Engine cut out at speed. Backfiring?
#1
Engine cut out at speed. Backfiring?
Let's see, Updating on another thread in case it matters for this problem. I had a fuel gauge problem I tried to fix with a new pump. It stayed stuck at half after a 2nd adjustment. After running it out of fuel and refilling the tank it started down to empty again and the low fuel light is on with only 105 miles on a 22 gal tankfull. The last full tank ran out at 322 miles.
When the motor was cold, maybe 5 minutes after starting, I drove up a hill and near the top at 45-55 mph the motor started losing power then popped several times like a backfire. I let off the gas as I crested and it calmed down and on the ride down the problem went away. It definitely felt as if I had kept the throttle pressed it would have killed the motor. Almost like it was flooding or not getting spark or air.
I did my errands and on the way home with the motor warm it shwoed no signs of problem coming over the hill.
Also may be connected is a very prominent clacking lifter noise. Its loud enough to be heard over the radio with the windows closed at 55mph. I posted about that previously and am embarrassed to say I have not yet changed the oil as I said I would to see if that would fix it. ALso when I first bought this in Sept I put in a new EGR which fixed the revving problem and a new air cleaner. It is a very clean motor for a 94 with 137K miles.
Thanks for any tips on diagnosis.
When the motor was cold, maybe 5 minutes after starting, I drove up a hill and near the top at 45-55 mph the motor started losing power then popped several times like a backfire. I let off the gas as I crested and it calmed down and on the ride down the problem went away. It definitely felt as if I had kept the throttle pressed it would have killed the motor. Almost like it was flooding or not getting spark or air.
I did my errands and on the way home with the motor warm it shwoed no signs of problem coming over the hill.
Also may be connected is a very prominent clacking lifter noise. Its loud enough to be heard over the radio with the windows closed at 55mph. I posted about that previously and am embarrassed to say I have not yet changed the oil as I said I would to see if that would fix it. ALso when I first bought this in Sept I put in a new EGR which fixed the revving problem and a new air cleaner. It is a very clean motor for a 94 with 137K miles.
Thanks for any tips on diagnosis.
#2
#3
I changed the cap rotor and coil yesterday and it idled fine in the driveway. This morning I was nice to it going over the hill figuring the problem was as much being cold as it was the parts and it accelerated really well getting on the hwy. That’s an improvement until then I worried when merging as it took so long to gain speed.
I drove across town to warm it up and get an oil change. When they opened the hood there was coolant on the hood above where the hose comes out of the rad and the battery was soaked with splashing on other parts. We could find no obvious leaks and since the coolant level was not low they figured it had just happened. When I left they sprayed the bottom of the engine with something that made it steam up and as I write this I wonder if their pit guy didn’t spray that coolant up into the engine compartment as I pulled in????? hoping to sell a rad hose out of the deal. The guy who opened the hood went to the lower hose right away and made noises about the hose plumping until I pointed out the leak appeared to be on the other side of the motor. I know it sounds paranoid but the people around here would do anything for money. There seems to be no compunction at all about lying or deceit in them.
I drove home through town paying attention and all that I noticed was that something metal was rubbing on metal in the rotation of the motor. I had the impression it was near the drivers side of the bell housing. I can’t tell yet if the lifter noise has gone away with the oil change yet though I did not notice it on the way home. It generally needs heat or a lot of demand to show up.
When I got home the idle was up at 1200 when it normally sits at 800+ and calms down once I park it. It did not calm down after letting it sit and looking to see if something was stuck. It did this when I bought it and the new EGR fixed that problem.
I also wiped down the coolant spatter. There was no more when I got home than was there when I left that shop which makes me think my suspicion may be correct. Time will tell.
Edit: I knelt on the top of where the hood latch connects leaning over the motor to replace the cap and rotor. I cannot imagine that would have cause a crack or break in the seals. I think I would have felt it and most of my weight was on the body.
I drove across town to warm it up and get an oil change. When they opened the hood there was coolant on the hood above where the hose comes out of the rad and the battery was soaked with splashing on other parts. We could find no obvious leaks and since the coolant level was not low they figured it had just happened. When I left they sprayed the bottom of the engine with something that made it steam up and as I write this I wonder if their pit guy didn’t spray that coolant up into the engine compartment as I pulled in????? hoping to sell a rad hose out of the deal. The guy who opened the hood went to the lower hose right away and made noises about the hose plumping until I pointed out the leak appeared to be on the other side of the motor. I know it sounds paranoid but the people around here would do anything for money. There seems to be no compunction at all about lying or deceit in them.
I drove home through town paying attention and all that I noticed was that something metal was rubbing on metal in the rotation of the motor. I had the impression it was near the drivers side of the bell housing. I can’t tell yet if the lifter noise has gone away with the oil change yet though I did not notice it on the way home. It generally needs heat or a lot of demand to show up.
When I got home the idle was up at 1200 when it normally sits at 800+ and calms down once I park it. It did not calm down after letting it sit and looking to see if something was stuck. It did this when I bought it and the new EGR fixed that problem.
I also wiped down the coolant spatter. There was no more when I got home than was there when I left that shop which makes me think my suspicion may be correct. Time will tell.
Edit: I knelt on the top of where the hood latch connects leaning over the motor to replace the cap and rotor. I cannot imagine that would have cause a crack or break in the seals. I think I would have felt it and most of my weight was on the body.
Last edited by onemore94dak; 11-18-2013 at 02:12 PM.
#4
I added a can of seafoam yesterday and it made it run a lot better. The RPM's calmed down and it seems to be doing better.
I took off the wheel this morning. The grinding wasn't the bearings it is the pads, they were down to metal. If there is any pad left I could not see it. I ordered new hub assemblies, bearings and pads for both sides.
This 2wd has rear only abs. After this plugs and wires then research into disc brake conversion for the rear end.
Oh yea I noticed there was fogging inside the instrument cluster plastic cover. Is this common, its 20 years old?
I took off the wheel this morning. The grinding wasn't the bearings it is the pads, they were down to metal. If there is any pad left I could not see it. I ordered new hub assemblies, bearings and pads for both sides.
This 2wd has rear only abs. After this plugs and wires then research into disc brake conversion for the rear end.
Oh yea I noticed there was fogging inside the instrument cluster plastic cover. Is this common, its 20 years old?
Last edited by onemore94dak; 11-20-2013 at 08:50 PM.
#5
I haven't done anything to the motor since the last post. I was driving yesterday and it started losing power like it had stopped running and then backfiored from the extra gas that was pumped in from me pumping the peddle. I was moving at 20-30-mph in traffic.
Before this it had lost whatever improvement the Seafoam and partial tune up had given.
So aside form replacing the plugs and wires it occurred to me to ask how do I test the PCM? Seems like I read something on here that said these were symptoms of a PCM on its way out or a wiring junction may be shorting out.
Does coolant cause wire corrosion?
Before this it had lost whatever improvement the Seafoam and partial tune up had given.
So aside form replacing the plugs and wires it occurred to me to ask how do I test the PCM? Seems like I read something on here that said these were symptoms of a PCM on its way out or a wiring junction may be shorting out.
Does coolant cause wire corrosion?
#6
#7
I've changed the plugs and wires now. I used the Lifetime Napa wires and regular Champion plugs. Seems the previous installer used Bosch and didn't bather to gap them correctly. They were all over .045! the gap on the hood label says it should be .035.
I've driven in about ten miles and it seems a lot better. I did hwy and in traffic without that bothersome cutting out/stalling backfiring mess.
It does still have that noise I think may be lifters. It loses power before picking up when under load and I demand it. And it doesn't pick up as much power as a 3.9 V6 should. How hard is it for a novice to do a valve job on one of these?
I am now also suspecting an exhaust leak where I think I heard the metal on metal noise on the driver side.
I've driven in about ten miles and it seems a lot better. I did hwy and in traffic without that bothersome cutting out/stalling backfiring mess.
It does still have that noise I think may be lifters. It loses power before picking up when under load and I demand it. And it doesn't pick up as much power as a 3.9 V6 should. How hard is it for a novice to do a valve job on one of these?
I am now also suspecting an exhaust leak where I think I heard the metal on metal noise on the driver side.
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#9
The simplest thing to do is what I was told to do that is cap, rotor, coil (not sure on your motor) plugs and wires. That improved my motor a lot.
#10
Popping/backfiring through the carb or throttle body can be exhaust valve or timing related. Under load (going up hill, accelerating, etc.) a very retarded timing or leaky exhaust valve can cause this. In the case of retarded timing, the valve isn't quite closed when the combustion starts & in the case of a leaky valve, enough combustion heat leaks into the intake manifold to ignite the mixture there.