines and causing Confusion. Who knows. Got me. All I know is, that my gnd on the rotor housing is Perfect but if I remove the additional gnds at the ECU, I can create hesitation once more.

Series four car.

 

ok so i got the 02 sensor in. no go
swapped for the r-tek. no go
i suppose ill be adding some ground wires this weekend.
i was also told to check the boost pressure sensor...
make any sense?

 

Check and make sure your BOTH of your secondarys are coming online at 3800 rpm.

Also make sure your boost sensor is working. Looking at the MAP on the Palm if it's a RTEK2.0 and if not then look at the voltage on pin 2B to see if that voltage matches the FSM figures at idle.

Actually BOGGING makes me think of too much fuel. Hesitation makes me think of lean on fuel.

I recently had a hesitation caused by me accidently ripping a wire off the front secondary injector.

 

which rtek did you put in?

 

now that you mention it when i put on my new alternator i got some sparks. ill check that tonight.
ill also check the map by replacing it with one we know works

thanks again.
ill keep everyone posted on what happens

 

it was the alternator.
installed a different one tonight and she runs like a champ.
thank you everyone who had input!!!!!!!


THANKS!!!!!!!!!!!!!!!

 

nice.

 

This makes me *wonder* if *some* of the hesitation problems people have, are really due to a marginal alternator output or one of the diodes in the alt blown and putting a/c on the dc output line, confusing the ECU.