5.7L Engine Miss. Very Frustrated! Tried Everything.

Hello,I am a new member.I have a '94 4x4 silverado 1500.I am having a problem with a miss in the engine.I had a mechanic that works for a GM dealership to look at it.He scanned it and his scanner found no problems with it.It idles fine but when you give it a little throttle,it starts to miss and tries to stall.Its like it loses ignition totally or fuel flow.He unhooked the hose from the egr solenoid and it would run smoothly when giving it throttle but would still cut out and miss while driving it.I replaced the solenoid and that did not fix the problem.He also noticed the fuel pressure regulator was leaking so i replaced that too but it did not fix the problem.The fuel pump,fuel filter,and distributor were all replaced about 15 months ago as well as the coil and it ran fine until about 2 months ago then it started having the miss gradually.I have tried different plug wires ,new rotor and dist. cap and new plugs and nothing seems to help.The engine starts getting the miss after it warms up when sitting still and misses at all times when driving.The engine is a 5.7L with TBI.Any help with this would be greatly appreciated as i have tried everything i can think of.
Thank You,
John

Hello John,
I have the exact same problem w/ my 95 G20 van w/ 5.7 TBI. I just purchased the van. I tuned it up. Still lugs. Have you fixed the problem yet? Anyone else with this problem? Solutions?
Thanks

It may be a knock sensor. I don't know for sure, but I know a bad one will make it run rough.

Hello,
I have a 1997 Silverado K2500 4x4 with the Vortec 454 5 speed standard having the same problem. I've replaced the plugs, wires, cap, rotor and knock sensors with no improvement. It'll smoke the tires thru 4th till it warms up then gets a dead miss and will hardly move out of it's own way. Anyone with any idea's would be greatly appreciated.

It could be the timing not adjusting after intial warm up. I don't know what would do that though. You may want to call a good shop and ask for suggestions. If it has happened to 3 of you undoubtedly in diferent areas that almost has to rule out bad gas. You might also ask if cam sensor going out could cause this and have the computer not firing the cylinders at the right time. I'm sorry but I am just as lost as all of you on this one.

I have heard of the cam sensor causing this on other trucks. I'm putting the truck on a diagnostic computer Sat morning for a full workup. I'll post what I find when I get home. By the way, I'm in North Texas and gas quality is fairly good around here.

A cam sensor seems to be about the only other thing I can think of. If it dosen't cost to much and it isn't hard to get to you may want to replace it anyway.
Let us know what you find out re_boot1

OK, ran a full diagnostic on the truck. narrowed it down to the in-tank feul pump. The computer reads that all of the electronic components of the pump are running at optimal, but a pressure guage connected to the feul rail on the intake showed the pressure was 58psi at an idle and it dropped to 45@ 2000 rpms. 58psi is minimal for a big block, 60 is optimal. The book shows the small block should be around 50 to 55 psi for optimal pressure. The drop in feul pressure causes the engine to lean out under a load such as accelerating and pulling and could cause the engine to burn a piston from the increased cyllinder temp. The pump for mine is $150 at the dealership and it's easier to lift the bed and slide it back than to drop the tank. Hope this helps.

Guys I have been chasing this exact same problem and finally cured mine but not saying it will cure your problem. I have a 98 GMC K1500. I replaced the plugs with OEM AC Delcos and that did not fix it. I replaced the cap and rotor with OEM AC Delco and that did not fix it but that did need to be done, a lot of build up on the points. I then went in and replaced the coil and plug wires with MSD parts and that finally seemed to fix the stalling problem. Now the truck seems to run better than it ever has.

One other thing that I did that may have helped. When I replaced the coil there is a little electronic box with a heat sink on it mounted to the same bracket as the coil(sorry, I forgot what this part was called). I removed this and the heat sink from the bracket, cleaned it up because it looked as though it had heat sink compound on it, the same compound that I use on my home computer CPU heat sink. I put a new layer of compound on it and then remounted it.

Now one or all of these things might have fixed it but not sure which one but I have driven over 1000 miles and still works great.

Good Luck!

Hey,
I Am The One That Posted The Orig. Message.Since Then I Have Replaced The EGR Valve itself And that seems to have fixed the problem with it idling smoothly but cutting out when you rev it up.But it still runs rough when you drive it.Rough When you start going but as you gain rpm it runs smooth thenwhen you are at speed and the rpm drops back down you can feel it jerking like it is cutting out.I also replaced the timing chain which it did need but it did not fix the problem.I Had a guy check it with OBD I Scanner and he cannot find anything wrong with it.Since April I have replaced:EGR valve,EGR valve Solenoid,dist. cap,rotor.,plugs,plug wires,fuel pressure regulator,MAP sensor,Alternator,and timing chain.I have even redone the engine from the heads up with new head gaskets and all related gaskets from there up and adjusted the valves 2 or 3 times but i am still having problems.Within the last 2 years I have replaced the Fuel pump,distributor,and throttle pos. sensor and probably more stuff i cant even think of.where mine is a '94 i dont think it has a knock sensor,camshaft pos. sensor,or crankshaft pos. sensor and everything changed for '96 and after.well, I Thought I'd Give Y'all an update
P.S. The guy that checked it with the scanner said maybe it could be the computer (ECM) but i dont want to pay $100.00 and that not fix the problem.Hopefully I Didnt cause a vacuum leak after i put it back together after doing the head gaskets.

P.S.
I Have also replaced the coil with no luck.

Could be a possible fuel injector(s) going bad. When 1 fuel injector is going bad, it gets too hot and will foul out, causing a miss. It can also cause other fuel injectors to foul out too, but that is some what rare. Fuel injectors can be tested w/an ohms meter. Sometimes even running a really top of the line fuel cleaner in your tank will clean things up too. I have a 1997 1/2 ton 350 Vortech and when I had this problem it was the distributor cap. It had a hair line crack in it that could only be seen under magnification. I still have the truck and it is running great. Keep me posted if you would w/what ever solves your problem.

Good luck

Ryan

i have this same problem on my 89 chevrolet. i replaced the fuel filter, fuel pump, and ran some fuel injector cleaner through a tank of gas. the problem has not improved one bit. i am going to soon replace my throttle body, and maybe that will help. if not, im going to take it to a shop.

Wow you people love to throw parts at cars. I know it's hard to put them in the shop but if you honestly don't know how to diagnose the car then don't waist your money. Now you have thrown all this money into which probly most of the parts probly didn't even need to be changed and then you might even have to put it into the shop. Just doesn't seem very smart to me.

For the guy who started the thread have you even checked for vacume leak yet? Easy way is to take a spray bottle full of water and spray down the vacume lines and listen for the motor to change rpm some.

I would also check the fuel injector to see if they are spraying good. Take off the breather and hook up a timing light to one of the spark plugs and aim the light at the throttle body. You should be able to see spray the fuel injectors are putting. You should look like a mist and be very consitant and uniform. I would suggest this also to the guy above with the 89.

I have to say that sometimes you are right NCHEVYHEVN but when this happened to my truck I did go to the dealer and they could not find anything wrong. It seemed if they could not plug into the ECM and find the problem there wasn't one. Oh, and this happened at two dealerships. I fully agree with SS70CHEV about the hair line crack especially if you went back with AC Delco cap. They have had some problems with this over the years. I feel your pain on this one dartlord2001, it does not seem like much is left for you to try.

Well if 2 dealerships can't figure out why an older motor is missing then well their idiots. Their are only a few things to make it miss so not sure why they couldn't figure it out.

I know their are hack techs. or well they shouldn't even be allowed to be called techs. but parts changers that have no idea what they are doing. It sucks cause it gives all the other techs. a bad name.

The only reason I don't take things to a dealership is because I don't trust them and half the time they don't fix things the way they should. I recall NCHEVYHEVN even saying that at 2 dealerships he knows of they will not change a tranny filter. The rest of the time it is like yekots says, they won't try to fix it or just say their is nothing wrong with it.
I would much rather take it to a mechanic I know because they will fix it right and do what I ask.

Yea, if your mechanic knows his stuff then definatly take it to him. When you take it to the dealership it's kinda hit or miss when finding a trusty mechanic that knows his/her stuff.

I'll admit their are complete idiots in dealerships that have no idea what's going on and they refuse to keep up on the technology. Then their are super smart guys that will treat your car better than their own.

I just see alot of times that dealerships are better at finding the harder problems because they have the training/technology at their hands unlike a smaller local shop that may not know how something works on a certain brand of vehicle.

i am steadily putting performance parts on my truck, and at the same time, hoping they will fix the problem...

i just put in my 670cfm throttle body...the problem is still there. when the truck gets hot, thats when it starts...third gear is so bumpy and misses all the time.

do you guys think it could be an oxygen sensor? it really does affect the performance of your vehicle...im sick of it, and have tried it all.

I have never seen an oxygen sensor make anything run bad (rough/miss/ect). It's not the greatest thing to do, but they will only make them run a little rich or lean.

well, i finally called a shop, and im going in tomorrow morning. he said more thank likely, its something very minor and he would have to drive it to tell. i hope all goes well. he also said if it happens more when your going up hill, its probably your spark plug wires...this might be my case...ZT.

I DON'T KNOW IF YOU ARE STILL HAVING THIS PROBLEM, SEEING THAT YOUR POST WAS IN MAY. HOWEVER, I WOULD LIKE TO HELP. I HAVE A 97 Z-71 WITH 5.7. I INSTALLED A NEW GM CRATE MOTOR IN 10/04. SEVERAL MONTHS LATER, I BEGAN TO HAVE A MISSFIRE IN CYLINDER 8 AND 6. CYLINDER 8 MISSFIRE WAS CONSTANT, WHILE CYLINDER 6 WAS JUST EVERY ONCE IN A WHILE. THIS PROBLEM WOULD ONLY OCCUR AFTER THE ENGINE WARM-UP PHASE. THE ENGINE RAN PERFECT WHILE COLD. I WAS ALSO HAVING AN OIL CONSUMPTION PROBLEM. I PULLED ALL OF THE SPARK PLUGS TO FIND THAT 6 AND 8 WERE OIL AND FUEL SOAKED. A COMPRESSION TEST REVEALED 6 AND 8 WERE LOWER THAN THE OTHER CYLINDERS, BUT THEY WERE STILL IN SPEC. WHILE REMOVING THE INTAKE MANIFOLD, THE BOLT CLOSEST TO 6 AND 8 CAME LOOSE WAY TO EASILY. ONCE I REMOVED THE INTAKE, THE GASKET AROUND 6 AND 8 HAD BEEN PULLED DOWN BY ENGINE VACUUM SECONDARY TO THAT LOOSE BOLT. THIS ALLOWED FOR THE MISFIRE IN THOSE 2 CYLINDERS WITH 8 BEING THE WORST. THIS ALSO EXPLAINED THE OIL CONSUMPTION BECAUSE OF THE GAP CAUSED BY THE DISPLACEMENT OF THE INTAKE GASKET. I BELIEVE THAT THE EXPLANATION OF THE ENGINE ONLY MISFIRING WHILE WARM: WHILE COLD, THE INTAKE SITS FLAT ON THE GASKET, CREATING A GOOD SEAL. UPON WARM-UP, THAT ALUMINUM EXPANDS AND CAUSES A GAP, ALLOWING CONDITIONS FOR A MISFIRE. MY SOLUTION: WHEN I INSTALLED MY CRATE MOTOR,
I WAS VERY PRECISE WITH MY TORQUE SPECS, BEING A FORMER BMW MASTER TECH. HOWEVER, WHEN I TORQUED MY INTAKE BOLTS, I USED JUST WHATEVER LOCTITE I HAD IN MY TOOL BOX. I BELIEVE THIS IS WHY THE BOLT BACKED OUT. BE SURE TO USE THE APPROPRIATE HIGH TEMP LOCTITE SO THIS DOES NOT RE-OCCUR AND OF COURSE, TORQUE TO PROPER SPECS IN A STAR PATTERN. HOPE THIS HELPS.

dartlord2001
What did the first set of plugs look like when you pulled them? I only ask cause it seems like you have done everything you can and should have fixed this by now. But if you have 1 cylinder with a particularly bad set of rings it may be fouling out the plugs, and if one is bad the rest will surely follow suit. Have you done a compression check yet. I can't remeber for sure but I think they should each be within 10 psi of each other.

This is a reply to the start of the thread.

My '95 Z-71 is having similar problem. Runs ok, but lacks a little power, until warmed up good. Then has very poor acceleration and sometimes feels like it is even missing. I too suspected EGR valve or EGR solenoid. EGR valve holds vacuum with engine off, but doesn't hold with engine on. The lines hold vacuum all the way to the EGR valve. I replaced both the EGR valve and the EGR solenoid. Nothing changed. It was also overheating a bit with the A/C turned on. For grins, I changed the thermostat and the fuel filter. Doesn't overheat any more but still have the power problem.

The only thing I have been able to do to get the engine to run ok again was to disconnect the vacuum line to the EGR Solenoid and plug it.

chevyblues

Hey
This is the one that posted the orig. thread. as I said before,I had a guy check my truck with a scanner and he found no problems.I found an advance auto parts with an OBD I scanner.They checked it and their scanner showed a code 42.The printout says Ign System problem-Elec spark timing circuit fault.They said a knock sensor could cause this but they didnt know that for sure.My Haynes manual says knock sensor problem would be code 43.I have tried to locate the elec spark control on the motor but I cant find it.The Haynes manual shows it right by the TBI on the right side but its not there on mine.I cant find the 4 wire plug for it either.Is anyone familiar with this?The truck is a '94 W/5.7L
Thanks