jagvette

OK next question I have a 1988 C4 Manual 4/3

On start up the idle bounces between 500 and 1500 rpm for about 2 minutes then settles, its also running rich.

I have cleaned and rebuilt the throttle body plus replaced the IAC and oxygen sensor.

I'm going to replace plugs.

it has a hooker straight through exhaust (too loud) which I am going to install standard mufflers.

any ideas on what it might be or what else I can do would be helpful.

thanks Girls and Guys.

Jagvette

aklim

Let's start with the IAC. Set it using a scanner. Also see what you are talking about in the O2 sensor voltages

ctmccloskey

Hello there,
What is the ambient temperature while you are doing all this?
Does it only happen when the engine is cold? After the car has been driven does it still do it?

My gut tells me to check out the cold start injector and the engines controls Temperature sensor. If a temperature sensor fails and is telling the cold start injector to come on it might make the idle go up while it warms up the engine, even in 95+ degree weather.

This would explain the rich running smell as well as the idle speed variations.

If you can find the connector that supplies power to the cold start injector you might try unplugging it to see what happens.

I hope that you find the components that are causing the problems without too much work! Good Luck!

jagvette

Yes it only does it when I first start it, I live in AZ so air temp is usually above 90, but I didn't know this beast had a cold start injector I shall have to locate and test it, plus your other suggestions and also check out the other forumers suggestions,

Thanks guys I let you know what I find.

Jagvette




Hello there,
What is the ambient temperature while you are doing all this?
Does it only happen when the engine is cold? After the car has been driven does it still do it?

My gut tells me to check out the cold start injector and the engines controls Temperature sensor. If a temperature sensor fails and is telling the cold start injector to come on it might make the idle go up while it warms up the engine, even in 95+ degree weather.

This would explain the rich running smell as well as the idle speed variations.

If you can find the connector that supplies power to the cold start injector you might try unplugging it to see what happens.

I hope that you find the components that are causing the problems without too much work! Good Luck![/QUOTE]

billschroeder5842

Coolant temperature sensor. Swap it out as it will take you 15 minutes and cost $15.

It is great PM if it is not the culprit, but I bet it is.

aklim

After some checking, it seems that I might be mistaken. The CSI ends on model year 88 not 87. If this is the route you want to go, the issue you need to test for is 2 fold. http://garage.grumpysperformance.com...injector.2861/

I would check if it is leaking. Not sure how to test it on the rail and if you are going there, I would send it to FIC for cleaning and testing. What injectors do you have? If they are Multec, toss them. IF they are not, it probably won't pay for you to have them cleaned. Might as well ask Jon at FIC if he can send you all 9 injectors that are reman and you send him your CSI after you get it out. Maybe he has a spare one lying around. If not, send him the 9th injector and get the other 8 when he sends it back.

aklim

Great PM to throw other sensors without testing? IMO, I wouldn't. All you do is introduce more variables since the wrong sensor could be in the right box (ask me how I know) or the new sensor could be bad too. Bad habit.

I'd scan it and hit it with an IR thermometer. See if it is having the same temp as the ECM says that it is saying. All the way from cold to stable operating temp