Start up problems (only when engine is cold)

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jer

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Jun 3, 2003
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Houston,tx
I'd like to see if someone can figure this out. If you can figure this out(unless it is the engine temperature sensor)then you are the god of mechanics.

I have been trying to diagnose this problem and I can't for the life of me figure out what it may be. I have a list of components that I could look into but it would take forever.

(('93 cavalier 2.2 160k))

Here is the problem. When I start my engine up(cold)it won't start. Try it again and it will shudder very very badly. It's as if the car
is choking on a piece of chicken bone. At this point the whole car is shaking very erradically. I turn off the car...start the car again and
it's a little smoother...but I have to push on the gas to clear up the rough idling. The car feels fine after that.

My vacuum lines are fine, my egr valve is fine, my rotor seem fine(no rough driving on the road), my fuel pump is fine, my engine temperature sensor seems fine, MAP sensor looks fine, uhhh....I think there are a few more I can think of...

I also changed my gasoline brand(was using chevron...now I'm using shell)and used octane 93 with bg44k. After 2 more tank fills of just the octane 93 from shell.....no improvement!nothing.

I had such a strong gut feeling that this may be caused by a engine temperature sensor(TCC). I checked the ohms on it and got the following:

cold engine = .874
hot engine = .341

now my only thing is ... is that the manual states that the ohm reading - when the engine is hot - should be equal or greater then 500 ohms ... to that of the cold engine. Well, I have the opposite effect. Yet I do have the 500 difference. To double triple check I took out the sensor to look for corrosion and I only saw a little bit. I took a wire brush and cleaned it up real good. Stuck it in and waited till the engine had really cooled off. Turned the car on....no improvement.

One time I even left the sensor unplugged while driving(forgot to plug it back in) and I didn't notice any performance issues.

so...AHHhhhhhhh!! What the "blank" is going on here?!

oh wait. One more thing before I stop here. I did clean out my throttle body(the butterfly) with gumout. It seems that ever since I did that... this problem seemed to have creeped up. Now this could be a coincidence....

-jer
 
Disclaimer: I've never worked on your engine.

Fuel injected cars don't have a choke in the classic sense, but they nevertheless must have that function served in one way or another. Some do so through throttle butterfly positioning; the cold "rest" position is more closed than the warm "rest" position. If your system works like this, it would be instructive to measure the opening and ensure it is within spec. It sounds like your engine is not choking down.

Cheers, 3MP
 
jer:

Same disclaimer as 3mp. That said, however -

Do you have any way of checking/verifying fuel pressure? Don't most GMs have a Schrader valve on the fuel rail? My FI system has a check valve in it between the pump and the fuel rail to maintain system pressure after the engine shuts off. If the check valve is bad, the pressure bleeds off and you get a hard cold start.

Does your system have a "cold start injector?" A leaking one will give you a flooded-type of condition, a non-functional one will give you a hard cold start.

When you cleaned the throttle body, did you replace the gasket with a new one (possible vacuum leak) and/or get the throttle position switch out of adjustment? Or does your mod even have a throttle position switch (not sure).

Finally, what do your plugs look like? Probably not the problem, but many of those fuel system cleaning products will end up fouling your plugs with some of the crud they've removed elsewhere.

Good luck with it.
 
I have to go with Mike242GT on this one. Sounds more like a fuel starvation problem at start up. I would also check the main fuel pump pressure.
Try this first, turn the key all the way but not not far enough to engage the starter and wait 10 seconds. After 10 seconds engage the starter to start the car. If it starts right up then it is the check valve that went bad.
 
Make sure you're not losing any radiator fluid or notice any in the exhaust on start up. A head gasket leak of radiator fluid into a cylinder might cause this.
 
ok, lots replying to do here. Hey 3 mad ponchos.
smile.gif


quote:
Fuel injected cars don't have a choke in the classic sense, but they nevertheless must have that function served in one way or another. Some do so through throttle butterfly positioning; the cold "rest" position is more closed than the warm "rest" position. If your system works like this, it would be instructive to measure the opening and ensure it is within spec. It sounds like your engine is not choking down.
Click to expand...
I have thought about that, but if my choke is not set quite right what would be the appropriate measure? I have gotten some feedback on this once and he mentioned that if I cleaned out the butterfly too well, then I could have caused a bad seal or leak around the butterfly. Because after 10 years of having that butterfly move back and forth ... can cause a bit of wear. If wear has occured then the carbon deposits would have deposited itself around the butterfly/choke. Helping to compensate for what was worn out. So if I cleaned all that out...it could cause the problem that I have now.

Then again It could just need some readjustments. Actually come to think of it, when I did clean out the TB...Gumout said that I should move the choke back and forth while spraying its product. When I moved the choke back and forth...sometimes I felt like I was moving it *way* too much...rather then just being reasonable about it. huh...I might have misaligned it...I'll have to look into that again.
===========================================
Hey Mike242GT,
quote:
Do you have any way of checking/verifying fuel pressure? Don't most GMs have a Schrader valve on the fuel rail? My FI system has a check valve in it between the pump and the fuel rail to maintain system pressure after the engine shuts off. If the check valve is bad, the pressure bleeds off and you get a hard cold start.
Click to expand...
I looked *everywhere* for that Schrader valve and I can't find it. I don't think I have one. I did find out that I could get an adaptor for my car, but I can't find that either...unless I buy the fuel pressure gauge kit. I was going to check the regulator, but I thought....If I had a problem with pressure wouldn't I detect bad performance in my car while driving or in idle? Because I have no problems with any of this...except when the car starts-up after it hasn't been in use for about 8 or more hours.

quote:
Does your system have a "cold start injector?" A leaking one will give you a flooded-type of condition, a non-functional one will give you a hard cold start.
Click to expand...
I don't know...I have to check....

quote:
When you cleaned the throttle body, did you replace the gasket with a new one (possible vacuum leak) and/or get the throttle position switch out of adjustment? Or does your mod even have a throttle position switch (not sure).
Click to expand...
well I never replaced the gasket. BUT I'll tell you what. GM put out a bulliten about 8 years ago concerening a intake manifold gasket being misaligned...I believe a GM guy said it had a 100,000 mile lifespan.

But yes, like I told "3 mad ponchos"...when I moved the choke back and forth...I might have been to forceful on it and misaligned it.

But yes...I do believe it has a switch.

quote:
Finally, what do your plugs look like? Probably not the problem, but many of those fuel system cleaning products will end up fouling your plugs with some of the crud they've removed elsewhere.
Click to expand...
my spark plugs? throttle cleaners shouldn't effect spark plugs...do they? Well I did check my spark plugs(before I cleaned the TB) and they looked fine. But if the spark plugs were fouled...I should have noticed performance problems when driving....

=====================================

Hey ALS,

I've tried that method before. I turned the key to the on position...waited a few seconds....turned it back to the off posisiton....and did it again a couple of times. When I tried starting up the car. SAME problem as always!

-jer
 
3 mad ponchos,

I'm having flashbacks now.

I do remember trying find out how to set the throttle position, but...the manual would not tell me because it was too complicated of a situation. They suggested that I should have the dealership fix the problem.

-jer
 
a service manual....

you know I never did get one because I thought it was pretty much just an overpriced repair book that has about the same info as chilton or Haynes.

I have the Haynes book. Tried to get Chilton, but they don't have a book for my model car.

well ... I guess I need to at least take a look at them so I know weather its fluff or not. But you know...if memory serves me right... I believe Haynes mentioned that it may be necessary to disassemble the entire TB unit to fix the alignment problem.

gulp...

-jer
 
No way pardner, a factory service manual is worth every penny if you do much service at home. I buy one for every vehicle I intend to keep more than a year. Some are better than others but I've never bought one and wished I hadn't. Parts books are great too if you can get your hands on 'em. A zillion exploded diagrams.

Cheers, 3MP
 
timzak,

I have not checked the fuel filter or o2 sensor. But I have not really gotten myself up to checking them. If I had a bad fuel filter then my car's performance would be noticable...if my 02 sensor was bad I would probably seriously notice bad performance. I have not seen any light come on to indicate an 02 sensor problem. So...I don't know...

see that's the problem with all of this. Horrible cold startups...but if you take that factor away...then its as if my car runs "perfectly". that's what makes this so difficult to diagnose. That's why I keep coming back to my cold start up sensor(engine coolent sensor). if the sensor is bad enough it could be a little screwy when the engine is cold. It could get mixed signals....it may think... oh...the engine is warm...no need to do what I'm suppose to do when I'm cold. Maybe I should check 3 things. The throttle plate, engine coolent sensor, and fuel pressure.

if those are not the problems...then it is a much deeper problem. ugh...

-jer
 
3 mad ponchos,

if anything, that is one thing that I DO need.

"exploded diagrams!"
grin.gif
grin.gif
 
Had a similar problem with my 4.3 GM V6 truck.
Know what it was? Freakin' bad spark plug wires and rotor cap did not seal well. For what it's worth, but I'm SURE that was the first thing you did check!!!!!
wink.gif
 
quote:
Had a similar problem with my 4.3 GM V6 truck.
Know what it was? Freakin' bad spark plug wires and rotor cap did not seal well. For what it's worth, but I'm SURE that was the first thing you did check!!!!!
Click to expand...
uh....I sure did!!
wink.gif


ok I lied. nah...I did check it BEFORE the problem occured and of course it was OK. sigh..alright I'll check the plugs, wires, and rotor cap.

I don't know, I just figure if those were the cause of the problem then you would constantly have problems driving down the road(very rough handling). Did you have rough driving conditions when you had this problem? Or ... just like mine...it only occurred when the engine had cooled off completely?

-jer
 
My 1992 Chevy truck is running about the same. When it start cold, it runs for about 2-3 sec's and then almost dies out but catches and idles very rough, with the engine shaking a little. Giving it more gas smoothes it out. I have put in new plugs, PVC, air air filter fuel filter, cap, rotor(were all needed), ran bottle GM fuel system cleaner with a tank of gas. Still the same. Talking with a fella who is a GM tech, he says he would look at the injectors. TBI injectors can malfunction. What could be happening is that when you start the engine cold, the computer senses this and gives a signal for more fuel. If the injectors is dirty (very common on TBI systems) or gummed up it can't deliver the right amount of fuel and the engine starves for gas when cold. Mine runs perfect after about 5 minutes but will do the same thing every am. Often the injectors are worn out and need to be replaced. Its a common replacement part.

[ June 05, 2003, 06:33 PM: Message edited by: Mike ]
 
jer...has the car ever backfired along with the rough idle when you first start it up?...i have seen your problem in some similar vehicles...check your catalytic converter to make sure there is no blockage...in a cat the blockage can be intermitent(loose pieces inside)and can cause your symptoms even if the car is not backfiring...any power loss at wide open throttle?
 
shoboosted,

I've thought about that too. I seem to get some backfiring(very light and muffled), but I think this backfiring is caused by the fact that fuel(for whatever reason) doesn't seem to be getting into the system or ... bah... my mind went blank.

But I have checked the cat and didn't notice any loose pieces inside. When I drive slow...fast....nothing. no performance lost.

ok ok...you just gave me a thought here. I am in the process of changing out my tranny fluid soon. When I was planning out everything(I'm doing my own flush)...I drove the car to warm it up and I noticed something. When I accelerate on the car...just slightly... I hear a very ryhthmic clanking, vibrating,??? noise. At first I thought it was the transmission, but after have some second opinions I think I can rule that out. If it was the transmission I would REALLY feel it. But now that you mention about the cat...perhaps my cat is starting to act up. The timing would be right(I have 160k on the car). But like I said..I noticed no loose parts in the cat....

hmph.....

-jer
 
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