Surging Idle, Hesitation on Acceleration
Hi, I've been looking through your forum for solutions the last two weeks and have tried to cover most of what I've been able to find using the search.
First the car: 1995 Camry 2.2L Auto @ 200k
Recently the harmonic balancer's "dampening" material deteriorated. At the time I was on a 900mi trip and all I could do was tighten the accessory belt excessively tight to keep the balancer from wobbling around and possibly damaging the crank.
I returned from the trip but I could not change the balancer right away due to time constraints so I drove it for a week like this. Then the car developed a new issue where it would "buck" and hesitate under acceleration. I parked the car and waited until the weekend to look at it.
I changed the harmonic balancer, easy job that only took about an hour. I replaced the belts while I was there. Cranked the car and it runs fine.
Now, the issue that remains was the surging idle. This is noticeable until you let the car run for about 1-2mins once it starts to warm up a little. It is less noticeable in park, but with a good ear you can still hear it surging. In drive or reverse it is very apparent as the RPMs will dip a good 200-400 rpm and then return back to idle. It will constantly do this once @ operating temperature and in reverse or drive (worse in reverse). I have driven the car like this and at higher RPM (3,000+) under load the car does not do this nearly as bad. I can use the shifter to hold gear and when engine braking it is not apparent either.
Well I decided to pull the spark plugs and see what they looked like. They were white so I knew it was running lean. So I thought maybe I had a fueling issue. Since the fuel filter was original I decided to replace it. Sure enough there was a bunch of brown gas and some debris that came out, the outlet side was clean though, so the filter was still doing it's job. However this did not fix my issue.
I tried to think of what else might be causing the car to pull timing, I assumed it was pinging, although I can't hear it pinging to save my life. I played with the TPS and it was within spec, I event purchased a new one, but it did not solve my problem. The reason I did this is when I pulled the TPS sensor plug it idled perfect, but later I realized this was the car going into "limp" mode and wasn't relying on the sensors for data. This helped me determine that it must be some sort of external engine issue (sensor, egr, etc).
I also noticed that pulling the vacuum reference sensor also causes the car to go into limp mode. I tried spraying carb cleaner on EVERYTHING and nothing made a difference so I dismissed vacuum leaks (possible I missed something?). I went under the car to spray too just because there were so many lines that could be culprits that I couldn't get to. Next easy thing was to check the injectors wiring and everything there seemed to be in order. I suspected maybe an issue with the FPR, but I wasn't sure how to test it.
I did some searching here and around the web and found that the vacuum ports in the throttle body are very small and can commonly become clogged with carbon. I pulled the tb off and cleaned it up real good (also cleaned out the IAC port) with throttle body cleaner, a screw driver (to scrape the carbon off) and the air compressor to blow all the ports out. I also read the EGR could be at fault and looking inside the intake a saw a ton of carbon build up so I pulled the EGR, verified the valve was working and cleaned it out really well. I noticed I could blow through the EGR tube (using my breath as "exhaust") and a tiny bit of air could get past the valve (a very VERY little amount). I wasn't sure that this was normal, but I figured I'd put it back on and see what happens.
Well I reassembled and still no luck. I did leave off the intake tube and noticed a horribly loud buzzing from the IAC. I tried a trick I read either on here or elsewhere online where I out my hand over the TB to cover the majority of the intake and this will cause any vacuum leaks to become very loud and very apparent. Well I didn't hear anything and about caused the motor to die due to air starvation.
I've checked the distributor cap and rotor button, everything there was pretty new since I did a tuneup not too long ago. The wires aren't arcing (tested in a dark garage) and the electrodes on the plugs are still good other than discoloration from the lean condition.
My next culprit is the ignition coil. I've been told it is under the distributor cap. Is there any way I can test it or should I just take it to a parts store?
Does anyone have other ideas or similar experiences? I am not sure where the MAF is on this car. I haven't found one and I've found no signs of a MAP either (I am used to GM cars and I don't see the little square guy I call a map . There is a vacuum sensor of sorts on the firewall right behind the throttle body that I thought might be the MAP. Is that what it is? If so do they often go out around this mileage and age?
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