lost compression #3 cylinder not firing

[HenryJ]

Well I ended up having to pay someone to change the distributor because we couldn't do it ourselves. After replacement it does run sorta better, but the #3 cylender is not firing. He says I have lost compression on that cylinder completely so it looks like this may be the end.

Sorry to hear that. Pop the oil cap and see if you have excessive blow-by. Might be worth popping a valve cover off and looking at the valvetrain too.
How many miles were on it?

[killian96ss]

Did they do a compression test or tell you why you have lost compression on # 3? What kind of compression #'s did they get on the other 5 cylinders? I'm just curious what caused the loss of compression; a broken top ring, broken valve spring, or something more serious? If you take off the valve cover that's over #3 you will be able to see if it's a broken spring.

Steve

[ApproachMedium]

How do I tell if I have excessive blow by? I dont know a damn thing about taking the valve covers off but thats not to say I couldn't do it with proper instructions and maybe someone with a little experience.

I got a phone call from my dad and he told me that the mechanic he had look at it said I had no compression in the #3 cylinder. I don't know how he tested it but with the couple thousand I have invested in this box you bet your right hand I am getting a second and 3rd opinion on it lol. I have owned this truck since it had 189K, it had a misfire on the #3 when I bought it. I had a mechanic look at it then and replaced all of the spark plugs wires rotor and cap, but not the distributor. When he did that he also redid my intake manifold and installed a new fuel injector and the spider. When he tested it then, 2 years ago, he told me I had compression on all the cylinders. After that fix was done I continued to drive the truck up until now at 237K because the misfiring and idle hesitation got so bad I just didn't want to deal with it. I tried to tackle the problem myself by replacing the spark plugs again which were in fact fouled up and destroyed.

After replacing the plugs the truck ran perfectly and idled perfectly till it reached operating temp, at which then it continued to misfire on the #3 and immediately throw the misfire code again after resetting the computer. We checked the wires and saw I was randomly getting spark at the cylinders which is when we decided to replace the distributor along with what I learned about the commonly known problems with the distributors on this truck. Since we didnt have the proper tool to do it and I didnt have the time with my job I had my dad pay someone he knows to do it. Maybe that was a mistake....

[HenryJ]

To check for blow-by, take the oil fill cap off with the engine running and watch for it puffing air out.

If you are wanting to confirm no compression, pull that plug and have a friend bump the engine over while you hold a finger over the open hole. It should suck and then push pretty hard if it has compression.

Sounds like you are doing things right. Personally , at 237k miles, I'd be looking for another engine. That one is not worth investing more in it.

[ApproachMedium]

Sounds good. Ill give that a try later today or tomorrow. If its lost compression/no compression there isnt much you can do about it? Ill probably be looking to part the thing out because I cant afford a new engine right now along with all the other things I need to do to this truck to make it complete again. It needs about 2 grand in body work done after this last winter.

[HenryJ]

Yikes, the body damage doesn't sound good. A lower mileage used engine can be picked up pretty reasonably. Looks like there are several close to you for around $800. Add that much for a few parts and installation. You'll have to decide if parting it out is worth more than what you need to invest.

[ApproachMedium]

True. Ill be in DC next week for work, I have a week to make up my mind about what I am going to do with it. Its one of those split situations, I have a lot of money into it but at the same time it still needs a good amount of money into it to make it perfect again. I never had a problem doing that thought because its a fully loaded truck, and I love it but the engine might be the final straw.

The body damage is the pass side rear door and bed. The cost of replacing the bed wasnt worth it so I was just going to pay for the body work to get done.

Talked to my dad and we are gonna play with it tonight when he gets home from work. I really dont believe that a year and a half later Ive lost total compression on one cylinder. Is that possible? Wouldnt there be a warning sign or some kind of change?

[ApproachMedium]

OK just dug into this a little deeper, finally got my hands on the truck today to mess with it after a long day of dealing with the car.

First off, there is now blow by. Took the oil filler off and didnt have any air puffing out it only had minimal suction when I placed my hand over it.

Second, it was a little dark by the time I got to mess with it so I couldn't dig into doing a compression test but will look into this tomorrow.

I ran my computer scanner on it and the only DTC I am currently running is P0300 random multiple cylinder misfire. The engine is running as if someone screwed the firing order up. It idles funky and when i put it in gear the whole truck kicks around and stumbles along like its going to stall. It looks like he used my old cap, i think the job was rushed there are also some tools left under my hood. Not letting this guy near the truck again!

Tomorrow I am going to double check my firing order. What is it for the 4.3L in the 2002? What is considered the #1 on the flat cap? and how is the numbers of the cylinders layed out on this engine? Is it the same as its always been on the 4.3L?

[roadrunner]

With all the problems you're running into I'd change to a new cap before even checking firing order to wire orientation. I had cap troubles a while back and got the codes you're getting till one day it would not start at all and sounded like the distributor was out of time. Finally ended up replacing the fairly new cap with oem and problem was solved. Cut the old cap apart and split all the runners with a sawzall and VOILA!!! There was a short between two sets of runners molded in the cap hence it acted just like mis-installed distributor or wet cap neither of which was the case.

[ApproachMedium]

I bought a new cap, the idiot did not install it when he put my new distributor in

Im bored, I think I am going to pull the nose in the garage now and play.

[roadrunner]

I bought a new cap, the idiot did not install it when he put my new distributor in

Im bored, I think I am going to pull the nose in the garage now and play.

Well, on the bright side at least you don't have to go buy a cap to try the replacement suggestion. I trust you've read or are aware of the warnings about the screws and the care needed in their removal/replacement so as not to damage the plastic housing of the distributor?

[ApproachMedium]

Absolutely! In fact I am going to make sure that when I pull the screws out that the idiot used the ones I left out that I REMOVED the locktite from so that it would not get jammed up in my new distributor!

[ApproachMedium]

OK turns out crummy barely drivable running was improper firing order. Idiots! It still runs like crap under 1,000 RPM like its missing somewhere. When I fire it up cold start it runs fantastic untill it reaches operating temp. Back to square one same place I was a year ago! Ill still check compression tomorrow when I have help and I am going to look at getting a new coil, and an AC Delco cap to eliminate thouse two variables. The new cap I picked up with my distributor was a Napa Echlon.

[roadrunner]

I'd still put the cap on and you might also try cleaning the MAF sensor since as you say it runs good cold and not warm. The Napa Echlin cap should be of good quality but if you feel better with oem go that way for peace of mind. Let us know what you find or if you have more questions.

[ApproachMedium]

I did, I used the brandy new napa one. I am gonna look for the AC delco though I am smelling arching under the hood so something just is not right with these crappy caps. So cleaning the MAF might be another option? Someone mentioned that to me in the past? I seen some spray you can buy at the parts store labeled MAF sensor cleaner would that be good or is there a better way to do it?

[killian96ss]

CRC MAF sensor cleaner works pretty good! Clean the 3 tiny sensors inside front and back.

Steve

[ApproachMedium]

Gotcha... Will go grab some now and give it a shot!

[killian96ss]

You can also use that stuff to clean the IAT sensor which is the small sensor plugged into the air intake tube.

Steve

[ApproachMedium]

What does the IAT sensor do? This sensor is missing on my friends 94, the truck still runs but has a SES light, maybe thats the problem LOL.

[raven2510]

IAT= Intake Air Temperature

[HenryJ]

Still waiting to hear about what you found for compression on #3 before I start looking further.

[ApproachMedium]

Yea, had to put that off again for another day. That requires disconnecting the steering shaft to get that spark plug out so we haven't done it yet heh. Spent the afternoon getting my sisters boyfriends car ready to move to south carolina. The MAF cleaner didnt do a darn thing but at least thats one less variable in the mix.

[killian96ss]

Do you have a compression tester or a parts store near you where you can rent one? The threaded ones work better than the rubber tip style. If you are going to pull the #3 plug, you might as well do a compression test while the plug is out. You can also test a few other cylinders for comparison. Are you still getting a #3 cylinder misfire code or the P0300 random misfire code?

Steve

[ApproachMedium]

I don't have a compression tester, I have a friend who says hes going to bring one over and help me do it. The plugs are brand new we just changed them last week so only reason its coming out is to do the test. The only code I am getting right now is P0303 Cylinder #3 Misfire detected. There are no other codes, the engine runs just fine still when cold and then when it gets to its lowest idle you can feel it missing. It moves enough you can actually see the whole truck move with it lol. Once the truck is in gear and your driving it, it runs smooth as silk and you would never know theres a problem. Sometimes when you stop at lights it idles perfect, sometimes it does not.

Just waiting on doing that compression test so I can eliminate that also as being an issue, hopefully.

[HenryJ]

Do it sooner rather than later. I have a 454 here that displayed similar symptoms. Missed like a 'mutha at idle , but at higher speed it was hardly noticeable. It stuck a valve. Unfortunately it also tapped a piston. Bearing, gaskets, piston, recon rod, recon heads. Close to $1k

[ApproachMedium]

Yikes! Well since its all still a mystery of whats exactly wrong and I am trying to save myself from having to replace the engine I have not been driving it since we have messed with this. I test drove it around the local streets once or twice but yea... Not letting it get far until I know whats up.

[ApproachMedium]

OK removed spark plugs today and I am defiantly getting good compression. Was not able to obtain a gauge, but I defiantly do NOT have lost compression on any of the cylinders. My father could not keep his finger over the spark plug holes so he says it cant be bad, and all cylinders have equal feeling there.

In the meantime up until today I also threw a few other parts at it out of random thought, a new coil, and a new IAT sensor. Truck still gives me the same runs fine while driving under load etc, but idles like crap and reports Misfire #3 when left idling with no load (in P or N) Sometimes when I plug the computer in it gives me Random multiple cylinder misfire but usually its just the #3. I am at a loss here with this, what else could it be? Ignition system is completely new now and firing correctly to each cylinder so it appears, fuel pump was replaced last oct, fuel injection system was all new as of 2 years ago, except the fuel regulator which I was told was good at the time of the systems service.

[HenryJ]

Sounds like you have compression.
Swap the plug and wire to a different cylinder. I assume you have checked the cap and rotor and they were good. Now see if the problem moves. If swapping the plug and wire continutes to set the cylinder #3 misfire, at least we have eliminated those.

Ok, next step is to look for intake leaks. Your description of poor idle characteristics leans to that. You can use a spray can of throttle body cleaner. Spray it around the intake gaskets and base of the throttle body. Listen for changes in the idle. Any changes will indicate a leak. None are acceptable.

Have the intake gaskets been replaced? If the answer is no, it might be a good idea.

Once all that is checked, my next suspect would be injectors. I hate to invest too much into this high mileage engine, but the updated spider assembly is the best option for new injectors.

[ApproachMedium]

Yes, cap and rotor were brand new with the new distributor that was installed 2 weeks ago, All new plugs too. I will have to try switching plugs tomorrow. All intake gaskets were brand new when the fuel injector etc was replaced 2 years ago because they were leaking.

I believe my spider assembly was changed with the new injectors? I will have to double check my work order in the pile of papers I have for this thing and get back to you on that too. I will get some throttle body cleaner and do that test anyways just to eliminate one more variable.

[HenryJ]

Don't forget to swap the wire too.

Testing the fuel system is a good idea. Beg borrow or rent a gauge. That will rule out problems in the fuel system.

[ApproachMedium]

When testing the fuel system, what would the proper readings be?

[HenryJ]

It is in the Fuel System Diagnosis , Testing fuel pump thread.

[killian96ss]

For some reason I have a strange feeling that the problem is related to the injectors or spider assembly even though they have already been replaced. You can tell a whole lot about whats happening inside each cylinder just by looking at the plugs. Compare #3 to a few other plugs. Is it darker or lighter? Dark or course means too much fuel, lack of ignition, or oil burning, while lighter usually means not enough fuel. That fuel pressure test will also tell alot.

Steve

[ApproachMedium]

Went to my friends today and his fuel pressure gauge does not fit my truck, maybe because its for big Diesel rigs. Anyhow, we checked the plugs and #3 and #4 were BLACK. the rest were normalish brown. Replaced all plugs again with AC Delco plugs, and still having the same issue. Compression was checked on #2 and #4 cylinders since they were easy to access and we were running out of time so I did not get to check all of them. Compression on #2 is 110PSI and #4 is 90PSI. We pulled up on his diagnostic computer the misfire page and at idle, the #3 does not fire period. It just continues to give a misfire. The #4 will also misfire, but will fire now and then and nowhere near as bad as the #3. IF engine speed is increased the misfires disappear from the diagnostic screen, completely. Engine runs smooth and shows NO misfires on any cylinders!

We removed the plug wire from #4 and #3 and tested both with an external spark plug tester and were getting good spark, so there is no ignition issue there. With the #3 plug wire removed, the engine runs no different than with it connected which leads me to believe that either its A: getting totally flooded out, since you can smell the fuel in the exhaust. or B: its lost so much compression, that at low RPM it just wont do anything. The diagnostic computer my friend has allows you to do an array of tests on the engine and engine management systems. One neat test is a fuel pump relay test. You can continue to keep hitting the enable button to prime the fuel pump with the key on. We did this continually trying to see if we could flood the engine out, should the injector be leaking and had no success. You can smell some fuel in the intake manifold if you open the butterfly but nothing increased with the continual running of the fuel pump, and no visible fluid was found inside the intake thru the throttle body.

I will be renting the fuel pressure gauge if I can tomorrow before I go to Delaware for a week for work and get those numbers to add to the mix, but I am starting to lean towards the fact that I have most likely have lost compression on this engine and its a lost cause citing the data I found off the #2 and #4 cylinders.