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After continuous work, a vacation to Nashville with a corvette museum, and more work on the Corvette it still does not run right. So far, plugs and wires, coil, cap and rotor have all been replaced. The MAF has been replaced because the Snap On scanner we used showed Code 33. As of today, it still backfires out of the plenum, shows code 33, and is running lean. Any ideas?
More great news, the condenser has a hole in it so after two attempts of charging the A/C and lubricating the compressor, that is still not working and on hold until the car runs right.
After continuous work, a vacation to Nashville with a corvette museum, and more work on the Corvette it still does not run right. So far, plugs and wires, coil, cap and rotor have all been replaced. The MAF has been replaced because the Snap On scanner we used showed Code 33. As of today, it still backfires out of the plenum, shows code 33, and is running lean. Any ideas?
More great news, the condenser has a hole in it so after two attempts of charging the A/C and lubricating the compressor, that is still not working and on hold until the car runs right.
This may not help but I recently had my pu (Toyota) give me fits and everything you did was done plus a bunch more (super duper fuel injector cleaning $100 and even pulled the gas tank. Turned out to be the O2 sensor.
This may not help but I recently had my pu (Toyota) give me fits and everything you did was done plus a bunch more (super duper fuel injector cleaning $100 and even pulled the gas tank. Turned out to be the O2 sensor.
I just picked up a new O2 sensor, so I'll work on getting that out in and we'll see what happens. It definitely can't hurt and for $20 it's not breaking the bank either.
I was going to say it might be the injectors if you have not replaced them already, BUT you said it back fires out the plenum. Have you verified timing? Make sure that your dizzy hasn't moved around on you a little.
I was going to say it might be the injectors if you have not replaced them already, BUT you said it back fires out the plenum. Have you verified timing? Make sure that your dizzy hasn't moved around on you a little.
Today my dad and I went back at it with a timing light. Neither of us were familiar enough with it to judge well enough, but we believed the timing was still right. We checked the order of plugs and wires, all of which were correct. The ignition system has pretty much all been replaced. It idles much better and runs well at high RPMs, but there is still a small amount of plenum backfire and a miss under low RPMs and light acceleration.
Today my dad and I went back at it with a timing light. Neither of us were familiar enough with it to judge well enough, but we believed the timing was still right. We checked the order of plugs and wires, all of which were correct. The ignition system has pretty much all been replaced. It idles much better and runs well at high RPMs, but there is still a small amount of plenum backfire and a miss under low RPMs and light acceleration.
Did you make sure you unplugged the electronic vacuum advance wire when you checked timing? Should be an easily accessible tan? wire near the dizzy. Just trying to go through everything and be sure. If that checks out, I would unplug each injector one by one and see if the miss changes at all when you kill cylinders one at a time.
Could there be other vacuum lines leaking? Check the condition of all the vacuum lines. On mine, after 16 years in 2012, a lot of them were rotting and splitting.
Code 33 - could be a MAF sensor. Here's a link to another forum's thread about the differences between MAFs for different years. You may want to check it out. http://www.thirdgen.org/forums/tech-...ible-code.html
Have you tested the EGR system? Another member had an ongoing problem with low rpm hesitation and even though the EGR valve seemed to be okay, it still ended up being the valve. After replacement with a new one, it solved the problem. He used an AC Delco replacement if I remember correctly. And sometimes they don't set a code when they are sticking or the passages aren't clogged completely. I had a hesitation problem for years on an F150 I couldn't figure out and only after it set a code was I able to track it down to a stuck EGR valve and clogged passages.
Here's an article about EGR systems on C4 Corvettes with a corrective post after it by our own Cliff Harris.
So I just went out and started the car, and the usual symptoms are back. It just bucks down and RPMs drop under and sort of throttle, it still has a miss in it and it did not sound right at mid range RPMs either. The backfire is still out of the plenum and the car is still running lean based on smell. As far as the stuff that has been replaced: plugs, wires, coil, cap, rotor, ignition module, MAF and the upstream O2 sensor. To be checked again is the timing and I just picked up carb cleaner to use to check for vacuum leaks. I'll also try to plug it in to the scanner to check for any new codes, but i would bet its still the 33. The weather is too good right now to not be driving this car! So much for the rush to get the A/C recharged and condenser replaced
So finally I have good news from the project that hopefully someone in the future finds useful. The source of problems described above ended up being the TPS and Idle Control Valve along with a gummed up throttle body. So after replacement parts and cleaning it runs really smooth and shifts even smoother. It feels like the car gained 20 horsepower. It still has a stumble for about 5 minutes or less after start, which might be the cold start injector. All issues clear up after a really short drive though
Last edited by junkyard_dog72; Aug 23, 2016 at 01:08 PM.
So finally I have good news from the project that hopefully someone in the future finds useful. The source of problems described above ended up being the TPS and Idle Control Valve along with a gunned up throttle body. So after replacement parts and cleaning it runs really smooth and shifts even smoother. It feels like the car gained 20 horsepower. It still has a stumble for about 5 minutes or less after start, which might be the cold start injector. All issues clear up after a really short drive though
This weekend my Dad installed the ebay used condenser and my uncle lubricated and charged the system with R12, and the A/C is ice cold! It really is a different car with working A/C and is much better in the August heat. As my uncle said, "I don't care what anyone says, nothing gets cold like 12". It actually got chilly on the drive this morning.
In other project news, it still stumbles for about 5 minutes or so of driving after cold start unless it idles for a bit, but really drives well after that. Hopefully we can get that narrowed down, but right now its just nice to be back behind the wheel. I appreciate all the help and support in this thread and others
This weekend my Dad installed the ebay used condenser and my uncle lubricated and charged the system with R12, and the A/C is ice cold! It really is a different car with working A/C and is much better in the August heat. As my uncle said, "I don't care what anyone says, nothing gets cold like 12". It actually got chilly on the drive this morning.
In other project news, it still stumbles for about 5 minutes or so of driving after cold start unless it idles for a bit, but really drives well after that. Hopefully we can get that narrowed down, but right now its just nice to be back behind the wheel. I appreciate all the help and support in this thread and others
great job. was the smell you were getting the kind that would stick to your clothes after?
great job. was the smell you were getting the kind that would stick to your clothes after?
The exhaust did have that kind of smell that stuck to your clothes, but I don't notice it nearly as much as I used to. Between the 72 and now this 85, I've grown to like it a little bit But after the car was running round I get again, the exhaust started smelling like a normal newer car which I suppose is a good thing.
Last edited by junkyard_dog72; Aug 23, 2016 at 01:12 PM.
Since the last update there has been a few updates to the car. First, it now has about 121,000 miles on it so its definitely being driven. Its running a little bit better after turning on the TPS and lowering the idle from where it was. Its been on a short road trip from Cincinnati to a little North of Dayton and really did well. Theres a bunch of wind noise even though the weatherstripping is new, so theres a little diagnosing there that needs to happen but nothing to worry about now. On the trip it ran well the whole time and stayed cool, which was a nice relief. One of the bigger updates is the new radio installed. Its a Pioneer from Crutchfield with the rest of their kit which includes the front plate and adapter and the install went well. I have also taken it to Cincinnati Cars and Coffee twice, and a few people really liked the car, especially the color and digital dashboard. Now for the pictures:
But after the car was running round I get again, the exhaust started smelling like a normal newer car which I suppose is a good thing.
