I have a 95 Dodge Caravan with the 2.5L TBI engine. This van is really on its last leg, but I’d like to keep it running if possible while I look for a replacement vehicle with the features I want. It currently has about 129,000 miles on it.
The engine has always had a noticeable misfire until warmed up, though it usually runs adequately once warmed up. I have replaced numerous parts over the years that I owned this van, but it did not help.
Now, the problem is that I drove it to work last week, and when I attempted to start it to go home, it just misfired a lot and stalled out. If I kept my foot on the accelerator, and kept the RPMs over 1000 then it would stay running but misfiring a lot, and if I kept the RPMs over 1500 then it seemed to run ok, but the moment I took my foot off the gas, the RPMs would drop to about 250, it would misfire a lot, and stall out.
I tried to start it several times over the week and a half since then, and could not get it to stay running. Yesterday, while I was waiting for my wife to come pick me up at work, I decided to start the van, and keep my foot on the gas to maintain the RPMs high enough for the engine to run properly. Once the temperature gauge was above 25%, I took my foot off the gas, and amazingly it kept running. I drove it around the parking lot a few times, then I drove it home, with my wife following in our other car.
Since it ran ok once warmed up, I am not really sure what I’m looking at. I had suspected a crack in the engine block between a cylinder and water jacket, because the coolant doesn’t pressurize properly, and it randomly overheats but then magically drops down to normal.
Is the temp sender unit that sends its signal to the computer, and its wiring, working?
I assume so. As long as I have owned the van, it has had an issue that when driving, it will randomly overheat, the temperature gauge will creep up to the maximum, the alarm will sound, and then a minute or so later it drops down to 40%. I initially thought the temperature sensors were defective, and replaced both several years ago.
Eventually, it really did overheat and cracked the head, so I replaced that, along with numerous other parts. It has always had an issue with misfiring/jumpy RPMs at cold startup, but at least it would stay running in the past.
It may be running too lean when cold. Vacuum leak, clogged injectors, failure of the function that injects more gasoline based on coolant temperature, etc. Of those I’d guess a vacuum leak is the most likely.
Start the engine cold, if it is misfiring stop the engine, remove the spark plugs a check which one has coolant on it.
If you are loosing coolant then a coolant leak in at least one of the cylinders seems logical. Checking the spark plug conditions hopefully will show which cylinder has trouble. As was already stated, a vacuum leak seems probable also. Squeezing off vacuum lines one at a time, while the trouble is occurring may turn up something.
Today, I pulled all the spark plugs, and inspected them. They were NGK GR4 “V-Power” plugs, and they all looked worn out, even though they only had less than 10,000 miles on them. The insulator had turned brown, and there were carbon deposits around the rim. None looked “steam cleaned” or anything like that.
I replaced them all with Autolite AP65, which was the cheapest spark plugs the AutoZone near my house had in stock that fit this engine. I started the van from cold, it misfired for several seconds, and I could smell gasoline, but it did not stall out. I took it for a drive of a few miles, and it ran adequately, though the temperature gauge “pegged out” and then dropped back to 40% twice on this trip. I am hoping to replace this vehicle pretty soon, anyways.
Now, I am dealing with the hassle of trying to buy a used car and not get ripped off. Already, I have dealt with two attempted scams: one used car that I considered had an electronic lien on the title, so even though the seller had a notarized lien-free title, there would have been no way to title and register this car. Another person wanted me to meet her at a shopping center to see the car, because it was allegedly at her sister’s house, who didn’t feel comfortable having strangers come by. I explained that I needed to start the engine from cold to see how it runs at startup, but that was not persuasive. Whatever, I guess I’ll just keep looking…
Did you remove the spark plugs within a few minutes of the misfire episode?
Delayed thermostat opening can be caused by combustion gasses trapped behind the thermostat or a plugged heater core (a condition somewhat unique to the slant 4).
I’m not sure what kind of air sensor this engine has but perhaps cleaning it may help improve the running condition.