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Eractic idle then stalls....any ideas?

Pulled a 305 TBI out of a 89 transam and put in my truck for fuel injection. Ran fine for awhile, but playing in the mud took it's toll. Had to rebuild engine. Put back in and now it won't idle in gear at

600-650 like it should. Idled fine before but now will idle for a minute then like something kicks on and it almost dies(sometimes stalls) and goes up to about 1000 rpms before trying it all over again. If its warm and you let it idle while trying to put it in gear it's 90 percent chance of a stall. If its cold it's fine but the rpms are above 1000. Looking for any suggestions as I'm stumped and the dealership is of no use(see below).

What's been done: Rebuilt engine, new rings, rod and main bearings, crankshaft, cam bearings, gaskets, timing set, and oil pump. Reused roller cam and lifters. Heads rebuilt. New plugs, plug wires, rotor and cap. New idle control actuator, throttle position sensor, coolant temp. sensor, oil pressure sensor, pcv valve, air filter, egr plugged and disconnected.

No codes registered by computer.

Tried swapping top half of throttle bodies with a spare I have - no effect.

Tried swapping new ignition module - no effect.

Done compression check. After 3 turns all cylinders hit at least 90 psi. After 5 turns all cylinders where at maxium of 150 psi. So I believe that is fine.

Oil pressure is about 65 psi when idle and cold. After warm-up comes down to around 45 psi.

Ran out of ideas so took to dealership to let them try. Then claim it had a weak magnet on the distributor shaft and the pick-up coil was weak. So I brought it back home and swaped out the spare distributor I had and still no effect. Called them back and they said it HAS to be a new distributor to fix the problem. I'm not above buying a new one but about half the money I spent on this thing was trying to fix this stupid idle problem. So I want to make sure that will fix it before I spend the money. That and I don't think it would be just a problem at idle if it was the problem. It has great power(it's a 305) and runs fine as long as it's not around 600-700 rpms where it wants to start floating around and then stall. Right now I drive with both feet keeping it about 800 rpms when in gear and it's fine.

A/C is not hooked up and the 700r4 trans behind it was fine before the rebuild. The valves rattle when under load so I'm going to recheck the valve lash this weekend. Timing is at zero with computer disconnected. Although I don't think it would cause the idle problem would it?

Any help or suggestions would be welcome. TIA!

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Full Name
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I put my timing to 4 advanced not zero.. also sounds like a vacuum leak.. or bad IAC motor. ALSO did you go to big on the cam size ?.. if you did , try a

Reply to
ChEvRoLeT

What about the torque converter? You mentioned it starts, then in a short bit it stops. What if you hold the idle up?

Reply to
Bill

~:~ MarshMonster ~sips his crownroyal..takes a toke..wish's all op's could be as precise as the one in this thread~ ~:~ =======

Reply to
Marsh Monster

====== ======

my gawd.......

a techs dream........

a customer with pinpoint, concise, detailed...... history and failure reports.

i think i love you.

anywhooooo..........

a guess..only a guess..... and what comes to mind first........ A Vac leak.

where?

how the fk do i know...??...this is the internet..not my shop bay!!!

anywhooo..... see my reply to Chevy's reply, i agree....ck the IAC.

and because i voted you "Most Helpfull Customer" of the year because of the info you posted and the WAY you posted it.......

here's a bonus so you don't have to do "too" many follow ups.......

If the IAC is sealing and operating, not carboned up or sticking.... then be SURE you don't have some remedial Vac leak somewhere that's causing the problem only at idle. You "seem" or have expressed, that perhaps you have access to, and know how to use, a fairly reputable and usefull scanner to read "data". If this is the case, moniter the misfire data and the O2 data. Scrutinize the readings, looking for a lean condition, which i think is causing your problem based on the info you gave. (and cudo's on the detail and preciseness of your post). Basically jest make sure all the Data Parameters on the scanner are within spec and there's nothing iffy look'n that you might want to add to your OP above. There is the "slightest" of possibilities that a piece of carbon "may" be causing your problem, causing something not to seal. By your post....i would think you could figure out that the word "something" could entail quite a bit. As an informative bit to this reply.....in case you don't know, which i think is doubtfull after reading your op, spraying carb cleaner or starting fluid around is a perty decent test for exterior vac leaks on a stalling engine that runs well above idle. If the RPM's pick up at idle doing this....a leak is a given. ( again, from your op, i think you prob know this already)

anywhooooo.........

gut shot....quick draw....diagnosis..(guess)...... don't concern yerself with the timing, firing, or anything pertaining to the primary or secondary ignition system.

Focus on the air/fuel.....and highly suspect.......

Air/Fuel ratio troubles....caused by something sticking, not closing completely, due to carbon or jest plain failure, that noticeably affect drivability ONLY at idle.

where???

like i said....how the fk should i know...this is the internet, not my shop.

however......i can guess as well as the next guy.....

IAC...or Valves would be my main suspects. Though, you should be prewarned..i'm probly wrong.

again... good post.

~:~ marsh ~sips his crownroyal.....and ponders the phrase....... "the perfect customer"~ ~:~

Reply to
Marsh Monster

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Full Name

Reply to
Full Name

Check the TBI to manifold gasket too as they fail with age. I had one go bad on me once and cause idle problems.

----------------- TheSnoMan.com

Reply to
SnoMan

One other thing you might want to check is the valve adjustments. You said you can hear them rattling... if you have loose ones you might have a tight one. It could be causing a problem in a few different ways, if it is allowing a poor burn on a cyl the O2 sensor can be calling to lean it out causing a lean condition more noticeable at an idle. It could also be an intake valve causing a slight amount to be coming back up into the intake causing a problem more noticeable at an idle. Just a guess hearing you talk about rattling valves. Also you reused the cam... did you put the lifters back onto the same lobes they came off of ? if not it may be why they are rattling...

Reply to
69SScamaro

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