Advice needed on idle issue

[MopàrBCN]

Hi,

before I start: The car is a 1989 Lebaron GTC 2.2 Turbo II

I feel I am dealing with potentially 2 idle issues which perhaps I have to look at serperately:

1. The car is idling constantly at rd. 1000 RPM which I feel is rd 200 RPM above spec.

2. Between Shifts, when I Engage the Clutch the engines idle DOES NOT drop. It stays at around 1500 - 1800 rpm. In fact it only drops when the car is coming to a stand still.

Meanwhile the first issue does not worry me as such, the second issue does.

Right now I am searching vacuum leaks.

One observation I made is, that the previous owner could have installed a 58mm throttle body. When installing the BOV we did measure its diameter resulting in 58mm but I can not remember if we measured the outside or the inside diameter. The only figure I remember is the number 58mm.

This would explain to me the high idle when the car is stopped.

But I really need hints on my second issue! Vacuum is a clear candidate. But what else should I look at?

THANKS !!!

[turbovanman²]

You measure the inside and I doubt its a 58mm t/b, maybe 52 and even if it was, it won't affect your idle unless the gasket is leaking.

Check for vacuum leaks, dirty and/or misadjusted tb, bad tps or idle motor. Any codes?

[MopàrBCN]

Hi Simon, I don't have codes besides the usual ones (12), this is why I am looking for clues. The TPS was one of my suspects. The throttlebody I honestly do not remember how we measured it. I am pretty sure that we measured it from the outside. It was done to help us doing fabrication for the BOV.
You say "unless the gasket is leakin"... you are referring to the tb gasket between intake and throttle body? This could be a clue! Thanks!!!

[turbovanman²]

You can't measure it from the outside as the blade dictates the size.

Yeah, the gasket could be leaking and of course, triple check your vacuum lines. I had one where the stock BOV was leaking internally causing a high idle condition.

[MopàrBCN]

Hi, ok, I won't mention TBs again :-)

But vacuum was a good starting point. Changed the grommet at the PCV valve and one line going to the MAP.

Even though, I have not sorted it out entirely!

That idling issue between shifts is a bit better but not solved as yet. The engine basically does not brake if I let of Gas. I am steady at around 1500RPM until I come to a standstill. Then it drops to 1000 - which as well is too high, I think.

The strange thing is though, that it does not seem to affect my gas milage which is nearly scaringly good.

[turbovanman²]

Check your throttle blade adjustment, someone could have messed with it. Its a torx screw. I back it off so the blade catches the housing, then adjust until it stops.

[MopàrBCN]

First of all and as always: THANKS!

It is incredible: I am always the first to suggest "read minimopar" and haven't done it in my own case - don't know why.

Meanwhile all my problems (inkl. your suggestions) are described over there in detail..............I shouldn't be taking more of your time!

Thanks for your help as always!! I have found my homerwork for tomorrow :-)
I will let you know what solved the issue.

[MopàrBCN]

Ok, got it. Minimopar had the answer. The problem was a completely loose hose going off the break booster.

The Problem is: I do not know where it came from. I suppose I would have to raise the car which I can not do right now. The vacuum line in question is not as big as the one which goes from the manifold to the break booster. However it is long and I needed a 10 mm bolt to tap it. I pulled it from beside the air box.

BTW: Anyone a clue?

Fact is, tapping it did the business. I am now idling at 900 and feel stronger breaking power.

[3nglenn]

On mine, which is an 88 T2 set-up in a 89 Spirit, there are two more lines coming off the booster besides the one going to the intake. One of them REALLY restricts down and supplies the vacuum for heat/cool/ defrost control module inside the car. The other comes off the booster and goes into a splitter. One side goes into the air box but has a check valve in line before it reaches the air box. The other one is the vacuum supply for the cruise control. Hope this helps. G.P.

[bill patton]

I have the same problem on my 87 shelby z,and have not solved it yet.It is totally stock,gave code 15 for the vss.i replaced the vss and now no codes but the same delayed idle down problem.i cleaned the throttle plates,set the iac,no cable binding,lol.....One other thing is it will start fine when cold,but when warmed up it won't start unless you mash the gas pedal a little,any ideas? It idles around 1800 rpm for about 10 seconds when stopping,then drops to 800 rpm...thanks

[1966 dart wagon]

funny my car does almost the same thing especially what your discribing as it not droping rpms (1200) till i come to a complete stand still, a friend (topdollar69) and i were thinking it could be cause its runnin an auto cal in a 5 speed car. But i do have the same symptons of the engine doesnt idle down when the clutch is pushed in to change gears, only when its cold though. I also noticed my 'flutter' at 4k and up has come back and it has a new mopar tps sensor still have codes 12(bat) 15(vss) 25(ais motor)

good luck on the fix, but it is common

[chilort]

They shouldn't idle all the way down until you come to a complete stop. I don't know why, someone else here likely does, but they hold a few hundred rpm above idle until you stop.

[bill patton]

I found my problem this evening,even though the ais was fairly new,and there were no fault codes referring to it,i replaced the ais with one off my 88 es turbo automatic car(parts car)set it and the car idles down like it should,plus you don't have to press the gas to start it after its warm now...maybe that will help someone else..........thanks