Hesitation stumble

[spoiledred94]

My 01 SSEI is a great car. No serious issues and still excites me. But now it kinda hesitates with a loss of power for a second. It's only at launch and it's happening more often.

My guesses are
Fuel pump
Fuel filter
Injectors
bad fuel

Plugs
Wires
Coil
Ign Mod

TPS

Anything else?
How do you prioritize this?

[robauto]

1st check for any codes, start with checking fuel trim (stft/ltft) with the scan tool, it may be a vacuum leak, also check the fuel pressure. It can be many things, sounds like a lean condition. Start with the scan tool. If you do not have any and can't rent it or go to someone, then try chevron techron fi cleaner, change the filters, check for vacuum leaks, clean the throttle body with a throttle spray cleaner. Next step would require the scan tool. google acceleration hesitation, there are few sites that walk thru diagnosis. good luck

[MKMike]

Robauto has offered some good advice, which I'll add to.

First thing is to check for any codes that can clue you in as to where the problem may be.

I would then inspect/replace the spark plugs, air filter, gas filter and pcv valve, unless they've been replaced with top quality parts in not too distant past .
If the spark plug wires are original or are anything besides top quality replacements, then change those, too.
You can read this Maintenance Schedule to see how often these should be replaced http://www.pontiacbonnevilleclub.com/fo ... 40156.html

Next check fuel pressure to be sure a failing pump isn't the issue. Details here http://www.pontiacbonnevilleclub.com/fo ... re#p454105

Be sure to check carefully for any vacuum leaks; cracked or split hoses, disconnected fittings, leaks around the fuel injectors, intake manifold gasket leaks, etc.

Clean the MAF sensor, throttle body and IAC valve.
Detailed instructions here http://www.pontiacbonnevilleclub.com/fo ... =48&t=1661

This way you have eliminated the most common causes of troubles.

The throttle position sensor should be tested.
If you have a scan tool, you can check to be sure the values are very smoothly changing as you open and close the throttle.
You can also check it with a DMM (digital multimeter) and details on testing it are here http://easyautodiagnostics.com/gm/3.8L/ ... n-sensor-1

A failing oxygen sensor could be the problem.

There are other things that can cause the problem including weak coils or failing ICMs.
If anything else is wrong that you think wouldn't affect the car, such as an ECT or thermostat--then take care of those.
They affect much more than you think.

[robauto]

right on, good write up, I have used that easy auto diagnostics web site many times over the last few years, it is excellent

[spoiledred94]

1st check for any codes, start with checking fuel trim (stft/ltft) with the scan tool, it may be a vacuum leak, also check the fuel pressure. It can be many things, sounds like a lean condition. Start with the scan tool. If you do not have any and can't rent it or go to someone, then try chevron techron fi cleaner, change the filters, check for vacuum leaks, clean the throttle body with a throttle spray cleaner. Next step would require the scan tool. google acceleration hesitation, there are few sites that walk thru diagnosis. good luck

Very good selection of choices and methods. I do not have access to a full on scan tool forone enough to help. I do have a small blue tooth scanner but it is good for pulling codes. There are no codes on the session light. . Ill Do a look for hidden codes. And a FP check.

Thank you

[spoiledred94]

MMIKE, thank you for chiming in. Plugs, wires, air ftlter, ICM, and coils recently replaced with good quality parts. The fuel filter is only 6 mos old but it's been replaced 3x now by me. Each time it was full of crud. I'll get some more sensor cleaner and take care of the sensors. The CPS was replaced last summer. Is there a way to test the TPS with a DVM?

I was sitting waiting in the car for my wife the other day. As I reved the engine slowly it starts coughing at about 900 to 1000 RPM. Sometimes it'll cough sometimes it won't. As the engine fully heats up it stops doing it for the most part.

I really appreciate you guys getting back to me,thanks a lot

[MKMike]

Since the fuel filter was "full of crud" each time you've replaced it, that's probably a good thing to change again.
ACDelco fuel filters are pretty cheap at Rockauto and the forum discount helps,too.

A DMM and DVM are very often the same tool.
DMM= digital multimeter , since it can measure things besides voltage
IIRC, in the link I provided earlier, all TPS testing is done by measuring voltage with a digital meter.

[spoiledred94]

Thanks you guys for such a lot of support and I will fix it. I've got a lot of things going on and I'm going to find the time to go out and try some of these things next couple days. I'll post when I do thanks again.

[spoiledred94]

I got a p0442 leaky EVAP system ses code. No other codes, but I should have checked pending and historic codes. Read up a bit and it looks like there is probably not a connection for the code and my rough launch. Cleared the code and reseated the gas cap. Still waiting.

Cleaned the MAF a few weeks ago

I'll get a fuel filter this week and a PCV too.
.
I'll check the FP tomorrow, it has given consistently low numbers. Just barely clearing the min spec.

The TPS and other sensors I will get to as time allows

You guys are a pretty helpful, thanks a lot.

[spoiledred94]

I tested the TPS,
0.45 v to 4.5 v. W\ smooth signal roll.

And the FP:
eng. off 45 psi steady
eng. idle 48 psi
eng. accelerating 48-50 psi
eng. running FPR hose off 52 psi steady

[spoiledred94]

I reseated the TPS connector. I also reseted the plug wires at each end. That's about all I did but the hesitation hasn't appeared for a few days. I'll keep you posted. %/)

[spoiledred94]

No worries anymore. I used to catch myself wondering if that was it again but not lately. I guess I need to pay a little closer to attention to my spark plug connections. thanks for helping out and it does give me a place to go for resources when I do have a TPS or coil related problem.

[spoiledred94]

You might want to wait a bit before you reply to this message I think I need to double-check some connections give me a couple hours and I'll repost.

[spoiledred94]

I went to Napa and warranty returned my Napa Belden premium 8 millimeter wires. The old ones were a little loose and actually one was not on and others may have been broken. I drove it and I got no missing or no hesitation no dying. So I'll keep you updated