Hi all
This car can barely get up to speed from 0-30 then runs well , once on the highway seems to be able to go as fast as I want , I am looking for where to start checking to improve low end performance ?

Ohm test your knock sensors and fuel injectors. Chances are pretty good that after 25 years one or both of the KS are dead and don't be suprised to find a dead or dying FI or 2 also.

http://q45.org/ohminjectors.html

goody90q45 wrote: ↑

Wed Aug 08, 2018 8:21 am

Ohm test your knock sensors and fuel injectors. Chances are pretty good that after 25 years one or both of the KS are dead and don't be suprised to find a dead or dying FI or 2 also.

http://q45.org/ohminjectors.html

Agree completely with this.

So did you fix the problem? Usually it’s repaired with the suggestions posted above.

Well this '96. Q is acting up again, similar to your '91.

Probably the knock sensors or ignition coil.Cylinder coils 3 and 5 were replaced 3000 miles ago with same symptoms . I suggested to change all of them though only the service guy said towait.
So will find out Tuesday if another 2 grand goes into her. Oh Well
.

Coil failures are pretty rare on this series of Q45. Fuel injector failures are pretty common.... it's also possible to have a fouled spark plug on the corresponding cylinder with the failed fuel injector.

goody90q45 wrote: ↑

Wed Aug 08, 2018 8:21 am

Ohm test your knock sensors and fuel injectors.

My 1992 has similar problem, though not so pronounced: It is just cold shouldered, often times backfires though intake when throttle is opened abruptly, as in accelerating from stop, or will stutter and stumble until throttle is let off and reopened, and engine RPM increases, then sometimes bucks when opening throttle at 45mph when in high gear after coasting. It really just seems lean.

I've never tested or replaced KS's. FI's are Deatschwerks retro fits, I've replaced all hoses under plenum, fuel pressure regulator, coils 2,4,6,8, tested for vacuum leaks, swapped MAF, and throttle position sensor, to no avail. Will KS's cause lean AFR?

Go ahead and ohm test the FI and KS to verify all is good. A couple of other things to check...

Sounds like the engine may be fuel starved. Could be the FPCU going bad. Try bypassing the FPCU with a jumper from the connector pin shown in the pic to ground. FPCU is under the rear deck and you can get to the connector through the trunk. The FPCU will run in high speed only while bypassed and if the acceleration problem goes away you've found the issue.



The MAF and TPS connectors are not waterproof and can corrode. Tighten the female pins, clean off any corrosion and coat with dielectric grease. Can't hurt, should help.

KS's ohm tested at 600K, and 10M, so looks like at least one is fouled. Wow, if this is the reason mine sometimes runs like hammered sh*t, that's an economical fix, except for the pain of the plenum.

Update : KS ohm test failed ,injectors OK . I finally got brave enough to tackle replacing the KS's , it has been an ordeal , previous owner had run over a traffic cone damaging the radiator and fan , overheating the car .
When removing the intake manifold most hoses crumbled and knock sensors were melted into a puddle .
As a former pipe-fitter and plumber I was able to re-plumb the many vacuum lines after installing new knock sensors . I added an electric fan for the radiator , car finally ran like the engine should . Test drive resulted in steam from under the intake , appears to be the hose immediately behind the thermostat housing .
Stuck thermostat now ?

Wow... That sounds like one heck of an overheat!

First one I bought had a bad rad and 2 injectors, knock sensors were a melted mass, plastic label on oil filter shriveled from the heat, ran strong after repairs but had a piston knock in the morning. That engine was shelved in fear it would give up, car got/still gets picked for parts...

Stuck thermostat wont make steam there, did you find the water leak?