Finished putting this thing together a couple of weeks ago, and wanted to see how much power I could squeeze out of a 93 5.0L LX hatch, leaving the longblock almost stock. Im running Fords E-cam and up until yesterday the stock rockers. It ran great! It sounded really good and made some power(I have every single bolt on u could possibly imagine). Yesterday I came across Crane Cams' 1.72 roller rocker arms and decided that that would be the last thing I needed(for now). I put them on, torqued them down to 19 ft. lbs. put everything back together and the car wont start. It backfired big time this morning! What did I forget to do????? It seems like its totally off time, but I didnt mess with the distributor or anything...... Gettin kinda worried......Could somebody please help me. Im stuck at this point and dont really know what to do. Please help asap, I gotta get this thing running. Thanks, MARK
Please help! Car wont start, backfiring
- Thread starter vetteslayer
- Start date
Me again...
Apoligize for not introducing myself, as I am new to this online forum stuff. Well its a 93 LX hatch with all the bolt ons and I just was pretty stressed this morning and didnt know what to do? I dont see how this would affect the cars ability to start. I actually torqued them down to almost 20 ft. lbs. Maybe they're too tight??? I didnt rotate the crank either, just pulled the valve covers off and replaced them. Was the backfire caused by maybe one of the valves being open and the rockers being too tight?????
Im stuck and anything would help. Please answer back assuming I know nothing. Anything would be greatly appreciated, Thanks again, Mark.
Apoligize for not introducing myself, as I am new to this online forum stuff. Well its a 93 LX hatch with all the bolt ons and I just was pretty stressed this morning and didnt know what to do? I dont see how this would affect the cars ability to start. I actually torqued them down to almost 20 ft. lbs. Maybe they're too tight??? I didnt rotate the crank either, just pulled the valve covers off and replaced them. Was the backfire caused by maybe one of the valves being open and the rockers being too tight?????
blackened88lx
Active Member
You will probably get a better response posting this in the 5.0 Tech section. This section is for Tuning.
Backfiring out the intake is either a valve stuck open or a lean mixture or spark plug wire(s) connected to the wrong cylinder(s). Check compression on all cylinders and then look for vacuum hoses loose, cracked, misconnected. Check the line for the vapor recirculation system – it is easy to knock loose and not see it when you connect the air pump plumbing. If the vacuum line for the EGR valve and the air pump are cross connected, some very strange things can happen. Check the mass air flow electrical connection and see that it is tight, the same goes for the fuel injection wiring harness connectors up on top of the manifold near the firewall.
Sticking valves: If a intake valve is bent, has a bad spring or is misadjusted, the engine will sometimes backfire through the intake. Use a vacuum gauge connected to any convenient spot on the intake manifold. Run the engine at 1000 RPM & look for 18-21 inches of vacuum with a steady needle. A problem intake valve will make the vacuum gauge needle sweep 5-10 inches.
Lean fuel mixture breaks out into several sub categories:
A.). Vacuum leaks
B.) Air entering the intake without passing through the MAF.
C.) Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D.) Leaking exhaust gases from EGR valve at WOT or EGR opening when it should not be open.
E.) Poor fuel delivery due to bad fuel pump, clogged filter or bad fuel pump wiring. Look for low pressure or fluctuating pressure. Standard injector pressure is 39 PSI at idle, with the vacuum line disconnected from the regulator and capped.
F.) Clogged fuel injectors.- see the cylinder balance test below
H.) Fuel injector wiring problems causing injector not to deliver rated flow.
I.) Computer problems: (computer problems are not common like sensor problems)
J.). ROM has bad data in fuel or timing table. This should also set a code in the computer.
K.) Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one. Use a noid test light to test the injector wiring & injector drivers,
L.) MAF calibration off or mismatched to injectors.
M.) ACT or ECT bad. Sometimes the sensors will be off calibration, but not bad enough to set a code. If they falsely read too high a temp, the engine will back off fuel delivery.
Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure
Sticking valves: If a intake valve is bent, has a bad spring or is misadjusted, the engine will sometimes backfire through the intake. Use a vacuum gauge connected to any convenient spot on the intake manifold. Run the engine at 1000 RPM & look for 18-21 inches of vacuum with a steady needle. A problem intake valve will make the vacuum gauge needle sweep 5-10 inches.
Lean fuel mixture breaks out into several sub categories:
A.). Vacuum leaks
B.) Air entering the intake without passing through the MAF.
C.) Failure of the MAF, BAP/MAP (Baro or Manifold Air Pressure, same sensor, different name), ACT (air charge temp), or ECT (engine coolant temp). These should set a code in the computer.
D.) Leaking exhaust gases from EGR valve at WOT or EGR opening when it should not be open.
E.) Poor fuel delivery due to bad fuel pump, clogged filter or bad fuel pump wiring. Look for low pressure or fluctuating pressure. Standard injector pressure is 39 PSI at idle, with the vacuum line disconnected from the regulator and capped.
F.) Clogged fuel injectors.- see the cylinder balance test below
H.) Fuel injector wiring problems causing injector not to deliver rated flow.
I.) Computer problems: (computer problems are not common like sensor problems)
J.). ROM has bad data in fuel or timing table. This should also set a code in the computer.
K.) Failure of one or more of the computer's driver transistors for the fuel injectors. No code set on this one. Use a noid test light to test the injector wiring & injector drivers,
L.) MAF calibration off or mismatched to injectors.
M.) ACT or ECT bad. Sometimes the sensors will be off calibration, but not bad enough to set a code. If they falsely read too high a temp, the engine will back off fuel delivery.
Cylinder balance test:
Warm the car's engine up to normal operating temperature. Use a jumper wire or paper clip to put the computer into test mode. Start the engine and let it go through the normal diagnostic tests, then quickly press the throttle to the floor. The engine RPM should exceed 2500 RPM's for a brief second. The engine RPM's will increase to about 1450-1600 RPM and hold steady. The engine will shut off power to each injector, one at a time. When it has sequenced through all 8 injectors, it will flash 9 for everything OK, or the number of the failing cylinder such as 2 for cylinder #2. Quickly pressing the throttle again up to 2500 RPM’s will cause the test to re-run with smaller qualifying figures. Do it a third time, and if the same cylinder shows up, the cylinder is weak and isn’t putting out power like it should. See the Chilton’s Shop manual for the complete test procedure
Well found out what it was.....
Well, decided to take one of the rockers off and look at it just for kicks, and found out rocker risers were not installed........ All pushrods got bent along with 1 valve. Well, needless to say it hasnt been a very good week. I think ive decided to start this project all over again and do it right the first time(only a matter of time before I did this anyway), and what better time than now, right? Really bummed and broke too, but "If you wana play u gotta pay".......... Thanks for the technical advise, really do appreciate it. And on we go with the project!
Well, decided to take one of the rockers off and look at it just for kicks, and found out rocker risers were not installed........ All pushrods got bent along with 1 valve. Well, needless to say it hasnt been a very good week. I think ive decided to start this project all over again and do it right the first time(only a matter of time before I did this anyway), and what better time than now, right? Really bummed and broke too, but "If you wana play u gotta pay".......... Thanks for the technical advise, really do appreciate it. And on we go with the project!
