Hard start / dies when hot.

[doorunrun]

Why yes it was PBCF; not long ago I included a couple of cross forum links and got chided for it. No big deal.
I have some bumper trim on mine that I'd love to find a replacement at the yard. It's the plastic wrap-around strip. On the right side of the front bumper it's torn and sort of hanging down. It will be a mess if it comes apart. I love the car, I just keep putting off a trip to the body shop. Soon the headliner will be down.
The SC version is a blast to drive....with 250k on it I just got 27mpg on a trip to my mom's. All the best!

[Sweepspear]

Update:

Replaced MAF sensor, removed and cleaned the throttle body and IAC valve.
(it was pretty crusty.)
Runs well, and gas mileage has improved.

Still has to spin over quite a bit before it starts though, compared to my Mother's '94 Park Avenue which you just tap the key into the start position and it fires off.

I've read about a sticky check valve in, or near the fuel pump.
What are thoughts on this being part of the problem?

Perhaps this is just how the car is, and I will have to live with it. But if I can cure it all the better.
Especially with winter approaching the less cranking the better.

The car has always had this threshold of -12*. Any colder and forget it.

[Scrapper]

well have you replaced cps since you've had it? and have you had your fuel pump tested latley? a air filter could cause that to. and you might want to take hose off and spray that little butterfly in the multiport fuel injectshon they tend to stick if not cleaned with the spray.because also yours should just be bumped to get it started like you say your moms pa bump and it takes right off.good luck........

[Sweepspear]

Originally Posted by scrapper1

well have you replaced cps since you've had it? and have you had your fuel pump tested latley? a air filter could cause that to. and you might want to take hose off and spray that little butterfly in the multiport fuel injectshon they tend to stick if not cleaned with the spray.because also yours should just be bumped to get it started like you say your moms pa bump and it takes right off.good luck........

From my first post.

"Maintenance items that have been done over the past year other than fluids.
New AC plugs.
New AC Plug wires.
New fuel filter about 90 days ago.
New coil pack and ignition module to correct a rough running / stutter problem.
At the time I was diagnosing the rough running / stutter problem, I tested fuel pressure and it was within spec at 45 lbs. (If I recall correctly)
No codes are ever stored when I check."

I failed to mention the air filter, but it is fairly new also.
Throttle body has been cleaned.

CPS?

[HotZ28]

Still has to spin over quite a bit before it starts though, compared to my Mother's '94 Park Avenue which you just tap the key into the start position and it fires off.

Try a double pump prime before starting; turn the ignition switch ON until the fuel pump primes and shuts off, (usually 2-sec) then turn OFF ign switch. Repete the same procedure and wait 2-sec then start. Let us know what happens.

[Sweepspear]

Originally Posted by HotZ28

Try a double pump prime before starting; turn the ignition switch ON until the fuel pump primes and shuts off, (usually 2-sec) then turn OFF ign switch. Repete the same procedure and wait 2-sec then start. Let us know what happens.

Gave it a shot.
It still spun over quite a bit before starting. Perhaps 3-4 seconds, and once it started it acted as though it wanted to die until I gave it a little gas to keep it running.
Once running, if I shut it off and turn the key again immediately, it pops right off.

[HotZ28]

and once it started it acted as though it wanted to die until I gave it a little gas to keep it running.

Actually, if you open the throttle, you are giving it air, not gas. What is your TPS voltage on the blue wire @ closed throttle? Will it start quicker with the throttle partially open? Personally, I could not tolerate an engine that did not start within 1-sec!

[Sweepspear]

Originally Posted by HotZ28

Actually, if you open the throttle, you are giving it air, not gas. What is your TPS voltage on the blue wire @ closed throttle? Will it start quicker with the throttle partially open? Personally, I could not tolerate an engine that did not start within 1-sec!

Ahh yes! you are correct! adding more air is what I am doing.
You knew what I meant though.
It will start quicker if I partially open the throttle as I crank it over.
Over time this is what I have done without really realizing what I was doing.

I'll have to check that voltage tomorrow. What range voltage should I be looking for?
And yes, it has been very annoying to live with.

I can go out to my garage right now and with one pump and a turn of the key my '70 Riviera will start right up and run smoothly even when it has sat for weeks!
I am far better at performance tuning a Quadrajet than I am fuel injection.
'ol school ya know.

Thanks for all your help and education on doing these diagnostics!


(Hope it's ok to add smileys not provided by the board)

[HotZ28]

I'll have to check that voltage tomorrow. What range voltage should I be looking for?

You should have .45 to .55 @ closed throttle. Do you have a scanner?

[Sweepspear]

Originally Posted by HotZ28

You should have .45 to .55 @ closed throttle. Do you have a scanner?

No, just a multimeter.

[Scrapper]

maybe a cps or coil so what you say now.lol.oops maybe fuel pump getting hot and ready to go.

[Sweepspear]

Originally Posted by HotZ28

You should have .45 to .55 @ closed throttle. Do you have a scanner?

Checked the voltage this morning.
It was at .52 volts.
My Buick service manual says it should be between .38 - .42 volts with the throttle closed.
I adjusted the TPS so the voltage was right at .40
While it started and ran, I will have to drive it today to see if it made any improvement.

[Sweepspear]

So far, so good after adjusting the TPS.
The car seems more responsive and starts much faster.

I really need to pick up a scanner for future troubleshooting.

Thanks!

[Sweepspear]

Well, I was still having a problem with it stalling when I let my foot off the gas, and it idling slow. (400 rpm in drive.)
I have been driving around the last couple of weeks with my eye on the tach whenever I had to let my foot off the throttle to catch it when the tach needle would drop abruptly.
I could blip the throttle a little to prevent the stalling and the RPM's would recover.
This is usually an issue when making a turn at a stop sign after sitting at idle for a few minutes, accelerating from a stop, and then letting off a little while making the turn, though I can sometimes induce it while going down the road.
Never when cold, just after the engine is to full temp. I imagine it runs fine cold since it is in open loop mode.

After doing much research, it logically seemed to point to a sticking, slow responding idle control valve.

(There never have been any codes stored, or any service engine light activation.)

Yesterday I picked up a new IAC valve and installed it last night.
In test driving last night, and driving to work this morning the abrupt drop of RPM's when de accelerating seems to be cured, but it still idles at 400 in drive.
(I was able to make it stall, but I was really trying. )

At what RPM is considered normal? 400 seems a couple hundred low in my mind.
Is there any way I can physically raise the idle to 550-600?

Also, I am wondering how does moving the TPS setting one way or another effect performance?
Is it better to be on the high side? (.42 volts) or low side of that setting? (.38 volts)
As mentioned earlier, I have my TPS set in the middle at .40.

[HotZ28]

Move it up to .45 or .48 if you can. RPM and throttle response will be better!