Truck behaving strangely; ideas?

[BrokenPaw]

On the way home from Home Depot this weekend, my truck (98 Dakota 4x4, V8, 5-speed) started behaving pretty strangely. 

The first symptom was that it stalled at a red light.  It started right back up, so I didn't think too much about it.  Then, it did it again.  I found that the only way to keep it from stalling while stopped was to leave it out of gear, and run the RPMs up to about 2000-2500 (it normally idles at ~1200).  If I ever let it drop below 1500 or so, it would stall.

Then, it began having severe issues under load; the engine would be happy as a clam at 2000 RPM under no load, but any kind of load at all (even running it up to 3000 while stopped, putting in in 1st, and then letting the clutch out very slowly) would make it buck and knock and sound like it was going to die.  After the first time it did that, the Check Engine light came on.

The problem got worse as I limped home.

I've been given to understand that the Check Engine light is almost always a sign of a failure somewhere in the Emissions Control system (the manual for the truck even obliquely alludes to that).

So.  Anyone have any ideas?  Bad oxygen sensor?  Angry spirits in the cylinder head?

I'm debating buying a code scanner to see what the OBDII has to say.  I know Autozone will pull codes for me for free, but I don't know that I want to make the 4-mile trip there to have them do it.

-BP

[mtnbkr]

Is there any way to pull the codes without a scanner?  Many vehicles have some sort of "shadetree engineer" method such as using a paper clip in the sensor port while reading the CEL flashes, etc.

Chris

[cassandra and sara's daddy]

i know a guy in fredericksburg will loan you his code reader....

[BrokenPaw]

Is there any way to pull the codes without a scanner?  Many vehicles have some sort of "shadetree engineer" method such as using a paper clip in the sensor port while reading the CEL flashes, etc.

I was trying to find that info on the web somwhere, because I know that at least some cars have a magic incantation that you can use to do that.  I had no joy finding out how to do it for the Dakota.  It may only be that my google-fu is weak.

i know a guy in fredericksburg will loan you his code reader....

C&S, I may take you up on that if I can't find a loaner one closer by.  Thanks.

-BP

[mtnbkr]

Third post in this forum: http://www.dodgedakotas.com/boards/v8/10221.html

Better info in this thread: http://www.dodgedakotas.com/boards/v8/251.html

Chris

[BrokenPaw]

Third post in this forum: http://www.dodgedakotas.com/boards/v8/10221.html
Better info in this thread: http://www.dodgedakotas.com/boards/v8/251.html

   See above, re:  my google-fu is weak.

Thanks.

Rather, my Paying Attention Skills are lacking; I'd seen that first thread you referenced, and I read the part about turning the ignition on and off, but I failed to note the part about the code appearing in the odometer; I was looking for CEL flashes.

Have to try again tonight when I get home and see if I'm just that much of a dumbarse.

-BP

[mtnbkr]

I probably jinxed you with my comment about CEL flashes.  On all the cars I've pulled codes without a reader, it was always the CEL that flashed.

Chris

[Jim147]

If the SEL came on while it was bucking it may just be a p0300-p0308 code. Telling you it was misfiring.
I would take a close look at the distributor. I had to replace two of those on a family members Dakota.
IIRC, they seemed to wear out a piece under the rotor.


jim

[BrokenPaw]

If the SEL came on while it was bucking it may just be a p0300-p0308 code. Telling you it was misfiring.
I would take a close look at the distributor. I had to replace two of those on a family members Dakota.
IIRC, they seemed to wear out a piece under the rotor.

Ok, I'll look for those codes, thanks.

Would a worn distributor as you describe explain the stalling and odd behavior under load, but the OK running when not under load?

-BP

[Boomhauer]

We ended up buying one of those OBD II scanners since we replaced most of our family fleet with post '96 vehicles, and it has been invaluable.

[AZRedhawk44]

Would a worn distributor as you describe explain the stalling and odd behavior under load, but the OK running when not under load?

I'm probably the worst shadetree mechanic out of all the members here, but that makes sense to me.

If you're not delivering spark at the peak compression point of the cylinder, then you're losing power.  High RPM's would be attainable under no load, but add some resistance to that weakened combustion stroke and you can stall or buck.

Had an 80's pontiac 4-banger that exhibited that same problem.  Solution was changing the spark wires in that case... if the Dakota is known to wear out its distributor, then I'd look there if it were my truck, and work my way forward to the plugs.

[red headed stranger]

A lot of auto parts stores will read your codes for free or a very small fee. 

[French G.]

The distributor will be an electronic of some sort, they usual failure mode is to refuse to work at all when hot. I do not know Dakotas, but I suspect fuel delivery issues either from a pump, a bad load of gas you got on your trip, or most likely a fuel filter. I'm not much on changing fuel filters as routine, bad lazy mechanic. When the on on my ford T-bird went the symptoms were so bad I thought the transmission was dying.

[Jim147]

I went out to see if I still had one of those distributors around here but couldn't find one. I think the plate holding the pickup came loose and the timing was bouncing all over the place.
The wear in the distributor caused some very funny misfires and stalling under load.
Something else that popped into my mind would be a very large vacuum leak. A small vacuum leak would cause a high idle but a large one would stall out at idle and lean out under a load.
My next thought would be was it raining? Could have gotten some water in the cap or coil.

Since it would run at 2000 rpm but not idle I'm not think it would be a fuel pump or air flow related problem.

Did you have a chance to pull the codes? 

jim

[Nick1911]

Maybe you have a bad cylinder:


Nah, I'm just teasing you.  Sounds like an electrical issue.  If the codes don't reveal anything interesting, secondary ignition is usually the culprit.

[crt360]

I was going to say check the fuel filter, then I saw how insanely difficult that is on a 90-something Dakota.  :o  Check other stuff.

[RocketMan]

BrokenPaw, I had a similar issue on my '97 Dakota, except mine is the 6 cylinder, 5 speed.  It wasn't quite as severe as yours, but very similar.  Pulling the code out via the odometer showed an O2 sensor failure.  The '97 has two, one fore and one aft on the exhaust assembly.  I had a local parts store pull the code for me and that pinned it down to the front unit.
Swapped it out and everything was back to normal.

[Strings]

Nick, what the hell is up with that?

Only time I've had major engine trouble (in my 92 Eclipse), this was the problem:

[KD5NRH]

Something else that popped into my mind would be a very large vacuum leak. A small vacuum leak would cause a high idle but a large one would stall out at idle and lean out under a load.

+1 there: I had an '80s Nissan do exactly what you're describing, and it turned out to be a vacuum line popped loose.  Trimmed the end, hooked it back up and all was well again.

[drewtam]

I'm going to put my money on a fuel delivery problem with this one. Either clogged fuel filter, trashy fuel tank, low fuel level in tank, bad fuel pump, or bad fuel pressure regulator at the rail.

The way the problem gets worse as he drove makes me think it is not electrical. Electrical should be on/off, it works or it don't.

[Nick1911]

Nick, what the hell is up with that?

Only time I've had major engine trouble (in my 92 Eclipse), this was the problem:

Ha!  Mine was a 92 talon.  The tensioner failed and it jumped time.

Small world.

[Jim147]

Electrical should be on/off, it works or it don't.

I wish it always worked like this.
All those years of flat rate warranty service would have been made much easier not chasing cold soldier joints and burnt relays and switches that would work sometimes and fail others.
It was a good day when you had power to a component and no output.

jim

[BrokenPaw]

Ok, so I tried the method that mtnbkr linked to (turn ignition key on and off three times, leaving it on the final time), and had no luck.  I tried all different variations of "on", also.  But the odometer showed nothing but miles.  So I'm a bit puzzled as to why that would be.

Now I'm back to either buying a code scanner, trying to find a local one to borrow, or trying to limp the truck back to autozone for them to pull the codes.

I'm really hoping that it's not something that requires me to pull the distributor cap; it's all hidden back in a nice inaccessible place.

If it turns out that it's an O2 sensor, how big of a hassle is that to replace?

-BP

[Jim147]

Just a thought did you try restarting the truck when you couldn't get a code out of it?
A soft code may not of set.

The front O2 sensor is not to bad. Buy the correct socket for it and hit it with some Liquid Wrench or something first.

A code scanner and a half dozen VOhm meters are things I find it hard to live without.

Run a quick check on all the hoses and wires you can find to make sure nothing has broken or come loose.

jim

[BrokenPaw]

Jim,

I did try restarting it, and it started up fine, and I even drove it (just a few yards -- more than enough to have seen the issue last time), and it didn't appear to have any problems.

The CEL is still on, though.

The fact that the problem seems to have gone away for the moment suggests to me that it may be heat-related.  BTW, in answer to your question earlier in the thread, no, it wasn't raining on the day that all of this happened, and it hadn't rained in a few days before that, so I don't believe it's water-related.