91.3.1 'warm' starting issue

[ktetch]

Wifes car is a 91 lumina. got it 30 months ago with 70k miles on it, it's now at 175k.

It's started having problems running and starting. Specifically, it'll start when cold. Run it and drive it around, it goes decent. If you stop it, it'll restart within the next 10-15 minutes, maybe. If left any longer, it won't fire at all. It'll turn over nice and fast, but there's no firing. after about 70-90 mins, it'll fire, and run, but often be lumpy. barely coughing through at times, and surging a little. If she cruises a parking lot for a minute or two, it becomes drivable.

It'll also act like it's got bad turbo-lag at times, where the throttle's put at, say, 25%, and it'll accelerate slowly, and then suddenly come onto power.

Problem is, it's our only car at present, and she's fighting to keep her job, so taking the car off the road for a few days isn't an option, while I tear the engine apart.

I had the 'low coolant' light stuck on too, for the last 2 years, but the coolant's fully topped up.

Any thoughts/suggestions as to where my problem is?

[ktetch]

ok, I've checked and replaced the electronic temp sensor, cleaned out the throttlebody (lotsa carbon in there). Even tried cleaning out the low coolant sensor (that didn't work) (and also did a coolant and oil change at the same time)

A lot of the 'tubo lag' is gone, but it's still having a hard time starting when 'warm' (between 15-90mins of a long run)

I guess the next stage is fuel pressure, right?

Oh, and plugs i've already checked. I replaced the plugs and wires already.

[inafogg]

yes thats what i'd check if you have a gauge.
low coolant light is probaly the sensor,would'nt worry about that right now)
fuel filter fairly new??
good luck
btw you refer to turbo lag... its tuboless right??

[ktetch]

Yeah, I figured the low coolant light was the sensor. I pulled it out and cleaned it a bit last night when I changed the electronic thermostat switch.

We've had the car 2 1/2 years and put about 100k miles (upto 176k now), and we've not touched the fuel filter (it's all I can do to get the wife to check the tire pressure and oil once a week)

ys, it's turboless, but i've driven a few turbo cars in the past (UK MG Metro turbo's, and saab 900t's), that was just the best way to describe things. as in put your foot down, very little happens, then 'whump' accelerates. I guess you could also call it a power 'flat spot'.

I had a look at rent a fuel pressure gauge at autozone yesterday, when i got the sensor (and a nice big bottle of carb cleaner for the throttlebody) but the guy could only tell me 'it costs $150 to buy the kit...'

So, tomorrow or maybe Saturday, i'll try and see if someone more knowledgeable is there, and about renting it, and may get a filter for the hell of it (only 10.99)

[jeffcoslacker]

There's several items on that motor that can fall victim to heat soak...ignition module, coil packs and crank position sensor are most common....

A neat trick is to heat the ignition module and coil packs with a hair dryer or heat gun until really warm when the engine is stone cold, and see if you reproduce the heat soak starting problem...if so, you're on the right track...

Also check where the crank sensor's wiring ducks past the crank pulley...known to come loose from the holds, and "sag" into the pulley when warm...which grounds it out, once the insulation is gone...

[ktetch]

Ok, so I found some of my coolant issue. Was the radiator cap/ the cold-syphon valve (to pull in coolant from the expansion tank when the engine cools) was broke so it was venting pressure through the expansion, which meant i wasn't loosing coolant, but I had no coolant pressure either.

I've also done the fuel filter.

Regardless, It's still having problems.

I think it's the injectors next. Yesterday, it fired up fine, ran for about a mile, and then just 'died'. Luckily a very nice man in a jeep compass winched me out of traffic and into a parking lot.

Is it normal for the plenum to get too hot to touch? One thing the guy tries yesterday was using the fuel pressure check valve, to 'bleed' the engine. It was gas coming out of it (smelled of fuel, but still, not liquid fuel) each time the pump was primed. I know that's not normal.

So, any more thoughts anyone?

[inafogg]

did you ever check the fuel pressure

[ktetch]

yes, yes I did.
Was at spec's, once I'd changed the fuel filter.

Someone has suggested to me a sticking intake valve, causing it to run lean (although he's more an import guy)

[ibbobud]

A stuck intake valve would almost cause a miss unless it was stuck open.

What was your fuel pressure readings with engine running and idling?

Have you ran test on the fuel pressure regulator to see if the pressure changes when you disconnect the vaccuum?

If the regulator is not kicking up the pressure when accelerating it could cause it to lean out. Could have a fuel volume issue too. Its pumping anough to keep pressure at idle but not when you accelerate causing a lean condition.

Does it do it when its cold or hot or both? once its warm it relies on sensor data to control fuel. If you have a bad map or o2 sensor it will cause that issue too.

[ktetch]

Sorry for the delay in get back on this, things kept cropping up.

Originally Posted by ibbobud

A stuck intake valve would almost cause a miss unless it was stuck open.

What was your fuel pressure readings with engine running and idling?

I can't remember now.

Have you ran test on the fuel pressure regulator to see if the pressure changes when you disconnect the vaccuum?

I hadn't, no. I was unaware of such a test

If the regulator is not kicking up the pressure when accelerating it could cause it to lean out. Could have a fuel volume issue too. Its pumping anough to keep pressure at idle but not when you accelerate causing a lean condition.

Does it do it when its cold or hot or both? once its warm it relies on sensor data to control fuel. If you have a bad map or o2 sensor it will cause that issue too.

When it's cold, it'd take 4-5 times to get it to start. When it's Hot (been run in the last 10 mins) it starts straight away. Whenn 'warm' (between 20mins and an hour or two) it won't start at all. The plenum is red hot, and even the coolant overflow tank is quite warm.

So, new developments. Wednesday night, my wife had problems coming home. When she got home, I jumped in and took it for a spin around the block. it got maybe 1/4 mile then cut out, and has not started since.
here's a video I took with my phone
http://www.youtube.com/watch?v=aEb6bdChHBE

I got a neighbour to pull me back to the house. I've checked the spark as much as I can (I don't have a lot of the fancy diagnostic stuff). but I've changed the plugs, checked the wires, the coils, and the ignition module. My haynes says to test for battery voltage between the fuse and the 5-pin (6 spot) connector that plugs into the module for battery voltage, and there was 11V there.

I'm now thinking it's fuel related. I can't hear anything but the relay click when turning the ignition on. Sometimes I'll; hear the clitter-clatter (how else to describe it) when it goes off. I don't have a fuel pressure gauge to hand (it's a friends, and he's 90 miles away) but doing an unscientific test, there's sod all fuel pressure. First, I'm manually activating the pin in the scherer valve. When at the 40psi it should be at, it should spreay a good head of pressure. this was more of a dribble. when we used the fuel pump tester lead (that single pin connector attached to the fuel pump relay/fuse block) to power the pump with the valve open, it's giving its impression of the worlds weakest fountain - maybe 1/4-1/2" in height, nowhere near 40psi worth.

The other thing is, the car had a BAD overheating problem. If it's stood idling for 3-4 minutes, it'll overheat and die. I think it's to do with the red-hot plenum which surrounds the fuel rail - it's vaporising the fuel BEFORE the injectors, so they don't work right. The cooling temp switch for the fans was replaced 2 months ago. When the cable is unplugged, the fans run fine. when plugged in, they don't run at all. At first I thought it was the radiator cap, because it seemed like the valve that allows fluid to the overflow was not sealing, so it was pushing hot coolant into the overflow where it'd condense. Without that holding pressure, it'd never reach the 230F to trip the switch.

So two problem, first it won't start, and second, when ti does, it overheats.

[ktetch]

ok, had some progress.

I finally got the plenum off (had some MASSIVE problems with the EGR stuff)

The PCV valve was completely crudded up. I mean dead blocked.
EGR passage was so fouled it had maybe 1/4 the bore left.

Also, checked the injectors.
all were above 12ohms except #6 (diver side, on the front) which was 1.4

Those two things my cause of the non-firing?

*edited to add*
Oh, and there was a nest in between the fuel rails, made using insulation from the under-bonnet insulation. lots of acorns too. they look fresh. Wife was off work from the 24th to the 31st of may, so it wasn't driven, when she drove it on the 1st, that's when it died entirely.
I really hope this is everything....

[ibbobud]

You will definately have to replace that one injector. In our cars the injectors are gang fired 3 at a time. If you have one thats bad or out of resistance it will affect all 3. These cars wont even sputter on 3 cyl and hardly on 5.

Replace the injector, then soak the upper plenum in a tub of degraser for a hour or so and clean out the egr passage. The car will run like new! mine is a race car now!

I have pics if you want from when i replaced all my injectors and fixed all the egr issues :-) just send me a message.

[ktetch]

Originally Posted by ibbobud

You will definately have to replace that one injector. In our cars the injectors are gang fired 3 at a time. If you have one thats bad or out of resistance it will affect all 3. These cars wont even sputter on 3 cyl and hardly on 5.

Replace the injector, then soak the upper plenum in a tub of degraser for a hour or so and clean out the egr passage. The car will run like new! mine is a race car now!

I have pics if you want from when i replaced all my injectors and fixed all the egr issues :-) just send me a message.

I had the plenum soaking overnight, so it's a lot better now.

Just trying to get the fuel rail off right now and stopped for lunch. (undone the bolts, and the fuel lines and its pulling up with a rocking motion, right?)

Thanks for hte feedback

[ibbobud]

yea rock them back and forth while applying upward pressure. Mine where stuck in there pretty good.

**CAUTION** Make sure the are around the injectors is good and clean!

As soon as you pull the injectors out all the crud built up around them falls right into the cyl!

After removing the injectors and fuel rails place paper towels in the intake runners and in the injector ports so nothing accidently falls in....

[ktetch]

ok, its that precarious? damn. I've loads of crap in the area, mainly from that nest but also the plastic bundling the wires has dried out and cracked in a lot of places, so I've semi-circles of black plastic in there too. Would be a LOT easier to clean without the rails in.