Dean_Fuller

1989 I did a full intake rebuild with new seals, idle control valve, knock sensors, all vacuum lines, ISV , TPS....car ran GREAT afterwards. Now some weeks later I was driving and it just shut off. Very hard to restart....got it back home with some difficulty. Now the car will start but idle surges with no throttle from 1000 to 3200 over and over...very steady.

Could this be a BAD NEW idle control valve ? Bad NEW ISV ? Maybe a bad MAF ? Computer ? I have my brothers 1987 I could trade out some parts to see what if anything works. I assume the 87 and 89 parts are interchangeable.

Stumped.

soontobered84

Dean,
Maybe the connector for the new ISV just came loose?

John Speake

Sounds like false air getting into the intake. Double check that the bottom of the MAF hasn't come out of the rubber elbow to the throttle plate.

Also check any vac hoses you can see going into the elbow

Kevin in Atlanta

Here's when my 88 started doing yesterday. I assume a hose split under the intake.

dr bob

Dean --

Start with the relatively easy stuff.

-- If the LH controller hasn't been rebuilt, try swapping in the one from the other car. The high idle and surging are not typical LH failure symptoms, but it's an easy and simple/fast way of eliminating that as a possible cause.

Then, going back through the work you did, starting at the outside and going in as you disassemble the easy stuff::

-- Trace the routing of the throttle cable around the pulleys and stuff under the air filter housing. If the cable has rolled off one of the wheels or something is incorrectly touching it, the throttle may stay open a little. This looks towards the high idle but not the no-power symptom.

-- The MAF and its connector are possible issues. These are relatively easy to access after the air filter housing is removed. The connector housing, the boot and the individual pins are available for service. I had a funny symptom, slightly different from what you are reporting, that was caused by a tiny bit of corrosion on one of the MAF pins. Cleaned that and the connector and it was good to go. This looks towards the no power issue but not the high idle.

-- The switch on the throttle is critical to proper operation of the Idle stabilizer (ISV) valve under the intake. Specifically, look at the idle contact to make sure it closes (switch closed) when the throttle is closed. This looks at the poor idle issue, but usually that is a too-low rather than the too-high that you report. It does nothing for the no-power symptom.

-- An un-metered air leak at the boot. This can be the boot itself, or at any of the crankcase vent hoses or connections. The boot is popular especially if it wasn't replaced. Because you were so diligent when reassembling those parts, the clamps are readily accessible for tightening/loosening via the passenger side of the manifold, using a socket and a long 1/4-drive extension. The vent hoses for the crankcase were soggy when you disassembled, so were all replaced. If they are not secured and an end came off a connection, air will leak in under the throttle when the engine is running. This supports both the high idle and low power symptoms you describe.

-- Make Sure the oil filler cap is snug closed. A missing or leaking cap allows un-metered air via those crankcase vent hoses.

-- The hoses at the ISV came loose. Same deal as the oil hoses, with un-metered air leaking in.

-- John suggests that the ISV connector may not be fully engaged. This would give a low idle rather than high, and does not support the low-power symptom. Still a Good Idea to inspect that. The connector is sort of accessible from the front of the intake but it's a chore. A good inspection mirror or, better, a good inspection camera, will make verification possible without full disassembly. There's an interesting tool for reseating that connector with the manifold bolted down. It's only marginally better than using a parts grabber and a screwdriver though.

-- The MAF: Your symptoms don't point directly to MAF failure, but since you have a donor car there go ahead and try the other one. A failed MAF causes "limp home" mode, supporting the poor power symptom but not the high idle speed.

Good luck, and try to stay dry through the storms today!

the flyin' scotsman

Sounds like the MAF or something associated has come loose or gone bad.

If it all checks out then possibly one of the ISV hoses either loose/ came off/ split.

Dean_Fuller

All good suggestions. I will do some swapping and digging and will report back. Thanks guys!