99 sc2 dohc won't start after it's warmed up. Help...
 

Hi all,

So here is what's been going on. My car began to stop starting after it's been driven to temp and parked for 10-20 minutes, then it would eventually start. Finally it threw a crank position sensor code so I put in a new one and the light went out but the problem continued. Well it was due for a time up so new coils, wires, copper core plugs and fuel filter. Car runs awesome but still, same problem. Did some research and found that the coolant temp sensor could be at fault. I replaced that, the thermostat and both oxygen sensors because I figured, why not, they're cheap and easy to install. Temp gauge goes just slightly warmer than before but I always felt it seemed to read cooler than it should (on or below the 1/4 line. Came home from work today after replacing these parts yesterday and boom! Guess what? It's at a warm temp and won't start until the engine coils. My next step maybe? Fuel pump getting weak? Plugs were gapped perfect to spec, etc... Problem persists. Any suggestions before I go dropping my tank go a pump swap? Maybe air pump? I'm at a loss and thought I had it figured out but, nope. Please help me.

Also, just to add... fuel pump kicks on, injectors are clean as a whistle and so is the maf sensor. If this rules anything out. Thanks again everyone.

Ken

Where did you buy the CPS and ECTS from?
Please don't say Autozone

Rock auto. Delphi ects and AC Delco cps.

Just tried gas cap... possible vaporlock... no dice. No check engine light. Scratching my head. Just threw in some techron and see if it helps.

Ok. That's a relief.

What condition is the CKP (Crank Position Sensor) pigtail in?

I've only ever heard 10 people with S cars ever report the PCM actually threw the CKP code when they had a misbehaving intermittent CKP issue. Congratulations!
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If PCM detects fubar'd or missing CKP signal, no spark and no injector pulse. Since you're at home with your tools, pull a plug (gently, hot aluminum head) and ground the outer electrode to the block. Spark = CPS NOT the issue, no spark = CKP IS most likely the issue (or the associated wiring). Reading resistance of CKP while hot will usually come back open circuit (inf resistance)


Same question for ECTS pigtail. Any corrosion or coolant muck from previously failed sensors can and will have the PCM sensing a Mega high resistance, meaning -40 C, when in fact it should be about 200 or 300 ohms at operating temp.
Inspect the wiring of the connector very carefully. Rube had an ects pigtail fail where the wire actually separated from one of the pin sockets, leaving it open circuit, -40 C etc

I did look at them but I will definitely take a second look. The contact points I made sure were clean the cps code went out and has not come back on. Been about 2 weeks since replacement and cps code. I'll have to look more closely at the ects wiring. Such a thin gauge wire... Like a single strand of hair... Well maybe not that bad. One of my friends has had a few S cars and had 2 other ecu that came off of running cars so I'm ALMOST willing to bet ects wiring. Thank you derf. I will post back after double checking the pigtail. I might just run a new one to be thorough. Just shy of 200k! I'm hoping to go another 100k, I really like that little SC and don't plan on parting ways with it.

Yep, that pissy little squeeze connector on mine just about drove me nuts. It may have, IDK. But, after replacing that pigtail assembly along with the new ECTS, I had no more engine problems. That crappy TAAT 4 transmission was another issue!

It's such a cheesy piece of junk connector. I had the same issue today but I drove through a quarter tank of gas and now it's starting at any temperature. Maybe my injectors aren't as clean as I thought. Maybe the techron worked... We'll see over the next couple days. Supposed to get 3" of rain tomorrow and Monday and I only have a parking lot to work on the car so I won't be tackling the pigtail in the next few days if the problem persists. I'll update you when I get it resolved. Thanks everyone.

Well, it' been 3 days since I last checked in. After 2 days of downpours and getting out of work late today... Happy Halloween, I haven't been able to figure deeper into the issue (maybe). It's now starting at all temperature without any hesitation. Fires right up every time. I'm thinking my fuel system is dirty. I just don't know. Never got an idiot light and it' running like a new car. Any suggestions on what I should do to see if a dirty fuel system was the culprit? Why would it only do this when the engine was hot? I'm stumped. Any ideas?

What did your gas gauge read while you were having issues, and did you fill it up before or after issue self-resolved?
If it does it again, check for fuel at the test port under the hood (schrader valve). Cover with a rag and depress center pin (like a tire valve). No fuel =no pressure = pump or clogged fuel filter.

When it started having the issue I'm pretty sure I had about 3/4 of a tank and had not filled up for 2-3 days. I replaced the fuel filter after the problem started and filled the tank the day after I replaced the fuel filter. Problem persisted. Another couple days went by so I added the Techron and filled up again. Since then, no more issues. But, before the problem went away, the car was getting spark and fuel. I checked this upon tune up. Plugs gapped to .040, ac Delco factory wires, copper core plugs, Delphi ects and AC Delco fuel filter. Pigtail for ects has power at the connector and everything. She's breathing well runs like a top for now so unless the problem persists, I'm chalking this up to dirty fuel system, bad gas or gremlins.

You may never really know what the problem was. Just be thankful that it's doing good for now and put a bottle of Techron in it every 10,000 miles or so. That's some good stuff!

Yes it is. Seed recommended it a while back when I was doing an mpg by octane comparison. I usually just put a bottle of the complete system treatment in as Winter arrives and again as Summer arrives. This time I just threw in the Techron injector cleaner. Hope that's all it needed. A little miracle in a bottle. I plan on keeping the car as long as I can. I take damn good care of it in and out. Tune up every 30k and regular maintenance as needed. I keep it clean. Hope to get 300k out of it. I'm just shy of the 200k mark now. I want to thank you and derf for the input. If it happens again I'll resurrect this post and go from there.

It's doing it again. Check engine light this time codes po336 and po141. Keep in mind I just replaced the cos and both o2 sensors already. So derf, you think I might be #11. Ecu? Ects and pigtail replaced as well. Happens after about 10-20 minutes after the car is parked after it's warmed up. I'm gonna try another cps in Case the one I got was defective. I don't know.

Where are you getting the sensors, Ken? If at Autozone, please get your money back and try at least NAPA. I used to work for the zone years ago and they sell the cheaper versions of electrical parts that are just borderline good. They've done some very unscrupulous things with vendors over the years which just added to the list of reasons that I quit working for them after 5 years of BS. I just got fed up with the way they were going and refused to go along with things that I thought were both morally and ethically wrong.

AC Delco crank position sensor and NTK (NGK) O2 sensors. Ects is a Delphi with factory replacement pigtail, NGK copper plugs, AC Delco wires, AC Delco coils, AC Delco fuel filter, AC Delco pcv valve all replaced after the problem started (due for it anyway). Also, I used dielectric grease where applicable. So, my new crank position sensor will be in by Monday at the latest. Keeping my fingers crossed. Didn't know if those tri codes in conjunction with each other would throw a red flag up for anyone here that may have had the same problem. Just keep ruling things out until then. I should replace the gas tank straps soon, think I'll look at the fuel strainer and pump next. The fuel filter I replaced was dissected by me afterward and it was awful. I had replaced it just 2 years earlier and you' swear it had been the original with 200k on it. So, I'm sure the fuel system could use some attention. I wouldn't be doing all this if I wasn't planning on keeping the car for at least the next 2-3 years, but that's the plan. After cps, if issue persists I'll go for the ecu and fuel pump/sending unit. I know nothing points to this except maybe ecu, as it's getting plenty of fuel and spark but hey, it won't hurt.

Oh yeah. Check engine light went out on its own upon restarting the car the time after it came on about 45 minutes later.

P0141 is for the rear 02 heater. The rear is just the policeman. does not affect air fuel mix.
P0336 MAY set after several failed attempts at starting, but I believe ONLY if there is a real issue with the CKP or its circuit such that at least one of the failed crank attempts didn't generate an acceptable CKP signal, thereby flagging the PCM to throw the code. Once the car has started up successfully, I'm sure there is a predetermined amount of time after which the PCM says all clear and the SES goes out.

Keep your scanner in the car. Clear the codes.
As soon as you fail to turn it over when warm, turn key to run and read the codes, If the CKP circuit is acting up, you should have a pending 0336.
Pop the hood and do the fuel pressure test I mentioned and recheck spark.

Never use anti seize around O2 sensors. They rely on accessing atmospheric conditions as a reference for their reading. Anything that can heat up and run may clog the hole through which the sensor accesses the environment.

As far as P0141, check the connector for corrosion and wire integrity. I'd tell you to check the heater fuse but since your SES turns off at times, the code is being cleared, which says to me poor connection or heater bad on the sensor (did you perhaps drop kick it in frustration?)

Lol... No dropkick and no antiseize. I used electrical grease on the plug boots/ends and around the edges of the coils only, just to keep water and corrosion away. The crank position sensor should be in at the beginning of the week. I'll check the lead to it but I cleans up all contact points where my sensors plug in. We'll get there eventually! Thanks derf and ruby.

Don't thank me, Ken. I'm done. You and derf are getting way over this old mans head with this stuff. In all the years I've owned cars, I've NEVER had to replace an 02 sensor. And I've had a LOT of different cars with well over 100,000 miles on them.

You are the emotional support...hahaha. No but you make valid suggestions and I appreciate that.

Do you always get gas from the same places?

I once had the fuel filter on my Geo Metro clog on a cross country trip a few years ago as a result of getting bad gas at a hole-in-the-wall gas station out West. Had to replace it at night in a Walmart parking lot in Arkansas with a pair of vise grips I borrowed from the people overnighting in a motor-home in that same parking lot. That filter was the last one the Advance Auto (shudder) in that town had and they were the only place that was still open that night (they locked up when I left).

Long story short (too late), only one tank of bad gas can wreak havoc on your fuel system.

Not all the time, but I steer clear of the no name gas stations. Usually I fill up at Sunoco, occasionally at Shell and rarely at Exxon/Mobil. All of which are owned by the same franchise in the northeast here. Kind of a monopoly out here between 3 franchise owners with different fuel brands in each franchise. I see the same transport company filling the fuel supplies at two of the franchises and the one I use has their own fuel delivery tanker trucks. Just prefer the one I use because I've never had fuel related problems before and they offer a pretty attractive rewards program.

I think it's worth mentioning that I always run 87 octane and have used Techron fuel system cleaner a couple times a year. I've owned the car for a little over two years and I don't know how well the previous owner maintained it. I would guess, not that well based on the fact that I have replaced the fuel filter twice now and the first time the filter that was on the car when I purchased it was probably the worst I have seen. I just performed my second tune up since owning the car and the plugs, wires, etc... That came on it surprised me that the car even ran. Keeping up on oil changes has improved oil clarity upon changing it. I feel like I'm reversing years of neglect. In essence, I have polished a turd and now I have a clean running, nice looking car that I'm proud to feel that I gave it a second life. This is just a bump in the road that I will eventually correct. I will post back after I get positive results. Hopefully tomorrow night as my new cps just came in. :D

*UPDATE * Changed CPS again and the problem persists. BUT! As derf suggested, depress the Schrader valve at the fuel rail to see if I'm getting fuel to that point. I tried this and it's definitely getting fuel to the rail. Fuel does spray when depressed. When it's cranking and not starting, if I purge the Schrader valve the fuel sprays as it should and shazaam, like that, the car fires right up. What gives? No check engine light on start up when I do it this way. If I wait a half hour after crank and no start, the car will eventually fire up (this is when I don't depress the Schrader valve) but it will hard start and throw the po141 and po336. I just can't make sense of it. Anyone ever heard of this? What does it mean? Thank you everyone who is helping me through this mystery.

I will guess insufficient fuel pressure.Why?
I drive a 97SC2. They were known to have been built with fuel pumps that mostly failed. When functioning normally, the fuel system in these S cars holds fuel pressure between starts. There's a spec you can test it to (PSI drop at the rail vs time) to determine if yours is bleeding off too much pressure per unit time.

The problem with the 97 fuel pumps was that they bled obscene amounts of fuel pressure when at rest, making starting and restarting difficult.

It took me several YEARS to figure out that there was a "sweet spot" time wise during which I had to crank the engine and have it fire right up regardless of when I was trying to start it.
It took time for the fuel pressure to build back up.

That sweet spot to crank it for me is right after the SERVICE (not service engine soon) goes out on the start up bulb check. Works 99% of the time. IF I wait LONGER, it is not happy, though. I would think the pressure would be trying to get to the upper end of the acceptable pressure range. It may be, but the damn car won't start so I go by the timing of that light.
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Fuel pressure regulator comes to mind but I think they are internal to the fuel filters on the 3rd gen coupes like yours.
The regulator on the 1st n 2nd gen coupes is a discrete one and is after the Scrader valve. But if not functioning properly, it can still lead to problems.
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Do a loan a tool or use a fuel pressure gauge and compare to key on engine off, key on, engine on, and do a pressure bleed off test. I know the ranges are in a Chilton's book I have. Lemme see (groans to get up)

I am assuming you are hearing the 3 second priming going on when key on engine off.

Basically, you relieve the fuel pressure at the test valve with the engine off, then hook up a gauge, THEN start the car (AFTER cleaning up any stray gas =flammable) and look for the following

Fuel System Pressure: 40 to 55 psi AT IDLE (vehicle at operating temp)
Fuel System Pressure DECAY (first 5 min after shutoff) : 8 psi MAX
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98 and up: THe fuel press regulator is integrated into the fuel filter assy.
Also, 98 and up are returnless which means there is no line that returns to the tank. Sometimes the return lines on the older S cars develop obstructions, but I don't think yours has an obstruction because you don't have a return line.
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It may be that you have a small fuel leak in a line or an intermittently leaking injector that is bleeding off pressure and fuel. I suppose you could "flood" 1 cyl if it was an injector sticking open now and then, but I don't think that would take too many engine rotations to be jettisoned into the cat.

Sorry for the train of thought oozing of info -- just how my brain wanders, circling the wagon
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The fact that the techron made the problem temporarily disappear has me leaning in this direction (leaky /dirty injector not closing all the way -- maybe more of an issue when warm. you can try the bleed test when it's not acting up and when it is and see if the rate of pressure bleedoff is the same\
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If your car never had the "magic window of starting" like mine, it prob hasn't grown one
Do not condemn the fuel pump unless it does not meet specs as is by deduction proven to be faulty.



Note I said GUESS.

Sounds about right to me. I will be doing as you suggested. Thanks again!

The 8 psi is the MAX bleedoff in the 1st 5 min
(sorry bout that)

Remember, if there is an excessive pressure bleedoff, you're only going to catch it when it's acting up, which means after a drive and sitting hot.
I'm thinking now that I am not half asleep that you may just want to slap the pressure gauge with key on, engine off on there without a purge, because iwhen you purge it, you purge away the "caught you red-handed" evidence you need.

But it must be key on engine off.to compare apples to apples.

Then purge and retest, If an injector is leaking or pressure is bleeding off at the pump or somewhere else you should see it,

When I do not get my car started on the 1st or 2nd crank, it seems to easily flood and then I have to hold the pedal down to clear it while it fights, turns over, lets out a nasty plume of exhaust, then smooths out,

I run techron from time to time. It greatly improves throttle response but doesn't do a damn thing about starting for me. The fact that it seems to be directly related to the presence or absence of the symptoms for you points me towards the injectors.

The part of this I fail to yet understand is why it continues to throw a CKP code unless there is an intermittent wiring issue, either at the connector or possibly at the other end where the signal goes into the PCM.
Have you been able to park the car and read the codes for a pending CKP code BEFORE trying to restart it?
Check for this, as it will help us differrentiate between whether the CKP trouble is occurring BEFORE an attwmpted HOT restart or AFTER and attempted HOT restart. THere are of course other issues that cause CKP codes but don't wanna go there. If the car is running, it can't be that serious. I'm guessing electrical contact a the pigtail or PCM is involved

"This is only a Guess."
---Violent Femmes

No. As soon as I shut the car off the codes go away. Yesterday I changed the oil and got a better look at the cps pigtail, unplugged it and the rubber boot that houses the male end of the pigtail just fell apart. Luckily I had another one and when I plugged it back in, it was much more snug. The pigtail itself is getting the proper ohms, so I'm hoping that was the fix for that portion of the problem. With the old boot, the connection was very loose. I can only hope. It hasn't thrown a code since but it's barely been a day. As for the crank no start, it only does it when the engine is warm. If I let the car sit for about 1/2 hour, it'll fire right up. That is unless I purge the Schrader valve at the fuel rail. If I do that when I get crank no start, it'll fire right up. Might just replace the injectors if they're cheap enough. In the meantime there's a couple small fixes I'm going to tackle.