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Hey guys! Okay I’m tired of racking my brain on this, hoping someone can help. I’m having an intermittent issue. 305 TBI, its searching for idle after it warms up, during load it has a random misfire, if I slam on the brakes it will not hold idle and cut off, but when I’m coming to a stop normally it will hold the 1k 1200 rpm for about 5 seconds or so after I have stopped and car is in neutral. If I’m going down road at constant speed like 60, it will surge. Now, I’ve replaced fuel pump, verified pressure holding steady at 12 even during the hunt for idle. I’ve replaced O2 sensor, TPS, IAC, air charge sensor for hat, coolant sensor, new Dizzy and plugs and wires. Looked at plugs and they are perfect. The MAP sensor is correct on vacuum. Cleaned injectors. Verified spray pattern. It looks good. Manifold vacuum is 20-23 until it hunts for idle then it fluctuates from 18-25. The regulator is adjustable, so i kinda eyeballed the pressure. Didnt change the way it ran though. It’s intermittent because occasionally it will just run fine. No issues…I been at this for about 3 weeks now. Any help would be appreciated
I have looked everywhere for a vacuum leak, but I’ll look over again. The egr is brand new, I meant to put that in there. I did test with vacuum. At idle I get none, and wen I rev it I get 10 vacuum and then 0 when I let off.
Start spraying carb cleaner around your intake, throttle body, vac lines. If they RPM changes, you have a leak. Also, check your fuel pressure. These cars can run on a dying pump, albeit horribly at that.
Connect a scan tool, verify EVERY sensor and computer output.
Verify vacuum booster. Pinch the hose shut, see if the idle is still screwed-up.
Another somewhat common vacuum leak is where the intake gasket seals to the cylinder head. I've had repeat problems with those gaskets, probably due to a somewhat-warped intake manifold.
Have you popped the tamper-proof cap off the base-idle screw? Everyone who dicks with the base idle screw seems to regret it.
Have you cleaned the throttle plates/throttle body including the IAC passage?
Have you verified the magnet on the TBI distributor? REALLY common for them to be cracked (usually but not always through the riveted area) and providing the ignition module with faulty information.
10-09-2023, 06:38 PM
