1G Engine surges, idle issues also....

[jbull70]

Hi. I'm new to the forum and looking for some advice. I recently purchased a 93 Talon TSI AWD and I have a problem. The car always starts, but seems to idle a little too low (usually around 600 rpm.) The main problem is that it surges or hesitates when you get on the gas up until around 45 mph when it hits overdrive, then the surge pretty much disappears. There has been 3 occasions where the check engine light came on and the car would barely move. If I shifted the trans manually and kept the rpm's up while feathering the throttle, it would gradually speed up. If I shifted the car into drive and tried to gas it it would fall on it's face and barely move. After a few minutes, it would clear up and go back to the normal surging/hesitation that it usually has. It also has run really well at some points, where the surging was barely noticeable. The car seems to run fine at cruise speed and also the surging mostly goes away at wide open throttle. If anyone has any guesses to point me in the right direction I would appreciate it, or if there is an article covering this particular issue, a point in the right direction would be appreciated. Thanks in advance for any help. BTW, the car has 98,000 miles on it if it matters much.

 

[dbritt]

Does it surge at idle or just while moving? As far as the hesitation, there are a lot of things it could be. This is a pretty common problem with un-tuned vehicles. The cause that made me have that problem when I first bought the car was that the car was running very lean. A little tuning with my S-AFC II fixed the problem in no time. If you don't have any mods done to your car (even the free ones...check the tuning guide on this site for what I mean), then the problem may be cured by a new fuel filter and/or good (and properly gapped) spark plugs.

Boost leaks can cause some funky problems too...if the other stuff doesn't work, I'd run a leak test.

 

[jbull70]

Thanks for the reply to my question. The car surges under acceleration. It generally idles fairly steady, it just seems to idle lower than it should. I have noticed that sometimes when I stop and start to shift into reverse, sometimes the idle raises up to around 2000 rpm then slowly comes back down. I have noticed a couple times when it was hotter outside that the surging didn't seem to be as bad, but the temperature may or may not have had any effect, it may have been just a coincidence. If there is any more information that I could supply that would help, please let me know. I'm not sure how to do the pressure check for a leak, so I will do some research to see if that is something I can get set up to do. Thanks again for any help or advice that you give.

 

[dbritt]

There are a lot of HOW-TO's at www.vfaq.com (including a leak test). Always check that site when you need to know how to do something, there's a lot of good stuff there.

I recently read a post that said someone solved a similar problem by replacing the spark plug wires because one of theirs was frayed and was grounding out on the valve cover. Other people report that changing their spark plugs to the NGK #BPR7ES and gapping them correctly solved the problem. In my case, it was a fuel issue. The guy before me had removed the honeycombs and silencer in the MAF and it had exactly similar problems as you described. When you have the intake out of the car while performing the leak test, check inside the MAF to see if either/both are removed (there's a VFAQ on this too). I did every possible fix as far as parts that I could. I replaced the ISC, the TPS, Fuel Pump, Fuel Filter, installed a 2g intake, rewired the Fuel Pump, cleaned the TB, you name it. Bottom line is: I did a lot of extra work that I didn't have to do.

Be sure to keep records of when you do any part swapping in your car. Especially stuff that needs replacement regularly (e.g. fuel filter, spark plugs, spark plug wires, etc.)

Here's what I would do if I were you:
1. Check the MAF and make sure all the honeycombs and silencer are still in there. If they're not there and you still have them, put them back in. Otherwise try to get some.
2. Perform a boost leak test (like at the VFAQ site). Make repairs as needed.
3. Check your plugs/wires to make sure everything is OK there. Replace them if you have not since you bought the car (just for peace of mind).
4. Replace the fuel filter if you have not since you bought the car (just for peace of mind).

** Here's where it starts getting pricey **

5a. Get an S-AFC II and see if richening the A/F (Air/Fuel) mixture cures the symptoms.
5b. Rewire the fuel pump.
5c. Replace the fuel pump.

Those last 3 should all richen the A/F mixture enough to make enough difference to tell if that's the problem. If your car is 100% stock (and I mean the FULL ONE-HUNDRED percent), then the plugs/wires/filter will probably fix your problem. A clogged filter can restrict your fuel enough to cause what you described. Don't do any of the 5 a-c steps until you do the previous 4, and do them in order. Let us know what happens before jumping to the 5th stage options. There is no sense in spending $100-$400 if you don't have to.

Good luck, and I hope your spark plugs just need replacing.