: 2000 seville sts misfire



jonathan13
03-31-09, 09:33 PM
Okay guys, hopefully this is in the right section- if not please let me know and i will post in the correct place. I have been a longtime fan of hondas and use many honda forums but never a cadillac forum.

Here is my problem.. I have a 2000 Cadillac Seville STS and it has a misfire at idle and also when cruising down the interstate. It also has a hard time starting sometimes and wants to die or actually does die out the first time i start it and i have to start it again. There is currently no check engine light on but previously it had a code for low coolant temp.

I have replaced the spark plugs
and boots but the misfire is still there. Where should i go from here?- Clean injectors? coil pack replacement?

Also I have had issues with hondas that have misfires usually having a bad head gasket. Could this be my issue? I would like to get rid of the car asap if so.

Thanks for the help in advance.

Submariner409
03-31-09, 10:08 PM
Read up on the "sticky" threads at the top of this, Northstar Performance, and Cadillac Technical Tips down below titled "How to pull codes....got codes look here" and see what your car is telling you. (You do not need an aftermarket scanner: it's all built in already.)

What about gas mileage ??? 14 - 18 city, 23 -26 highway???? If not, pull the engine cover, start the car, and pull the vacuum fitting (careful.....) off the nipple on the Fuel Pressure Regulator on the rear fuel rail, driver's side. Any gas ??? New FPR. Simple hairpin clip and O-ring grease job.

Hope you used ACDelco 41-987 plugs. Check the individual injector conectors and the coil pack (cassette) ignition (ICM) connectors.

Check the PCV pipe at the rear cam cover - tight on the nipple ?? (Fixed orifice, no rattle valve after 2000......)

Spray a tad of starter fluid or choke cleaner at the base of the intake manifold-to-throttlebody connector plenum (black rubber with s/s hose clamp). Any idle change ?? Vacuum leak.

Ranger
03-31-09, 10:29 PM
It also has a hard time starting sometimes and wants to die or actually does die out the first time i start it and i have to start it again.
Might also check the fuel pressure.

jonathan13
03-31-09, 11:36 PM
okay the code came back and its the low coolant temperature code.. which it said could be thermostat malfunction or faulty temperature sensor.. would this cause the trouble i am having.. yes the plugs were replaced with Ac Delco and gas mileage is good.. right in the range you described.. but for some reason i was getting better mileage before the spark plug and boot job. and no vacuum leaks.

Submariner409
04-01-09, 09:27 AM
A temp sender fault will not normally cause a misfire such as you describe.

Do the checks outlined a couple of posts back and get that out of the way, then we'll try again.......vacuum leaks might cause just what you describe.

The coolant temp sensor is down under the lower rear of the throttlebody, actually at about 5 o'clock if you're looking at the engine from the rear (transmission end). Not fun to get to, but pull and reconnect the plug first, before you try to change the sensor ($8 at www.rockauto.com). The thermostat is not difficult, either, just takes a while.

jonathan13
04-01-09, 02:07 PM
okay thanks for all the help. ill get that stuff knocked out of the way and we'll see where we are from there.