Cavalier 1.6 Idle Misfire

[ben1992]

Hi there guys, new to the forums and just aquired my first vauxhall, car has a few problems and I thought someone here might be able to assist me with rectifying them!

Firstly I have a 1995 Cavalier 1.6 running on a carb, which had a slight misfire at idle and low to mid engine speed, I have changed the Distributoe, coil pack, plugs and leads, and althoug it runs and starts slightly better, it still misfires, I was thinking that it could be the intake manifold gasket, or the fact that the hot air tube to the airbox is missing however it shows no signs of the carb venturi 'icing' as despite the misfire the car does pull very hard under load, furthermore I ran a compression test on the engine dry and acheived 170psi in all 4 cylinders, and checked the oil and water for signs of a blown head, both are clean and the car uses neither.

The problem is starting to nag me now as I am unable to diagnose it despite various expeirience I have had repairing and servicing vehicles in the past... I have heard from more then 1 person that perished and split vac hoses can cause the problem especially the brake assist vac line...

Ideally I'd like to get the car running smoothly for the winter as my current daily runner is absolutely crap in the snow!

P.s. The car has a K&N kit however it has not affected the running other than giving a little more throttle response (perhaps I'm imagining it :s)

Any help or advice would be greatly appreciated!
EditReportReply

[planetc]

You covered the ignition, so there is a fair chance it's an air leak. Check all the hoses and unions on the manifold, undo and plug the servo pipe union to eliminate the pipe and servo and if you haven't found anything start spraying wd40 or something similar (carb cleaner is good) around the inlet gasket area. Don't forget the carb baseplate gasket too. A leak will give a change of engine speed when you spray it.

[DiplomaXE]

a 95 1.6 carb. blimey, didnt know they went that late on a carb. sure its not a late SPI one?

if its 1.6 carbed then I ought to think it's a 16SV like my 91.
double check the little vacuum pipes and their little adaptors on the carb to airbox and the carb to MAP sensor, mine were tired. then I had a running fault which I traced to a bent pin on the EZ Plus ecu connector, which is bolted on the bulkhead.

More I think of it though, a 95 car ought to be INJ, even though the injection unit looks like a carb.
has the car got a manual fuel pump between the "carb" and the timing belt area?

[planetc]

Good point, I missed the 95 bit.... If it's a single point injection then look at the small pipe that comes off the servo pipe too, it runs to the tank vent valve which often leak air and create an air leak on no4. Fold the pipe to block it and see if it smooths the idle. Black Lucas dizzy caps on 16n2 track at the back of the king lead connection leading to lumpy idle. Which engine is it? If you are not sure can you upload a photo?

[Ritchie]

check the temp sensor hasnt unclipd had tht witi my c16nz cliped bk in runs perfect

[cavalier1990]

Got a one eight spi 95 and had to replace the inlet manifold a while back, although wasn't a concentrated misfire on one plug just dirty tickover etc. Also my brake servo pipe was split under the bend where it turns to go to bulkhead area, plus the little vacuum pipe L shaped connector on the side of the carb unit was split. As has been said check all your vac pipes as they are prone to drying out/splitting.

If you have time best thing to do is take all the rubber vac pipes off 1 by 1 and cut a little bit of rubber off the end where it has expanded and probably split; result - new tight fit and no splits; can't do this with the L shape connectors though, I just wrap duck tape round them so it seals the split or try and get new ones.

Andrew