I've just installed a brand new 355 TPI and all the sensors have been replaced except the TPS and MAF of course. It cranks and starts and dies quickly within a second or two. If you feather the throttle sometimes you can get it to stay running but it runs horrible. The service engine light never comes on, but oh big surprise here.. code 34 is logged. I have adjusted the TPS to .54 and it has a brand new walbro 255ltr. pump also. Also have replaced all 3 relays, burnoff, power and fuel pump. Connector to MAF has been cleaned and inspected and I have even swapped the MAF from my 86 Iroc and it still throws code 34! (yet won't light it up you have to go to diagnostic mode) I clear the codes (disconnect battery) and check before start and get 12. Start the motor, cough, sputter, dies.. Code 34 is back. I have checked the archives and studied this topic but nobody seems to have a motor that just wont run at all with that code. General concensus seems that the car will run just fine without it even plugged in, so I tried that too.. During one attempt out of about 5 or 6 tries, it jumped to 2500 RPMs and held(I shut it down right away). During the other attempts it just coughed and sputtered as ususal. Can the MAF circuit actually cause the motor not to run at all like this? I know my old 86 300ZX riceburner would hardly run when the MAF died but that was after it warmed up. Could this be a problem with my coil or the distributor? I took the ESC module off and cleaned the contacts e.t.c. and put dielectric grease on the base during the repower cuz it was covered with corrosion. Might the trigger be bad? By the way, it was behaving EXACTLY like this before my repower, so I am not off 180 and I really don't think its anything mechanically wrong..Any ideas would be helpful, I am stuck at the moment!

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Mike C
88 Iroc 5spd
355 TPI, AFR 190s and lotsa other mods
86 Iroc in pieces!

 

Mike, uplug your MAF, if the car stays running with out help, go to the store and buy a /maf relay. Power and burnoff are the same so swap out one at a time. I doubt it's the MAF itself.

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"I don't want to be right - I just want to know if I'm right"
-Einstein

 

Well, I did all that already.. I guess you must have missed it in my post cuz all 3 relays are new and I tried the disconnecting route too..

 

Mike,

The '34' you are getting from the ECM ROM is telling you that the MAF is measuring less than expected intake air flow. This does not necessarily mean the MAF is bad. It might be measuring the air correctly, but the flow is indeed lower than the ECM expects at a given engine RPM and throttle position.

There are several other possibilities that could cause a low intake flow or low MAF measurement. A low measurement will result in a lower fuel delivery, and artificially lean mixture which will cause a very poor idle (if the engine idles at all).

The intake air boxes/ducts could have leaks or cracks. GM had a TSB on the plastic air boxes for failures at the seams. Loose or poorly fitted ductwork can allow unmetered air to enter the engine.

Vacuum leaks anywhere in the intake system can result in unmetered air. Check hoses, the PCV vent line, brake booster, etc.

Remeber that the PCV air must come from the throttle body fitting. Using a breather-type oil filler cap will admit unmetered air and completely screw your MAF reading.

Late valve timing or ignition timing can result in extremely low vacuum, causing a low MAF reading and lean mixture.

As for the ignition system, you'll need to make certain everything is functioning properly. Any number of things can cause weak spark and intermittient no-spark conditions. You can meter the ignition coil primary and secondary resistance, and test the pickup coil resistance. The HEI module is difficult to test without the correct apparatus, so unless you have a power supply, triggering device, and load resistance, it's easiest to take it to an auto parts store for the genrally free testing. The cap and rotor are pretty sraightforward. The reluctor should be relatively clean (light surface rust is O.K. and have no cracks.

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Later,
Vader
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"No matter how hard you try you can't stop us now"
Adobe Acrobat Reader 4.0

 

O.k., this is embarassing but I'd rather share my experience so that it might help others in the future. It turns out that I left the freakin plenum to runner bolts loose on the passenger side! This would explain the code 34 from all the unmetered air going into the intake. Now everybody is thinking.. how the hell did he get this thing to run in the first place if he forgot that??!! I guess sometimes its the basics that kick our *** right?!! Wooohaa problem solved!! My motor finally runneth!!

[This message has been edited by MikeC.86Roc (edited January 03, 2001).]