1986 Won't stay running. Code 34.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Code 34 sets when the ECM has seen low air flow, less than 2.5 gm/sec when engine is first started or above 600 rpm or TPS (throttle position sensor) above 6% (2300 rpm in neutral). One symptom is rough unstable idle. Unplug the MAF and if idle becomes more stable, then replace the MAF. MAF unplugged and engine running, the ECM should set a 33 and if after resetting codes and unplugging the MAF and 34 is reset, the MAF wiring or ECM is at fault. Check dirty or misadjusted throttle body. Also check air ducts for tightness and not cracked. Code 34 will set also if the idle speed is set too low.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Unplug the MAF and see if it will start and run. Also, if the idle is set too low, the engine will start and immediately quit (hold a little throttle during starting). I also recommend watching the fuel pressure to see if it is between 35-42 psi and it holds up after the ignition is turned off and also if it holds up during starting. You might have leaky injectors (won't hold pressure, ign off) or a defective fuel pump (won't hold pressure during fuel delivery), or a fuel filter clogged (won't hold fuel pressure during fuel delivery).
Thread Starter
Heel & Toe
Joined: Mar 2010
Posts: 15
Likes: 0
From: Buckner Mo
MAF Burn off relay and Power relay>? Where do I find these? I have called every part store and no one has them, or even has a part listed. I came up with part number AR227SB for the Power but no matches online. I call local Chevy dealer and they say the same part for both relays>(?) I have called Ecklers and they are only showing the burn off relay no Power relay. Help. I figure if I'm taking apart the MAF I might as well replace the relays while I'm in there.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
The mass burn off relay and the mass control relay are both on the firewall in the engine compartment on the left side and above the jump start terminal. There is no relay called, "power relay". Don't take the MAF apart! there isn't anything inside of it that is owner serviceable! I gave you some things to try, what are the results?
Racer
Joined: Apr 2007
Posts: 351
Likes: 0
From: washougal wash.
Power relay pn.# 10067925, burnoff relay pn.# 10094701, specific for m.y. '86. Bought from local chevy dealer last week. They had them in metro area, delivered in 2 hrs to dealer. (portland/vancouver) Went to dealer because napa was coming up with multiple other p.n.'s, a little more money, but their the correct ones. You can also buy online, google the p.n.'s. I'm beginning to wonder if my issues were a wet wiring harness. Car ran fine until I washed it, sat for 4 days, went to start it and threw 2 codes. Coincedence? maybe. Also ck your fuel pressure at the rail, start with the simple.
Thread Starter
Heel & Toe
Joined: Mar 2010
Posts: 15
Likes: 0
From: Buckner Mo
Power and Burn Sensor
Thanks. I just called the Local Chevy dealer and he couldn't get for a couple days. I got the product/part # from him and called O'Reilly. They will have them for me in the morning. Also I removed and cleaned out the MAF and started up and died like it always has. Thanks for the info.
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Thread Starter
Heel & Toe
Joined: Mar 2010
Posts: 15
Likes: 0
From: Buckner Mo
The mass burn off relay and the mass control relay are both on the firewall in the engine compartment on the left side and above the jump start terminal. There is no relay called, "power relay". Don't take the MAF apart! there isn't anything inside of it that is owner serviceable! I gave you some things to try, what are the results?
Thread Starter
Heel & Toe
Joined: Mar 2010
Posts: 15
Likes: 0
From: Buckner Mo
Fuel pressure
Unplug the MAF and see if it will start and run. Also, if the idle is set too low, the engine will start and immediately quit (hold a little throttle during starting). I also recommend watching the fuel pressure to see if it is between 35-42 psi and it holds up after the ignition is turned off and also if it holds up during starting. You might have leaky injectors (won't hold pressure, ign off) or a defective fuel pump (won't hold pressure during fuel delivery), or a fuel filter clogged (won't hold fuel pressure during fuel delivery).
Is there a standard gauge or is there one made for this car? Do you recommend a fuel pressure gauge?
Racer
Joined: Apr 2007
Posts: 351
Likes: 0
From: washougal wash.
Pick up a fuel pressure test gague when yer at the auto parts store. Mine came with correct adapter already fitted, with a ford adapter in the pkg. Fuel filter is right behind the pass. front tire on the frame rail. You can get it with a jack and stands just fine. I'm betting on fuel delivery issue. I may go so far as to buy f.p. gague first and ck. b4 buying relays. New f.p. at napa was 150ish? very ez to change.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
You can not go wrong buying tools or test equipment. Fuel pressure gauges are about $12 at parts houses and extremely valuable for trouble shooting. You can learn how to fix your own cars and it is MUCH less expensive than repair shops charge!!!! The MAF relays aren't very expensive and they don't last forever, so I don't see anything wrong in replacing them. You can test with a voltmeter to see if they are switching power to the MAF to prove that your relays are good or not. Another valuable thing to own is a VOM (voltmeter, ohmeter, milliammeter), so you can measure resistance, current, and voltage. You don't need an expensive one, you can buy a digital VOM from Harbor Freight for $8 and it is accurate. I own two of them. On sale, I have bought them for $1.99. 
Thread Starter
Heel & Toe
Joined: Mar 2010
Posts: 15
Likes: 0
From: Buckner Mo
Still out of commission!
Changed out the relays. Started right up. Ran for about 5 minutes. Thought Great. Then I shut it off, started it back up, and what do you know, died after a sec or two. I checked fuel pressure, couldn't get a reading even while trying to start it. Who knows, Maybe didn't hook it up right, didn't look like there was a wrong way. Just frustrated. I attempted to change the fuel filter and couldn't get it to loosen at all. Taking a break.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Attach the fuel pressure gauge and turn the key to "on". You should get a reading on the gauge in the neighorhood of 34-40 psi. If you don't get a reading, you are likely not getting fuel.
Have you tried to remove the intake air duct and spray starting fluid in the throttle body while someone cranks the engine?
Did you reset the ECM and check for codes again?
Have you tried to remove the intake air duct and spray starting fluid in the throttle body while someone cranks the engine?
Did you reset the ECM and check for codes again?
Cruising
Joined: Jul 2024
Posts: 14
Likes: 1
I had the same issue and code. I have an 89. I purchased a good new MAF unit off rock auto and replaced the 2 relays by the battery. Car only running for a few seconds is a sign the MAF is done. My Corvette had the original Delco unit so 35 years old. After replacing disconnect the battery for 30 minutes or so and that will re-set the codes the re-connect and start it up. My Corvette has run fine after I replaced these a few months ago.
