Car won't run - missing, backfiring

[FNFAST VR4]

We were heading back to Auckland from Napier, and I felt the car miss a couple of times, and I thought I saw the rev counter dip a little out of the corner of my eye, but I dismissed it and thought I was seeing things! Soon after it started violently jerking, like the whole car would lurch forward, then seem to misfire. So we nursed it to Taupo and called the AA. He couldn't get his reader thing to read the error codes so he disconnected the battery to reset the computer. He fiddled with the screw on the throttle body, and said that because the computer was responding to him adjusting the screw all the vacuum hoses must be ok. I drove it round the block and it was pretty much back to normal. He thought it was water in the petrol, and advised me to put a bottle of meths in to disperse the water. He said it would help get it through the system and we'd be laughing about it by the time we got to Tokoroa... we weren't. It drove nicely for another 45 mins or so, then started to shudder again. I basically had to drive it home in 3rd as with the revs around 4000 it would still pop and miss a little but nowhere near as violently as when the revs dropped. It would drive perfectly when I put my foot down, but at lower revs and with less throttle it would misfire, shudder, and occasionally add a backfire or two.

After a nervous drive we got it to a mates place in Papakura, then got it towed home as I wasn't willing to risk driving it through Auckland. It had taken multiple starts to get through each set of lights to my mates place.

Now when I start it it sounds like there is air coming from somewhere round the plenum, but it will only run for about 30 seconds before dying so it's hard to check. I checked/pulled off all the hoses off and even removed the plenum to have a look underneath but can't find anything obvious. I don't know where to look now. I wondered if it was a sensor or something, but that wouldn't explain the air leak sound.

I'm at a loss as to where to look next. Any advice would be appreciated.

[Subaru ETA]

Check the rubber o ring around the throttle body to intake hose.
What does it run like with the MAF unplugged?
To me it sounds like a spark issue or MAF

[FNFAST VR4]

The plastic elbow and rubber ring were replaced a year or two ago. and it was tight when I removed it. I'll reassemble it and unplug the MAF.

[FNFAST VR4]

So I reassembled it, and it ran fine for a few minutes, then started with the occasional miss, then it got worse. I did notice that the revs were going up bit by bit then dropping again. Weird. When I unplugged the maf it ran worse. I borrowed the maf off the mrs vr4, but it made no difference. I also borrowed her coils and put them into my car which also made no difference. I checked my leads while they were off. One of them would test at .67, then when I'd retest it it would say like 1 or 3, then back to .67. I wouldn't think one lead would cause all my problems though would it?

[Nick Mann]

If you have another vr4 there, I would swap all the coil packs and leads between the two. I would also put new spark plugs in. It sounds more like an ignition problem to me if it is worse when hot.

[Davezj]

We were heading back to Auckland from Napier, and I felt the car miss a couple of times, and I thought I saw the rev counter dip a little out of the corner of my eye, but I dismissed it and thought I was seeing things! Soon after it started violently jerking, like the whole car would lurch forward, then seem to misfire. So we nursed it to Taupo and called the AA. He couldn't get his reader thing to read the error codes so he disconnected the battery to reset the computer. He fiddled with the screw on the throttle body, and said that because the computer was responding to him adjusting the screw all the vacuum hoses must be ok. I drove it round the block and it was pretty much back to normal. He thought it was water in the petrol, and advised me to put a bottle of meths in to disperse the water. He said it would help get it through the system and we'd be laughing about it by the time we got to Tokoroa... we weren't. It drove nicely for another 45 mins or so, then started to shudder again. I basically had to drive it home in 3rd as with the revs around 4000 it would still pop and miss a little but nowhere near as violently as when the revs dropped. It would drive perfectly when I put my foot down, but at lower revs and with less throttle it would misfire, shudder, and occasionally add a backfire or two.

After a nervous drive we got it to a mates place in Papakura, then got it towed home as I wasn't willing to risk driving it through Auckland. It had taken multiple starts to get through each set of lights to my mates place.

Now when I start it it sounds like there is air coming from somewhere round the plenum, but it will only run for about 30 seconds before dying so it's hard to check. I checked/pulled off all the hoses off and even removed the plenum to have a look underneath but can't find anything obvious. I don't know where to look now. I wondered if it was a sensor or something, but that wouldn't explain the air leak sound.

I'm at a loss as to where to look next. Any advice would be appreciated.

if you can hear air being sucked in at idle then do a boost leak test to see what is leaking.
the rubber seal around the throttle body can be a real pain in the backside to fit correctly. i had a new seal and plastic elbow, and it was so tight to fit it on the new seal would continuosely fold in on itself as i push the elbow on, but when i took it off it again the seal sprung back to where it chould have been sat inside the plastic elbow, i would never have found the leak without a boost leak test.
i even used wd40 to try and make it easier to fit and it was still really difficult to fit.

when you fitted the plenum back on did you get the metal gasket round the correct way as it will fit the wrong way round and it will leak, so you may have fix the original issue and introduced another one be a mistake.

this is just a thought.

[FNFAST VR4]

When I reassembled it I couldn't hear the air sound. I think I got the plenum gasket on right. Yeah the rubber gasket on the elbow was a pain and I resorted to wd40 to get it to go on too. I'll probably buy new leads and plugs and try that. It had new plugs a couple of years ago, but if I'm going to pull the plenum off again I may as well do them as well as the leads I suppose.

[Davezj]

When I reassembled it I couldn't hear the air sound. I think I got the plenum gasket on right. Yeah the rubber gasket on the elbow was a pain and I resorted to wd40 to get it to go on too. I'll probably buy new leads and plugs and try that. It had new plugs a couple of years ago, but if I'm going to pull the plenum off again I may as well do them as well as the leads I suppose.

sorry hayden, i was not very clear with gasket comment, i meant the plenum to throttle body gasket.
i leave the throttle body attached to the engine when i take the plenum off as it is easier to do it that way for me as i have an auto.
i don't think the plenum to inlet manifold gasket can go on the wrong way round.

i now make my own inlet to plenum gaskat out of silicone sheet to ensure i get a good seal, i have pushed my boost back up to 1.5 bar as i love the low down touque. i have tested the gasket to 2 bar and it holds pressure so it good for me.

[Colin Wiltshire]

Interesting read, as this sounds similar to what I get, although the engine doesn't stop.

[FNFAST VR4]

I've been a bit slack as the mother in law has loaned me "the family hack" as she refers to it. It's a 97 Galant VR, so isn't too shabby. t's no VR4, and it's definitely showing it's age, but it's been a life saver!

Mine's all back together with new leads, and it's still not happy. It runs really badly even when cold now. I did the diagnostic test, and it gave up fault codes 22 and 23. Which are Cam position sensor and Crank angle sensor. Is it likely that both of these have failed together? Is changing them something I can do myself? I did the first cam belt change with help from a guy Matt that used to be on this forum, so I'm not afraid to pull things apart haha. Would I just buy new ones from Mitsubishi/Ralliart?

[Nick Mann]

Is the car still timed up properly? I mean is it possible that the belt has slipped?

[FNFAST VR4]

It was similar to before in the way that if I could get revs over 4 it would sound sweet, so I wouldn't think so?

[Gly]

i doubt the sensor is at fault, more like a broken wire, on one of them,
one being faulty could cause a false trigger

would be a relatively simple job compared to a cambelt,

[Subaru ETA]

I had a similar problem come to think of it in me st-r after going through a puddle too quick. Crank sensor got full of water. Unplug it and make sure it dry a clean of corrosion etc

[FNFAST VR4]

Excellent, thanks I'll have another look.

[FNFAST VR4]

I removed the bolt that holds the two cables against the cam cover, slid the two plugs off the bracket, popped the rubber grommet out of the cover, started it, and it's now running perfectly. I've pulled the wires, wiggled them, jiggled the plugs twisted and shaken things but it won't run badly again... This isn't ideal as I can't trust it without finding the fault!

[wintertidenz]

It's possible that the plugs were loose and by wiggling them around you've just seated them.

[FNFAST VR4]

It's all back together now, and I drove it around for about an hour tonight. Seems to be all good. Thanks for the advice guys.