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I'm new to corvettes. I picked up my 85 z51 about 2 months ago. The car sat for 15-20 years without moving. I cleaned the fuel tank replaced the fuel level sending unit and housing a well as the pump. After putting in a new battery the car starts and runs but it ran super rich and would not rev above 2.5k. I have done many different parts on many occasions and can't remember what I did on each occasion so I'll lump them into 1. The car has new injectors and fuel regulator and fuel filter. It has a new coolant temp sensor. A 9th injector delete. A smog pump delete. It also has new spark plugs wires and cap and rotor. The car idles but if I ease into the throttle I can get it up to about 2300 but if I go wide open it bogs and sits at 1.5k while doing this there is white smoke and a very strong rich smell. When I tried to pull codes I got a 34. I followed another procedure that said to disconnect the maf and battery for ten second reconnect the battery (leaving maf unplugged) run car at 2.3k for 1 minute (more like 2k for me) re-pull codes. I then get a code 33. Its an 85 so maf sensors run about $150-250. I want to be sure before I spend anymore money. Anyone have any ideas on what I should start with/check? The car only had 35k miles btw if it help narrow anything.
Last edited by Skylerjm1209; 09-22-2018 at 05:00 PM.
Reason: Missed Some Info
After replacing the maf no codes. Haven't had a chance to get a fuel pressure gauge on it but the whole fuel system has been replaced besides the tank itself and lines and the fuel rail
After replacing the maf no codes. Haven't had a chance to get a fuel pressure gauge on it but the whole fuel system has been replaced besides the tank itself and lines and the fuel rail
Could still be a bad injector.. Even if new.
I had a bad PCM that behaved exactly the same way once.
Hello All,
"this there is white smoke and a very strong rich smell"
white smoke means water/coolant, sickly sweet "rich" means burning coolant.
Blue smoke means oil.
Black smoke means rich/fuel.
Just my 2 cents.
Thanks
Welcome to the Corvette Forum! We are glad you have joined us here!
Check your oxygen sensor, they go bad from sitting around. We are supposed to replace them after every 50k miles according to the manufacturers. I suspect that yours has corroded over or failed somehow. It is what controls the air/fuel mixture when the car is running in the closed mode. Do the problems occur when in your car is in the "open mode" or the "closed mode"?
Did you verify that your new Coolant temperature Sensor is working properly? A bad sensor would have the wrong information going to your ECM which might think it is cold and the car needs extra fuel to start up or it might think that the engine is hot and doesn't need any extra fuel. Incorrect readings make for big problems, take a Volt Ohm meter and test the resistance and verify that your new sensor is in the right range temperature wise. We have seen people buy and install the wrong or even defective sensors.
On my 1988 C4 I believe that I have two coolant temperature sensors, one is for the gauge and the other is for the computer. I even believe that the out-puts are different, one is a simple type that you can calculate the temperature from a chart using the resistance to indicate the actual temperature reading. The one for the computer is a 0-5 volt type that uses a "reference" voltage in calculating the temperature. Needless to say they are not interchangeable. This is one of the reasons that ground straps are so important on these cars, if you don't have a solid ground on the engine then you are going to have problems. Be sure all the grounds are working properly.
A plugged or blocked catalytic converter will cause rev-limiting problems as well. Remove the O2 sensor and see if there is excessive back-pressure in your exhaust system. If there is any kind of blockage you will know right away as all the exhaust will try to come out of the O2 bung. If the car revs better without the O2 sensor installed you might have a bad catalytic converter or blocked muffler.
The white smoke could be stuff burning or trying to burn off in your catalytic converter. White smoke that smells like coolant is REALLY bad news as it means you have a head gasket failure. White smoke is frequently just steam coming out of the exhaust system, if there is water in the pipes it might make steam a bit longer than usual.
Over time catalytic converters do get plugged up naturally as I left a car while I went on a several month boat trip and when I got back the car would start and idle just fine. When you pushed the gas it would just cough and sputter. I opened the hood and as I hit the gas a balloon appeared in my engine compartment, it turned out to be a rubber cap on a "sniffer" pipe that went to the exhaust ahead of the catalytic. I removed the cap and was able to drive at no more than 25 mph but I made it to a gas Station who removed the catalytic converter and re-installed it. I took the converter out behind his shop with a long screwdriver and a hammer and broke the ceramic piece into a zillion pieces before re-installing it. That same day I drove 400 miles and never had any problems after that. That particular car actually passed emissions without a catalytic Converter.....
Take a look at the points I mentioned, I hope that I can help you in some way. Corvettes are so much more fun on the highway than in your shop! I wish you the best in solving this issue! Be sure to tell us what it was when you figure it out!
Thanks I'll have to check those. I'm currently a full time student and only get a day to work on the car here or there so I only get a few things done each weekend but I'll definitely check those out and continue updating this thread
I pulled the cat off and it ran a million times better. It has plenty of power and can rev to near redline but only for a few minutes before it goes back to the way it was before bogging down when put into gear and not being able to go uphill or give more than 15% throttle before it bogs and dies.
I figured while is was all pulled apart i would install new headers (hedman longtubes) and do an egr delete. I also replaced the apparently stuck pcv valve ill updated either later this weekend or next weekend.
welcome....lot's of very knowledgeable guys here with 85's.......guessing you've eliminated a few vacuum lines, I'd recheck for leaks and check the tps then the timing...stock is 6, if you want a little boost, go to 8.....essential to an 85 is a fuel pressure gauge....hooked to the schlader valve on the passenger fuel rail......not very much at any parts store....tape it to the windshield until you've found the problem....36-38 psi......there are quite a few steps involved in setting the idle...it's covered in several threads here or in your fsm...assuming you have one...you'll need one....e-bay.....good luck.....
Fuel Pressure Regulator case cause that. Check the vacuum hose to it for gas and if there is gas then check your oil because this can cause the oil to be diluted with gas.
I had the same problem many, many years ago. ECM/PCM was the problem. Hesitating, bucking, stalling, cutting out completely - running way rich (soot on my bumper). Total mess making the car scary to drive. Prob explains why your car sat for so long. Dealer finally "fixed" it after multiple visits. They threw parts at it until it was solved. I am sure you have other fuel related problems given the age of the car (injectors, ruptured puslator) but my money is on the bad pcm.
Sorry about the late update (work/school) I replaced the fuel tank and put new fuel in aswell as another new fuel filter and another set if spark plugs. The car ran great that weekend I drove it around and took it to a trunk or treat. Later in the weekend though I was driving it to the dmv to get it registered. I stuffed some mufflers on after the headers in order to try to quite it down a but so I could drive it. The driver side muffler was a little close to the transmission linkage. On my way there I lost reverse and neutral. This caused the car to sit for the rest of fall and now that were getting back into cold weather ~30° during the day the car barely runs when it ran really well before. I heard about a retaining clip in the 700r4 that when it breaks you lose reverse and neutral. Anyone know about this. Also what should I do to improve the way it runs in cold weather? I dont plan to actually drive it this winter but just so I can move it around without it possibly dying.
have you verified fuel pressure while its chtting out?
you have spent alot of money throwing parts at it.
fuel pressure gauge can be installed and taped to your window while revving engine and verify u have fuel pressure.
then id be verifying timing/spark
because u had a bit of success after running with a removed cat, it is possible it is related to o2 sensor, though im just guessing. I can only say that removing the cat would have increased flow and kept the o2 a bit cooler for a bit longer. so perhaps its related.
have you verified fuel pressure while its chtting out?
you have spent alot of money throwing parts at it.
fuel pressure gauge can be installed and taped to your window while revving engine and verify u have fuel pressure.
then id be verifying timing/spark
because u had a bit of success after running with a removed cat, it is possible it is related to o2 sensor, though im just guessing. I can only say that removing the cat would have increased flow and kept the o2 a bit cooler for a bit longer. so perhaps its related.
as for your fwd/reverse, ive never heard this.
I've used a fuel pressure gauge it sits pretty steady at 40psi the car also has a new o2 sensor right now the car is running long tube headers with the o2 mounted right before the collector ball and socket joint. And is open header
Fuel Pressure Regulator case cause that. Check the vacuum hose to it for gas and if there is gas then check your oil because this can cause the oil to be diluted with gas.
09-22-2018, 04:58 PM
Poor Running 85. Limp Mode?
