85 Coupe HELP
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
85 Coupe HELP
I bought a 1985 Red Coupe back in september for 5500, and ever since i had it, it hasn't been performing very well. The car is somewhat hard to start, it cranks for about 4 seconds before firing off. When i first got it i put in a new cap, rotor, plugs, wires, PCV valve, ran 3 tanks of gas with fuel injector cleaner, seafoamed it (smoked like a bitch), cleaned the TB twice, and fuel filter. Helped a little bit. Later, me and my GF's dad set the timing on it to 6 degrees BTDC. (it was at 4) Again, a little improvement. Then about in the middle of october, the MAF went out.(2 days before my 17th birthday) I replaced it with one from Advance Auto Parts (microtech one, i heard that they dont require the burnoff module because it is not a "hot wire" MAF). When i drive it though, the throttle is still not very responsive. I'm pretty sure that im not expecting too much from the car because my other car is a 93 lesabre with the series 1 3800.
TBH, im getting tired of throwing money at it lol im only 17 and i work at a grocery store so i dont have a lot of money to throw around.
TBH, im getting tired of throwing money at it lol im only 17 and i work at a grocery store so i dont have a lot of money to throw around.
Last edited by Pwnage1337; Jan 16, 2009 at 03:30 PM.
Burning Brakes
Joined: Nov 2007
Posts: 1,213
Likes: 2
From: Cincinnati oh
My 85 did the same thing do 2 things check your fuel pressure and fuel volume, I replaced the fuel pump (easy to do) and the fuel pressure regulator I threw a ton of money at mine as well and it turned out to be a simple thing. do your self a favor Buy AC DELCO parts ONLY, you get what you pay for. I bet a hundred bucks this fixes it
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
A few more details may help us help you.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
A few more details may help us help you.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
The stuff you did already to the car is money well spent...good maintenance. Get a hold of a fuel pressure gage and do some pressure checks at the fuel rail before you throw any more money/parts at it. Also check the car for stored engine trouble codes.....for the sensor related issues mentioned above. Other component that may be relevant to your situation and would cause a lot of the same issues you described is clogged cat/s.
Drifting
Joined: Aug 2007
Posts: 1,672
Likes: 0
From: Hereford AZ
My 85 was acking the same way when I bought it. I threw a complete tune up, super coil, msd wires etc. it got better but not right. Then with the advice from people on here I replaced the fuel injectors and BAM it was a whole different VETTE. It ran like a monster!! It was still a little hard starting every now and then when it was hot. Once again with the advice givin to me from here I replaced the cold start injector and BAM it starts like a dream everytime. Just remember the 85s have 24lbs injectors not 22lbs like alot of people think. Good luck with your Vette, wish I could of had one when I was your age. I had a 79 Trans Am with a 403ci and it was FUN!!
Bob
Bob
Drifting
Joined: Aug 2007
Posts: 1,672
Likes: 0
From: Hereford AZ
A few more details may help us help you.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
Bob
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
A few more details may help us help you.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
How is the idle? Is it smooth or does it have a stumble?
I assume the car is down on power from your description. The lack of power and the hard start could mean bad fuel injectors. Luckily, you have an early C4 and they used the Bosch injectors which can be serviced/rebuilt and returned to new condition cheaply. www.cruzinperformance did the ones in my 86' and I have been happy with the work. but before you spend any money on repairs, you should do everything you can to determine the problem/problems.
You will want to check the ohmage of the injectors, and see if you can check the fuel pressure as well. If the injectors are leaking, fuel pressure will drop off faster than it should once you turn the car off.
You said the timing has been set, have you had a chance to look at the harmonic balancer? The balancer can slip and that will throw off the location of the timing notch and even though the car will show it is set for 6 degrees, in reality it is not. I have a pics of a bad balancer if you are interested.
You could have bad sensors (O2, MAP, IAT, etc) as well.
Where are you located (roughly)? Perhaps there is a forum member who can offer an up close opinion/inspection.
You might also check with the previous owner to find out if a modified chip was installed. They can cause problems as well.
Good luck. You'll find that some of the forum members will badmouth the early C4's, but I have found the 85 to be a good year for do-it-yourself owners. Just have the patience to research the problems you encounter and ask for help when needed.
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
I checked FP, it reads 39, I checked it when we redid timing. I don't remember checking it if it was dropping off quickly or not. I forgot to mention I that I replaced O2 sensor and I also have an accel super coil. Do u think it would be a good idea to just have the injectors rebuilt bc of their age? And the idle is ok.
I live in Central Wis. and the car has collector plates, so i cannot drive it in January. I store the car in my garage from late nov to april (or whenever the f***'in snow melts)
I live in Central Wis. and the car has collector plates, so i cannot drive it in January. I store the car in my garage from late nov to april (or whenever the f***'in snow melts)
Last edited by Pwnage1337; Jan 16, 2009 at 07:56 PM.
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Instructor
Joined: Nov 2008
Posts: 170
Likes: 0
From: Odessa Tx
When you put that accell super coil on there did you have to do anything to the ECM, as far as the program, or did it do just fine with the original ecm chip? I have an 85 and I cant get it to run like I want either. Its good off of the start but sluggish at higher rpms. Im about to put on my new MAF tomorrow.
Melting Slicks
Joined: Mar 2008
Posts: 2,141
Likes: 76
From: Santa Maria, CA
I checked FP, it reads 39, I checked it when we redid timing. I don't remember checking it if it was dropping off quickly or not. I forgot to mention I that I replaced O2 sensor and I also have an accel super coil. Do u think it would be a good idea to just have the injectors rebuilt bc of their age? And the idle is ok.
I live in Central Wis. and the car has collector plates, so i cannot drive it in January. I store the car in my garage from late nov to april (or whenever the f***'in snow melts)
I live in Central Wis. and the car has collector plates, so i cannot drive it in January. I store the car in my garage from late nov to april (or whenever the f***'in snow melts)
Fuel pressure should be 33-34 at idle and 39 with throttle. Sounds like your pressure is OK. I suspect your fuel pump is fine for now. They tend to either work or not. I found that out 150 miles from home.
Check to see how quickly the pressure drops off when you shut off the engine. If the pressure drops off quickly it can mean you have a leaky injector or a bad regulator. There's a simple test to check the fuel pressure regulator and injectors. There should be plenty of threads describing it. Do not try to rebuild the injectors you have. The original injectors were garbage. FIC can set you up with Bosche III 24 lb injectors that flow better than the originals. You'll find lots of threads about FIC injectors and some videos. First do some testing to verify the injectors are bad.
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
I will check the dropoff of pressure on the fuel rail tomorrow. How long does it usually take to drop off? should i be able to notice it happening rather quickly?
http://fuelinjectorconnection.com/sh...ad#read_review
those must be the injectors you're talking about.
Any HP gains?
http://fuelinjectorconnection.com/sh...ad#read_review
those must be the injectors you're talking about.
Any HP gains?
Melting Slicks
Joined: Jan 2001
Posts: 2,940
Likes: 5
From: Chesapeake VA
Unless your injectors are running quite badly, you should not see any power gains from injectors alone. Injectors can only pump more fuel when there is more air. Until an engine has been modified to bring in more air (which on an L98 means an intake manifold mod, different heads/cam or forced induction) the injectors will be adjusted by the computer to maintain a specific fuel/air ratio. Adding fuel will not significantly increase power and will cause problems if too much more fuel is added.
Race Director
Joined: Jun 1999
Posts: 14,924
Likes: 9
From: Merritt Ils Fl
With all the work you have done did you set both the TPS voltage and idle "by the book"? Either can cause issues as you describe. I am confused on the Microtec MAF. Are you sure that thing is a direct replacement for the Bosch MAF?
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
Likes: 190
From: Custer, WI
I have a feeling that my injectors are not performing anywhere near where they should be.
I have a multimeter with a 1k setting and a 10 setting for ohm. Which one do I use and what should the injectors test at? Or what SHOULD thet be?
I have a multimeter with a 1k setting and a 10 setting for ohm. Which one do I use and what should the injectors test at? Or what SHOULD thet be?
Instructor
Joined: Mar 2006
Posts: 127
Likes: 0
From: Stockbridge GA
PM Jon. He has one of the first sticky's up on the board about injectors. Provide him your number and he will give you a call and walk you through how to check everything you need to to determine if your problem lies in the fuel delivery.
Another thing with Jon... he is honest and knows his stuff. And his prices are the best. Period.
I would also suggest changing the cats on the car. Get rid of the pre-cats and get you a good main cat. There are kits out there that will bolt right up and eliminate the pre-cats or you can have shop cut them out. Your choice. But open up the exhaust and you will feel a difference.
And move somewhere warm so that you can drive that thing!!
It is easy to check the injectors even without being able to drive the car. And since you are stuck until spring, you have time to save money to do the exhaust.
The biggest gains in power and performance I got with mine (90 L98) was with the loss of the pre-cats and a really good high flow cat and a set of Flowmasters. Budgetwise, not to bad on the wallet and alot of bang for the buck.
Another thing with Jon... he is honest and knows his stuff. And his prices are the best. Period.
I would also suggest changing the cats on the car. Get rid of the pre-cats and get you a good main cat. There are kits out there that will bolt right up and eliminate the pre-cats or you can have shop cut them out. Your choice. But open up the exhaust and you will feel a difference.
And move somewhere warm so that you can drive that thing!!
It is easy to check the injectors even without being able to drive the car. And since you are stuck until spring, you have time to save money to do the exhaust.
The biggest gains in power and performance I got with mine (90 L98) was with the loss of the pre-cats and a really good high flow cat and a set of Flowmasters. Budgetwise, not to bad on the wallet and alot of bang for the buck.