Hesitation and rough idling

[tallbump]

Ok, so my 98 SE has seen better day.

It's had a hesitation for a while now. It doesn't want to go at first from a dead stop. If you floor it or let off and get back on it, it's fine. It only does this from a stop, it's fine once you're going. It runs and shifts fine. At first I though it was fuel related. I put a new fuel pump/sending unit on last fallish (BEEP!) and that didn't change a thing.

Lately, the idling has been real rough. Rough enough that I was stopped across the street from church the other day, and our Pastor happened to be outside. He was probably at least 200 feet away, and he said, "wow, that doesn't sound good."

Popatim was visiting last week and we put new plugs in. Properly gapped them. We did have one problem with one wire, but we fixed that, and I don't think it's an issue. We (he) also cleaned the MAF sensor.

Well the hesitation and rough idling are still there. I also have some type of wine (remember, I'm NA) when accelerating. It seems to be coming form somewhere near the middle of the firewall. Tim thought maybe the power steering? It does it even when not turning though

I am running a K&N filter in a gutted box (done by Boosty) that has probably 20K on it since the last cleaning, but I think you can go much longer on that without cleaning.

Thoughts, suggestions? Someone not familiar with the 3.8 suggested maybe the IAC.

[J Wikoff]

Warm idle fuel trims will be helpful to know. Did you try the mist test on the plug wires?

[tallbump]

Warm idle fuel trims will be helpful to know. Did you try the mist test on the plug wires?

No idea what you're taking about

I've been too fr out of the loop for far too long.

[SSEBonne4evr]

Pull off your vacuum hoses and check them for cracks or leaks, then take out the IAC valve and MAF sensor
and clean them. Take the intake hose off and clean the throttle.
Be very careful with the MAF. special cleaner for it.

[MKMike]

A good idea is to always start with the basics.
When was the fuel filter last changed? Is the air filter clean?
How often it needs to be attended to depends on whether or not conditions are dusty or sandy where you drive.
Spark plug wires ancient? Maybe the spark plug wire problem isn't truly resolved.
What J Wikoff was referring to was misting the spark plug wires , preferably after dark and seeing if it produces a "lightshow" of arcing, indicating the need for new wires.
Fuel trims would be shown with a scan tool.
As SSE mentioned, check your vacuum hoses--there can be cracks or sometimes hoses actually collapse while vacuum is applied.
Is the check engine light on?
Checking for trouble codes is a good idea.
Maybe the "whine" is the whistling of a vacuum leak or it could be coming from the transmission.
May as well check the tranny fluid level when the engine is fully warmed up and on a level surface.
After checking these basic things, then I would investigate other possibilities.
A bad fuel pressure regulator is another possibility and is most easily checked with a fuel pressure gauge connected to the Schrader valve on the fuel line.
Though not ideal, you can check for a few things that a bad FPR may do without a gauge.
Here are some ways to check the FPR without a fuel pressure gauge http://www.doityourself.com/stry/7-symp ... 59z5Ysg-Uk
A bad throttle position sensor can also be a cause.
Bad sensors don't always set troubles codes.
SSE suggested cleaning the IAC and MAF which are also good ideas.
There are others sensors whose input is essential for the car to run and idle properly , as well as other electrical troubles such as bad coils, and even mechanical engine problems but you've gotten good suggestions for where to start looking.

[tallbump]

Not sure on the fuel filter. I think it was changed when the pump was changed, but can't remember. I'll ask my mechanic (he goes to my church).

I need to check the air filter to be sure. I showed my buddy a pic of the plugs, he said it looks like it is running lean. Not sure what would cause that.

The plug wires are about 5 1/2 years old. All of that was done when I got the car. In the last 2 years I have done the starter, alternator and battery.

No CEL is on. Not sure which lines are the vacuum lines. I did check the tranny fluid and it is fine. .

As far as misting the wires, do you just spray anywhere on the wires, or on the boots? I tired looking for a vid but couldn't find anything.

Not sure where the sensors are besides the MAF.

I know the MAF is the yellow one in this pic. What are the other 2?



I was poking aroudn under the hood this morning and noticed this....



See something missing? Going to have to track down another one At least it's an easy fix. Would an auto parts store have one, or do I have to get one from a JY?

I kow I sound like a n00b. For those that know me, I you'll remember I am far from a gearhead. FOr those who don't know me, well, now you know

[Jfridge92]

No worries, I'm sure there are only a handful on here that know everything about these cars, but that's what we're here for, to educate and learn. The two sensors you have circled are the Idle Air Control valve (IAC) and the Throttle Position Sensor (TPS). The IAC can be cleaned with some throttle body cleaner, just be careful not to push in the plunger or spray cleaner up inside the sensor bore (you'd see it once you had the sensor off).

The bolt on the back of the alternator is just another bracket. Just needs a bolt and you'll be good to go.

If it's running lean, +1 on checking all vacuum hoses for leaks and cracks, check around the intake manifold for leaks in the gasket.

As for misting, put some water in a spray bottle and mist all over the plug wires where they contact the coils, connect to the plugs, and along the wires. It's easier to do this when it's a bit darker, because then if any wires are arcing, you can see the sparks a bit easier. Also, make sure the rear plug wires aren't touching the O2 sensor or wires.

[MKMike]

One nice thing is that there is actually a vacuum hose diagram on a sticker on the top of the radiator mounting bracket.
The hoses branch out from a multi-outlet vacuum manifold which is mounted towards the passenger's side from the throttle body.
The hoses are typically plastic with rubber ends but can be replaced with entirely rubber hoses if necessary, so long as they're vacuum tight.