Misfire at idle and cruise
My reliant has been giving me a small issue since the second day I owned it. It's a 2.5 tbi auto. After the car warms up for a while, 40 mins of driving or so it's starts to misfire. I've narrowed it down to it being cylinder 4 that is missing. So far I've changed the plugs to auto lite 985, did wires, cap and rotor. In the stack of paper work the previous owner gave me it showed the pickup coil had been replaced. The only other thing I can think is that maybe the distributor is going bad? I had a similar issue in an old mk2 gti 16v. Any input is appreciated. It's supposed to be my wife's car but with the misfire I've been driving it.
Re: Misfire at idle and cruise
Further issue, doesn't misfire on accell or decell.
Re: Misfire at idle and cruise
check the pickup wheel under the HEP in the distributor for loose plastic welds. maybe tighten up the plug gap, 0.028" ish I think 0.032" is what mopar wanted. I find it helps. how about a compression test?
Re: Misfire at idle and cruise
I had galled the plugs to .035, could close them up some but it's acting the same as the plugs that came out. Ill check out the pickup wheel tomorrow. Am I going to have to reset the timing if I do that?
Re: Misfire at idle and cruise
no just take the cap off and pull your roter out and then lift the HEP sensor, you'll be able to see the pickup wheel and the plastic welds that hold it down. any codes logged?
Re: Misfire at idle and cruise
No, no codes logged yet. Thanks for the help, I'll take a look tomorrow when I get a chance, dark outside now.
Re: Misfire at idle and cruise
Re: Misfire at idle and cruise
Wiggle it? Is it loose?
Do a compression and leak down test.
Re: Misfire at idle and cruise
The whole assembly was a little loose, it rocked back and forth a degree or two. I don't have the tools for a leak down test but I can do a compression test by the end of the weekend.
Re: Misfire at idle and cruise
Not that i think it will do anything but swap the #1 and #4 plug wires and see if the miss follows it.
How are you determining that it's a cyl4 miss?
Re: Misfire at idle and cruise
When it's good and hot (40 mins of driving) it almost steady misfires on cylinder 4. I've got brand new plugs wires cap and rotor. If I pull 4th cylinder it stays idling just steady miss. If I pull plugs 1-3 it just about dies.
Here's a quick video I took of the exhaust while it was missing hard.
http://www.youtube.com/watch?v=Nucdv8LJsYs
Re: Misfire at idle and cruise
Quote:
Originally Posted by
INVUJerry
When it's good and hot (40 mins of driving) it almost steady misfires on cylinder 4. I've got brand new plugs wires cap and rotor. If I pull 4th cylinder it stays idling just steady miss. If I pull plugs 1-3 it just about dies.
Here's a quick video I took of the exhaust while it was missing hard.
http://www.youtube.com/watch?v=Nucdv8LJsYs
I bet you've got a valve hanging up or a bad lifter.
Re: Misfire at idle and cruise
Well, maybe the compression test will tell you something. I doubt it's in the HEP as the sensor itself is clearly working 75+% of the time (out of 4 cyls), so it would have to be a problem with the corresponding part of the trigger wheel if anything, and any problem there would be visible to the naked eye. So i doubt it's that. Likewise, a problem with fuel delivery would affect the other cylinders as well since it is TBI, so the only possibility there is uneven carbon buildup affecting #4 more heavily than the rest, which seems unlikely.
I vaguely suspect hard parts in the motor at this point (something to do with valve sealing), so a compression test is next, and if that doesnt tell you anything, i think some stores rent a leakdown tester.
The lifter idea might lead somewhere. If you are inclined to try, you can swap those lifters to another cylinder for testing with nothing more than a large screwdriver, once you get the valve cover off.
Re: Misfire at idle and cruise
It would be really strange that a lifter would go bad only after you drive for 40 mins though. I had a lifter go on my neon but it would only miss and make noise when it was cold. Once warmed up it would be quiet and smooth. Ill borrow the compression tester from my buddy and go from there.
Re: Misfire at idle and cruise
Well I went and got a timing light. Decided to hook it up to cylinder 4 for shits and giggles. The light drops off whenever it would misfire. Time for a distributor? Also, it's sitting around 9 degrees, not 12 like it should.
Re: Misfire at idle and cruise
Quote:
Originally Posted by
INVUJerry
Well I went and got a timing light. Decided to hook it up to cylinder 4 for shits and giggles. The light drops off whenever it would misfire. Time for a distributor? Also, it's sitting around 9 degrees, not 12 like it should.
Nope, HEP won't just cut out on one cylinder. You've got a compression problem or possibly the computer is going out. The sound it makes in the vid is like a valve hanging open.
Hook up a vacuum gauge and see what happens when it acts up.
Re: Misfire at idle and cruise
If the light cuts out with the miss the problem is on the spark SUPPLY side because even if you have the spark plug out in open air waving it around, as long as it has a ground path it will spark and the light will light up.
At this point i would move the timing light pickup to the coil wire and see if you can discern that it is missing some sparks there too. If not, the problem is between the coil and the spark plug wires (coil wire, cap, rotor, plug wire and all associated terminals in between). If it DOES miss sparks then you've really got a weird problem.
Re: Misfire at idle and cruise
I literally bought a new cap, rotor and wire set the weekend after I bought the car, and the pickup coil had been replaced in June by the PO. I put the timing light on the coil wire when I was trying to isolate the problem earlier but at 16rpms a second it's hard to see one miss. I had a short happen in the distributor of my 89gti, not the cap or rotor so that's why I was leaning towards that. I did swap plug wires 1 and 4 with the same issue so it's not the wires. If the coil was cutting out it wouldn't be on just one cylinder, but more randomnly.
Re: Misfire at idle and cruise
Like I said earlier, put a vacuum gauge on it and see what happens. If it starts to miss and the gauge stays steady, then its electrical, if the gauge starts jumping, compression/valve issue.
Re: Misfire at idle and cruise
I just put a $100 injector in my dad's car because i couldnt believe his new wires could have a problem (you can guess the rest), so there's a reason i suggested ruling it out anyway. Sounds like you did, though, with swapping 1 and 4.
Back to the worse options, then.. Something in the head. At least swapping the lifters is pretty much free.