1985 Manual misfiring
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
I know you get what you pay for, but I'd rather not buy a super-expensive timing light if possible. Amazon is my friend, as I get amazon points and gift cards from work all the time. Can someone recommend a decent one that won't break the bank?
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Team Owner
Joined: Jul 2004
Posts: 28,497
Likes: 3,298
From: Hartford WI
If you get the basic timing light, it might be harder to read for older eyes so I'd get one which can advance your timing reading. So when I turn mine on, not only do I get a tach, my light flashes when it is at the 6 degree mark. That said, I can advance my timing light so that when the light comes on, the mark is at the 0 mark, making it easier. Especially when you want an odd degree like say 5 or 7 or 9 degrees.
Burning Brakes
Joined: Nov 2016
Posts: 761
Likes: 79
From: Buchanan GA
$190 for a rebuilt set from FIC. I wouldn't even worry about what you have in their now, go ahead and replace them. Mine were blue.
Last edited by Silver85; Mar 20, 2017 at 12:33 PM.
Instructor
Joined: Dec 2016
Posts: 241
Likes: 77
From: Arlington VA
Some new info-I got the gauges working, and I'm getting a whopping 8 MILES to the gallon! whoop!
I feel like that's a little low considering I'm driving it like my grandma (who is not the little old lady from Pasadena).
I'm pretty sure it's related to the misfire. I'm actually not getting any codes on the ECM anymore (that's a good thing, right?) so I think as far as it is concerned, we're running pretty well. I still haven't done the compression test or checked timing, have to buy the stuff to do that first. Just thought the high fuel consumption might be a clue to what's happening.
I feel like that's a little low considering I'm driving it like my grandma (who is not the little old lady from Pasadena).
I'm pretty sure it's related to the misfire. I'm actually not getting any codes on the ECM anymore (that's a good thing, right?) so I think as far as it is concerned, we're running pretty well. I still haven't done the compression test or checked timing, have to buy the stuff to do that first. Just thought the high fuel consumption might be a clue to what's happening.
Good to hear you're making progress. Get all the basics done/fixed/set and it'll be easier to find bigger problems if there are any.
Team Owner
Joined: Jul 2004
Posts: 28,497
Likes: 3,298
From: Hartford WI
Possible. Did you reset the fuel usage? I get about 8-10 when I've been working on the car, a bunch of idling and quick trips around the block bring that number down. When I'm not messing with it I can manage 12-15 around town and 20-21 on the highway. That is if I stay out of the gas!
Good to hear you're making progress. Get all the basics done/fixed/set and it'll be easier to find bigger problems if there are any.
Good to hear you're making progress. Get all the basics done/fixed/set and it'll be easier to find bigger problems if there are any.
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Burning Brakes
Joined: Nov 2016
Posts: 761
Likes: 79
From: Buchanan GA
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Team Owner
Joined: Jul 2004
Posts: 28,497
Likes: 3,298
From: Hartford WI
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
But seriously, thanks, I'll try to calculate manually. Although with all the testing of stuff I'm doing I know it's gonna kill the MPG anyway.
Team Owner
Joined: Jul 2004
Posts: 28,497
Likes: 3,298
From: Hartford WI
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Took the car to good mechanic I know-he drove it for about 2 minutes and came back and told me he thinks the problem is an aftermarket cam that's wrong for the car. He says it's running on all 8 cylinders but that cam is throwing the timing way off, especially in lower RPM range. from 1500-2000 is really rough, but by 3000 RPM the engine runs near perfectly.
This goes well beyond my current skill level. I'm willing to do the repair, but...
1-What is the difficulty of swapping the cam out? Anyone aware of a good writeup for this job?
2-How accurate do you think this diagnosis is? I highly trust this mechanic and he's very good, but I still am looking for opinions.
3-While I'm taking all of this apart, any other suggestions for things to take care of?
Thanks guys!
This goes well beyond my current skill level. I'm willing to do the repair, but...
1-What is the difficulty of swapping the cam out? Anyone aware of a good writeup for this job?
2-How accurate do you think this diagnosis is? I highly trust this mechanic and he's very good, but I still am looking for opinions.
3-While I'm taking all of this apart, any other suggestions for things to take care of?
Thanks guys!
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
Likes: 1,174
From: Southlake, TX
Before you put your car under the knife, can you post a decent video of your engine running through the RPM range. Sound is super important along with the video. We need to see idle, increasing RPMs and when it "smooths out." Please shoot video of the engine itself and not from the driver seat.
You mechanic is undoubtedly honest and knowledgeable, but these cars are over 30 years and unless this guy has been working on them for that long, it may be real easy to make a misinterpretation.
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
Swapping a cam is tantamount to out-patient surgery. Doable and relatively minor, but still something gets cuts, bleeds and needs to heal.
Before you put your car under the knife, can you post a decent video of your engine running through the RPM range. Sound is super important along with the video. We need to see idle, increasing RPMs and when it "smooths out." Please shoot video of the engine itself and not from the driver seat.
You mechanic is undoubtedly honest and knowledgeable, but these cars are over 30 years and unless this guy has been working on them for that long, it may be real easy to make a misinterpretation.
Before you put your car under the knife, can you post a decent video of your engine running through the RPM range. Sound is super important along with the video. We need to see idle, increasing RPMs and when it "smooths out." Please shoot video of the engine itself and not from the driver seat.
You mechanic is undoubtedly honest and knowledgeable, but these cars are over 30 years and unless this guy has been working on them for that long, it may be real easy to make a misinterpretation.
It's considerably more pronounced when going down the road and the engine is under load, rather than just revving in neutral.
There have been a lot of hands on this car, so it's a mystery if someone has messed with something else.
Thanks for being willing to take a look! You guys are the best!
Burning Brakes
Joined: Nov 2016
Posts: 761
Likes: 79
From: Buchanan GA
If I were in your shoes I would spring for a scan tool to really see what's going on. Looks like a mt2500 on ebay used is in the $150 range? I'm betting you can turn around and resell it when you are done with it for about the same amount.
Oil Producer
Joined: Apr 2014
Posts: 9,380
Likes: 2,744
Took the car to good mechanic I know-he drove it for about 2 minutes and came back and told me he thinks the problem is an aftermarket cam that's wrong for the car. He says it's running on all 8 cylinders but that cam is throwing the timing way off, especially in lower RPM range. from 1500-2000 is really rough, but by 3000 RPM the engine runs near perfectly.
This goes well beyond my current skill level. I'm willing to do the repair, but...
1-What is the difficulty of swapping the cam out? Anyone aware of a good writeup for this job?
2-How accurate do you think this diagnosis is? I highly trust this mechanic and he's very good, but I still am looking for opinions.
3-While I'm taking all of this apart, any other suggestions for things to take care of?
Thanks guys!
This goes well beyond my current skill level. I'm willing to do the repair, but...
1-What is the difficulty of swapping the cam out? Anyone aware of a good writeup for this job?
2-How accurate do you think this diagnosis is? I highly trust this mechanic and he's very good, but I still am looking for opinions.
3-While I'm taking all of this apart, any other suggestions for things to take care of?
Thanks guys!
realize though, that this will create a bunch of while you're in there type of things. And that is OK. But the job is going to become more than just a cam swap. It's important to be honest about that. Fasteners are going to break hoses will be discovered to be rotten. gaskets will have to be replaced, they'll be many things that will be fun and enjoyable to do if you have the time and financial resources to purchase the required components.Personally I would enlist the help as offered by Bill and others. I would take as many videos as possible and post them here.Normally I would recommend that you invest $40 in the ALDL cable and use the free tuner pro RT software. however the 1985 car does not possess the capability of being recorded at normal operating conditions. The only way to view the 1985 car on a scanner, is what's called field test mode, and unfortunately field test mode commands dez. M to make some changes. I believe it retards timing as well as holds an idol to 1000 RPM and I believe it also gets rid of the knock sensor monitoring. There are other things it does as well. Unfortunately the 1985 computer Will not allow us to view it and scan it while it is in normal operating mode. The reason this sucks, is because there's no way for us to record a data trace well you're car is experiencing the problem is. It may still experience the Misses well it is in field test mode at 1000 RPM, but so many of the other sensors are being told to hold certain levels that we cannot get a clear picture of what is happening during normal operating procedures. I discovered this with my 1985. starting in 1986, you can view the computer and record what's happening in the car well normally driving down the road.All this to say that before proceeding I would take as many videos and upload them to YouTube using your iPhone or your android phone and accept the help of guys like Bill.
edit: furthermore I would like to agree with Bill, your mechanic maybe trustworthy and I'm sure he is. However if he does not have experience working on C4 Corvettes, specifically early ones with the L 98, unfortunately honestly doesn't matter. You may have somebody close by you on this forum that might be able to help dial it in. And well that person may not be a professional mechanic, the specific experience with the C-4 Corvette is more valuable than being a professional mechanic. I would reach out for help on the forum for people close to your proximity.
edit: furthermore I would like to agree with Bill, your mechanic maybe trustworthy and I'm sure he is. However if he does not have experience working on C4 Corvettes, specifically early ones with the L 98, unfortunately honestly doesn't matter. You may have somebody close by you on this forum that might be able to help dial it in. And well that person may not be a professional mechanic, the specific experience with the C-4 Corvette is more valuable than being a professional mechanic. I would reach out for help on the forum for people close to your proximity.
Last edited by VikingTrad3r; Mar 22, 2017 at 12:09 PM.
Thread Starter
Drifting
Joined: Mar 2017
Posts: 1,897
Likes: 165
From: Nashville TN
2017 C4 of Year Finalist
you can definitely do it. I assume the car is not a daily driver.
realize though, that this will create a bunch of while you're in there type of things. And that is OK. But the job is going to become more than just a cam swap. It's important to be honest about that. Fasteners are going to break hoses will be discovered to be rotten. gaskets will have to be replaced, they'll be many things that will be fun and enjoyable to do if you have the time and financial resources to purchase the required components.Personally I would enlist the help as offered by Bill and others. I would take as many videos as possible and post them here.Normally I would recommend that you invest $40 in the ALDL cable and use the free tuner pro RT software. however the 1985 car does not possess the capability of being recorded at normal operating conditions. The only way to view the 1985 car on a scanner, is what's called field test mode, and unfortunately field test mode commands dez. M to make some changes. I believe it retards timing as well as holds an idol to 1000 RPM and I believe it also gets rid of the knock sensor monitoring. There are other things it does as well. Unfortunately the 1985 computer Will not allow us to view it and scan it while it is in normal operating mode. The reason this sucks, is because there's no way for us to record a data trace well you're car is experiencing the problem is. It may still experience the Misses well it is in field test mode at 1000 RPM, but so many of the other sensors are being told to hold certain levels that we cannot get a clear picture of what is happening during normal operating procedures. I discovered this with my 1985. starting in 1986, you can view the computer and record what's happening in the car well normally driving down the road.All this to say that before proceeding I would take as many videos and upload them to YouTube using your iPhone or your android phone and accept the help of guys like Bill.
edit: furthermore I would like to agree with Bill, your mechanic maybe trustworthy and I'm sure he is. However if he does not have experience working on C4 Corvettes, specifically early ones with the L 98, unfortunately honestly doesn't matter. You may have somebody close by you on this forum that might be able to help dial it in. And well that person may not be a professional mechanic, the specific experience with the C-4 Corvette is more valuable than being a professional mechanic. I would reach out for help on the forum for people close to your proximity.
edit: furthermore I would like to agree with Bill, your mechanic maybe trustworthy and I'm sure he is. However if he does not have experience working on C4 Corvettes, specifically early ones with the L 98, unfortunately honestly doesn't matter. You may have somebody close by you on this forum that might be able to help dial it in. And well that person may not be a professional mechanic, the specific experience with the C-4 Corvette is more valuable than being a professional mechanic. I would reach out for help on the forum for people close to your proximity.
I also happen to be a professional wedding videographer, so...recording audio/video isn't an issue! Small victory there, at least.