99' Laredo sputtering issue

[bowlerguy92]

Hey all, I have been researching and becoming proficient in cars the past year or so and now actually seem to have my own issues with my car this time........

Basically I bought this car used in great condition with about 160,000 miles on it, always well maintained yada yada yada, I'm sitting at a stop light waiting it to turn green so I can make my left turn and the car begins to shake like it wants to stall out, the engine picks up again and I lift off the brake expecting it to pull me forward and it doesn't. It shudders again and comes back and the light turns green, I hit the gas and we start moving slowly. Down the road I figure maybe we dropped a cylinder because it didn't feel like there was any power behind the pedal. So I decide to give it some real gas and only get it up to about 40? I arrive at the movie theatre and I restart the car after the movie and all is well again.

Take 2! I am merging into traffic on a main road and I hit the gas to get into the traffic flow and the car kind of sputters at me and lurches and then finally picks up again. I typically let the car warm up for 2 or 3 minutes before I actually go somewhere but this doesn't seem like normal behavior. I originally thought it could be water in my fuel and used HEET and that seemed to make no difference.

I have talked to my Auto teacher and he suggests it could be a catalytic converter issue or simply spark plugs and told me to wait until it was dark pop the hood and check to see if I could visually see sparks from the plugs, I just got back in from doing that and have had no such luck. I'm going to schedule an appointment in my school garage and have it looked at by him and the students.

What is your best guess as to what's going on here? I'm pretty much out of ideas!

Thanks for reading this long ass post.

[fredjacksonsan]

4.0 engine? I'd guess Crankshaft Position Sensor.

[bowlerguy92]

Originally Posted by fredjacksonsan

4.0 engine? I'd guess Crankshaft Position Sensor.

Ya the 4.0L Inline 6. If that were the case though then wouldn't my car ALWAYS be doing that? If the crankshaft gets out of position then it would always be out of position until it was corrected wouldn't it?

[fredjacksonsan]

Nah, it's not the crankshaft, it's the sensor. Do a search and you'll see that almost without exception it's an intermittent issue.

[bowlerguy92]

Originally Posted by fredjacksonsan

Nah, it's not the crankshaft, it's the sensor. Do a search and you'll see that almost without exception it's an intermittent issue.

Hmmm, ya that was stupid guess I can't read anymore. But ya I know what your talking about I have seen many threads with issues relating to the sensor. So basically what's happening when I'm hitting the gas and its sputtering? If you could elaborate for my personal learning it would be great, I always need to know why!

[fredjacksonsan]

The CPS picks up the position of the crankshaft at each revolution. When it's starting to fail, it is inconsistent in sending the information to the computer, so the computer can't spark at the correct time.

IF it's the CPS then it should return to normal as soon as you have the new part. There are other things it could be (throttle position sensor comes to mind) but the CPS is usual for that many miles.

Are you getting any codes?

[bowlerguy92]

Originally Posted by fredjacksonsan

The CPS picks up the position of the crankshaft at each revolution. When it's starting to fail, it is inconsistent in sending the information to the computer, so the computer can't spark at the correct time.

IF it's the CPS then it should return to normal as soon as you have the new part. There are other things it could be (throttle position sensor comes to mind) but the CPS is usual for that many miles.

Are you getting any codes?

How would I go about getting codes other than using a computer? My check engine light isn't even on I don't think though it actually might be, I will have to check.

[fredjacksonsan]

Originally Posted by bowlerguy92

How would I go about getting codes other than using a computer? My check engine light isn't even on I don't think though it actually might be, I will have to check.

Sorry, I just assumed you knew....

OK, go from the vehicle off.

Turn the ignition switch on (but not to start) and back again to off, 3 times in 5 seconds, leaving it on.

The odometer should flash up some codes. "55" is the last one which signals finish.

Post back what you find and we can go from there.

[bowlerguy92]

Originally Posted by fredjacksonsan

Sorry, I just assumed you knew....

OK, go from the vehicle off.

Turn the ignition switch on (but not to start) and back again to off, 3 times in 5 seconds, leaving it on.

The odometer should flash up some codes. "55" is the last one which signals finish.

Post back what you find and we can go from there.

I just got done reading a post on a message board explaining to someone that they got rid of that feature starting with the 99' models and that now it requires a computer to read the codes.

[fredjacksonsan]

Hmm my mistake maybe, but it's worth a try. If it doesn't work, then you can take it to Autozone or Advance Auto (or similar) they will usually read it for free.

[bowlerguy92]

Alright I will try taking it to V.I.P Auto tomorrow and seeing what I can do about getting the codes read, I will also talk to my auto teacher about what you suggested and report back with any codes that are found! Thanks for your help and I will let you know what I find tomorrow.

[fredjacksonsan]

OK; good luck. BTW my '04 will show codes; that's why I assumed yours would also.

[bowlerguy92]

I had the guy at VIP take the handheld one and hook it up inside my car and it returned no codes. I'm really not sure what this means then, maybe I'm just over reacting and the car just wasn't warmed up yet?

[fredjacksonsan]

what codes did you get, if any, from turning the key?

[bowlerguy92]

I didn't even bother, I don't see that coming up with codes that a code reader wouldn't find.........I guess I can try it but I don't think it will even work.