TABBOO

I am getting Code 33 & just want to understand exactly what it is for. My car is an 87 TA 305 TPI code F.
I have been having an idle problem where it would stumble when starting & then go into fast idle also it would stumble during idle when warn but only it acted like it just missed a fire & then would go back to idleing OK. It would do this about once every 30 seconds.
My question iis the 33 in this car for is it for MAF volts only or MAP (manifold air pressure?) also. If it is for MAP how do I test for this. Also I would like to know if the Microtech MAF is the best thing to buy.

TPI

My car does exactly the same thing you describe.
Drivable, but.. very sluggish at idle.

If I let my car idle in my garage, it does exactly what
you just describe, idle speeds jump around, sounding
good at one time and very rough at another.

My SES light is lit the whole time, and it is the
dreaded code '33'.. is yours lit the whole time upon
start-up?

MAP? your car is a '87.. you have MAF setup still? or
were you referring to the Air Temperature sensor at the
bottom of the plenum?

MAP= Manifold Absolute Pressure, in correct terms,
& a completely different TPI system for the most part.

I'm slowly trying to troubleshoot my car, If I have any
success.. the first thing Ill do is post up on all recent code
'33' threads..

flaming-ford

iTrader: (7)

yah i'll third this as a common problem for me but, weirdly enuff mine is intermittent. although my idle does always search about 50 rpms and is a little rough let me knw via pm if you guys find something out that i didn't know and i'll do the same for you 2 if i figure it out quicker.

currently i already cleaned my maf sensor and its a aftermarket bosch, cleaned the tb real good and added a new fuel filter. after rep[laing the ff it didnt do it for a few days after but, it started doing it again so i assume that didnt fix it.

my problem realy seems fuel related but, im very new to tpi. ive heard things about a cold start injector and my issue when mine is realy acting up badly not the slight searching for idle seems like a hugely over rich mixture.

who knows ill try and figure mine out and g/l to u 2.

Vader

Your '87 did not come with a MAP, so unless the system was changed to speed/density, the ECM is trying to tell you that it is reading a MAF signal which is too high at a given TPS and engine RPM range.

The MAF is a sinking input device. In other words, the ECM supplies a current-limited 5VDC supply to the MAF sensor, and the MAF will ground that signal down closer to 0VDC at lower detected air flows. If the logic circuit ground connection to the MAF is not continuous, or is not properly grounded, the MAF cannot pull down the 5V signal as it is designed to do. Similarly, if the MAF signal circuit suffers from poor connection or continuity, the signal may be higher than intended. All wiring and connections must be intact.

The MAF burnoff system can also cause this code to set if the MAF burn off relay or circuit has problems.



You really don't need anything more than a good volt/ohm meter to diagnose the system. With the igintion ON and engine not running, make sure the correct voltage and grounds are present at the MAF terminals.

Test the MAF Signal Voltages

1. The MAF signal circuit (Terminal C) should be less than 0.3V with the ignition on and engine not running.
2. Disconnect the MAF electrical connector and test the voltage again. There should be a 5VDC reference voltage from the ECM.
3. Verify that the TPS voltage is between 0.47 and 0.61VDC.
4. Test for voltage in the MAF burn off circuit (Terminal D at the MAF) while the ignition is on, engine off or running. Any voltage present can cause the MAF signal at the ECM to be too high.

Diagnosis

A code 33 is set when the ECM has detected an intake air flow above 45 grams per second (about 2.2 volts) for one second when the engine is first started or at ant time when the TPS is less than 1/4 throttle and RPM is less than 2,000.

If you discover problems in the voltage or grounding checks, re-seat the connectors at the ECM and check all the circuit grounds. Make sure the connector at the MAF itself is intact.

If there is a problem with the 5VDC reference voltage from the ECM, re-seat the ECM connectors and/or test for the correct voltage directly at the ECM terminal B12. If there is not 5VDC source (± 0.6V) present, the ECM itself may have a problem.

With the ECM connectors clean and connected, if the reference voltage is significantly higher than 5VDC, there may be a problem with the other wiring shorting to that circuit on the vehicle.

If you are able to read voltage at the MAF burnoff circuit, remove the MAF burnoff relay and retest. You can even run the car in this mode, but will eventually set a "36" code for the burnoff failure.

If all voltages are correct, and all grounds and connections are intact, the MAF itself may have problems. A MAF failure causing a "33" is uncommon, but I suppose it is possible. It is generally more common to find circuit problems or a TPS adjusted too low.

Connecting a 12VDC power source to the fuel pump test terminal ("G" terminal of ALDL) will provide power to the MAF sensor, and the MAF signal circuit should create a low voltage (less than 250 mV) signal to the ECM. Monitoring the MAF signal voltage in this mode and wiggling the circuit connectors and wiring may allow you to detect any intermittent problems. Similarly, an erratic MAF signal with the engine running may indicate wiring or connector problems.

If you determine the MAF has a problem, the MicroTech 491018 units are decent replacements. They are identical to the old Wells SU-145 units.

TABBOO

Thanks for all the info. As usual Vader has all the best data on tpi problems.
From what I have read in searches I hope I am correct in observing that idle searching (variances in idle or rough idle ) is a symptom of a bad MAF. I didn't think I had a MAP but I wanted to make sure since it lists it in the code explanation. As for the choice of replacement MAF I am happy to get conformation that the Microtech is a good piece. There seemed to be a lot of controversy on that in the past posts. I will try to diagnose the problem with the info Vader gave, but I suspect the MAF because it is original (20 years old)
& I removed the screens about a year ago & have since read that may have been a bad move. I will also try the tap test on the MAF since I read a past Vader post & that sounded like an easy test to find a bad maf.
I will post back with what I find.

TPI

Yea Vader, Much appreciated..

as you killed 2 birds with 1 toss of the stone.
Ill comb that article over carefully.


Taboo, I did the same thing! descreened the original
MAF sensor (170k) after I rebuilt my L98, got 6000miles
on her before this came up..

TABBOO

Well I checked the MAF voltages as per Vader's post, cleaned the MAF with electronic parts cleaner, replaced the MAF burn-off relay(I had a spare so I did this first), then I cleared the code.
Car started up fine. It used to act like it didn't want to idle then fast idle would catch & the code would show 33. This time fired right up right to fast idle then idle went down like supposed to.
I still have slight tick in idle only when in drive & holding brake(maybe IAC trouble).
I will drive the car to a car show in Massillon tonight & will repost if trouble comes back.

Vader

Oh, never fear - Trouble will come back. It may be in a different form, but since it has wheels on it, it's probably going to cause some kind of trouble in the future.

TPI

I had gotten a remanufactured Bosch MAF today, I
didn't want to wait for them to ship a Microtech to me.

Well, It didn't work.. Code 33 5-8 seconds in, car sounded
smoother though.. maybe the code didn't clear? at least I have
a MAF with screens now!

Ive followed Vader's steps, but nothing yet..

The last thing the car did before I got the code,
was run out of gasoline.. So, I'm stumped as to
why it happened all the sudden.

Ill be in the garage all weekend at this point!

TPI

Im trying to determine what relay this is... Ive posted
pics in the past & even searched and could not get a
definite anwser..

I was on TPIparts.com and found the relay, but it
has so many applications, I cant guarantee it's MAF
related on my car.. Even though my car is a '89,
I dont think my MAF burnoff or power relay is the
newer style weatherpack relay (oval)

This relay sounds like a maraca when shaken..

The Connector contains:

Tan/white
Black/white
Green/white
Solid Red
Solid Orange

Im having a hard time verifying if this is
my burnoff/fuel pump or power, likely my
code 33 problem.

Even if it not MAF related, would it interfere
with the burnoff or power operation?

I didn't want to start a new topic over
a redundant subject.. sorry!

TABBOO

Here is a picture identifying the relays for MAF. I hope this helps. Good luck.

TPI

I have the same picture, and a few more pictures as well
of relay placement.. But, even that doesn't guarantee anything.

Thanks anyway! appreciate the effort!

TPI

Fixed.. I cannot believe it, I did it!

Replaced that relay shown above, along with
a oval weatherpack relay in the same location.

Soldered in a new MAF connector, replaced MAF
with remanufactured Bosch, the relays, a new CTS,
and It vanished!

Idles exactly the way it did when fired on day one.

Thanks Vader for the troubleshooting guide, as
It worked like a charm.. none of the above was
a waste of money, the connector was badly worn
and my MAF was in bad shape.. CTS is routine
maitenence..

Relays were suspect all along though.

TABBOO

CONGRATS!!!!!! I would be interested in seeing the other relay pics if you have time to post them.

alloy

iTrader: (16)

I just came up with a code 33 yesterday on my car, and that's how I found this thread looking for a solution to the problem.

What I found in my case were that the wires to the relays were bare in some case up to an inch away from the relay sockets. Looks like possibly the insulation shrank back somehow.

In looking at the relay sockets there is a little flap that opens and unlocks the wires so you can push them out the front of the socket. I did this and cleaned the wires with contact cleaner, and slipped some shrink tubing over the wires and heated it up. Worked great. No cutting or soldering, and I now have good insulation on the wires.

I did run into one small problem in the past with my fuel pump relay I should mention. I had replaced the relay some time ago, and just recently I got a code for low fuel pump voltage. Did some checking and found out when I installed the new relay, one of the wires pushed back in the relay socket and finally worked it's was down enough to lose full contact. I just pushed the wires back into the socket and that cured my problem. There is a lot of play of the contacts inside the socket, so when changing a relay out be sure to push the wires up into the socket completely. It took me several hours to find this problem the first time it happened. Hopefully this will benefit someone and they won't have to go through what I did.

TPI

Alloy, I too had the same thing happen to me on a few connections
on some relays.. The wires can easily lose contact due to wear &
just overall age, and cause problems that can be a nightmare to
diagnose.

TABOO, ill post up photos of all the relays I replaced.. I believe
all of them need to be in working condition in order to eliminate
the code(s)

I remember tryin to swap relays around to see if the code
would disapear, but never did.. somehow I believe the replacing
the MAF had a bigger effect than anything else.

The car runs better than it ever has!