2000 LS1 ignition/fan issues

[away8907]

Reposted, accidentally put this in the S-series forum :/


Hello, I've been working on repairing my sister's LS1 2.2 - The main issues were a rough idle, trouble starting, hesitation under acceleration, poor fuel economy, rough sounding exhaust, and constant radiator fans at full speed. Sorry if this gets a little long-winded, but I've tried to be as thorough as possible.

I've replaced all plugs with NGK's - this solved the idle and starting issues.

Pulled codes - got back cyl 2 misfire and camshaft pos sensor A (research tells me that a) no camshaft sensors on this motor, and b) it's usually an indicator of an ignition issue elsewhere)

Tested the coil packs for spark against the valve cover, sure enough, cylinder 2 had no spark. All 4 boots function properly. Replaced the ignition control module, smoothed idle out a bit more but did not fix the misfire. (The exhaust tone, acceleration, and fuel economy all clearly point to it being down a cylinder.)

Prior to replacing the ICM, I'd get a solid SES light which would flash occasionally (about a minute at a time, every 20-30 minutes or so) - After replacement it's a constant flashing SES. I haven't been able to rescan it, but will get it done Monday at work.

My next step is to replace the coil pack, my impression is that the coils are the final point of failure I haven't yet addressed. Am I right in this?

As for the fans, I've replaced the coolant temp sensor, which didn't solve the problem. I drove it long enough to get the engine up to temp, and the temp gauge is reading just a hair below 1/4 (the first notch) - is that the proper temp? I'm leaning towards replacing the thermostat, should that do it?

If I've missed anything, or if there's a simple way to try and keep troubleshooting these issues, let me know! Thanks in advance for the help, everyone.

Alex

[fdryer]

As mentioned in your other thread;

1-The L-series have the flat nosed brass coolant sensor. The S-series didn't until '01. If you replaced a round nosed plastic coolant sensor then you have a S-series car/engine.

2-Definitely replace the thermostat with a 195F one. The temperature needle should always be above the 1/4 mark.

[away8907]

It's an LS, replaced a flat nosed brass ECTS.

I'm only finding 180F thermostats locally, any chance you have a part number I can look for online?

Thanks again!

[fdryer]

Its strange that the service manual points out 90C/194F as the thermostat and you're having difficulty finding this one when 180F seems to be the one listed. I don't have part numbers. Perhaps checking with GM may help if you ask what temperature rating is specified. If 180F is all that's available, use it.

[away8907]

I'm gonna run it by our diagnostics guy on Monday (I work in Toyota service), but from what I've read elsewhere on the forums, the Stant 14279 seems to be the way to go. I can get it from Amazon for ~25 shipped, so I'll probably go that route.

I had a thought this afternoon though; Even if the t-stat failed open (which would explain the low engine temp), why would that trigger constant fans? Just seems counter-intuitive. AFAIK the only condition that forces full fan is when A/C is enabled, which it is not.

[fdryer]

Some words of caution may be needed. Replacement t-stats show a large sealing ring going around the diameter of the sheet metal disc. The best description I can use for now is an O-ring with a square shaped profile instead of round with a slit going around the inside diameter. This slit fits over the steel disc to provide a seal in the t-stat housing. If this ring fails from heat over the years then coolant is allowed to flow sooner to keep the cylinder head cooler than ideal. Be sure your replacement is the same dimensionally as the original.

[fdryer]

There's more going on electronically than meets the eye. Since electronics depends on signals, coolant signals are varying in relation to coolant temps so the electronics has a range that it needs to see this temperature sensor operate in relative to time from the moment the engine begins running. The pcm always compares actual temps against programmed parameters relative to time and if this doesn't match then a default is used - the cooling fan is turned on despite what you see as a cool engine. The default program is to protect the engine from possible overheating. In addition, your car may use multiple speeds to control air flow through the two radiators, the a/c condenser coil and engine radiator. If your car uses a fan control module, some have issues with it running incorrectly. Its a black plastic box next to the battery.

[born again]

The coil pack could be your problem. The 2.2's don't lose many of these, but some other engines have much more trouble with failed coil packs (some Saab owners carry a spare in the trunk).

Re the TStat- I had that rubber ring on the valve plate disintegrate and cause a cool running condition. I thought that one was OEM. I had to flush out all the rubber bits.

[away8907]

Thanks for everything so far. I should have this all buttoned up by Friday, I'll hop back in here for an update.

[bluesl2]

I agree it sounds like the coil pack may be bad. They will dump one cylinder like that when they go bad. Usually if cylinders 2 and 3 quit working, it's the icm that's failed. It's common for the fans to activate when there is a cylinder drop out problem like that. I'd get a 195 thermostat for it as well.

[away8907]

Spent the afternoon replacing the coil pack and changing the oil. Good news, everyone - all problems solved. Took it for a 45 minute test drive, CEL went away, fans turned off, fuel economy went through the roof (in comparison), idle is steady at ~690, coolant temps are back above the 1st notch (guessing being down a cylinder + full fans were holding it down, t-stat seems to be OK.)


Long story short, Thanks everybody, and may this thread help anyone who has these issues in the future!

The only thing I'd do differently in the future is replace the coil pack before the ICM, based on the different symptoms of failure.

Thanks again,

Alex

[away8907]

Wanted to post a follow-up after a week - Here's what I've noticed.

The car likes 89 gas a LOT more than 87, not only in the butt dyno, but in measured MPG (using odo vs gas pump) - Not willing to bet anything above 90 would help it additionally, but it is what it is.

I haven't had any issues mechanically - the only thing I've noticed is that while coasting, it likes to sit around 1500-1700 rpm - assuming this is normal.

Other than that, everything is working as expected, and I again thank all who chipped in. GREATLY eased the process!

[smoothaseggs]

amazing, i did a search for this and came up empty, tried different ways and here it is. having identical issues with daughters car. tougher for me to diagnose as i am a state away. thinking of all the parts i need to take with me

[away8907]

If you can afford to throw parts at it, I'd say you'll be okay with a new coil pack, ignition control module, and plugs. Without any sort of in-depth diagnosis, those 3 things would pretty much overkill any sort of ignition issue.

I got a slight discount on Napa parts through work, but expect the coil and ICM to cost 80-100 each.

[smoothaseggs]

just posting a follow up for anyone doing searches. had similar problems, replaced ICM and problem persisted, removed coil pack to inspect sprk plugs. two plugs were horrible looking so i replaced them all, problem persisted. replaced the coil pack and all issues resolved. went as far as installing the original ICM to confirm it was the coil pack that failed