Pontiac Problems? Ask a Mechanic for Answers ASAP
So at higher rpm's it does not misfire.At idle you should have a bright orange spark.
new expert here
i am sorry for the long wait
was it misfiring before at idle ?
most of these that will misfire at idle then go away when you bring up the rpms off idle and stop missing end up being a vacuum leak from the lover injector o-ring or a vacuum leak in area of the # ***** cylinder usually the upper intake
can you be sure there are NO vacuum leaks testing with a can of carb cleaner ?
if you swap # ***** injector with # ***** injector will the skip move ?
I would be doing a leak down test on Cylinder 3, since swapping injectors, coils and spark plugs has not moved the fault. Clearly the fault is within the cylinder. If the engine wasn't misfiring prior to the intake coming off, did a piece of foreign material or gasket fall into the intake port of cylinder 3?
Seen gasket material under valve seats too many times to count now.
I had an engine recently, identical fault to yours, had a valve not seating due to one collet missing, can you believe that? Lucky it didn't drop into the cylinder, took a lot of effort, but did the whole repair without head removal.
Please do the leakdown test, compression test may not reveal your fault.
The 24x would be engine speed, the engine may still start and run from the cam sensors.
Does it start with the crank sensor disconnected?
Are all the injectors connected to the correct harness connector for each cylinder?
What pressure did you have on the first gauge with the second gauge at set?
100 psi is what I use.
Ok, that's a good sign.
Can you get that the NO.3 injector without lifting the intake?
I want to know does it have injector pulse with a noid light while the engine is running?
Have you swapped the spark plug, injector and spark plug wire to other cylinders?
Have you checked the oil pressure? I have seen valves not seating from excessive oil pressure.
Ok, I will await your reply.
Best of luck for today.
Are the cats factory or aftermarket?
Is the the grinding noise from the starter motor or the flywheel ring gear?
Where is the crankshaft sensor located?
It is entirely possible you have a valve problem from the lean condition that existed with the poor injector harness connection and the vacuum leak.
What O2 sensor voltages do you have at idle, pre and post cat?
Ok, sensor 1 is certainly lean. Is the 700-800mv post cat for that bank?
Can you swap the front o2 sensors bank for bank?
What is the cranking voltage?
Are all the ground points clean and tight?
Did it have the noisy starter prior to the no start condition (BCM failure)?
I can see I would be starting to "throw in the towel" as well, LOL.
Can you check the crankshaft endfloat?
Had a customers car that had a complaint of noisy clutch, ended up being no thrusts left on mainbearing. New engine required. Lack of servicing.
How about at the crankshaft balancer?
I had one engine that I needed to verify crank endfloat. I was able to use a dial indicator and consistently get .005 as my reading, for which I was happy.
If you can do it at the balancer, and you end with .020+, I say that's a good place to start.
Then sump off for inspection.
How many miles has the engine done?
I'd say at 200k+ miles, it's probably getting a little "long in the tooth".
I remember spending 30 hours looking for a fault another young tech caused, it took me about 10 minutes to fix it once I found it. All ok while under warranty, but who pays when retail?
Difficult to quote a customer like that, and you are now in the same predicament.
I feel your pain with this, does your customer understand, and are they still willing to spend, or have you proposed to them "what do you want to do now etc?".
I would like to be with you, sometimes difficult to advise when I can't hear or see what's going on.
Your thoughts now?