| Author | Message | ||
     Thumper74 |
2001 Chevrolet Venture, 3.4L, 2wd, Cali Emission A good friend's Venture was consuming coolant. We pulled the heads to find that there was some pitting/erosion betweeen the coolant jackets and the cylinders on both heads, so we replaced both with reman heads. Since then, there has been a misfire on cylinder 5 and runs like crap. With the head gaskets, we obviously did intake gaskets and fuel injector o-rings. Compression and leakdown tests are normal. We have swapped the coil and wire with no change. I wasn't expecting it to, but it was cheap We found that that the tab on the plenum was cracked so we changed the plenum. That did not help. We redid the lower plenum for shits and giggles with no change. I've been doing this for 15 years and I'm stumped. It's acting like a vacuum leak, but I can't find with starter fluid, propane, or a smoke test. It will misfire badly at idle and at higher rpms, basically off idle, it will smooth right out. The only code we get is for the misfire on cylinder 5. The idle count was maxed out at 255 and we adjusted down to about 100 in gear. Hell, if you up the idle to about 1,000 rpm, the miss goes away. I'm on the verge of pulling the rear head and taking to the machine shop to be looked at, along with the upper and lower intakes to check for cracks. Obviously, I don't want to do that again, so I figured I would check with other people before walking barefoot through hell again. Thanks! | ||
| Reepicheep |
I'm by no means an expert, so take all this with a grain of salt... But did you check the fuel injector? | ||
| Hughlysses |
Bad spark plug? I put brand new plugs in a V-6 Taurus once; apparently I dropped one during the install and cracked the insulator without realizing it. Drove me nuts before I figured out one of my brand-new plugs was bad. (Message edited by Hughlysses on December 04, 2016) | ||
| Hootowl |
+1 on the spark plug. Easy enough to swap out. | ||
| Brother_in_buells |
Spark plug gap correct? Have had this once with a 2.8 v6 blazer that the gap was to small and it was running like crap from idle. | ||
| Glitch |
I had a chevy pickup with a v6. I also had to change the head gasket. After that it wouldn't run. Turned out I had messed up the injectors when I took the intake manifold off. | ||
| Teeps |
Bent pushrod #5? | ||
| Cycleaddict |
Thumper, lean miss up to 1,000k, it has to be a vacumn leak . | ||
| Darth_villar |
Sounds like a fueling problem. Try swapping injectors from cyl 5 to another one, see if the problem persists. If the problem stays on cyl 5 it could be the electrical harness for the injector. Both are pretty easy to do/check. Also, maybe a clogged fuel filter? Doesn't hurt to check. | ||
| Etennuly |
Yeah, I'd start by swapping the plug and injector to a different hole. Don't rely 100% on scanner for code. Are crank and cam sensors sinc'd? Check grounds, connectors, iac/ maf damage. | ||
| Ratbuell |
ALWAYS check wiring when you have that much stuff taken apart...chances are extremely high that something got pinched, pulled, or sliced... | ||
| Bandm |
canister purge valve leaking? EGR valve leaking? what is fuel trim at idle? at 1000 rpm? what is MAF at idle? what is the ECT reading in volts? what is IAT? | ||
| Crusty |
canister purge valve leaking? EGR valve leaking? what is fuel trim at idle? at 1000 rpm? what is MAF at idle? what is the ECT reading in volts? what is IAT? But Professor; who threw those pies? | ||
| Bandm |
Ha Ha, a clown  | ||
| Thumper74 |
To clarify, once you're past idle, it smooths out and gets 21 mph on the highway. It's not acting like fuel or spark. It's acting like vacuum. canister purge valve leaking? No codes, nothing on a smoke test. EGR valve leaking? Nothing on the smoke test, BUT cylinder 5 is the closest, however the EGR is right after the throttle body, so it should affect all cylinders...) what is fuel trim at idle? at 1000 rpm? I don't recall, but I'll get it. what is MAF at idle? I don't recall, but I'll get it. what is the ECT reading in volts? I don't remember, I do remember it was reading the correct temp. what is IAT? It was reading ambient. I'm tempted to swap the injector and see what happens... |
