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- Code 24 (I guess it's residue code from when I drove the car with gauge cluster removed)
- Code 33 (MAF High Voltage)
- Code 44 (Lean Mixture)
- Idle is rough (yet the exhaust sound is so damn great at the same time
- When idle is rough - engine is smoking excessively (especially visible when I'm leaving intersection after some time) - I'm not sure if it's grey or white smoke
- Hesitates under throttle and doesn't have much power
- But sometimes it runs great (idle is fine too) only to start acting up again (today morning I was driving to job and it drove great - plenty of power and stable idle, and when I was driving home now - it was horrible! - rough idle, stalling, but sometimes it was smooth too).
- Backfires a little when I let the throttle off
- MAF sensor is original I think
All symptoms started 1-2 weeks ago (recently I was driving hard during a track day) but it wasn't immediately prior the problems started...
After studying the service manual I guess MAF dies on me - am I correct? Or maybe it's just burn-off relay?
Before you start replacing parts, I suggest checking all your vacuum lines. Also check wiring at the maf sensor and maf relays, tps, etc. These cars are 20+ years old and wiring problems tend to creep in. On the older style relays, the wires tend to pull out the back of the connector and cause shorts. Also check your fuel pressure.
Update on the issue - right after start this morning car was blowing black smoke (until the exhaust warmed up a little - then it turned white/grey). Disconnecting the MAF harness helps a little. Wires on the relays, TPS and MAF sensor seem solid. Vacuum lines are OK. Next week I'll visit my mechanic to check the fuel pressure, replace the fuel filter and check the MAF.
My Mechanic diagnosed the faulty MAF. Fuel pressure is OK. Also after disconnecting the MAF car drives OK (maybe even better than before the idle problems first occured). I just ordered a new MAF and few other parts from Rockauto...
Parts arrived today... Quality of the Spectra Premium MAF is HORRIBLE. Sensor is leaking air all around the body seams which (unlike the stock one) is made of two halves. I just put some epoxy on the seams but I suspect it may leak air around the electronics housing too. Also it was very loose when installed in the air snorkel, so I had to put some electrical tape around it to cure this problem...
Internally it's different than the stock Bosch MAF (looks exactly like Wells or Rich Porter MAFs).
Look at the pics - feel the taiwaneese cheapness!!!
I have a bad feeling about this sensor, but I'll give it a shot... If it won't work then I'm switching to EBL flash.
Code 33 went away, but code 44 (lean exhaust) is still present...
- No more rough idle, backfires and excessive exhaust odours but:
- engine stalls when switching from N to 1/2/D/OD/R
- idle fluctuates (500-1000 rpm) when the transmission is in 1/2/D/OD/R up to the point the engine stalls
I removed the new MAF and used automotive black silicone on all of the seams as I suspected some vacuum leaks still were present...
I also raised idle a bit with the screw on the throttle body (and it helped with fluctuation) but full TPI tuneup is needed anyway...
This week I'll have the intake checked for vacuum leaks, spark plugs replaced and exhaust gaskets replaced (because I have exhaust leak for sure between engine block and manifold which may cause lean readings on the O2 sensor)... but I'm one step closer to updating stock ECM to EBL Flash...
Just for future reference - problem is most likely solved.
After 8-9 hours we chased the problems down to: igition retarded way too much (over 30* ) and IAC/TPS set not correctly. Probably there was also a problem with alternator providing too small voltage (it was 13,8V at battery terminals, but at the same time it was just over 11V at the gauge cluster). After setting the ingition timing and IAC valve (and TPS) we idle was stable and there was no more stalling when in Drive. But first battery and then alternator died on us during testing procedures and car started stalling again. After replacing the alternator and charging the battery it was over 14V at the battery terminals and over 13V at the gauge cluster (and again - no more stalling). Spark plugs and O2 sensor were replaced as (heavy carbon buildup) but I don't think it was the main problem. No exhaust leaks at manifolds found, but there is a leak on the Y-pipe that needs fixing.
I returned home with no problems at all and car runs better than ever but car was alredy warm. I will check the cold start tomorrow.
Unfortunately... car will stall when the engine is cold. I need to hold throttle slightly until it's warm, then it idles with no problems (no matter if in neutral or in park). Unfortunately when I was cruising I could feel immediate loss of power and SES light turned on (code 33 again) also started backfiring a bit when decelerating. When I was driving home it didn't flash SES and car had pretty normal power (maybe it was a bit sluggish)... so the problem seems intermittent...
Tommorow I'll replace both MAF relays and Coolant Temperature Sensor...
After replacing MAF power relay and CTS problem is still present... I'll try to replace the burn off relay as well, altough I don't think this new thick film MAF uses it due to it's design... I will set IAC and TPS again and see if anything changes... I also discovered that my dirt cheap FTDI adapter can be used as an interface for WinALDL/TunerPro so at least I will have a bit better insight into what's going on...
Mechanic replaced the IAC with one which was previously in my car (cleaned it too), and once again set idle rpm and it seems it cured the problems - no more stalling when engine is cold.
I'm having the same issue your having, I installed a granatelli maf because a friend gave it to me when he went carb and I'm still getting code 33. Did the IAC fix your problem?
I'm having the same issue your having, I installed a granatelli maf because a friend gave it to me when he went carb and I'm still getting code 33. Did the IAC fix your problem?
I'm sorry I'm late with the reply.
New IAC didn't fixed the problem. But setting the ignition kinda fixed it. But from time to time car still looses power for a moment, no Codes usually though.
I'm setting the idle just like the GM workshop manual says, by setting TPS to 0.54V, turning the ignition on for around 30s, disconnecting the IAC, turning the ignition off, then starting the car and setting the throttle possition to desired engine idle speed (with car in D with wheels blocked), then shutting down the engine, connecting the IAC, resetting IAC valve by starting the engine with slightly depressed throttle and shutting it down again after 10-15s, then setting the TPS again to 0.54V.
I still have some of the problems - car sometimes looses the power when driving with slightly depressed throttle, usually letting the throttle off fixes the issue. The problem usually occurs when the car wasn't driven for a day or two and when it was raining... connectors look good. I was able to catch the problem today with the Tuner Pro... What do you think?
GREEN - spark advance
YELLOW - engine RPM
RED - TPS voltage
BLUE - car speed
PURPLE - MAF readout (grams)
RED - engine RPM
GREEN - spark advance
PURPLE - MAF readout (grams)
DARK GREEN - MAF readout (raw data)
The power variation is visible. Other sensors / battery voltage etc are stable. I can attach the Tunerpro log if it will help.
I bought Walker MAF from eBay, replaced the Spectra Premium thick film MAF. It immediately fixed the problem. New MAF gave me Code 36 (Burn-off circuit) at first, but after resetting the codes Code 36 didn't came back (at least not yet), car drives great, starts great, no more power variation issues or hesitation...
11-05-2015, 02:54 PM
) and IAC/TPS set not correctly. Probably there was also a problem with alternator providing too small voltage (it was 13,8V at battery terminals, but at the same time it was just over 11V at the gauge cluster). After setting the ingition timing and IAC valve (and TPS) we idle was stable and there was no more stalling when in Drive. But first battery and then alternator died on us during testing procedures and car started stalling again. After replacing the alternator and charging the battery it was over 14V at the battery terminals and over 13V at the gauge cluster (and again - no more stalling). Spark plugs and O2 sensor were replaced as (heavy carbon buildup) but I don't think it was the main problem. No exhaust leaks at manifolds found, but there is a leak on the Y-pipe that needs fixing.
