Help! Changed cap/rotor/wires and now won't start!

[goinstrong]

Yes, power to everything else. The battery is pretty new, so it still cranks strongly. Do you think the coil is bad? Thanks...

Tim

[kingston]

Is it a new coil? Wired correctly to the plug wires?

[TwoJ's]

Did you disconnect the coil when you did the change? Any chance you hooked it up improperly? Have you gotten the multimeter out and tested the impedance of the coil? Tested for voltage during cranking?

Like Luke already said, if you haven't already you need to take everything back apart and do it again.

[goinstrong]

I took off the cap and rotor, verified that each wire was going to the right spot, and put it back together. I removed the black cover over the cap so it would fit in easier to avoid any chance of messing up the spring loaded part on the cap.

I didn't remove any wires to the coil other than the one in the spark plug wire set. The spark plut wire set has the shroud, so it is hard to mess it up.

We pulled a plug, then put it into the spark plug wire, and held it against the valve cover. No spark at all when cranking...

If the sensors are backwards, (I don't think they are), would it make it so the coil wouldn't spark?

Tim

[kingston]

Pulse generator connected? Man, struggling to think what else could be wrong. Keep feeling like something must have gotten inadvertantly disconnected...

[kingston]

Check fuse 10...

[goinstrong]

I know! I am frustrated...this should be a simple improvement...not a dead on arrival issue!

Tim

Yes, the sensors are connected. I can go swap them again, but it didn't change anything last night. Plus, the wires are all bent to connect like I have them connected now. When I swapped them, I needed to take them out of the housing to make the change.

[goinstrong]

I will check #10 again...it was fine 1/2 hour ago though!

Tim

#10 is fine...in fact, they are all fine!

[TwoJ's]

Do you have a multimeter? If not, you really should go buy one. They are cheap, and very useful. If you're in a pinch, I live really close to you so you can come borrow mine if you want.

Have you tested for 12V at the coil? Did you test the impedance of the coil? You should also test the wires to ensure they aren't defective spmehow.

[goinstrong]

PM sent to TwoJs...

Tim

[89AlpineM3]

why not put al the old parts back on and see what that does? Thats worked for me before

[e46s54dr]

why not put al the old parts back on and see what that does? Thats worked for me before

Yeah, you should definitely try that. I remember ordering a brand new bosch dist cap and rotor ad when I installed the combo, I kept getting a slight misfire on a single cylinder. After a hour or two of fiddling, I decided to swap the old combo back on and it fired up right away.

[goinstrong]

Well, this issue is now resolved. When my son and I went to change the pulse sensor wire, we tried to remove the old one from the wire guide. It was stuck on the passenger side...so we had to cut it from the driver side. Unfortunately, the wrong wire was cut, so the CPS wire was not connected.
With a new CPS, it started right up...
We had debated just leaving the extra wire, but thought it would be better to clean it up. What should have been simple ended up taking 4 hours to resolve. Be careful about what you cut! Lesson learned...even though we thought we were being SO cautious and methodical about tracing the wires...
A special thanks to Joel and Paul for their help cleaning up the mess we made!!!

Tim

P.S. Anyone have a trick to adjust the TPS without taking off the throttle body? The two bolts holding it on are obstructed by the intake manifold...

[TwoJ's]

Glad you got it sorted out Tim. I thought it was pretty strange that something so simple like new cap/rotor and wires would cause a no-start. I had a hunch there was something else going on. And I know what you mean, it is definitely a pain in the ass to get to those wires without taking all of the belts and radiator out... there's just not much room in there.

So what makes you think that the TPS is in need of adjustment? You may know this already, but on an m20 the TPS is actually just a WOT switch. I'm not going to claim to be an expert on Motronic, but from what I understand the ECU runs in closed loop mode under normal driving. So it takes readings from the O2 sensor, and if it is too rich, it lowers the injector pulse width to inject less fuel, and if it is too lean, it will increase pulse width to deliver more fuel. It does this hundreds (thousands?) of times a second and it should keep your car running at or pretty close to the proper AFR. When you go to wide open throttle, the TPS switch tells the ECU and it goes in to open loop mode where it has a set of fuel maps that it uses rather than taking input from the O2 sensor.

It is done this way because Motronic uses volume air flow (from the AFM) to calculate the amount of air in each cylinder. Some ECU's use throttle angle (Alpha) and engine speed (N), others use speed density (intake manifold absolute pressure and engine speed). If throttle angle is necessary for the calculation, then you need a true TPS, and the accuracy of the sensor is critical. Not so much for our m20s.

[goinstrong]

While everything was being sorted out, I cleaned my ICV, which was a little sticky. It had been "hanging" at about 1200 rpms before it would go to idle after taking the foot off the accelerator.

Now, the idle hunts a little bit. It was suggested to run a continuity check at idle. Doing that did not give the correct result, so we concluded that the computer is not registering that the car is at idle. It does a decent job adjusting things, but the idle will hunt after coming off acceleration. It will eventually work to get steady. If it pulses a little, a quick punch to about 1500-2000 rpms will usually resolve it. It runs fine other than this hunting, so that is how the TPS was kind of isolated as the culprit. What are your thoughts? Thanks!

Tim