CJs 928

I know this issue has plagued numerous people (from the many searches I have done on Rennlist). I have done some of the easy stuff-just making sure that I am on the right track before taking the $$MAF rebuild option.

1987 S4 AUTO (US). Car was running Ok last week and the few weeks before. The car has not seen a lot of driving in the past couple of years due to incorrect tires/wheels by PO and a lot of hosed hoses (fuel and oil breather). Finally got some money saved and replaced all. Then I backed my brand new Maxima into my 4 Runner; this = 928 DD. So for the past few weeks it has been driving Ok, new noises have crept up and it does seem to not have the power I would expect (very rarely will spin the tires). I was on my way to work, stopped for coffee and restarted and BAM-tach bouncing like mad between 200 and 1200. When I put it in reverse or drive I have to keep my foot on the gas pedal to keep it from stalling.

I have tried the following:
WD40 ISV hose trick (about 1/4 can with the engine revving)-no help
MAF cleaned with CRC cleaner-no help
Unplugged MAF while running-idle stabilized. Item of note: with the MAF unplugged, if I gun it-it stalls right away. If I slowly depress the gas pedal it is fine until I hit 2K rpm, then the tach starts to dance and will stall. Not sure if this is normal with the MAF disconnected. Right now I believe it is the MAF. Looking for the educated answer.

Recent Mx:
New Caps/Rotors
New Ign cables (Bosch)
New fuel injectors (Ford ones from Roger)
Intake refresh (about 1 year ago)-replaced knock sensors and CPS (as well as seals/hoses in/under intake and valve covers)
TPS was not replaced (suspect for WOT issues), but does click with slight movement of throttle
battery is approx 1 yr old (interstate)
replaced one of the the sensors on the water bridge (can't remember the name)
Fuel pump/filter/tank strainer about 1.5 yrs ago (but have only got about 500 miles through them).

Again-looking for the Rennlist approach to the issue before I send the MAF off for repair.

Thank you for any help,
Chris
1987 S4 Auto
Goldsboro, NC

Tampa 928s

Sounds like vac leak, test for that first.

CJs 928

I had thought about this after my intake refresh. I don't have 100% in my mechanical abilities. Just hooking up to the vac lines-they hold vacuum. I also tried Dwayne's idea/contraption for hooking up to the MAF, but I could not get it to hold tight-kept popping off. I just bough the mityvac 8500 (came in the mail Friday), but I do not know how to do the vacuum check with the engine running (haven't attempted yet either).

CJs 928

I assume I just hook the mityvac to the vac line on the driver side (after the brake booster one way valve) and watch the gauge with the engine running? If it's above 21ish and is stable-then that would be good right (or wrong)?

Catfood

I have had a few drinks and briefly read through your post but the idle stabilizer valve pops to mind. WD-40 plus removing the intake manifold may fix your problem. I really hope my incoherence is correct!

CJs 928

Thank you for the reply Catfood. That was my first thought, ISV-WD40 trick, but it did not work. I did not spray it directly though, just through the hose with the engine running/revving. I was leaning toward the MAF because the idle stabilized when the MAF was unplugged. What threw me was that I could not rev the engine past 2k without it stalling (MAF still unplugged). That got me thinking it might be something else (or two things). Looking for a punt list of candidates or a yup it's the MAF based on a few measurements.

CJs 928

Ok, going to play with the vacuum checks and try to pressurize the intake and see what I see. If all checks well, I'll pull the ISV and clean the crap out of it.

Tampa 928s

If you have emmissions testing find a garage that has a smoke tester. I own one and found leaks in places you could not imagine. Call around money well spent put this to rest. If the tester you built blows off turn down the pressure make sure the clamps are correct size and clean the maf and boot with brake cleaner to remove all oil. A little carb cleaner around the intake boots maf and any major connection point while running look for an increase in idle speed.

CJs 928

Thank you for the replies Tampa 928s. I will do as you mentioned tomorrow. As for the smoker-I will start calling around. Any idea what the charge for something like this is?

Tampa 928s

Should be a diagnostic charge about $59-79, just note what you need to repair, bring a camera.

CJs 928

Copy all-thanks

Tampa 928s

Before you do this get a can of carb cleaner. Spray around the maf first and any large vacuum hoses, look for a change in idle,idlewill increase you have found your leak. Also spray each injector at the hole and each intake tube, do this slow not a lot and wait and listen, worth a can to test.

CJs 928

I tried the carb spray a couple of months ago, I thought I hit most of the areas (I don't recall if I actually sprayed where the injectors seat though). I will give it a go again since something has definitely changed recently to make this car run more like crap than it already did.

John Speake

The tach behaving eratically and a misfire indicates an EZK ECU based problem. The tach is fed from an rpm output signal from the EZK. The same signal is also fed to the LH pin 1 and is the signal that wakes up the LH, tells it to turn on the fuel pump, and fire the injectors.

Suspects are EZK relay, or bad connection from CPS (I see you changed that, so not so likely), or a bad EZK.

I suggest that changing the EZK relay would be a good start.

EZK ECUs are very relaible.

Tampa 928s

I maybe wrong but the tach is not the issue its the idle, correct?