1979-1993 & 94 Conv [Subscribe to Daily Digest] |
I hate to be another poster with another stalling / sputtering / hesitation issue, but i've put days into diagnosing this problem and have had no luck! Just hoping for some ideas on where to go next.
1989 900 Turbo 5 Speed
Ran great until I took apart the intake plumbing to fiddle with the bypass valve. After putting everything together, it now has trouble idling and RPM will drop to 0 and stall after letting off throttle and letting off engine load (neutral or clutch in). I can keep it from stalling by keeping throttle partially open (heel-toe-braking :D ). Only seems to be a problem at no-partial throttle. Under WOT, the thing boosts and runs just fine .. but it is scary driving at WOT all the time in the rain! Cold / warm engine makes has effect on problem.
Here is my fix attempt process so far:
- Checked and tightened all clamps on intake plumbing
- Checked all intake boots for cracks
- Cleaned MAF (AMM) and AIC with MAF cleaner
- Cleaned throttle body
- Vacuum tested bypass valve, FPR, Distributor: all hold vacuum
- Replaced all vacuum lines that start and end in engine compartment
- Replaced and tightened vacuum unions between intake manifold and charcoal canister
- Vacuum tested vacuum line to dash: holds vacuum
- Vacuum tested vacuum line to heater controls: leaks vacuum <is it supposed to? not quite sure. Plugging bung has no effect on idle.
- Replaced 3 intake manifold vacuum grommets and crankcase vent grommet on intake tube
- Attempted spraying all vacuum connections with starting spray, no effects on idle
- Attempted putting tube to ear to pinpoint vacuum leak sounds, nothing found except especially loud AIC hoses. AIC hoses checked all crack-free.
I have so-far been set on this being an intake / vacuum leak because of the sudden onset of the problem after I was messing with those components and did not touch anything else, but I am now going to do the cap/rotor/plugs/wires thing today, just to be safe.
Am I right in assuming that good power under WOT should rule out insufficient fuel / clogged air, fuel filters?
Anyone have any more methods of testing for leaks in intake tract? I am becoming suspicious of the large-diameter crankcase vent hose that runs under the intake manifold, but I can't think of any way to test it without removing the intake manifold :(
Thank you for reading all that!
Will
posted by 192.188.205...
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