Engine miss fire @3,500 rpm ???

chrisfiat · Post by **chrisfiat** » Sat Aug 18, 2012 6:57 pm

clean all the plugs keep track of #3 and put it into a different cylinder, take a drive and look at plug in # 3 cyl and the plug that used to be in #3,, if the old plug is still fouling then get a new one if cyl#3 is still missing then swap injectors and do the same test again. what brand of plug are you using. hope they are neither champion or bosch. i would use either ngk or nipondenso only

chrisfiat · Post by **chrisfiat** » Sat Aug 18, 2012 7:01 pm

ps you shouldn't see any " black fluffy deposits" on any of the plugs, keep in mind the cold start injector may be dripping too, this is a comom failure on this type of inj system. to test remove and securely plug the cold start inj hose and test drive

timinator · Post by **timinator** » Sat Aug 18, 2012 7:54 pm

Unfortunate choice of words. Should have said running without the exhaust would lean out the mixture the o2 was reading. The ecu would see the extra oxygen entering the system from the open pipe and would try to add more fuel. Not that the mixture commanded by the ecu would lean out because of the pipe being open. Sorry for the confusion. Check the body of your shiny black spark plug and see if the porcelain insulator is cracked on the plug wire side.

So Cal Mark · Post by **So Cal Mark** » Sat Aug 18, 2012 8:14 pm

do you have a infrared temp gun that you can measure the temp at each exhaust outlet? I'd also like to see the voltage reading from the o2 sensor, especially at 3500 when the misfire seems to be worse. Have you pulled the injector rail and looked at the injector spray pattern?

scooter55 · Post by **scooter55** » Sat Aug 18, 2012 10:18 pm

Chrisfiat, that is a good plan I will pull the fuel rail and check the spray pattern. If I see that #3 is not right I will jump for joy and replace it, if it looks good I will switch it with #2 and see if the problem moves to that cyl. I pulled the cold start injector and started the car and it did not leak at all. I will also try pinching off the line to it and taking a drive. By the way I am using NGK plugs.
Mark if the above does not solve my problem I will try to get a voltage reading from the o2 sensor while it is missing. I do have a temp gun but it is very difficult to get a reading . I guess I have to take of the heat sheld to see the separate branches.I would guess I would not see a temp difference unless I could shoot it when it is missing
Timinator I will check the plug but this is the second set . I did see a slight difference in the #3 plug on the first set but it was very slight because it had very little run time on it. I changed them right away because I thought the plugs could be the cause of the problem.
Also the gas mileage is awfull. Not a big surprise . I feel we are getting close to solving this problem. I think I have more time in trying to trouble shoot this than it took me to pull the engine and rebuild it

Thank you all for all your help this forum is a great service to everyone who loves these great cars and wants to keep them on the road were they belong.

majicwrench · Post by **majicwrench** » Mon Aug 20, 2012 12:01 pm

NOt sure if o2 reading is gonna be useful, but what the heck. Glowing conv is due to unburned fuel. Can be unburned cause there is too much, or unburned cause it is missing like mad. Test pipe not gonna do you much good, but at least it won't glow

Good luck,
Keith

scooter55 · Post by **scooter55** » Mon Aug 20, 2012 3:30 pm

I pulled off the fuel rails and checked the spray on the injectors . I have a question I thought that the cold start injector should only spray for 2 - 8 seconds. When I am cranking the motor over it will keep spraying as long as the motor is cranking. Is that normal? Or does the 2-8 seconds only apply to after the car is running? The spray on the 4 injectors looked Ok I did not see a difference in the #3 injector I am going to switch it to # 1 cyl and see if the problem goes there.

So Cal Mark · Post by **So Cal Mark** » Mon Aug 20, 2012 3:52 pm

yes, cold start sprays while the starter is working and should only spray for a few secs after starting

chrisfiat · Post by **chrisfiat** » Mon Aug 20, 2012 6:07 pm

cold start sprays only during cranking, time is temp dependent, based on the thermo timer, after start up cold start inj does not run. has any one tampered with the air flow meter??

scooter55 · Post by **scooter55** » Mon Aug 20, 2012 6:43 pm

Thanks , yes I just put it back together and checked the cold start it stops spraying when the motor starts and does not leak. I moved #3 injector to # 1 will test car and see if the problem moves to # 1

scooter55 · Post by **scooter55** » Mon Aug 20, 2012 7:18 pm

Well that didn't go well. I was test driving the car it drove fine for the first 10 min .once warm I parked it for 10 min and went on a second test all was fine . I went to turn around and it stalled . Would not re start. Will sputter and almost catch as long as the starter is engaged. But will not stay running. I will try it once it cools off and see if it starts when cold.

scooter55 · Post by **scooter55** » Mon Aug 20, 2012 7:44 pm

After towing it home I let it sit for a half hour and it restarted it seems like it was flooded. I think I am going to pull the cold start connector off for the next test drive it my be spraying fuel ? Or maybe it may be better to block off the fuel line going to it in case it is leaking fuel under pressure.

chrisfiat · Post by **chrisfiat** » Mon Aug 20, 2012 8:00 pm

block it off with a fuel pressure gauge, start it and check the pressures, let it run a whole, now also check the vaccume line from the fuel pressure regulator as well. It should be dry ( no fuel and no fuel smell ) your running pressure should bump up approx 10 psi with the vaccume line disconnected report back

scooter55 · Post by **scooter55** » Mon Aug 20, 2012 10:16 pm

Chrisfiat I will do that and let you know. The air flow meter was not tampered with it is original. I also switch it with another good one and there was no change.

scooter55 · Post by **scooter55** » Tue Aug 21, 2012 9:50 am

OK after removing the fuel rail and moving the injectors from #1 to#3 I now have a new problem. The car starts when cold and seems fine. In five min. It starts to run rough and will not idle an longer. If you let it idle down it will stall and not restart. I blocked off the cold start valve with a pressure gage the gage read 30 lbs steady . I did not get a chance to block off the vacuum side of the pressure regulator because it started to run rough and stalled. I thought it was running rough because it was flooding but I pulled a plug and it was not wet. I will try to restart after it sits for an hour.any ideas on what to look for now? Is 30 lbs enough pressure ? The vacuum side of the pressure regulator is dry and does not smell of gas.

Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???

Re: Engine miss fire @3,500 rpm ???