I've been chasing a few issues on my '97 today, including high idle, low idle, misfires, and some shifting issues. I know, testing the TPS is next. I plan to pick up an analog meter for that, tomorry.

Meanwhile, I did a smoke test today looking for vacuum leaks. Built a smoke generator using an El Cheapo heat gun, an empty paint can, some pipe, and a few odds and ends. Works great.

Found I have noticeable leaks in two places:

1. Around the IAC, at the back of it.
2. Around the throttle shaft, and there's noticeable play between the shaft and the TB when I apply side pressure. Basically, I can wiggle it.

That can't be good, but how bad is it? Is there a repair other than buying a new TB?

There are places that will put a bushing in (places that restore old carbs), but I would think it would be cheaper to pick up a JY TB.


Any pics of the smoke machine?

That's probably the best way to go. Is a '94 compatible?




Not yet. I plan to take some pics and post them. It was pretty easy. Sure doesn't look nice, but it makes good smoke.

Makes it easy to find vacuum leaks!

I'm assuming you have fuel injectors, ya? I wouldn't be concerned about the throttle shaft leaking a little. The amount of air entering there isn't really a 'vacuum leak' and won't affect idle.(check IAC) On a carbureted model, maybe, because they rely on the venturi effect. Our throttle bodies are just suckin' air.

Hmmmm. Are you sure the throttle shaft leak won't affect idle? It IS a leak past the butterfly valve....

I'm sure the IAC leak is a problem. Plan to call the dealer tomorrow to order a new one, along with a TPS.

So 5 years later, how did you ever end up with that? Was the leak causing uneven idle? I would think the IAC could compensate for a static, fixed leak, but where the shaft wobbles around, not so much.?

The IAC can compensate for a cracked vacuum tube elbow, but not a hose completely off, so I'll assume a leaking throttle shaft is within the parameters of the IAC. The TPS has a seal where it bolts to the throttle shaft that's designed to keep dirt out of the unit. There is an o-ring on the IAC that can be replaced and should be.

Merry Christmas!

No, it was a bad O2 sensor. My son had replaced it for me, so had ruled that out as the cause. Turns out he put the new sensor in the position behind the cat!

With a new sensor in the correct place, it ran fine. Of course, I ran it into a Suburban @ 55 mph almost two years ago, so that's how that story ended.

Would appreciate your input.
I have a 01 Grand Cherokee 4.0L(orig owner) 189k. I developed a high idle, fluctuating 25-50 rpm;900 */- after a new Jasper engine swap. I removed the throttle body cleansed completey with TB cleaner and gray scuff pad. I also removed the IAC which was loaded with gunk within the body and projecting shaft- cleansed completely as described above. Reassembled and now steady rpm/ no fluction but idles at 850, it had always been approx 700-720 Tonight my son and I did a smoke test in both directions from intake manifold elbow hose. Forward toward the firewall, found significant leak in the gray plastic vac tube- repaired with a splice of windshield washer hose no further leak there. Then a MASSIVE smoke leak under right headlamp assy. Hose connecting from the “T” connector and to the vac canister split badly at each connection- replaced with rubber line- no more smoke. Car restarted/warmed up with vac lines reconnected- rpm now steady and closer to normal, approximately 750. Of interest my internal dash air flow direction now works properly as does my cruise control.
Now my throttle body leak- so we then smoke tested in the direction toward the intake manifold- only leak was at throttle body shaft at the cable linkage side of the shaft- no other smoke/leaks. Is there a seal, washer or bushing at that area of the shaft?. Can it be replaced?
sorry for the long windedness- I just wanted to be thorough in explaining. Appreciate any feedback- thank you.