Intermittent idle issue codes 33 and 34
04-26-2016, 01:04 PM
#1
Intermittent idle issue codes 33 and 34
I have an intermittent idle issue on my 88 convertible. I have only had the car a few weeks, and 95% of the time it runs great. About every third start up, it will "hunt" for idle rpm, varying from 400-1200 or so. The other two times it will start up and idle fine around 6-700.
If I feather the gas, it runs smooth. A few times it has fallen off and died, only, but starts right back up. On a few occasions, the same situation happened at stop lights, after being fully warmed up. It finally tripped the check engine light with a code 33. Because I had them on hand, I swapped out the MAF and Burnoff relays with AC Delco new relays. Car started up and promptly started hunting for idle again, tripping the check engine with a code 34 this time. My thinking is that there is an issue with the MAF itself, or the wiring leading up to it having an intermittent short. Am I on the right track? I have a new pigtail coming.
If I feather the gas, it runs smooth. A few times it has fallen off and died, only, but starts right back up. On a few occasions, the same situation happened at stop lights, after being fully warmed up. It finally tripped the check engine light with a code 33. Because I had them on hand, I swapped out the MAF and Burnoff relays with AC Delco new relays. Car started up and promptly started hunting for idle again, tripping the check engine with a code 34 this time. My thinking is that there is an issue with the MAF itself, or the wiring leading up to it having an intermittent short. Am I on the right track? I have a new pigtail coming.
04-26-2016, 04:19 PM
#2
Safety Car
Don't rule out the IAC. I've had some rough to terrible running situations shortly after startup when it was cold out plus occasional high idle at stop lights. When the car went to crap (usually within a few blocks and it was under 30 degrees out), IIRC the SES light and a code 31 or thereabouts would come on. Would go crappy, turn it off and wait a couple of minutes and restart and everything was fine. It always seemed to happen while the engine was coming up to but not at operating temp, usually around 160 degrees on the display.
Thing was I kept coming back to the IAC because of the symptoms, regardless of what the FSM listed (lost signal to ECM IIRC). One day while looking I happened to have a plastic faced hammer with me, and gave the IAC a couple of raps just for the heck of it (plus it made me feel better at the time). Hasn't reoccurred since. I plan to change it out eventually but it lets me drive the car and do it on my maintenance schedule rather than it's.
Just something to think on.
One more thing. I'm not a big one for cutting good wires for a bad connector etc. I'd check them out well first and if you only need to change the connector, look for the Lisle tool, you can remove wires from old connectors without cutting them and put them in a new connector. Obviously if they are bad, that's something else but a splice in a good wire just introduces a future possible point of problems IMO. My 2 cents.
Thing was I kept coming back to the IAC because of the symptoms, regardless of what the FSM listed (lost signal to ECM IIRC). One day while looking I happened to have a plastic faced hammer with me, and gave the IAC a couple of raps just for the heck of it (plus it made me feel better at the time). Hasn't reoccurred since. I plan to change it out eventually but it lets me drive the car and do it on my maintenance schedule rather than it's.
Just something to think on.
One more thing. I'm not a big one for cutting good wires for a bad connector etc. I'd check them out well first and if you only need to change the connector, look for the Lisle tool, you can remove wires from old connectors without cutting them and put them in a new connector. Obviously if they are bad, that's something else but a splice in a good wire just introduces a future possible point of problems IMO. My 2 cents.
Last edited by hcbph; 04-26-2016 at 04:23 PM.