engine stumble

[insanegt1]

Have ask this a number of times but have not got a responce other than ( a lot of us have the same problem). I have an 86 with a stumble. After stoping at a light it will stumble at take off. After the rpms build a little it will jump right out there. Have tryed to solve it my puting in a new fuel pump-filter-injectors-plugs and wires with cap and rotor. New K&N filters.New MAF, Fuel pressure is on the money. Starts fine. At a ideal it runs at 600rpms. Seems a lot of C4 owners have this stumble. It also seems that someone would of solved the problem by now.

 

[JonM]

One reason could be a restriction in your cat (s)
Also check for restrictions in exhaust.

Have you checked your TPS? How about your CTS? and O2 sensor? How old are they?

TPS =Throttle Position sensor
CTS= Coolant Temperature sensor


Make sure EGR system is functioning correctly.

Any leakage in any of the injectors?

Check your purge system see if you have any restrictions.

My advise would be to get a Manuel and check all these things out.

 

[8388]

You can't attempt to solve a problem by just replacing parts.
Your car has an ECM and it depends on the sensors and programming for engine management. You may want to invest in a voltage meter and jumper harness which are available at MAD.
Or find someone that has a diagnostic tool such as a Diacom in order diagnose and pinpoint the actual problem. I had an 86 years ago, and it never had a stumbling problem.

 

[insanegt1]

stumble

A lot of ideas but that doesn't solve the problem. I don't just throw parts at an engine. I believe in preventive maintance and replaced the parts that were old and needed to be replaced. That way there is no second guessing on a part being bad.The car has been in to the shop and and every test run. Everything is right where it should be. The same as other owners haveing the same problem has done. But the stumble is still there. If the shop can't find it I guess I'll throw more parts at it.

 

[8388]

I understand your frustration, but understand that sometimes new parts can be defective, while the old parts may just be old but in good working order. Replacing parts because of their age does not always rapair the problem, sometimes they(new part) even create new problems.

If it only does it after idle, what is it that's loading up during the idle that is causing the stumble till the engines revs up and clears the problem.

Is there smoke present while it's stumbling?
Is there a rich fuel smell ?

 

[Robertwav1]

One thing that's overlooked a lot is a possible vacuum leak somewhere. Check all vacuum lines. Even though they look good they may not be. Most cars have the vacuum system layout under the hood...it shows all the vacuum lines and where they go. This is worth while checking out especially on an older vehicle.

 

[sidepipe]

Robertwav1 has a good point. I have a 94 coupe that has two vacuum lines above the battery. Looking down on them, the top surface looked good. But underneath they were corroded from acid vapor. Good Luck. Frank