Bad backfiring, won't stay running

[Reducto]

I pulled off the freeway and while in a parking lot it hesitated a bit when I hit the gas then started running ok again. Hoping it was a glitch I got back on the freeway. It did it again a few times but then happily cruised at 70 for another 30 miles. Then it suddenly started backfiring and losing power. I pulled over and it has not run for more than a few seconds and a time since. It will start up but die slowly when idling or die right away if I hit the gas.

Hoping it was my TPS which I knew was on the way out I put in the new one I already had, no change.

I had it towed to a mechanic and all they can tell me so far is they thought the timing had jumped but they checked that and it seems to be fine. When they do get it to start there's gray smoke coming out the tailpipe for the few seconds it runs. They fussed with it for hours but all they can tell me is they're sure they can figure it out. I'm not quite as confident.

No engine light, I'll call in the morning to see if it's giving any new codes. No fluid loss or obvious fluid co-mingling and normal engine temp.

[timsrv]

Just a guess, but sounds like a failed ignition coil (inside the distributor housing). Might also be an igniter. Very 1st thing to do is check for codes. If there is an ignition related code, then coil is most likely culprit. Coils are also inexpensive and easy to find. Good luck. Tim

PS: Anything is possible, but it's highly unlikely it "jumped timing".

[Reducto]

The shop called to tell me the van was ready. They found a melted breaker in the alternator wiring where the metal had come into contact with the frame and replaced it with a fuse. Then he told me there was still a little hesitation, but surely I'd noticed that before.

It didn't even make it out of the parking lot before behaving as before. I wasn't going to let those guys touch my van again so I limped to my hotel and will try to work on it myself. The problem was somewhat intermittent on the 1.5 mile trip. It would run while for a bit then idle just fine at a light but take a lot of coaxing to get moving again.

The only engine code is 51, which I had been getting for months. They put the old TPS back in so it could be that. I may just replace the coil and TPS (again) and see if that does anything, not sure where else to go here.

[timsrv]

That sucks. Hopefully it's the coil. Usually there's a code associated with coil failure, but not always. I learned the hard way to have lots of spare parts laying around. Sometimes it's just easier to swap a part as a form of troubleshooting. Has anybody checked the oil? Make sure it's up to the full mark on the dipstick. Tim

[Reducto]

I had topped off the oil a few hundred miles ago and it's still at full.

Can't get the coil off, the bottom left screw from hell is totally stripped. Ugh.

[Reducto]

Pro tip for anyone else who can't get at that screw holding the coil in place, take a hammer to the tab on the back where the distributor cap bolts on. This makes it much easier to get at the little screw below it with a dremel tool.

Old (original!) coil is destroyed and has been replaced, no change in how it's running.

Problem seems to be intermittent. Last night it was running semi-ok on the freeway and I stopped at a rest area for a long nap. When I got up it started then died as soon as I started pulling forward. The next morning it started up right away and ran well for 100 miles then started acting up again. I stopped for gas and have not gotten it started again. Doesn't seem to be heat related, I've been stopped for a few hours now with no change. Maybe it will be fine tomorrow, maybe it won't. Luckily I have a comfy bed, mobile internet, and 11 days to get the last 850 miles home.

Changed TPS, plugs, coil, melted fusible link. No change.

The second mechanic I took it to said it was bad gas. He flushed the injectors and told me to put in some heat my next couple of fillups to get rid of the last bits of water and gunk. It actually did get me 500+ miles but now I'm back where I started.

[timsrv]

The second mechanic I took it to said it was bad gas. He flushed the injectors and told me to put in some heat my next couple of fillups to get rid of the last bits of water and gunk. It actually did get me 500+ miles but now I'm back where I started.

A fuel system issue does sound likely. There's really no codes that will display for a failing fuel pump or contaminated gas. You might get a lean or rich running code, but I wouldn't expect one. If there is water in the gas, heat (basically rubbing alcohol) will act as a mixing agent allowing the water to absorb into the gasoline. This way it will run just a little bad while it's getting rid of the water (instead of trying to run on 100% water). You might try jumping your "fuel pump check connector" to verify the pump is running. If it is water in the gas, running the pump for a few minutes will help move it past the injectors and possibly get some fresh fuel up in there. Definitely put some heat in there. After such a PITA, I'm sorry to hear it wasn't the coil. Tim

[Reducto]

Forgot to add I did run two tank fulls of heat through the system already.

[Reducto]

I do hear the pump running when I short the check connector. I tried running it for a minute then starting, no difference.

[thetoaster]

I do hear the pump running when I short the check connector. I tried running it for a minute then starting, no difference.

Have you looked into the exhaust system at all? A clogged cat or muffler could produce those symptoms. A few years ago my van was driving just fine. I started down a long grade and it actually started to loose power. By the time I got to the bottom of the grade it shut down completely. It started back up after a few minutes but as soon as I put it into gear I had zero power and it would stall a few seconds later. I got out and checked over everything and it all looked fine. I thought it might be the motor going south. So I did what I always do in situations like that. I started her up and stood on the gas. The RPMs hit about 2000 and started to stop. I stayed on the gas and a second later I heard a huge pop. Whatever was clogging that exhaust got blown clean. It's driven fine ever since.

[timsrv]

Typically a failed cat is a long & steady degrading of power until it's done. Then it will start, stall, start, stall with no change. There will usually be heat related damage to the EGR modulator too. In this case it comes and goes (intermittent), so IMHO not likely to be the cat. Water in the fuel can be intermittent, but that doesn't seem to fit anymore as I think you would have flushed it all out by now (with the heat & 2 tanks of gas). You might try (carefully) pulling the gas tank drain plug and catching some in a jar. Inspect for heavy sediments and water. Sediments & water will go to the bottom of the tank, so if there's stuff there, it should come out 1st. If there's crap in the gas, then drain until it's clear & refuel.

It could still be a failing fuel pump. Usually they just stop, but sometimes they will slow down, stop, restart, run slow, speed-up, etc. Could also be an igniter or ECU as these components are electronic and these things can also give you fits of intermittent bad behavior. As with the coil though, an intermittent igniter will usually trigger a trouble code. Depending on the type fault, the ECU may or may not store a code if it is to blame. Other less likely things would be pick-up coil in the distributor or perhaps an Air Flow Meter. A failing ECU temperature sensor will make the van run bad, but probably not to the degree yours is. I know this probably isn't of much help as it's just a list of everything. At least you can rule out the coil :wave2:. Tim

Note/disclaimer: Before draining gas, make yourself familiar with safe handling and disposal of gasoline.

[Reducto]

No worries about the coil. I actually tried to replace it years ago and had the same problem so I'm kind of glad to have it done finally. It's a cheap thing to eliminate anyway.

Spark and compression were both good. The latest shop had nothing but great things to say about the condition of the motor other than it's running too rich and they have no way to diagnose it because it's too old. They won't continue unless I replace the cat (which is now destroyed due to it running so rich) but I'm hesitant to do that because the new one will just get destroyed too.

They believe they narrowed down the problem to the EFI system believing it's running lean and pumping in more gas to compensate. Eventually that causes the engine to flood at which point it won't restart.

I did replace the rear O2 sensor a couple of years ago, I guess I could do it and the front one again just for the heck of it. Maybe yank a computer from a junkyard and swap that in?