warm start - have to hit the gas

A bad fuel pressure regulator will also cause a warm start problem.

96RIVMANN wrote:

A bad fuel pressure regulator will also cause a warm start problem.

This is one of the reasons why I asked him to do the fuel pressure test.

Steve, Don't forget to try and start a Warm engine the way i mentioned above first and let us know. It could save you a lot of time and hassle if it starts good after leaving key in ON position before Starting.

I don't know if I'm thread jacking or not but my problem falls under the title as well.

Steve, this is absolutely not to say you should skip this stuff but just for the record, I checked fuel pressure, fuel pressure retention, combed the ignition system from pcm to plugs, I tried adding and taking away from startup AFR & timing. I have no detectable leaks of coolant, oil, air in the motor (gaskets are all still pretty new), no extrodinarily strange behavior of any data in any logs I've taken. Maf, TB, IAC, TPS are all pretty new and work fine - I tested the IAC and TPS. I have swapped in and out the ICM, coils, etc to make sure its not that and wiring is all replaced with a harness I inspected and pretty much refurbed. Case learn did not help. I'm going to try replacing the crank sensor next - probably tonight or tomorrow. Any more thoughts?

I'll report back with what's next.

I just replaced the sensor and I'm going to do a case learn now. Prey with me.

Crank sensor didn't do it.

I have a similar problem too, and have had it since August. Car cranks and starts awesome when cold, and runs great. But when it's shut off and left for half an hour or so when warm, I come back to start it and it cranks and starts fine. However, it feels like it's missing a cylinder or two. If I just let it run, it may or may not stall out. Usually it runs normal if it sits for a minute.

I'm following this thread closely.

Andrew,
I'm not sure you all are describing the same thing.??
Maybe you are but using different words.!!!!
I hope you all can figure it out and it is the same thing. Wouldn't that be a coincidence.

My problem is definitely not confined to warm starts but the need to open the throttle is rather strict.

Z-type wrote:

I have a problem too, and have had it since August. Car cranks and starts awesome when cold,

but when it's shut off and left for half an hour or so, I come back to start it, it cranks and starts fine, but feels like it's missing a cylinder or two, then letting it go, if it doesn't stall out, and it returns to normal. Same situation.
I'm following this thread closely.

Andrew,
Could you please try and re-write the part in bold as it is just about impossible to interpret what your trying to describe. Try to make individual sentences, if possible. It would help others to understand and may be better able offer some suggestions as to what to check and move forward with troubleshooting your problem. I know, I'm confused by the way it is written.

(Now we have 3 people (vehicles) on this one thread. Could get interesting.)

Sorry I didn't realize I had made a run-on. Edited! And I'm just going to take a backseat on this thread - just wanted to pop in and say 'you're not alone' , essentially.

I just wanted to try and help figure out what was wrong.

To reiterate, It will start with a warm engine yet feels like it's missing on a couple of cylinders.
If you let it idle, with foot off the gas pedal, it may continue to run rough or it may stall.
But most of the time, it will continue to run and smooth out on it's own, again with foot off the gas pedal and allowed to idle on it's own.
Do I have that correct.?

Z-type wrote:

I have a similar problem too, and have had it since August. Car cranks and starts awesome when cold, and runs great. But when it's shut off and left for half an hour or so when warm, I come back to start it and it cranks and starts fine. However, it feels like it's missing a cylinder or two. If I just let it run, it may or may not stall out. Usually it runs normal if it sits for a minute.

I'm following this thread closely.

Sounds like an electronic component getting "heat soaked" - for instance, a coil, or a plug wire that has a marginal connector or leaky insulation.

Have you checked the coils? Have you checked plug wires at night for coronas? loose connectors? separated wire?

Albertj

His last sentence says 'Usually it will "run normal if it sit's for a minute". I'm assuming this means "let it idle on it's own and it will clear up and run good at idle.

How about a dirty or sticking IAC, since it only happens at idle when warm. And if allowed to idle, when warm, most of the time it will settle down and run good by itself.
That is, if i have read his remarks correctly.
I think if you were able to scan A/F ratio during and after a warm start, it might help.
Some of you guys with tuning experience and the software to tune will be better able to specify what other parameters are available to you to watch.
I know if I had a scope, I'd be watching cylinder firing as well. But that isn't available in his driveway.

How does it run warm at higher RPM's and under a load.?

Rickw wrote:

His last sentence says 'Usually it will "run normal if it sit's for a minute". I'm assuming this means "let it idle on it's own and it will clear up and run good at idle.

How about a dirty or sticking IAC, since it only happens at idle when warm. And if allowed to idle, when warm, most of the time it will settle down and run good by itself.
That is, if i have read his remarks correctly.
I think if you were able to scan A/F ratio during and after a warm start, it might help.
Some of you guys with tuning experience and the software to tune will be better able to specify what other parameters are available to you to watch.
I know if I had a scope, I'd be watching cylinder firing as well. But that isn't available in his driveway.

How does it run warm at higher RPM's and under a load.?

Good points, makaes more sense than coils/wires.

Albertj

You are all correct in your statements - If it is let idle, it clears itself up and runs normally and most of the time. I've only had it stall twice in this situation. I am actually going to check the IAC tomorrow (been meaning to anyway). My bet is it's dirty. I have scanned on startup before and most of the time, the car is way lean in this problem situation. Fuel pressure is good at all times. I'll just start with the IAC since it's a buggar to get to, then swap in a good set of coils from my Lesabre T-type.

As for high RPMs and under load, it seems pretty powerful. I have no baseline comparison except it's slower than my dad's '04 GS and must faster than my T-type lol. I've put a few ricers in their place, but in all seriousness, it behaves very well, especially highway passing in 3rd or 4th gear. It'll seriously put you in the seat with a 3rd - 2nd downshift. I'm doubting an ignition problem. Heatsoak? Potentially. The car sat for two years before I got to it, though on concrete. I didn't want to hijack this post, but if it helps lead to a cause of the problem for all, I'll let you know what happens with my IAC tomorrow. Thanks!

Ok that's what my starts look like about 80% of the time.

I dunno Codith. It's like you're not getting a priming charge of gas in the cylinders on startup, but I doubt that's the case. My car did that when my fuel pump was *going* but the pump tested good at this stage. It failed some time (months) later.

Albertj

Codith,
TPS. What have you done to check the TPS, don't always expect a code from them. If it has a bad spot right at the beginning of it's travel it could do what your experiencing.
You will need a graphing meter to show you the resistance or should i say the impedance of the variable resistor (TPS) as it moves from one extreme of it's range to the other extreme. i.e. Closed throttle to Open throttle. If hooked to a Graphing Meter you will be able to "SEE" the variable resistor working and if it is working correctly.
Feels like you have a fault in the lower spectrum of it's range of operation. You can try checking with an Analog Ohmmeter and look very closely at the needle movement, but from experience i can tell you that can be difficult to impossible to see. Forget about trying to read it with a DVOM. the numbers moves to fast for that type of reading.
Try reading resistance at rest, throttle closed, then at WOT and see what you get for readings.
FYI, The Snap-On MT2500G will perform graphing functions on the TPS as will other scan tools.

All I've done to check the TPS is turn the ignition on and read the TP% on my aero force as I slowely pressed the gas. It looked normal. You dont think that's a sufficient test?

I don't know enough about the Aeroforce gauge to know if it is sensitive enough to read the finite measurements you are looking for to rule out a small "flat spot" if you will in the rheostat (TPS).
I know from experience that i chased a similar problem and using the testing equipment I owned, at the time I swore the TPS was fine, many times, and moved on to replacing other components, only because what I had to test them with at that time showed me hints that these other things were bad.
When I finally relented and brought the car to a not so close friend's shop, and after less than 5 minutes he confirmed a bad TPS and showed me on the Graph the hick-up of a reading which was causing my problem. Another 100.00 later and I was on my way with my tail between my legs.
Hell, that's just my little story. I guess I'm suggesting if you know someone, even if you have to pay them some money, and you can trust them to do a proper diag of all the suspect sensors and they have a proper graphing scanner and tell you which one is definitely bad, it's worth it.

The way Andrews car runs reminds me of a Northstar with a head gasket issue, when a (broken) hot northstar cools it leaks coolant into one or more cyls and misses for about 15 seconds in the morning while it blows the water out, otherwise they seem to run fine... just saying...Any coolant usage?

Codith, I am with Albert, you have a loss of prime or leaking down fuel pump or something, you need to put a fuel pressure gauge on it and watch whats going on while cranking, a slow rise in fuel pressure rather then almost instantaneous pressure will do this., What happens if you cycle the key a couple times waiting 2 seconds in between?

Rickw wrote:

96RIVMANN wrote:

A bad fuel pressure regulator will also cause a warm start problem.

This is one of the reasons why I asked him to do the fuel pressure test.

Steve, Don't forget to try and start a Warm engine the way i mentioned above first and let us know. It could save you a lot of time and hassle if it starts good after leaving key in ON position before Starting.

The fuel pressure regulator is new. It didn't make a difference if I left the key in the "on" position for a few seconds before starting. Normally my wife drives this car, so I traded with her and started driving it myself. What I've noticed is when starting the car after it sits for about 15 minutes, if I don't touch the gas, it sounds like some of the cylinders aren't firing for about 2 seconds, then all of a sudden the others catch and everything is normal. It's like the engine is getting a late signal.

do the rivs have a fuel pump resistor like the regals? that might be another thing you would want to look into because im pretty sure l67 cars with that resistor command max pressure through that resistor during start up.

Rickw wrote:

I don't know enough about the Aeroforce gauge to know if it is sensitive enough to read the finite measurements you are looking for to rule out a small "flat spot" if you will in the rheostat (TPS).
I know from experience that i chased a similar problem and using the testing equipment I owned, at the time I swore the TPS was fine, many times, and moved on to replacing other components, only because what I had to test them with at that time showed me hints that these other things were bad.
When I finally relented and brought the car to a not so close friend's shop, and after less than 5 minutes he confirmed a bad TPS and showed me on the Graph the hick-up of a reading which was causing my problem. Another 100.00 later and I was on my way with my tail between my legs.

My thinking on this is the TPS really shouldn't matter during a normal startup (that doesn't require opening the throttle). As long as the PCM sees 0% and no spikes or weird things, how can the TPS get in the way of anything? I did scan and it stays at zero with foot off.

Update is right now I'm playing with some tuning tricks to see what it does. I'm also going to try jumping the fuel pump at the relay so that it doesn't shut off after the prime cycle and I'm also going to see how it reacts to having charging voltage before and at startup. rather than battery voltage until the alternator is energized.

97 park ave wrote:

do the rivs have a fuel pump resistor like the regals? that might be another thing you would want to look into because im pretty sure l67 cars with that resistor command max pressure through that resistor during start up.

I'm fairly sure that Riv's don't have it. I don't think 1997 and down used a multispeed fuel pump program at all? 98+ I'd check into though.