Intake backfire, can’t drive, at wits end
Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
Intake backfire, can’t drive, at wits end
89 auto. 120k miles.
This has been a hell of a time. I’ve done so much research and tried/tested so many things. Found lots of parts that needed to be replaced but it’s just been running like crap ever since I did an air pump delete. It had an air fuel gauge that shorted which might have killed the last o2.
here’s the run down. Intermittent code 44 (lean condition) and intake backfire even after having done:
replaced o2
new injectors
new fuel pump
new EGR valve
new tps
new fuel pressure reg
new spark plugs
ive reset the timing to 6degrees
i tried a remanu ECM, runs the same
fuel pressure is good (but broke the test valve so now it’s just capped till I can get a new valve)
checked and checked and checked vac lines and plenum
had it at a local chev mechanic, couldn’t help
had injectors checked, they are good
Unless I did a terrible job at the timing (I don’t think so) I’m totally stumped and am not sure what else to do. What am I missing??
This has been a hell of a time. I’ve done so much research and tried/tested so many things. Found lots of parts that needed to be replaced but it’s just been running like crap ever since I did an air pump delete. It had an air fuel gauge that shorted which might have killed the last o2.
here’s the run down. Intermittent code 44 (lean condition) and intake backfire even after having done:
replaced o2
new injectors
new fuel pump
new EGR valve
new tps
new fuel pressure reg
new spark plugs
ive reset the timing to 6degrees
i tried a remanu ECM, runs the same
fuel pressure is good (but broke the test valve so now it’s just capped till I can get a new valve)
checked and checked and checked vac lines and plenum
had it at a local chev mechanic, couldn’t help
had injectors checked, they are good
Unless I did a terrible job at the timing (I don’t think so) I’m totally stumped and am not sure what else to do. What am I missing??
Le Mans Master
Joined: Aug 2017
Posts: 6,944
Likes: 1,490
From: New Jersey
As long as the bolts are tight it should be okay... my cousin had a similar issue... It looked fine but every single intake bolt was not even finger tight... new gasket set and it purrs like a kitten. He replaced everything you have as well until I suggested that...
Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
the 2 that are easy to get to are pretty tight. I’ve had the car a year and it really got bad and undriveable in the past 2 months.
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Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
it ran ok. I wouldn’t say totally fine. Always had a tough cold start and sounded like a slight misfire at idle. But drove pretty well. I always felt like it was not as powerful as it should be but again only slightly.
Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
I followed instruction on setting the time. The flashing of the timing light seemed to flash more often than the groove in the harmonic balancer came by the timing degrees bracket. Not sure if that’s normal. When it did come around it was at 6ish degrees. Yes with the ECM plug disconnected. Yes it’s reconnected after disconnecting the battery.
could it be bad plug wires?
Drifting
Joined: Dec 2015
Posts: 1,406
Likes: 230
From: right here
Anything is possible, but those defective parts would likely just result in rough running or a misfire instead of sneezing thru the intake. If you are 100% certain the plug wires are in the correct firing order (1-8-4-3-6-5-7-2) I would seek a better mechanic or dealer for diagnosis.
Thread Starter
Intermediate
Joined: Feb 2021
Posts: 48
Likes: 7
From: Seattle
Anything is possible, but those defective parts would likely just result in rough running or a misfire instead of sneezing thru the intake. If you are 100% certain the plug wires are in the correct firing order (1-8-4-3-6-5-7-2) I would seek a better mechanic or dealer for diagnosis.
compression test will be next if this does not work. I’ll need to get a kit. I don’t want to change the oil here because I have no where to get rid of it. Pulling the distributor would be a first for me, might be time to tow it to the corvette shop. ☹️
Drifting
Joined: Jan 2021
Posts: 1,315
Likes: 385
From: Northern California
In addition, you've done a ton of work here, and apologies if I've missed it, but I don't see where you've A/ checked and adjusted the TPS sensor to .540 volt, then B/ reset the IAC valve, C/ reset the Minimum Idle Air settings on the throttle plate / throttle body, and then D/ adjusted the TPS again to .540 volt.
The work you've done with the injectors / fuel components often results in the need to check and reset those things I mention above. If you've done them already then great. If not, I'd suggest you do them after you've verified for sure that you have 6 degrees BTDC timing exactly right.
Good luck!
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
There is a 1/2" diameter tube with rubber connectors from the throttle body to the rear of the RH valve cover. Be sure these are ok and not cracked. Also check the hoses, grommits and connections for the PCV valve on the LF valve cover. If either of these are leaking, it is an un-metered leak after the MAF sensor, and the engine will run lean. May set Code 44, which you have. And lean mixtures backfire in the intake. Look over all your hoses and connections.
^This^ would cause the symptoms, for sure.^This^, would not.