3.2 surging on acceleration
 

Suggestions/opinions/ideas would be appreciated relative to an intermittent surging/bucking problem I've developed when accelerating. I've recently replaced the following (most of which was done as a preventive measure): DME relay, Bosch plugs, Magnecore wires, cap/rotor, O2 sensor, CHT sensor, fuel filter..... the problem has not gotten any worse or better with any of these changes, so apparently, I've not hit the right issue yet. As long as acceleration is slow and smooth, no problem.....it is only present when accelerating suddenly/briskly from a slower speed. No such issues at idle or at a constant engine speed. For what it's worth, highway gas milegage is good at 26 m.p.g. I've not checked fuel pressure and/or volume (it really doesn't sound electrical......more like the mix is temporarily lean or rich???). I've also considered the possibility of a faulty or maladjusted TPS or perhaps a bad or dirty fuel injector.....just not real sure what primary circuits/sensors/components, etc. come into play in the "acceleration mode" as this appears to be the only scenario the problem will occur. Thanks for your help!!:(

Have you torqued your intakes lately? If they're loose it could be a vacuum leak you're noticing.

-Joe

Hi,

I’m a long time lurker and first time poster to Pelican.

I had a really bad case of bucking. I tired all the things you mention, and then some. The thing that finally made a big reduction in the problem was running a few tanks with fuel system cleaners. I did three tanks in a row before my last oil change. One tank with Techron (the stronger version), one take with Lubro Moly Ventil Sauber plus Lubro Moly Jectron, and one tank with Redline (full strength). Redline is my current favorite.

See my posts here:
http://www.pca.org/tech/tech_qa_question.asp?id={35D1FDDC-F4DF-4A07-9720-4213EF12B422}
http://www.pca.org/tech/tech_qa_question.asp?id={0D796FA3-8ED2-4521-BDAC-E13E9434BE3B}

I’ve since run another tank and it’s made another improvement. I’m currently running a tank with Redline at the maintenance dosage. I just purchased a bottle of Fuel Power and I’ll try it at the maintenance dosage as well. I don’t expect Fuel Power to be significantly better than Redline, but hey, they speak highly of it here: http://theoildrop.server101.com/ubb/ultimatebb.php

I find that the fuel system cleaner seem to work better in city driving rather than track days or long distance travel. They seem to work better with lower revs. The longer they are in the tank the better they seem to work. I’m guessing they can soak into the deposits more with lower revs. Also, some will stay on the back of the intake valve after engine shutdown and soak in. Perhaps they also soak into the piston deposits after engine shutdown as well. And it certainly sits in the injector after engine shutdown.

I don’t know if you have the same problem I did, but it’s worth a shot.

Good Luck.

Joe...have not checked the intake manifold bolts just yet, but undoubtedly, will be doing so in the near future. I would think a vacuum leak would cause problems at idle, run up and constant application of throttle. I note some mild surging even at constant throttle, but not otherwise. With regard to the fuel injector cleaner idea, I did note a fair amount of black/gray "gunk" out of the old fuel filter, so I'm working on a tank of Techron as we speak. Just for the record, after I posted my initial inquiry on this subject, I re-checked the new Magnecore wire connections to insure everything was solid.....nothing was grossly out of order here, but perhaps not by coincidence, I haven't experienced the surging/bucking problem on acceleration since then (???). I have read postings on this website about Magnecore wires...generally well thought of, but perhaps not unlike even brand new OEM stuff, connections can somehow become "unconnected", given enough vibration and other unsavory elements. I'm hoping that the "jiggering" of the plug wires will fix the bigger problem and Techron will minimize the otherwise mild surging issues. Thanks for your input!!

The only problem I see with Magnecores are the plug connectors and the amount of difficulty experienced getting them to snap on securely onto the spark plug. That is not to say that Beru connectors cannot be difficult too.

You might try deliberately pulling a plug connector off slightly to see if your surging/bucking returns as proof to yourself that it was the cause of your problem.

-Joe

As Paul Harvey would say, now here is "the rest of the story". After several days of both backtracking what I have done to my P in the last two months, in addition to exploring many new/different possibilities relating to my initial problem of "surging on acceleration", the bottom line is BAD BRAND NEW BOSCH SPARKPLUGS. I haven't bothered to isolate how many were bad, but I am suspecting at least two. All were firing at idle, but under load, they were breaking down terribly. Nothing against Bosch, but I've decided to give NGK's a try...so far, very nice at all engine speeds. Moral of the story...just cause it's brand new doesn't necessarily make it perfect (especially electrical parts)!!

What was the number on the Bosch plugs you put in the car?

Also, there is a country of origin on the plugs. I believe some can say India and some can say Germany.

Both old and new are WR7DC....as recommended for this year/model.