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Followup To
Question -
My sister in law has a 94 Saturn SC1 automatic with 225000.KMs on it.
Recently it had the timing chain and gears replaced due to severe wear and not long after that it started to surge at about 1500-1800 RPM it will almost stall and the it will catch itself and rev back up it will also do this at 4200 PRM i have hooked a vacum guage into the EGR system and when this surging starts the EGR is starting to open it seems like the pcm is allowing the EGR to open at the wrong time. there are no trouble codes it has had a new temp sensor,MAP sensor, and TPS instaled and still no luck.
Answer -
Darrell,
Kudos to you for looking at the EGR system!!! If I were you, I would replace the EGR solenoid, AND the Canister Purge valve solenoid (you'll want to do them as a pair, I promise). They can both cause the same condition (the surging that you describe). The EGR solenoid is easy, but have fun with the canister purge valve solenoid, it's a doozie!! Make sure that you don't have any vacuum leaks, and that your EGR valve will hold vacuum pressure (sometimes the diaphram un-attaches itself from the spring). Also, be sure that your engine is in time (mechanically), that could possibly cause your condition as well. Let me know how it turns out!!
Chris
Chris I checked the internal timing of the engine it is right on the money. Both the EGR and the canister purge solenoid's hold vacum. with a vacum guage and an ohm meter tapped into the canister purge solenoid it seems to be working fine. The EGR on the other hand is on all the time exept in the wide open throttle position. I also noticed this weekend that it will only start to surge after it has been running for around 1 1/2 - 2 minutes within the two minutes it will not open the EGR and doesn't surge. I am starting to think the PCM is not settting up a duty cycle.
DS
AnswerDarrell,
If the PCM is commanding a duty cycle for the EGR valve at idle, I'd assume that the PCM would be your problem. Since the EGR solenoid is not controlled by pulse width modulation, it is either on or off, no in-between. Without looking at this vehicle first hand, I'd have to say that you are on the right track.
Chris
