HELP! 1990 90Q 20v fault code, can't solve!

Posted: Tue Feb 22, 2005 6:11 am

Car is a "early 90" 1990 90Q w/ a 20v, hitachi electronics/isv/injectors etc etc, 116,000 miles on the clock, I purchased this car from a friend who got it in been sitting for awhile condition in new york, now lives in michigan, i've had it since december 2004 and here's what's been replaced by him and i:

-OEM catback exhaust
-Cap & Rotor (autozone)
-various vacuum lines & connections
-tri-electrode bosch oem plugs
-wires are blue and very new looking
-Bosch 13913 Universal O2 sensor
-various front suspension parts
-various interior illumination and small fixes
-ran BG44K/seafoam through it and extensively cleaned tbody
-valve cover gasket
-ohm'd out injectors, they're all even @ 2.5ohms
-new thermostat (still runs between 3 lines and 4th thin line <32f, higher)
-soaked ISV several times
-new air filter

Now, ever since I got the car I felt first the mileage was awful after the above replacements, roughly 15-16mpg city and no more than 22mpg highway... keep tinkering with it not finding anything wrong, the other day I installed a bulb in the check engine light position and dumped the codes.

Got 2143, first knock regulation sensor two, which I see is the one for cylinders #4 and #5, i run shell 93 octane fuel and the fuel filter & pump were done soon before he took ownership, car has a lot of documentation from 1996 when a dealer sold it to the guy before us, so I reset the ecu, verified the codes were cleared and took a drive.

Now with the light installed in the cluster i'm looking for it to flash when it's stored a code or otherwise do something to show me when it was upset, so I went WOT a few times (performance is lacking BTW) and didn't notice any flashing or anything, but then I got on the highway and held part throttle @ 70mph, light comes on and stays on, hmmm i think... so i let go of the gas, goes off, press gas to maintain speed again, comes on and stays on... so after a minute of playing with it making it my own personal cluster strobe light, i came back home to dump the codes... same thing, only 2143 (followed by 2.5 second blinks to alert me it's the end of the codedump when i attempt to pull the next code)

Now, I understand this code means it "thinks" it's hearing knock and it will reduce timing by 8 degrees, which i'm guessing is -8 degrees any time the code is stored in the computer because the performance and mileage plain stink at all times and the code comes back in a matter of seconds from a reset and a drive, but i'm not sure why it thinks it hears noises....

The only engine noise that's abnormal that I can hear by ear comes from the distributor, it's a slight slight rattle/vibration/grumble at idle that seems to clean up by 1200-1500rpms if you pull the throttle, I know this could be due to the plastic gear and/or endplay in the distributor, but I don't know how much this noise resonates at higher rpms (if at all?) and if the rear knock sensor would even be able to pick it up and identify it as knock hence the code?

Also, on a possibly related, possibly not note... the car starts up NO problem hot/cold and springs to life perfectly, but within i'd say 15 or so seconds of starting, it'll begin idle surging, say, 900-1200 rpms or so, won't threaten to stall, won't miss or run rough, just a idle surging sweep between these rpms and this will last usually no less than 10 seconds, no more than 40, then just says oh i'm sick of idle surging and rests at a stable idle (ONLY DOES THIS COLD, NEVER WARM)

When it's warm and I come to a stop, it likes to pick random idle points, between 900 and 1300rpm, totally random, smooth idle with no surge or hesitation, sometimes if i blip the throttle it'll come down a little, often times it'll go right back up after it does though, seemed like a vacuum leak but i couldn't find it

Other than the above I wouldn't say there's any noticable drivability problems, the sweep to redline during WOT is clean, feels like it's lacking power and where the horsepower should be strong 6000-6500rpm it acts like it just wants me to shift, if i go past 6500 it feels like it's strugging to hit 7000, most likely from the code being stored and the lack of timing advance

It never threatens to stall or "runs rough" or makes me feel like i'm going to be stranded but the mileage and lack of performance are enough to make me want my last B3 10v back, thusfar this one has proven to be identical in performance if not slower and a ton more problematic

also one more thing, when i try to engage the rear diff lock, the arm doesn't push far enough out of the diaphram to activate, i have to help it the rest of the way by hand, i've cleaned the rod very good and it moves good by hand, i'm wondering if there's a vacuum leak causing that or just the diaphram is bad and not holding enough vacuum?

thanks guys, i really need help on this one Sad

Posted: Tue Feb 22, 2005 10:14 am

Have you got another lambda/O2 sensor you can try in the car? From what I've read, poor MPG and wandering idle are classic symptoms...

Posted: Tue Feb 22, 2005 11:56 am

I read somewhere that a dodgy lambda probe can work intermittently and therefore trick the ECU into thinking there is no fault. My CQ20V had similar idling problems to yours last year, and a new model-specific Bosch lambda sorted them all out.

AFAIK, the ignition timing on these cars is pretty much set dead-on by the ECU and negligible advance/retardation can be achieved by a mis-aligned dizzy; if it's out by less than 5 degrees (approx) the ECU will simply kill the spark. As for the knock sensor, the only way I could confirm mine mine had gone was by the 'turbo-like' rush of accelleration at around 4750-5000 RPM, oh, and a fault code Wink

.

HTH (a bit at least... Smile

).

Posted: Tue Feb 22, 2005 3:27 pm

a have a new lambda, which we call o2 or oxygen sensor Wink

it's a universal bosch 13913 spliced in, proven to work fine

Posted: Tue Feb 22, 2005 9:54 pm

no suggestions?!

Posted: Tue Feb 22, 2005 11:44 pm

Shite american petrol?

I read somewhere that most petrol sold in the US, even though advertised at 93 RON or above is actually only about 91 at the pumps. From memory, the 7A engine is designed to run on 95 RON or above. Your problems could be the ECU pissing about with the mixture & timing to compensate for the lower RON petrol.

Run some 'premium' 97-RON through it for a few days to see if it helps.

Worth a try, and your engine will thank you for it.

Oh! And welcome to the forums, mate! Sounds like a nice motor you have there (yes, I am biased towards the 5-pot 20Vers Wink

).

Stick around, were a friendly bunch 'round here. Very Happy

Site Moderator Joined: Jan 31, 2003 Posts: 9144

Might be a faulty knock sensor or not bolted to the correct torque of 20 Nm.

Knock sensors are not expensive so it will pay for itself if you replace it and it fixes the problem.

I would also not recommend a wiring spliced lamba probe. Fit a Bosch OEM fitment type - they are more reliable.

Posted: Sat Feb 26, 2005 2:43 pm

Don't know what the 20v setup is like, I had this idle surge on my 10v.
Eventually located it, drawing in air past the injector seals, replaced seals-all ok.

Try going around various intake parts with a can of carb cleaner, have a spray about around joints in intake manifold and around injectors, if there's a leak the engine speed will alter.

Also check that there are no cracks around where the O2 sensor fits, could be drawing in a bit of air around there causing the ecu to over fuel quite a bit.

Posted: Mon Mar 21, 2005 11:05 am

presuming you are talking US gallons your fuel consumption is about right for a Q , mine is much more thirsty than my 10 v
with regard to octane ratings , presume you are quoting as per US , ie MON , which generally comes out with a number about 2 less than RON ;
one of the beauties of the MPI hitachi is that will set the engine to run on anything from about 87 MON upwards , of course with a loss of power , but it runs fine.....mine has run fine on 2 stroke mixture when I got stuck in the mountains due to a faulty fuel gauge .
but frankly I think you just have a faulty knock sensor which would explain why it runs out of breath at 6500 , as far as I can see this is is the only way it shows up as a fault code ; incidentally , how do you clear the fault code ? I have to disconnect the battery on mine to clear the code after fixing the problem , whatever it is .; other thing I don´t understand is that only california spec cars had the module which showed a light on the display when you have a fault

lebesset