Cadillac Owners Forum banner

1 - 20 of 21 Posts

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #1
I have a 1997 Cadillac STS that is having starting issues, rough idling, and getting hot at idle. When starting the car on a cold start it starts perfectly and idles high for like 8 seconds then goes down to 900 rpm then eventually to idle speed. At idle it is pretty damn rough and the RPM fluctuates. Now on a warm start I have to crank the starter for like 15 seconds to start the car. After starting it never idles high it goes straight to 600 rpm. Sometimes it even appears to almost backfire when starting it or it shuts down. This car gets average 12 mpg which seems way too low so I figure that it may be running lean from a vacuum leak or something along those lines.

I have tried pulling the EGR valve off and cleaning it out but that did not help at all.

Someone please tell me what I am looking for and what I should do to troubleshoot and issues.
Thank you so much!
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,793 Posts
Sounds like a leaky FPR. Pull the vacuum hose (red arrow) off at idle and look for fuel leaking from the FPR nipple. There should be none.

Yellow arrow is the fuel line. Yours should have been changed to a stainless steel line under the recall.
 

Attachments

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,516 Posts
Welcome to the Funny Farm !!! :highfive:

Lots of possibilities for hard hot start, rough idle (your cold start idle sequence is correct). Depending on the state of maintenance for the car, you can begin with a thorough throttlebody and cleaning, air filter check, air intake ducting checks (NO leaks), intake manifold integrity checks, ignition system and plug/wires tuneup, Ignition coil and ICM cleaning, ICM ground wire check, FPR, fuel filter - - -

Pull your trouble codes from the car's built-in code system - use the proper year/model group of instructions on this forum main threads page - "How to pull codes". Write down any found codes and whether each is Current or History. Return to the sticky and open the link to definitions of all OBD-II codes. Decipher your found codes and post it all here.

Study the entire Cadillac Technical Archive way up ^^^ in the top black bar. Written by a Northstar Powertrain engineer. Always study the sticky posts/threads in any forum of interest, especially this one, Deville, and Engines; Northstar. There is a TON of info on your question down in Item Specific, Cadillac Tech Tips.

To get your feet wet, Google "cadillac forums 1997 seville throttlebody cleaning" and go from there with your searches - always preceding the part/system/question with "cadillac forums ..........".

"getting hot at idle" - With no A/C compressor function set the engine will heat, under slow traffic or extended idle conditions, to 224 degrees, fans go to SLOW, the engine cools to 213, cycle repeats. With some A/C compressor function set, fans run in SLOW all the time, so the coolant should stay at 195 - 210 all the time. 224 degrees is NOT overheating.

(Looks like Ranger and I hit the Submit button at the same time)
 

Attachments

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #4
Sounds like a leaky FPR. Pull the vacuum hose (red arrow) off at idle and look for fuel leaking from the FPR nipple. There should be none.

Yellow arrow is the fuel line. Yours should have been changed to a stainless steel line under the recall.
Thank you so much Ranger! I am going to look into this tomorrow. Me and my dad were under the assumption it was running lean but I guess we were wrong. :confused:

Welcome to the Funny Farm !!! :highfive:

Lots of possibilities for hard hot start, rough idle (your cold start idle sequence is correct). Depending on the state of maintenance for the car, you can begin with a thorough throttlebody and cleaning, air filter check, air intake ducting checks (NO leaks), intake manifold integrity checks, ignition system and plug/wires tuneup, Ignition coil and ICM cleaning, ICM ground wire check, FPR, fuel filter - - -

Pull your trouble codes from the car's built-in code system - use the proper year/model group of instructions on this forum main threads page - "How to pull codes". Write down any found codes and whether each is Current or History. Return to the sticky and open the link to definitions of all OBD-II codes. Decipher your found codes and post it all here.

Study the entire Cadillac Technical Archive way up ^^^ in the top black bar. Written by a Northstar Powertrain engineer. Always study the sticky posts/threads in any forum of interest, especially this one, Deville, and Engines; Northstar. There is a TON of info on your question down in Item Specific, Cadillac Tech Tips.

To get your feet wet, Google "cadillac forums 1997 seville throttlebody cleaning" and go from there with your searches - always preceding the part/system/question with "cadillac forums ..........".

"getting hot at idle" - With no A/C compressor function set the engine will heat, under slow traffic or extended idle conditions, to 224 degrees, fans go to SLOW, the engine cools to 213, cycle repeats. With some A/C compressor function set, fans run in SLOW all the time, so the coolant should stay at 195 - 210 all the time. 224 degrees is NOT overheating.

(Looks like Ranger and I hit the Submit button at the same time)
Thank you so much for the warm welcome to the forums. I was not expecting such a thorough answer.

I have actually pulled the codes and there are a hell of a lot of history codes but only one code that is current. The code that is current is C1738 which is for "Exhaust Valve Solenoid Short to GND". I have researched this issue and it has something to do with the rear suspension air ride.

So the heating issue is normal? I know for a fact that the A/C compressor is disabled automatically because there is no refrigerant in the system.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,516 Posts
So the heating issue is normal? I know for a fact that the A/C compressor is disabled automatically because there is no refrigerant in the system.
The thermostat is set to begin opening at 188 and fully open at 206. Cooling fans (both run together) go to SLOW at 224 and FAST at 236. In heavy traffic, summer, idling it's entirely possible for the engine to warm to 224. Normal. Common. On the road or even stop & go suburban traffic the temp will stay (in a good cooling system) at about 190 - 205 at all times.

On the Engines; Northstar main page there are several sticky posts and threads. 3 of them concern cooling systems, fan operation and temperature gauges. Please read them. Also, the recommended Cadillac Technical Archive.
 

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #6
So I pulled off the vacuum line and fuel come pouring out of the FPR. Is there a temporary fix for the starting issue until I have the money to fork up for a new one?
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,289 Posts
So I pulled off the vacuum line and fuel come pouring out of the FPR. Is there a temporary fix for the starting issue until I have the money to fork up for a new one?
-------------------------
no -
the FPR has a rubber diaphragm in the middle of it -

one side of the diaphragm has gasoline -
the other side is vacuum -

during "normal" operation -
the hose supplies vacuum and pulls the diaphragm -

your diaphragm has a leak -
so when the engine is running -
the vacuum is sucking gasoline all the time -

------------------------

it looks like there are two types available -
one for a stainless steel fuel rail -
and one for the nylon fuel rail -

the part is less then $50 -
go to ROCKAUTO.COM -
select:
CADILLAC -
1997 -
SEVILLE -
AIR/FUEL -
FUEL INJECTION PRESSURE REGULATOR -

personally - I'd go with the DELPHI FP10016 -
DELPHI is a GM supplier -

the best price - with free shipping is $36.08 -
http://www.amazon.com/Delphi-FP10016-Injection-Pressure-Regulator/dp/B000CGM5J6/ref=au_as_r?ie=UTF8&Make=Cadillac|46&Model=Seville|413&Year=1997|1997&n=15684181&newVehicle=1&s=automotive&vehicleId=1&vehicleType=automotive
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,793 Posts
So I pulled off the vacuum line and fuel come pouring out of the FPR. Is there a temporary fix for the starting issue until I have the money to fork up for a new one?
It's trying to start very rich. Much like a hot carbureted engine with the choke closed. You might try starting it with the throttle partially or fully opened. That may help a bit, but you'll have to experiment.
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,516 Posts
Yep ^^^

The FPR recycles a staggering amount of fuel back to the tank. Like 60 - 80 gallons an hour.

Here's a basic FPR line diagram - if the diaphragm is ruptured it feeds raw fuel straight into the throttlebody vacuum nipple - not good, especially since the overly rich mixture at cold start washes all the lubrication off the cylinder walls. (Our FPR has a different fuel supply/return setup - this is for clarification only)

Replace it yesterday.
 

Attachments

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Okay guys so I go lucky and only had to pay 29$ for the fuel regulator and I installed it. When I first started it it was still running like crap and I let it idle for about 10 minutes. It runs like glass now. Starts up nice and easy on hot starts and even has some power now on WOT pulls.

Thank you guys so much <3
 

·
Registered
98 DeVille, 97 DeVille d'Elegance
Joined
·
7,345 Posts
It just needed to clean the plugs... I'd go beat the thing bet it runs even better after being so loaded up.
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,289 Posts
Okay guys so I go lucky and only had to pay 29$ for the fuel regulator and I installed it. When I first started it it was still running like crap and I let it idle for about 10 minutes. It runs like F***** glass now. Starts up nice and easy on hot starts and even has some power now on WOT pulls.

Thank you guys so much <3
-------------------------
take it out for a little "beating" -

and - with burning a LOT of extra gas -
do an oil change -
 

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #13
It just needed to clean the plugs... I'd go beat the thing bet it runs even better after being so loaded up.
Believe I am going to now :)

-------------------------
take it out for a little "beating" -

and - with burning a LOT of extra gas -
do an oil change -
Yeah now its burning oil pretty good on the start up I'm not sure if it's suppose to do that after running like crap for 3 months or not :|
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,516 Posts
If it has been running slow/rich for that long, the first few times you get on it the amount of crap that comes out the exhaust (rear view mirror) will scare the hell out of you.

After blowing out the cobwebs and the engine is nice and warm I would change the oil/filter. Oil dilution from rich fuel mixtures is not good for an engine. Exactly 7.5 quarts of whatever 10W-30 oil floats your boat and a WIX/NAPA 51522 filter.

Please go way up ^^^ to the top black bar and study the entire Cadillac Technical Archive - mostly written by one of the GM Northstar powertrain engineers. Especially the article "Occasional full throttle operation is good .............".

Before you begin to "exercise" the engine, make sure all the fluids are at correct levels - and the correct level for oil is NOT at the top of the dipstick hashmark. Halfway up - look at P.3 of the link in post #1.

http://www.cadillacforums.com/forums/northstar-engines-system-technical-discussion/198220-northstar-ring-cleaning-procedure-proper-oil.html
 

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #15
Even when it was running rich it still threw my ass back in the seat and lit up the tires a little bit. I can't imagine what it's going to do now :)

I'm going to check the dipstick to see if I can smell fuel or not I forgot to do that.
 

·
Registered
1997 Cadillac Seville STS
Joined
·
14 Posts
Discussion Starter #17
Hello guys....

So it has been like 2 weeks since I have replaced the FPR and I am having some issues still with starting.

Before It LOVED cold starting but now it barely even wants to fire on cold starts.

I have drove it 75 miles since I changed it aswell as disconnected the battery to hopefully reset the idle sequence.
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,793 Posts
When was the TB last cleaned?
Have you checked your fuel pressure?
 
1 - 20 of 21 Posts
Top