Feels like a cylinder is down/missing

[FFRSpec72]

Had Round 5 of NASA NW this weekend, car felt like it was missing, not firing on all cyls, replaced wires that were questionable, ran codes nothing major, 81, 82 84 and 85, I would expect these. Any suggestions ? Fustrating weekend being down on initial power.

Car was OK at high RPM (still lacking but was up to speed of 145), juts sluggish at low RPM and you could hear a miss.

[johngeorge]

exhaust crack?

[FFRSpec72]

exhaust crack?

So I do have a loose j-pipe where the j-pipe bolts to header as it will not tighten up. Its on the same side as what sounded like a miss. O did not think that could cause low end power issues?

[mhoward1]

I'd actually pull off the j-pipe. They tend to crack right at the bend or just below the flange.

[FFRSpec72]

No issue with J-Pipe except at the flange, engine still missing (feels down a cyl), replaced wires, plugs, distributor and Thin Film module @ distributor. I guess will have to pull the valve cover and see what is going on, any other suggestions?

[johngeorge]

all injectors firing?

[FFRSpec72]

all injectors firing?

What is the quickest way to test that, as I get no codes ?

[johngeorge]

take exhaust temps with a laser temp probe, or paint on exhaust, or use one of those stethoscopes to hear if the injector is firing.

[first time builder]

FFR Spec , with engine running and using an insulated plug wire pliers, pull off one plug wire at a time . If you do indeed have a clyinder not fireing when you get to that wire there will not be a difference in rpm. You can pull the wire either at plug or dizzy. This wont solve problem but will tell you which cly has the problem .

Kenny

[Mark Dougherty]

Check all exhaust tubes 2 inches off the head make sure there are no cold cyl. (With a laser temp probe
If there is a cold cyl. Tap on the injector for that cyl. And see if that cures it.

[FFRSpec72]

I pulled the valve cover and no issues I could see with the rocker arms or pushrods or valve adjustments. I checked the resistance on all the injectors and all the same (so no grounded injector), feels like each injector is clicking. I don't have a heat gun, so I used my hand and got burnt the same on each header tube. I checked the resistance on each of the spark plug wires and all are within the range for the length.

Last race of season this weekend, and I'm in the points lead for ITE by 6 points, if I don't run I lose and get second place, if I run and finish above 8th I can still win the championship but not sure the way the car is running and if it's a valve will I do more damage if I run ....

[FFRSpec72]

I just did a leak down test with a an OTC tester (not the cheap Harbor freight one) and all cyls on a 90PSI test were reading 82PSI so a 8-9 % loss (except #1 was reading 81PSI) so I find that acceptable (and no differences real differences between cyls) and no valve or cyl issue.

So still at a loss.

[Mark Dougherty]

tony
give me a ring when you get a chance

[CHOTIS BILL]

How about the coil? It looks like you check everything but I didn’t see anything about the coil.

Bill Lomenick

[FFRSpec72]

How about the coil? It looks like you check everything but I didn’t see anything about the coil.

Bill Lomenick

I replaces that also, but that was mid way through last season, so its fairly new

[FFRSpec72]

Here is a picture of the plugs on one side, the other side looks the same, I don't see any fowling, these look pretty good, not too lean, not sure about the 2nd one from left, seems a little white

21782

[FFRSpec72]

Had the injectors tested today and they are were equal in flow. One cyl is colder than the rest (measuring with infrared thermometer on the header) by about 100 degrees, but don't understand why, as everything check out.

[avgjoe]

I know it's no fun, but it maybe time to dig into the fuel cell to check the foam, sock and pump to fill plate hose. It doesn't seem logical that those things would cause a problem on one cylinder but so far you've checked all the easy logical stuff. Is it always the same cylinder that's cold?

[FFRSpec72]

I know it's no fun, but it maybe time to dig into the fuel cell to check the foam, sock and pump to fill plate hose. It doesn't seem logical that those things would cause a problem on one cylinder but so far you've checked all the easy logical stuff. Is it always the same cylinder that's cold?

It's always the same cyl. it may be just be normal with the way the header is formed. I get a constant 50PSI on the fuel rail (as I went through a cell issue last year and had the whole thing apart and replaced things) and have a fuel pressure gauge on my dash to make sure I don't hit that issue again. Since I have good fuel pressure and I cleaned out the rail I don't think that is the issue.

[skullandbones]

Hi Tony,

Have you considered the ECU as the problem? I have heard of the ECU dying but could it possibly be a compromised file such as a fuel map to that particular injector? I don't know if you have access to another ECU but if you do, changing it out would answer the question of an adulterated file. I know you are trouble shooting the easier possibilities first. But it shouldn't take too long to check that out, IMO. Good luck, WEK.

[2bking]

Have you checked cam lift? Sounds a little like a flat lobe. If you use an engine diagnostic software, it can tell how much HP each cylinder is making by the acceleration of the crankshaft as each cylinder fires. I think you have to drive it with the laptop hooked up to get the info.

[FFRSpec72]

Hi Tony,

Have you considered the ECU as the problem? I have heard of the ECU dying but could it possibly be a compromised file such as a fuel map to that particular injector? I don't know if you have access to another ECU but if you do, changing it out would answer the question of an adulterated file. I know you are trouble shooting the easier possibilities first. But it shouldn't take too long to check that out, IMO. Good luck, WEK.

I have a spare "new" (reconditioned) Autozone ECU so will plug that in tonight and see

[FFRSpec72]

Have you checked cam lift? Sounds a little like a flat lobe. If you use an engine diagnostic software, it can tell how much HP each cylinder is making by the acceleration of the crankshaft as each cylinder fires. I think you have to drive it with the laptop hooked up to get the info.

Could be, cam is new as of last season (entire engine was new last season), when opened up the top end all looked fine, but could not see all the cam. I have tried the cyl balance test (that the diagnostic readers have) and all passes, which cuts fuel and spark to each cyl and tries to see if there is a cyl not holding up its part.

[FFRSpec72]

Well replaced the computer with my backup and problem fixed, very odd, as I would not have expected just one cyl to go out but multiple or all to go out. No faults or anything, all the diagnostics ran, no signs of bad computer. So replaced with my backup Autozone remanufactured unit. I guess I have to get another backup now. Thanks everyone for your suggestions.

[Mark Dougherty]

Sweet
That is great news

[mhoward1]

Yes, glad to hear that