cyl 7 misfire
cyl 7 misfire Ok guys. I've searched and tried everything I could for the last 2 weeks except break my heads apart.
the story is.....
Get into my 98 formula and head to the office. reading 3/4 tank of fuel. On 13 mile trip I run out of gas just as I pull into work, still reads 3/4 tank = sgauge broken,
Get fuel in the car, fire it up and start driving home that evening. About 5 miles or so I get the dreaded SES Flashing Light. I pull to the gas station and fill the tank, clear the codes and drive home. Still misfires but only on cyl 7
A few days pass and I decide to take a look at the injectors, figured that they had a build up from crud in my tank, proceed to clean them out only to find that all 8 are really clean. SO at this point I put the injectors back on and drive around .... Smiling and enjoying no misfire. Then out of no where I get a SES light, but only cyl 7.
Get home and swap the coils, wires,injector, and install a new tr55 for good measure. Old plug shows little signs of wear (only 5500 miles since rebuild)
I tidy up and take the car for a spin, runs fine untill i get over 2k rpm or I try to accelerate hard. Any time I get below 2k, or have a light foot on throttle there is no problem. I let the car run for 45 mins on idle and there was no miss or SES.
Next step was compression test. All cyl read 172-175 except #7 = 167
What should I do next guys?
Mods are in my sig!
the story is.....
Get into my 98 formula and head to the office. reading 3/4 tank of fuel. On 13 mile trip I run out of gas just as I pull into work, still reads 3/4 tank = sgauge broken,
Get fuel in the car, fire it up and start driving home that evening. About 5 miles or so I get the dreaded SES Flashing Light. I pull to the gas station and fill the tank, clear the codes and drive home. Still misfires but only on cyl 7
A few days pass and I decide to take a look at the injectors, figured that they had a build up from crud in my tank, proceed to clean them out only to find that all 8 are really clean. SO at this point I put the injectors back on and drive around .... Smiling and enjoying no misfire. Then out of no where I get a SES light, but only cyl 7.
Get home and swap the coils, wires,injector, and install a new tr55 for good measure. Old plug shows little signs of wear (only 5500 miles since rebuild)
I tidy up and take the car for a spin, runs fine untill i get over 2k rpm or I try to accelerate hard. Any time I get below 2k, or have a light foot on throttle there is no problem. I let the car run for 45 mins on idle and there was no miss or SES.
Next step was compression test. All cyl read 172-175 except #7 = 167
What should I do next guys?
Mods are in my sig!
Forgot to add that I did replace the filter.
I cut the old filter apart, nothing really stood apart.
Maybe the filter sock is getting clogged? My pump has been humming since this started.
I cut the old filter apart, nothing really stood apart.
Maybe the filter sock is getting clogged? My pump has been humming since this started.
Do you have the SES light flashing on and off? I'd start with the plug, then wire, coil, then o2's. If that is in order, MAF could be dirty, or not tightened down.
From there, it could be a crank position sensor, a MAP sensor, IAC, TB sensor.
Do a visual check on the wiring, is anything cut, or frayed? I just discovered a broken injector wire, that got cut somehow. The only symptoms were the car was down on power, and I only got an occasional flashing SES light.
It could be anything, but now you have some more ideas.. make sure you run a code check, even if the light is not on. Good luck.
From there, it could be a crank position sensor, a MAP sensor, IAC, TB sensor.
Do a visual check on the wiring, is anything cut, or frayed? I just discovered a broken injector wire, that got cut somehow. The only symptoms were the car was down on power, and I only got an occasional flashing SES light.
It could be anything, but now you have some more ideas.. make sure you run a code check, even if the light is not on. Good luck.
Do you have the SES light flashing on and off? I'd start with the plug, then wire, coil, then o2's. If that is in order, MAF could be dirty, or not tightened down.
From there, it could be a crank position sensor, a MAP sensor, IAC, TB sensor.
Do a visual check on the wiring, is anything cut, or frayed? I just discovered a broken injector wire, that got cut somehow. The only symptoms were the car was down on power, and I only got an occasional flashing SES light.
It could be anything, but now you have some more ideas.. make sure you run a code check, even if the light is not on. Good luck.
From there, it could be a crank position sensor, a MAP sensor, IAC, TB sensor.
Do a visual check on the wiring, is anything cut, or frayed? I just discovered a broken injector wire, that got cut somehow. The only symptoms were the car was down on power, and I only got an occasional flashing SES light.
It could be anything, but now you have some more ideas.. make sure you run a code check, even if the light is not on. Good luck.
I will check the MAF
Have you scanned the car to see what the o2's are reading? If you haven't changed them in awhile, do so, it's something that keeps the car running smooth. I'd bet on that before the MAF, unless you have had the MAF off recently, and something damaged the diods.
The easiest way to mess with the MAF is to find a friend who has the same, or similar car, and switch MAF's & see if the problem follows.
Have you checked all grounds? The 2 on the back of the dirivers side head, and the one from the block to the frame (down by the alt.).
The easiest way to mess with the MAF is to find a friend who has the same, or similar car, and switch MAF's & see if the problem follows.
Have you checked all grounds? The 2 on the back of the dirivers side head, and the one from the block to the frame (down by the alt.).
Trending Topics
Sorry its been a few weeks. I've been under the weather and unable to work on it.
I am having the same issues, now the coolant light is flashing on and off too. A while back I replaced the passenger o2 and a few weeks later got a code on the drivers side - cleared it and never had trouble again.....the car has 176000 miles so i'll replace it for good measure.
Will check the grounds, vaccumes, maf, and replace that coolant sensor.
I am having the same issues, now the coolant light is flashing on and off too. A while back I replaced the passenger o2 and a few weeks later got a code on the drivers side - cleared it and never had trouble again.....the car has 176000 miles so i'll replace it for good measure.
Will check the grounds, vaccumes, maf, and replace that coolant sensor.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Well I replaced the drivers side 02 sensor. Drove the car down the road a few miles and it started again. I feel it start to misfire but I don't get a code.
I drove it about 5 more miles, stopped and gave it hell. (first time since rebuild last year)
Smokes like hell after 4k (white) and I got a little "studder" at 7k rpms....then it launched like a rocket. I then went about 5 more miles feeling great cause I did not feel another misfire.. My gas guage had went to E.(showed 3/4 when I started the drive...shocked I stopped to fill it up - held only 8 gallons and the needle worked fine after I filled it up.
That was last night. I drove her to work today and when I got about 80-90 it started misfiring for a few seconds and the smoothed out.
I will clean the maf sat if its not raining. I'm concerned about the studder at 7k. I also think that I may be on the Rich side....there is caked up black soot in my tailpipes....
Any thoughts?
I drove it about 5 more miles, stopped and gave it hell. (first time since rebuild last year)
Smokes like hell after 4k (white) and I got a little "studder" at 7k rpms....then it launched like a rocket. I then went about 5 more miles feeling great cause I did not feel another misfire.. My gas guage had went to E.(showed 3/4 when I started the drive...shocked I stopped to fill it up - held only 8 gallons and the needle worked fine after I filled it up.
That was last night. I drove her to work today and when I got about 80-90 it started misfiring for a few seconds and the smoothed out.
I will clean the maf sat if its not raining. I'm concerned about the studder at 7k. I also think that I may be on the Rich side....there is caked up black soot in my tailpipes....
Any thoughts?
Update.
I cleaned the MAF and pulled the valve cover on the drivers side to check the springs and pushrods. Everything looked great. I was able to tighten my headers a bit more.
Jot in the car and there is a hugh difference in power. Drove her about 75 miles yesterday with no problem.
I cleaned the MAF and pulled the valve cover on the drivers side to check the springs and pushrods. Everything looked great. I was able to tighten my headers a bit more.
Jot in the car and there is a hugh difference in power. Drove her about 75 miles yesterday with no problem.
Something else to try is to take the IAC motor out of the throttle body and clean it. It takes just a few minutes and can cause some strange problems. I don't think I've ever heard of it causing mis-fires but if it's never been cleaned I think you'll be surprised at the amount of gunk on it.
Did you clean your fuel rail out?
I had a similar problem, changed plugs, wires, 02s, coils, etc did everything but injectors.
Pulled injectors, number 7 ( my misfire cylinder also ) was filthy, cleaned it put it back in and it seemed to run better. 10 minutes into drive it went back to the same old bullshit.
Ordered 8 new fuel injectors and removed fuel rail and sprayed it, now car is running AMAZING.
Spray the fuel rail out with carb cleaner.
I had a similar problem, changed plugs, wires, 02s, coils, etc did everything but injectors.
Pulled injectors, number 7 ( my misfire cylinder also ) was filthy, cleaned it put it back in and it seemed to run better. 10 minutes into drive it went back to the same old bullshit.
Ordered 8 new fuel injectors and removed fuel rail and sprayed it, now car is running AMAZING.
Spray the fuel rail out with carb cleaner.
Did you clean your fuel rail out?
I had a similar problem, changed plugs, wires, 02s, coils, etc did everything but injectors.
Pulled injectors, number 7 ( my misfire cylinder also ) was filthy, cleaned it put it back in and it seemed to run better. 10 minutes into drive it went back to the same old bullshit.
Ordered 8 new fuel injectors and removed fuel rail and sprayed it, now car is running AMAZING.
Spray the fuel rail out with carb cleaner.
I had a similar problem, changed plugs, wires, 02s, coils, etc did everything but injectors.
Pulled injectors, number 7 ( my misfire cylinder also ) was filthy, cleaned it put it back in and it seemed to run better. 10 minutes into drive it went back to the same old bullshit.
Ordered 8 new fuel injectors and removed fuel rail and sprayed it, now car is running AMAZING.
Spray the fuel rail out with carb cleaner.
So far so good....other than my air not staying cold....I must have a leak in the hose.
