Well, to start out, I'm a newbie, so try not to be too hard on me. I have a 1994 Talon TSi AWD turbo, and when the car is at idle, it has a studder, or some type of cough to it. I have already taken care of the basics, plugs, wires, fuel filter, air filter, cleaned intake mani/throttle body. The timing belt, and intake manifold gasket were done in the last 4 months. Currently cannot find any vacuum leaks. The "cough continues until about 2500 rpm, and then goes away.Any help would be greatly appreciated;

thanks in advance

Bill Liscombe

When you say a coughing effect is the motor cycling up and down at idle?

When you get on the gas does the problem continue until 2500rpm or does it smooth out as soon as you get on the gas?

Did this happen right after the timing belt? was the belt tensioned properly?

Are your plugs gapped correctly?

I am trying to get a clearer picture of what the symptoms are. Any more details will help in getting to the problem. Cheers

The motor stays within proper idle range(750 rpm+-100)...the very odd time it goes on the fritz with the nitorious 1200-1500 occilation, but that's a rarity. The cough makes it drop about 50-100 rpm, and then goes back up again to proper idle, but the cough is fairly constant (on avg. about every sec. or so). I did not have the belt changed the previous owner did(don't worry, have all paper work from dealership to prove it was done at dealership!). Don't know if the belt was tensioned properly, as I am still trying to familiarize myself with the car. Don't know how to check it either...
The plugs are iridiums that do not require gapping. The problem is continuous to about 2500-3000 RPM, and becomes more constant as the RPM increases from idle.

Thanks;

Bill Liscombe

could it be my ECU caps??

I would swap in conventional plugs just to be sure, though anything should work fine at idle... It could be something else in your ignition system like coils. How does the car act at full throttle? If it's good then that's probably not it.

You should check caps but that's probably not it.

I would check that the timing belt is not off by a tooth.

Maybe injectors? Do all the spark plugs look the same?

It would be good to log it, at least monitor the o2 sensor or something. Check if there's an error code stored.

Well, just checked the plugs, and they all seem to be fine and dandy. The car runs fine at WOT, so I guess coils are out...don't know how to check timing on these cars(never owned a DOHC), maybe someone from the club can give me a hand on that sometime (I honestly have no idea how to do that???). Haven't checked injectors, but I'm sure the Hanes manual can help me out with that one...don't know how to check the comp. for stored faults either...I'm just a bloody lost sheep here!?!

Thanks for the help, I'll dig up some info, and see what I can figure out with this beast.

Thanks again;

Bill Liscombe

If your plugs all look the same, ie one cylinder's not running lean and the rest rich then it's not injectors.

There's sections in the haynes manual for all this stuff: checking timing, checking injectors, reading error codes. Find out how to read o2 voltage here: http://www.ecanfix.com/~mdhamilton/o2reading.html. Might as well, while you're playing with the voltmeter reading error codes.

I'd still check the timing belt man, make sure it's not off by a tooth. Apparently that gives a rough idle.

If you're unlucky it could even me an intermittent connection somewhere in ignition or fuel injection, that goes stupid at low rpm's with the vibration, but once it smooths out it's steady. Who knows.

could it be my turbo...the problem starts to die off once the car warms up a bit?
Just a thought.

Thanks;

Bill Liscombe

Well I hacked my maf and my car runs kinda shitty when it's cold. Not smooth at all, kinda lurching, at low or medium throttle. Also, my car pulls a lot shittier till the boost kicks in around 3k. But this could be a boost leak, I still have to check.

Anyways, my problems are due to a weird, lean mixture. Do you know if your maf is hacked or the mixture's weird for whatever reason?

The maf is not hacked, and I'm installing an a/f gauge shortly to get a rough idea of what I'm playing with. Get back to you shortly and let you know.

Thanks;

Bill Liscombe

Don't bother with the a/f gauge, use a voltmeter. I have one hooked up all the time while I'm sorting my car out. Way more accurate (if a bit slower) than the few leds on the af gauge. In general it's supposed to fluctuate high and low at idle and cruising. Somewhere in the mid to low 0.9 volts at wot, steady.

If you have a problem, you might be seeing no cycling, or abnormally low voltages at wot.

well, it gets better.

Just took my car into the dealership and got the computer checked out...there's nothing wrong, or so they say. It's not my electrical, vac leak, fuel pressure,...this sounds internal. My car only has 112k on it, and it's having internal problems? Is this normal? Have to get a leakdown test done to find out the real problem.
Keep you posted.

Thanks for the help;

Bill Liscombe

well, the car finally got taken to the shop(dealership), and logged...but nothing showed up!?!, no faults errors, or anything unusual...now I really need help with this one. The same darn problem just won't go away!!

Take the upper timing belt cover off and turn the engine with a socket on the crank. You might want to remove the spark plugs to make this easy. Get the cams lined up so that the dowels are pointing straight up on both. Now, make sure that the two little notches on each cam gear are pointing flat accross the head. You should be able to get down low and eyball right accross the lip of the head. If one of them is out a little then the timing belt is off by a tooth and can cause this. If you feel bad shaking then it's also a possibility that the balance shaft is 180degrees out.

if it is only a caughing and then a hesitation until 3000 then it could be your EGR.

I have that problem with my NT. when cold it has no lowend power and hesitates when floored. But idle is fine somehow.

the EGR hoses came off. but even when I fixed that the internals of the EGR were dirty so it apparantly is not blocking nicely.

Check that one too,

just my 0.02
Amin