What is going on here? I've posted this same question in the pst and I sm still having this problem. Also starting in March, sometimes the car won't start! It'll turn over and over, but just won't fire! Do you think my MSD box is bad? I replaced my ignition module in March. The EGR was replaced in January. I've disconnected the EGR in hopes that would stop it, but it keeps doing it. What causes this? Is it a hiccup in fuel? spark?...what? I have no idea!! Please help! Here's the signature off all the crap I have, it's a long list...Sorry!

 

I suppose it's a possiblity that the MSD box is malfunctioning. Maybe bypass it and see what happens. Also, if it's stumbling on acceleration, you might want to check the performace of the TPS. WIth the engine off and ignition switch on, simply tap into the blue (+) and black (-) wires with a volt meter on the TPS and watch the voltage as you slowly open the throttle it should smoothly increase from about .6V to over 4V. If it does not increase smoothly, replace the TPS.

Also, double check your ignition timing. It should be set at 6° BTDC.

 

Even if you bypass the MSD ignition and go back to the stock ignition - it may still stumble if the stock ignition module is fried.

Correct me if I am wrong - doesnt the MSD have to hook up to the stock ignition module? If it does - it it probably only used to get the position of the stator.

 

If the module is fried, it won't start at all, let alone stumble.

 

Yes, if it is totally fried. Mine would not get into the 3000 RPM range and it got progressively worse. I did not change out the ignition module until it would not get up over 2000 RPM. (on a hot day only).

Change the module - problem was gone.

 

I am not trying to start any trouble, but I have seen many ignition modules that are bad and/or going bad cause intermitent and RPM sensitive problems.

I would try what the others suggest. Do the testing first to eliminate possiblities. If you have a good service manual it should have some test procedures for the sensors and electronics. If you have access to a scanner that would help to.

 

The TPS checks out fine. I replaced the hose back onto the EGR. I had it just capped off, we'll see I guess. The module is an Accel module that I bought new and installed in March. Any more suggestions?

 

Sorrry, I double posted and it won't let me delete it.

 

Pretty tough call there. I'm no expert but I think if you've given the car a proper tune-up and you are getting proper fuel and spark at idle, there is something up with the MSD.

I have a 6al aswell. Last year I had a rolling run with a VR6 Golf on open highway and hit about 135 mph when the car started hesistating violently at slightly under 5000 rpms. It was like the spark was totally f'd up! I have never experienced that before. I had to shut down. It was almost like a rev limiter kicked it and the car went "blahhhhh.....". Could it be?? The car has run fine otherwise since. I haven't had a chance to test it out at higher speeds again.....but I am wondering whether your ( and my ) problems are MSD related??

 

You may have hit a limiter, I guess. You have the 6AL box which has a limiter, what is it plugged in at? Mine is just a 6A box, no limiter. I wish I had one with a limiter. Yesterday, after I tested the TPS, the car wouldn't start, but later on in the night, it started. What the heck?? It's making me sick! I can't diagnose this, if it's an on again off again problem, you know? That really sucks!

 

bypass the MSD box, and see what happens. 3000 RPM is coincidently the "crossover" RPM at which the box goes from multiple spark, to just one....... HHhhhmmmm, suspicous, eh??

 

I forgot to mention that at cruising speed (50 MPH) and in fifth gear, the RPMs are at about 1500 to 1600 or so. It does the stumblimg there too. It did this to me yesterday morning, but not at all in the afternoon.

 

That begins to sound suspicously like the ignition module. mine had a problem after driving for about 2 hours, it would just drop several cylinders..... makes freeway driving truly interesting, and might be a good weight loss program as well, what with all the shaking and such......

Change the module, they are relatively cheap, and you can get them at any autoparts store. (call around, see if you can find a "performance" module, I think accell makes 'em.....)

Good Luck

 

Yup - what he said

 

i installed the 6al a couple of days ago and and just like u said, a brick wall a 5k. now the car did this before the msd and i figured it was the computer or some built in limiter from the factory, then i was told that the engine should rev past 5K, bad ignition parts or something, but this would seem to feel like i plugged in a 5k chip and thats not the case., does anyone else besides us 2 have the same problem?

 

After replacing the module with an Accel piece in March, I still have the problem. Do I need to get another damn module? This makes the third or fourth module I've put in! I talked to someone the other day, and they said to check the MAP sensor. How do you do that?

 

If you are not getting any codes than you can check it with a scanner or a volt meter. The codes that monitor a MAP sensor are 33 and 34. If you hook a VOM to the leads for the MAP with the key on, engine off you should read about 4.5 volts. This will vary a bit due to weather and altitude. With the engine idling at about 18-20 inchs of vacuum you should read about 1.5 volts. Again that will vary for your conditions. If you have a vacuum guage hook it up also to see what your vacuum is. If it is higher or lower you voltage will vary. Higher vacuum less voltage, and the reverse for lower vacuum. I don't know if this will help, but there it is.

If you have access to a scanner ignore the above and use it. The scanner may read kPa so you will need to know that 100kPa is atmospheric pressure, engine off; key on. And at idle you should read about 35 kPa.

Good luck...