1995 Dodge Grand Caravan SE
3.3L, fwd
~180,000 miles

Over the past several months I have had drastically reduced fuel economy.

A couple of times over the winter I turned the key and the van did not start (did turn over, no ignition) until I turned the key off and back on.

As the weather is warming up, my symptoms are getting worse.

It started idling a bit rough.

I changed the evaporative canister purge solenoid (old was original, making lots of noise).

Symptoms continued. Changed my PCV valve (also original). Symptoms continued.

Rough idling increased with occasional jerking while driving.

Changed spark plugs (had done so a few years back but couldn't get to one of the six. This time got them all. Also ran fuel system cleaner through. No improvement (and possibly worse).

Changed the fuel filter. Again, no improvement.

Cleaned the throttle body. Again, no improvement.

With much warmer weather (today near 70) engine jerk was horrible. Leaving a parking garage stuck it slow traffic, engine was super rough at very low RPMs and if I very lightly touched the gas, it would lurch, then drag, then lurch, then drag... additionally, when driving at normal speeds it might lurch when accelerating through the low 40s and mid 50s. Have also had more instances of not starting on the first try.

There are no "key codes". The check engine light never comes on, but when turning the van off the engine might shudder and cause the check gauges light to come on for a second.

I running out of options. What else could it possibly be? I replaced the fuel pump a little less than 4 years ago. I am hoping it is not that again.

 

Although this is a very old van, I'd remove battery -ve connexion for a few minutes, reconnect and see. Costs nothing in time or money, and even at this age, something will be microprocessor-controlled.
An exhaust gas analysis should show if the system is running very lean/improperly, one would suspect the lamda sensor in the exhaust system. Some mechanics with good noses can smell if an exhaust is the result of an improper mixture ratio.
If this old van has fuel injectors rather than carburetion, remove them and clean or get them cleaned so there are no dribbles and give a good atomization. Be sure the same injectors go back in the same holes. (I would go for this injector-cleaning first, it's a very common one if a petrol motor has been standing a long time).
Of course, you'll be cautious about spending on repairs with a van this age, but if it's a no-hoper, at least you've tried.

Leedsman.

 

I would suspect an ignition system problem first - good that you have done the basic change plugs and fuel filter...you do not mention changing air filter, but presumably that would already be done, right?

With no fault codes, and without a basic gas analyser I would buy a set of spark plug leads and change these out...particularly as you noted that the problem worsened after changing plugs. They are not expensive and it's an easy job that eliminates a possible problem - just make certain sure not to muddle up the plug leads when swapping them over.

Note that plug leads, and distributor caps/rotors, and coils do suffer from the heat so the fact that the problem is worsening with warmer conditions points that way too. Embarassingly, I cannot recall if we have a distributor or coil pack on these vehicles...if a distributor, then a replacement cap/rotor is next, or at the least look for any signs of arcing under the cap - if not a distributor, then see if you can borrow a coil or coil pack.

Another likely culprit is a vacuum leak. With the engine running, can you hear any hissing under the hood? Feel around all those vacuum hoses to make sure none are split. At idle, you could spray some brake-clean or carb cleaner around the throttle body, intake manifold and vac hoses to see if the idle surges up - indicating a vacuum leak. Word of warning - you need a fire extinguisher handy if you spray these products onto a running engine - just in case.

Whilst you could have a solid state sensor problem (MAP/MAF/CTS/CPS) it is more likely to be the basic stuff. A good mechanic with a scope and gas analyser will be able to diagnose something like that pretty quickly, especially if not an intermittent fault. Good luck with it.

 

For some reason the forum didn't let me know about your replies.

Disconnecting the battery didn't help.

I have a parts van available that I could take the coil pack out of if need be. I'll actually probably give that a shot when I get home tonight.
Yes, the air filter was changed also. The spark plug wires were replaced when i last did the plugs, so they are only a few years old and all appeared to be in good condition.

I am bringing it to my mechanic on Thursday to see if he can sort it out. He said he already has an idea of what it could be. It's too haphazard for me to keep driving around like that and my work schedule has not made it easy to find time to tinker.

 

*fingers crossed*

I drove home from work. There was some sputtering going on. It particularly didn't care for backing up at the pizza place or into my driveway. About 30 minutes of driving.

Got home, took about 10 minutes to pull the coil pack from my old parts van and stick it in this one. Not long enough for it to cool significantly. Took it for a test idle, 5 minute drive, and reverse, and so far signs are looking good. Smooth as a robotic baby's bottom. If it keeps up tomorrow then I can't thank you enough. Will post final(?) result then.

Here's hoping!

 

Naturally it was randomly 35 degrees today.

Aside from that, I think the ignition coil was the problem. 100 percent better driveability. Even got back power that was lost during certain points throughout the acceleration range. Feels like an engine again!

 

Hey Quattj, great that it's fixed. I do envy you having access to a parts van - that's a really handy accessory...my better half would kill me though.

I don't know if you was the other post on here suggesting testing a coil pack with a spare plug to each lead in turn to confirm good spark from all 6 coil terminals. In the absence of a spare coil, that sounded like a pretty smart test for future reference.

Happy Motoring.

 

Pleased to report my fuel economy has jumped from an appalling 19.x MPG back up to 23.5 MPG on my last (first total since fixing) full tank of gas.

It's been running well since the fix, but I did have a couple of sputters yesterday. I ordered a brand new coil and hopefully that will sort out any remaining issue, as the replacement coil I used was from my old van which had its own special problems.

I have had a few instances of it not starting on the first key turn since then (also in the past few days) so I may end up swapping the starter as well (old van has about a year old starter)