Hi all,

I've problems with my car, hard starting and the SES light is giving me an error code 34.

The car will start and idle, but after driving 20 meters, the motor stops.

Starting the motor again is really hard. It takes 3 to 4 attempts to get it running. After 20 seconds the SES light is coming.


What I've done:

I've replaced the MAF burnoff relay and the MAF power relay and checked and cleaned the connections, but the error stays the same.

Before replacing the MAF (costs 375 € in Germany) I wanted to check other reasons for this problem.

The car is a GTA from 88 with L98 and auto.

Thanks in advance for your help.


Greetings from Germany

Jens

 

did u take off ur MAF and check the condition inside? is the sensor itself intact and looking clean and good? is the wiring to the MAF looking good, connections good, etc? ...u can probably find a MAF for 200 bucks or less and shipping cant be a lot on such a small thing...or TPIS has modified ones that actually add significant airflow...itd be worth the extra money to get one...then if you dicovered thats not the problem u can at least say u got something out of it...good luck

 

The code can also be set from a problem with the prom. As mentioned above, check the connection atthe MAF, pay particular attention to the female pins on the harness side as it is easy to spread them apart when hooking the connector to the MAF.

For a new MAF, check on the web for remanufactured MAF's, can usually get them for around $150 USD (no idea on the conversion rate for Euros/Marks), but there again you have the import tax and possibly mehrwertsteuer. You could always go check the junk yards around some of the closed Air Force bases and maybe score one from there.

 

Hi again,

first I want to say THANK YOU for the fast response!


I've taken off the MAF and tested it. The Burnoff function is ok, the wire is glowing.

The MAF is looking clean and good. Connected to a power supply, the output voltage at pin c is changing if I blow air through the MAF.

So as far as I can say the MAF itself seems to be ok.

I've also checked the connectors, they also seem to be ok.

I've started the engine again, but after a few seconds of idling it dies and the SES lamp comes.

Is it possible that the oil pressure switch can cause the problems?

@ Morley: You are right, I definitely will have to pay the Mehrwertsteuer!

Jens

 

To check the possibility of the pil pressure switch causing this (doubtful) Remove the connector from it and put a jumper wire across the harness connector. If it still does the same thing then the oil pressure switch is not causing it.
Have you checked your fuel pressure? Changed the filter?

 

The fuel filter has been replaced 300 miles ago, at this time the fuel pressure was ok.

I will check the oil switch tomorrow and will keep you informed.

Jens

 

Update - car is running again!

While disconnecting the MAF on Saturday I found the following:

The PCV hose on the passenger side wasn't stuck on the small connector on the valve cover.

I inspected the PCV valve on the driver side and found that somebody (maybe the previous owner) has rolled insolating tape around the area of the pcv valve where it sticks into the grommet.

Because of the heat the insolating paper has become stiff and one piece of it has coved the underside of the PCV.

After cleaning and "repairing" the car is starting again without problems and no error code is coming.
I've done a test drive for 30 min and it's just fine.

My questions to you are:

Is it possible that that the PCV-"faults" have caused the problems?
Is it possible that the alteration of the pressure has caused the MAF error code?

Jens

 

Yes, and Yes.
TPI engines are very sensitive to PCV problems. Without the breather line hooked up on the passenger side the throttle body was pulling in unmetered air and tripping the MAF code.

Glad to hear you got it sorted out. Now you'll need to get a new grommet for the driver side to keep the PCV valve snug and leak free.

 

Hi Morley,

I've ordered the PCV Components (grommets and hoses) from the GM dealer here in Essen.

Hope I will get them in the middle of the week.


Thank you all very much for your fast response and your help!


Jens

 

I'd hate to ask what those cost over there.

As an aside, the breather on the passenger side is made up of several components, an elbow in the valve cover, a short piece of tubing, another elbow, a long piece of tubing and an S shaped hose going to the throttle body. The only thing holding any of the rubber pieces to the tubing is friction, and as the rubber gets older it looses some of it's holding power on the tubing. To help keep the rubber pieces from slipping off the tubing, try putting a tiewrap around each one where the tube slips in, this may save some headaches down the road.

 

Thanks for your advice.

I haven't got the prices from the GM dealer yet, but I think they are high.

For example:

Window lift motor at autozone: $ 44,99
Cheapest supplier here in Germany: € 99

Exchange rate € to $ is 1,10...

Another one:

Door frame weatherstrip (original GM part) costs 279,50 €....for one piece!!!

Jens

 

After pausing for half a year (car was stored until may) the old problems were coming back:

Error Code 34, hard starting and the motor was stopping during driving.

I've checked it with Diacom and found out that the car was running rich (BLM's and INT at 108). The reason for this was found to be a defective injector. Ok, I've replaced all of them and I made a complete tune-up (plugs, cables, distributor cap and rotor, O2 sensor)

The throttle body has been cleaned and reassembled using new gaskets! The idle speed has been adjusted to 650 rpm in "D", TPS-Voltage is 0,52 volts.

For ONE week everything went well, but now the problems were back!

Where shall I start with my investigations now?

Jens

 

Two things,

First you should have started a new thread due to age, some will see that you've got responces and therefore won't stop to help. If needed just put a link back to older post.

Secondly, after reading your thread here is my conclusion:

Yes, a code 34 is the MAF sensor circuit.

Your symptoms include hard starting and engine dieing.

Diagnosis by Symptoms: Hard Starting

If engine cranks but will not start without long cranking, or if engine starts but immediately stalls, check the following:


Binding or sticking TPS, or high TPS voltage with throttle closed.
High resistance in coolant sensor circuit (see Trouble Code 15).
Incorrect fuel pressure or contaminated fuel.
Improper EGR operation, leaking, binding or sticking EGR valve.
Ignition system malfunction, worn damaged or fouled spark plugs.
If problem is primarily during cold weather, check cold start valve operation.
Defective in-tank fuel pump check valve allowing fuel to drain back to tank after engine is stopped.
On V6-173 (2.8L) if engine starts, then dies, open distributor bypass line. If engine starts and runs properly, replace pickup coil.
If engine starts then dies, disconnect Mass Air Flow (MAF) sensor. If engine starts and runs properly, and MAF harness and connections are satisfactory, sensor is defective.

Also if needed here is a flowchart for a 34 and text to go with it

Bill

CODE 34 - MASS AIR FLOW (MAF) SENSOR CIRCUIT (GM/SEC LOW)

Circuit Description:
The Mass Air Flow (MAF) sensor measures the amount of air which passes through it. The Electronic Control Module (ECM) uses this information to determine the operating condition of the engine, to control fuel delivery. The oil pressure switch or the ECM, through control of the fuel pump relay, will provide 12 volts for the MAF power relay which provides the 12 volts needed by the MAF sensor. The ECM provides a current limiting 5 volts on the signal line (CKT 998). The MAF sensor then changes the signal by dropping the voltage so that with low air flow the ECM sees a low voltage and a high air flow will cause the ECM to see near the 5 volts supply.

Test Description: Numbers below refer to circled numbers on the diagnostic chart.
Code 34 indicates ECM has seen low air flow less than 2.5 gm/sec. (low voltage) for one second when:
Engine is first started
OR
RPM above 600
Throttle Position Sensor (TPS) above 6%. To obtain 6%, the engine has to be running at about 2300 rpm in neutral.



A Code 34 may be caused by an engine that exhibits a low, rough, unstable or incorrect idle problem. If this condition exists, disconnect the MAF sensor. If the unstable idle still exists, refer to DIAGNOSIS BY SYMPTOMM - NO TROUBLE CODE STORED. (Rough, unstable, incorrect idle, or stalling.) If the idle improved with the sensor disconnected, replace it.
This test will determine if the conditions still exist to set a code or if the problem is intermittent.
With the MAF sensor disconnected, the ECM should see a high signal voltage and set a Code 33. If a Code 34 resets then the wiring or the ECM is at fault.
Diagnostic Aids:

A low, rough or unstable idle could result in a Code 34. Also be sure air ducts are tight and not cracked. Check CKT 998 for short to ground. Refer to "Intermittents" in DIAGNOSIS BY SYMPTOM - NO TROUBLE CODE STORED .

 

Sorry, forgot to state IMO I believe your MAF sensor is going bad.


Bill

 

Bill,

thanks a lot for your reply!

The problem is, if I clear the code the car will run fine for a few days with absolutely no problem! Idle is ok at 650 rpm and performance is good....

To see if it is the MAF sensor causing the problems I will change it with the one my buddy is having in his 305 tpi Formula.

I will keep you informed.

Jens

 

Well, all I can say is my car is currently doing exactly the same thing. I have replaced the ECM, MAF, burnoff relay, power relay coolant temp sensor, distributor, and ignition switch. I have a hard start, then a code 34. With some occasional stalling at idle. If I reset the computer and clear the code the car runs fine for two days and then the problem shows up again. I have been chasing this for six months and cannot pin it down. I have seen this code 34 problem and symptoms show up over and over again on the board and no one can every seem to fix it. The car's is almost always a 1988 model year. (I have also run every single test in the service book with still no luck.)

There is something consistently going wrong on these cars that is causing this problem that is not the MAF sensor itself or related relays. We all need to put are heads together and figure this out because its the same problem on car after car. I just wish someone like a GM engineer could at least tell us once what is wrong and we could make it a sticky.

Keep us posted on your results.

My car is a 1988 305 TPI
https://home.comcast.net/~brians133/

 

After reading the last two post I started wondering about something. First off I have to warn you, I've been teaching for several years now and even when I was "turning wenches" I don't think I ever worked on a 88 Camaro. Burnout88, you stated that this symtom mainly shows up on 88 models. Well I just did a little research while doing the reply, and it seems that this Ecm was used in 88, 89 & 90. I didn't check on 87. Under the 88 model year I got this:

TO: ALL CHEVROLET DEALERS

A condition may exist in which the female terminals in the connector to the ECM do not make a solid connection to the male pins in the ECM (see illustration). This can result in an intermittent condition, in any circuit operated by the ECM. The Service Manuals direct a check of connections any time an intermittent condition is found, and this may be the cause of some of these conditions.

Visually inspect the terminal using a flashlight, or use a .95 mm pin gauge. The gauge should not pass freely through the female terminal. Do not probe the terminal with anything other than the pin gauge, as probing could damage the terminal. If the female terminal does not grip properly, replace the terminal with P/N 12020757. General directions on wiring repair are shown in Section 8A of the service Manual.

But that doesn't explain the ablilty to reset the Ecm and the car run fine for a few days, does it.

When I check the 89 & 90 year model I came up with this:

Some control module's may have problems due to cracked solder joints on the circuit board. These internal control module problems can cause the following symptoms:

Failure to start or vehicle is stalling.
The "CHECK ENGINE" "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR" light will flash or light up, but no trouble codes will be present.
Vehicle instrument panel displays may be inoperative.
The control module may or may not communicate with the scanner.
Other intermittent driveability problems.
Incorrect PROM or MEMCAL removal and replacement can create solder joint problems or aggravate an existing condition. See PROM or MEMCAL INSTALLATION for proper procedures.

If a solder joint problem results in a "hard" failure, normal test procedures will usually pinpoint a faulty control module. Many symptoms caused by poor solder joints in the control module result in intermittent problems, but they may be hard to duplicate during troubleshooting. Control module's with solder joint problems are sensitive to heat and vibration. You can check for these internal control module problems in either, or both, of the following ways:

Checking Control Module For Bad Solder Joints

Remove the control module from its mounting bracket and extend it on the harness so that you can expose it to the vehicle heater ducts. Alternatively, use flexible ducting to route air from the heater to the control module location. Then run the engine and operate the heater at the "MAX HEAT" position. This exposes the control module to approximately 140°F.
With the engine running, tap on the control module several times with your hand or finger tips to simulate vehicle vibration.
If the engine stumbles or stalls, the "CHECK ENGINE" "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR" light flashes, or any of the previous symptoms occur, the control module may have bad solder joints on the circuit board.

Makes me wonder. How about you?

Do your flow chart style testing first and see what you come up with. Ecms are not cheap. It may also be a good idea to talk to someone that works on and has a good understanding of the electronics in the Ecm. After that mayby we can come up with a answer for everone. This might be a good question for some of those in the Ecm fourm.

Bill

 

Oh, Burnout88, Nice Ride!!! She looks real clean too.

Bill

 

Bill,

after 16 years of operation with temperature changes from -15° to +70°C in combination with a lot of vibrations the bad solder points are normal.
I've opened my ECM today and the PCB is full of these bad solder points, mainly where the diodes and the driver IC's are soldered to the board.

I think in my case a "new" remanufactured ecm will be the better way to go.

Jens

 

Your right, I don't disagree with you about the 16 years of harsh conditions causing problems with a Ecm. Although, My info is from around 1990 or 1991. I have a subscribtion to Alldatapro. There is a TSB out on the Ecm describing how to correctly proform the Tapping test for this condition dated 11 Aug 1991. This leads me to believe that GM was having trouble with this Ecm for this problem within 1 or 2 years after production. It could've even been some sort of factory defect that showed up over a period of time.

A "remanufactured" Ecm would be the best way to go i the long run. How hard is that to find in Germany?

Bill

 

Bill,

believe it or not: it is in stock here at my local GM dealer.

I think I will replace it at a first step.

Jens

 

I have a '88 Formula 350 with the same problems for almost 9 years now, getting used to it.....!

 

Jens

Keep us posted on the ECM swap, I also think the heat test can be simulated using a hair dyer. Would probably be easier then using the ductwork in the car. I am going to inspect my new and old ecm with a magifing glass to see if I can spot any solder breaks.

 

burnout88,

before replacing the ecm for a lot of money (340 Euros) I started with a few tests.

As a first step I've removed the plastic isolation which covers the underside of the pcb. Then I resoldered the bad solder points in the area of the connectors, the diodes und the driver ic's.

After 30min of driving with the heater on I've tapped the pcb with the plastic end of a screwdriver and nothing went wrong.

The pcb is hanging on its harness and becomes really warm.

I will go on with these tests for the next days/weeks.

I will keep you informed

Jens

 

Jen,

I have also began my testing. I have Inspected my solder joints on the ECM with a magifying glass very closely. And so far everything looks good. No cracks or breaks spotted. The heat test is next.

 

Hi,

I recently bought an 87 firebird with swapped 350 tpi. I'm having very similar problems. When I first bought my car It was running great. After about three days of driving it, my car started to not respond to throttle as well as before. Then, it started to idle rough and had rough starts. It finally got to the point where it wouldn't go over 25 mph and would suddenly die.

So i took it to a local mechanic to check it out. They told me that it was running code 34 (MAF) and a code for the EGR. They told me that it would be about 300 dollars for the MAF, which would fix my main problem. They also said that a couple tubes that are suppesde to connect wih my EGR are just desconnected and plugged up. I Decided to hold of on the work until i researched a little more.

I then noticed that my battery was not getting charged properley. So, I had the altinator checked and replaced. On my way back from getting a new130amp alt. installed my car died at a stop light and wouldn't restart. It would attempt and get very close but just wouldn't start.

So I had to get it towed back to the mechanics , where it currently is. I want to know if there is anything I can do to make sure the MAF is my problem, before I spend my money.

 

Jens, when you say the burnoff works, how long was it? After reading through this whole thing, I would lean toward one of the two relays. I have never seen a MAF unit on the out, it usually just dies. Relays on the other hand I have seen fritz.

For all...Before spending the money on a MAF or ECU, I'd look into the relays a bit more. They are much cheaper. I'd also test the CTS as well as the EGR, as both may cause problems. (sue me I'm cheap )

 

If the problem is my actual MAF not the relays, should I go ahead and buy an aftermarket MAF? If so, where from? and how much will it cost?

Another thing that I want to knowis how to change my air induction from the box on the side to a ram air style?