Engine shutters or has split-second loss of power during low RPM acceleration

JASON CORBETT

MEMBER
1997 SATURN SC2
1.9L
4 CYL
FWD
MANUAL
119,000 MILES

I have a 97 sc2 1.9 twin cam (vin 7). I am the second owner of this well-kept vehicle (the prior owner serviced regularly 3000 miles). I purchased it (as a steal from the auction) from the local dealer who wanted to get rid of it. I have, by my MECHANIC'S MAINTAINING HABIT, replaced the pcv at my first oil change @ 100k, cooling system hoses and flushed the system @102k, drained and refilled manual trans fluid @ 105k, replaced the fuel filter @105k, spark plugs and wires @105k, all 4 struts and outer tie rod ends and alignment by Firestone - a month ago @118,600 drivebelt and tensioner - a week ago. Been very happy with the investment because I know from 2 prior Saturns that this vehicle will last until someone wants to buy it from me.

My problem started about a month ago when I noticed as soon as the engine warmed up (I guess when it goes into closed-loop) it would shutter and buck like it had a dead-missfire. It feels like a bad TPS when you start to accelerate from closed throttle, it strumbles and goes away instantly. I checked the TPS and my readings matched the ones in the Chilton manual-not the issue either. It does not surge on a cold start up, only after I drive.5 mile. If I race around the gears, it is not so noticable. It lightly feels like a "quick slip or bog" when I shift at higher RPMs. Regardless, it feels like doesn't want to perform.
So my mechanic friend and I checked the ignition coils by GROUNDING OUT the each terminal with a screwdriver to determine a bad fire. None found. The ground test ruled out bad coils and resistance checking the wires was excellent too. (SALTWATER testing the ignition system ruled out any arcing of spark to wires, coils or ignition module) I checked the ignition module connector for corrosion at the terminals (beautiful like new). My mechanic friend suggested replacing spark plugs -due to thermal breakdown- so I did anyway (my new ones only had 10k miles).
I took the cheap test by replacing the crankshaft sensor (and still did not fix it).
We checked fuel pressure also. 55-60 psi normal-not the fuel pump. Checked fuel pressure regulator, no fuel leaking and RPMs increased with vacuum hose pulled- nope not that either.
Then I started unpluging items and took short test drives to rule out the operation of the MAP sensor, EGR valve, and ECT sensor, IAT sensor, and oxygen sensor. Each unpluged devices did not affect the shuttering or surge problem.

Today 5/17 --- I decided to unscrew the primary O2 sensor to check the restriction of the catalytic converter and take a quick drive - still shuttered like before! WHAT DO I DO NEXT?
I am probably going to kick myself if you suggest something basic to resolve this problem. I have read countless forums about Saturn owners and their problems. None of which have given this much detail of the problem they are trying to diagnose. I hope this is enough information for you to grind out a solution.

I am also a GM tech out of the field with no access to a great scanner!

THANK YOU AND MUCH RESPECT TO YOU EXPERTS THAT CAN DIAGNOSE MY ISSUE. Jason

4 Replies

JASON CORBETT

MEMBER
3 POSTS

Amendment
The throttle body and IAC have been thoroughly cleaned also by running the vehicle and liberally spraying the opening with 3 cans of throttle body cleaner. This is just like the FUEL SYSTEM SERVICE sold at your local dealership or service shop. This breaks down the deposits in your intake manifold and burns the gunk in the combustion chambers (without costing me $199.95 hahaha! Only $10-15 for your preferred brand chemical spray)

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Saturday, May 17th, 2014 AT 11:38 PM

SATURNTECH9

MECHANIC
30,869 POSTS

I would replace the coolant temp sensor even though you thought you ruled it out they fail so often.I have replaced so many over my 21 yrs of working on these cars. Also what kind of spark plugs are you using?Hopefully copper plugs?The engines dont like platinum plugs they carbon foul its best to run copper ngk or as a alternative bosch super copper. Also dont rule out the wires I have ohmed those wires saltwater tested etc and still have come across bad wires. Also a coil breaking down and starting to fail. But coils dont fail often that low of mileage on those cars its still possible. What I used to do when I worked for saturn I had a spare set of twin cam and single cam wires to swap and also coils and modules to eliminate and find the problem quickly. It was usually wires also make sure none of the wires are cross routed incorrectly I have seen that cause weird issues.I have seen bad coolant temp sensors cause so many different symptoms random surging car dieing and not restarting. Random no starts when I get a saturn for the first time for4 myself the first thing I do is replace the coolant temp sensor. Also look inside the coolant temp sensor and see if the terminals are blue or green instead of silver. The coolant temp sensors leak coolant into them corroding them.

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Sunday, May 18th, 2014 AT 8:57 AM

JASON CORBETT

MEMBER
3 POSTS

I had to replace my coolant temp sensor and harness because of corrosion on the terminals. Upon removing the CTS, I noticed a crack on the sensor (go figure). Is that a normal failure?
I also replaced my [platinum] spark plugs with Bosch Supper coppers. Amazing! I did not know that OBD 2 systems run on copper plugs. I thought they quit using those in the '80s pre OBD 1.
I am still dumbfounded that those copper plugs made the "deadness" go away. The car runs like new! I can accelerate after I am cruising at 70 and the car powers ahead without skipping a beat! I later replaced the plug wires by habit to complete the basic tune-up.
Thank you

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Wednesday, June 4th, 2014 AT 5:52 PM

SATURNTECH9

MECHANIC
30,869 POSTS

Yes saturn used plastic tipped coolant temp sensors up till about 2001 in there s model saturns and the tips cracked all the time letting coolant get into the connectors. Also shorting out the sensors then they finally starting making them brass tipped. But they still fail Ihave a 1999 sl2 have had it like 8 years and have went thru atleast 3 coolant temp sensors. The problem with running the platinum plugs in those s model saturns. Is they like to burn oil and it carbon fouls the plugs. The engines were ment to run on copper plugs and they run well on copper plugs. As far as obd2 cars not running on copper plugs thats not true at all. Alot of the dodges run copper plugs even the vws have some copper plugs. Just put a set in a 2011 vw jetta 2.0l non turbo. Also the 2010 chevy aveo copper plugs but thats a rebadged daweo. Glad I could help if you have anymore questions let me know iam the saturn expert on here. If you ever want to ask for me just start the question with this one is for saturntech9 and they will leave the question for me to answer.

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Wednesday, June 4th, 2014 AT 8:02 PM